Category: Photosynthesis

Photosynthesis and cellular respiration are energy reactions occurring in plant and animal cells. During photosynthesis, oxygen and glucose are produced from sunlight, water, and carbon dioxide. During cellular respiration, oxygen and glucose are used to create water, carbon dioxide and ATP. Both processes constitute the energy cycle required for organisms to function. The purpose of this paper is to analyze cellular respiration and photosynthesis and establish their similarities and differences.

Photosynthesis is the process in green plants that transforms solar radiation into energy that plants use for development and growth. It is basically a complex chemical reaction that happens inside the leaves of a plant, aimed to produce food for it to survive (Govindjee et al., 2018). The starting reactants are the light of the sun, carbon dioxide, and water. They get into the plant from the sun, air, and ground respectively. Photosynthesis occurs in chloroplasts in two stages: light-dependent reactions and the Calvin cycle.

During the first stage, chloroplasts capture sunlight and use it to form the molecules of ATP and NADPH. During the second stage, called the Calvin cycle, the energy generated during the first stage is used to make carbohydrates (Blankenship, 2014). Contrary to the first stage, the reactions of the Calvin cycle can occur without light. The overall process can be described as following: six molecules of carbon dioxide and six water molecules are converted in the presence of light into glucose and six molecules of oxygen. Glucose is used as an energy source for the plant, while oxygen is released back into the air.

Cellular respiration is a set of reactions that converts glucose into adenosine triphosphate (ATP), an organic compound that provides energy to cells. The purpose of the process is to produce energy that organisms need to function (Russell et al., 2016). The initial reactants are oxygen and glucose, with glucose entering the body with food, and oxygen entering the body when breathing. During cellular respiration, a glucose molecule is split into ATP, carbon dioxide, and water. The reactions occur in mitochondria in four stages: glycolysis, pyruvate oxidation, citric acid cycle, and oxidative phosphorylation (Campbell & Paradise, 2016, p. 124). The overall reaction can be described as one molecule of glucose and six molecules of oxygen yielding six molecules of carbon dioxide, six water molecules, and 3638 molecules of ATP (Campbell & Paradise, 2016). Carbon dioxide is transported to the lungs to be exhaled, and ATP is used in cellular work.

Both photosynthesis and cellular respiration are processes aimed at converting one form of energy into another. They both involve the same ingredients: water, oxygen, carbon dioxide, and glucose. However, the processes are opposite in their products and reactants. Cellular respiration takes oxygen from the air, while photosynthesis puts it back. Photosynthesis needs light to operate, while cellular respiration takes place both day and night in living cells.

The two processes complement each other in a mutually beneficial relationship. They are both a part of the cycle of biochemical reactions in which one type of energy is converted into another. Both processes are required to support the being of plants and animals. If one of them stops occurring, the other would also be unable to continue because it requires the energy produced by the other (Russell et al, 2016). They both constitute a cycle that sustains life on Earth.

Photosynthesis and cellular respiration are different processes that are connected to one another. They are two sides of the energy circulation process that supports the life of every living organism on the Earth (Treagust & Tsui, 2013). Photosynthesis produces energy for plants and releases oxygen that animals use to create ATP. In the production of ATP, carbon dioxide is released that is used by plants to make oxygen. In can be said that photosynthesis and cellular respiration form a cycle that provide energy necessary for all life on the Earth.

References

Blankenship, R. (2014). Molecular mechanisms of photosynthesis. John Wiley & Sons.

Campbell, M., & Paradise, C. (2016). Cellular respiration. Momentum Press.

Govindjee, Bjorn, L., & Shevela, D. (2018). Photosynthesis: Solar energy for life. World Scientific Publishing.

Russell, P., Hertz, P., & McMillan, B. (2016). Biology: The dynamic science. Cengage Learning.

Treagust, D., & Tsui, C. (2013). Multiple representations in biological education. Springer Science & Business Media.

Flowers are grown all over the world in gardens, greenhouses and in the wilderness naturally, and are shipped across huge distances. While the flower is still attached to the plant the flower benefits from the sugars that the plant’s leaves manufacture through the process of photosynthesis (SFGate, Unknown). Photosynthesis is the process used by plants to harness energy from sunlight and turn it into chemical energy. There are two types of photosynthetic processes which are oxygenic photosynthesis and anoxygenic photosynthesis. However oxygenic photosynthesis is the most common and is seen in plants, algae and cyanobacteria ( Aparna Vidyasagar, 2018). During oxygenic photosynthesis, light energy transfers electrons from water (H2O) to carbon dioxide (CO2), to produce carbohydrates(Giuseppe Tallarico, unknown).

There are numerous structures within a leaf that have important roles in the movement of nutrients and water throughout a plant. Each plant contains a branched system of tubes called xylem, which is responsible for water transport from the roots to the leaves where it is used in photosynthesis (University of California, 2019). Alongside xylem is another system of tubes called phloem, which transports the glucose formed in photosynthesis into the branches, fruit, stem and roots of the plant, as can be seen below in figure 1.

Water keeps cut flowers and other plants crisp because of one of the most important and natural processes happening in the world, and it goes by the technical name of osmosis. Osmosis is the process in which liquid water tends to move toward regions with a higher concentration of dissolved substances, such as minerals and sugars as seen in figure 2 (Steve Fentress, 2017). Water pressure builds up inside the cell, and that water pressure gives a healthy plant its crisp texture. However, if plants do not get enough water these cells lose internal water pressure and can result in the plant wilting and ultimately dying.

There are two different types of flower stems, which as woody stems and hollow stems. Woody stems usually have problems absorbing water. Whereas in hollow stems while the stem tries to absorb the water it draws the air up the stem until it reaches the neck of the flower. At this point the air has nowhere to go and acts as a block to any further absorption of water by the bloom. (Irish Florists, Unknown).

These flowers are then picked and cut, to be placed into banquets for decoration or gifts. There are two factors that affect the flowers overall health include growing conditions and genetic lifespan. Growing conditions, such as light, temperature, relative humidity, fertilization and crop protection have a marked effect on the post-harvest quality of the flower, such as length, shape, colour and deviation of stem and flower (Chrysal, 2015). These factors, however, do not affect the genetic lifespan expectations. The genetic lifespan expectations are affected by climatic conditions and other factor, such as any deviations from optimum care, which are different for each flower types. However, once any type flower is cut from the plant, the number of leaves providing food is greatly limited, as is the amount of light available for food production, and therefore as a result the amount of food available to the flower is drastically reduced.

Temperature and humidity are particular factors that can determine whether the cut flower will be delivered to the consumer in good condition after the harvest (Lynn Byczynski, unknown). Higher temperatures promote flower development, while humidity plays an indirect role in the condensation process during temperature fluctuations and promotes the growth of bacteria. Lack of hygiene promotes the development of micro-organisms, which can cause water to become turbid and smelly (Lynn Byczynski, unknown).

Some solution other than water that have been known to work for increasing the longevity of flower vase life are lemon juice, bleach, sugar water, and flower food. Lemon juice has been known to help extend the longevity of vase life, however this ideal is exemplified on how it is used. Adding to much lemon juice onto a plant can cause it to shrivel and compromise its ability to perform photosynthesis. This is because adding small amounts of lemon juice to the soil makes the soil more acidic, altering the pH, but pouring it over the plant’s leaves can burn them and kill the plant (SFGate, unknown). Bleach has been known to be beneficial for killing bacteria that is nestled in the flower stems, the vase or the water (Donna Thacker, unknown). Through killing the bacteria, it is unable to travel through the flowers stem and make the plant ‘sick’, preventing it from wilting and dying rather quickly. Bleach is a poison, and if it overused it will quickly kill your flowers, where as if it is used correctly it will cause little harm potentially causing the flower to fade a little in colour. Another solution that is commonly suggested in sugar water. Before being cut the flower benefits from the sugars that the plant’s leaves manufacture through the process of photosynthesis, however once the flower is cut from the plant, the number of leaves providing food is greatly limited, as is the amount of light available for food production (SFGate, unknown). As a result, the amount of food available to the flower is drastically reduced. To make up for this loss, sucrose is added to the water the flower stems are placed into to ensure the continued development of the flower and greater longevity (Sugar water? When cut flowers are bought from the shops or florists, they usually are given with a small packet of flower food. Flower food has a combination of ingredients which include citric acid, sugar and a small amount of bleach that are to be added to the vase filled with water. These ingredient vary depending on what brand and type of flowers that are bought.

Abstract

The effect of light wavelength on the rate of photosynthesis in baby spinach leaves was determined by recording the consumption of carbon dioxide for four minutes. Red, blue, and green light were tested to determine which color increased the rate of photosynthesis the most. Each color has a specific range of wavelengths to describe it, and the closer the wavelength is to the accepted, the more carbon dioxide was consumed. The graphs supported the prediction that as the wavelength of light changed, the rate of photosynthesis also changed. The ideal wavelength was found to be around 492 to 577 nm (corresponding to green light); however, more tests could be done to determine the ideal absorption range. If the accepted wavelength of individual plants could be found, larger amounts of nutritious foods could be produced decreasing malnourishment rates and feeding a growing population.

Introduction

Photosynthesis has two main functions— convert light energy into chemical energy and convert inorganic carbon to organic carbon. The created chemical energy is in the form of carbohydrates that can be converted into adenosine triphosphate (ATP) through cellular respiration. Photosynthesis is the reverse reaction of cellular respiration; the products of cellular respiration can be used as reactants for photosynthesis and vice versa. If there is no light present, plants can undergo cellular respiration to gain the energy they need; however, they will generate no biomass. Photosynthesis has two steps: the light-dependent and the light-independent reactions. During the light-dependent reactions, photons break water bonds, creating atmospheric oxygen and hydrogen ions in the thylakoid. Light energy, water, and carbon dioxide are converted into chemical energy in the form of ATP and NADPH. The light-independent reactions consist of cyclic reactions that occur in the stroma. The chemical energy from the light-dependent reactions is combined with rubisco and carbon dioxide to form simple sugars. Even though the light-independent reactions do not need direct light to occur, neither step could happen in the absence of light as the Calvin cycle requires intermediates produced during light-dependent reactions. Photosynthesis results in biomass through carbon fixation, allowing all life on Earth. Organisms that cannot produce chemical energy for themselves can gain the nutrients they need by consuming plants or other species that consume plants. Additionally, photosynthesis produces oxygen, which is essential for many species (Angilletta 2018).

As plants can only absorb a certain range of wavelengths, the hypothesis that different colored lights will affect the rate of photosynthesis was tested. Depending on the range of wavelengths the plant accepts, some colors will improve while others will inhibit plant growth. The more similar the color’s wavelength is to the acceptable range; the faster photosynthesis will occur. If the wavelength is dissimilar to the accepted range, photosynthesis will slow or stop altogether. The ideal range was unknown prior to the lab and was determined experimentally. To determine how different wavelengths affect photosynthesis, carbon dioxide concentrations were tested with a Pasco® carbon dioxide sensor for the red light, blue light, green light, and control trials. As the negative slope becomes steeper, the rate of photosynthesis increases.

If colored light does affect photosynthesis, and therefore plant growth, the knowledge can be utilized in a multitude of ways. Certain wavelengths of light could be used to either raise or destroy crop yield. The ideal wavelength could be determined experimentally in a similar way to discover what factors lead to higher, more nutritious crop yield. Sofia Carvalho and Kevin Folta discuss the possible benefits of using specific wavelengths to improve plant growth. Within their introduction, they state “variation in light quantity, quality, duration or combinations can be used to change plant growth, development or metabolism to influence a desired final product” (Carvalho and Folta 2014). Throughout the article, the key findings of researchers’ studies on a multitude of specific plants were summarized. For example, the growth of lettuce was tested under “blue, red, and a combination of red and far-red light sources… to adjust lettuce leaf size and shape, taste, color texture, and nutrient content when compared to white light” (Carvalho and Folta 2014). Multiple researchers found that “blue light exposure promotes growth, leaf area and biomass increase… while red-rich sources stimulate leaf elongation and lower growth rates” (Carvalho and Folta 2014). If a specific color were found to improve crop yields, more food, or more nutritious food, could be harvested with lower energy costs. Beth Johnson, Consuelo De Moraes, and Mark Mescher investigated the effects of light spectroscopy on parasites to determine ways of killing harmful plants without killing the crop. When exposed to far-red light, the plant’s growth was not affected. However, the “host location and subsequent attachment by dodder parasites was dramatically reduced in high-R:FR environments” (De Moraes et al. 2016). By determining how light affects different organisms, crop yields could be increased to feed a growing population while parasitic plants could be killed with no harm to the host. Additionally, more nutritious plants could be grown through light technology, which could solve the global malnourishment epidemic.

Methods

To test the effects of wavelength on photosynthesis, two leaves were subjected to different colored lights. The concentration of carbon dioxide was recorded every ten seconds to determine the rate of photosynthesis. If photosynthesis occurred, the correlated graph would have a negative slope because carbon dioxide is consumed during the process. The steeper the graph’s slope, the faster the rate of photosynthesis. In summary, the independent variable was the color of light while the dependent variable was the amount of carbon dioxide present over four minutes. As leaves must be alive to undergo photosynthesis, the negative control tested the rate of fake leaves. As many plants can grow under artificial white light, the positive control tested the rate of photosynthesis under a white CFL bulb. Even though a better positive control would have been natural sunlight, it would have been difficult to test the rate of carbon dioxide consumed outside, and other variables would have been affected. If the positive control was done outside, all the other tests would also have had to be done outside. Not only that, the amount of light the plant could consume throughout the experiment would change as the sun set. To ensure that no other factors contributed to the results, there were many controlled variables. The same sized leaves were used each time to ensure that the mass, the species, and the rate of each leaf was nearly constant throughout. Each trial was done within the laboratory to assure that the outside environment did not change individual samples. To adequately compare the rates of photosynthesis, each trial was tested for four minutes with the concentration of carbon dioxide recorded every ten seconds. Additionally, the same wattage was used for each colored light bulb to avoid the effects of light intensity. To control the wavelengths entering the container, aluminum foil was placed around the container and the lamp to trap the light in a relatively closed system. Even though the same leaves and sensor were supposed to be used for every trial, these two factors had to be changed throughout the experiment due to uncontrollable errors.

Before the effect of colored light on photosynthesis could be tested, the system was calibrated to set a baseline reading of carbon dioxide. To calibrate the Pasco® carbon dioxide sensor, the calibration button was pressed until the green light blinked. To ensure that the sensor adequately calibrated, all group members stepped away from the table until the light stopped blinking. SPARKvue was set up to record carbon dioxide concentration every ten seconds for four minutes. Two leaves were randomly chosen from the same sample and were placed in a clean container smooth side up. The sensor was attached with no openings present, and the container was then placed on its side which allowed more light in. To test the negative control, fake leaves were placed inside the container because they were not alive. After the negative trial was done, the graph was scaled to determine if photosynthesis took place and saved to the computer. To test the positive control, the two spinach leaves were added to a clean container with the sensor attached. A lamp was placed over the container, and a white CFL bulb was turned on. Additionally, aluminum foil was placed around the container and lamp to trap the light inside. Once the positive trial was done, the graph was scaled to determine if photosynthesis took place. The raw data of both controls were saved to the computer to be analyzed later.

Once the controls were done and saved, the effects of different wavelengths were tested. For the colored light bulbs, multiple trials of each were done with two similar leaves for four minutes each. To test red light, two leaves were placed in the container with the carbon dioxide sensor placed on top and the lamp overhead. After the three trials of red were done, the graphs were scaled, and the raw data was saved to the computer. The red light bulb was replaced with the blue light bulb in the lamp. Once the four trials of the blue light were done, the graphs and data were saved. The green bulb replaced the blue one for the last two trials. Similarly, the graphs were scaled, and the data was saved for further analysis. As the trials occurred, the raw data was analyzed to determine if the plants were truly undergoing photosynthesis. After all the trials were done, the lab station was cleaned and organized.

Discussion

Because individual plant chloroplasts can only absorb a certain range of the electromagnetic spectrum, the hypothesis that different colored lights affect the rate of photosynthesis was tested. Depending on the ideal wavelength range of baby spinach, the closest wavelength range should change the rate of carbon dioxide consumption. The hypothesis was somewhat supported by the collected data. The white, blue, and green lights had different rates of carbon dioxide consumption with green light being the most effective (wavelength of 492-577 nm). The negative control should have had no increase nor decrease in carbon dioxide, yet it had a huge rate of cellular respiration meaning something went wrong during the negative control trial. Similarly, the plant appeared to undergo cellular respiration under red light; however, any colors outside the ideal wavelength range were expected to undergo lower levels of photosynthesis or not have any change in carbon dioxide during the short time interval. It is possible that the leaves run under red light truly were undergoing cellular respiration rather than photosynthesis because it was too far from he accepted spectrum; however, it could also be attributed to error. More data would have to be gathered to determine whether baby spinach leaves photosynthesize or respire under red light. Of the three colors tested, the plant’s ideal absorption range is most like that of green; lying somewhere around 492 to 577 nm. Likely, the accepted range includes some values on the lower end of the spectrum because blue light also led to a rate of photosynthesis.

Many outside influences affected the recorded carbon dioxide concentration. Someone may have bumped the table, causing large spikes to occur in the graph. The same leaves were not used each time because the rates of consumption or production appeared to change as the trials continued. The leaves would not be crisp, and the rate went down even when the same color was tested. Even though the leaves were switched out to account for this error, each additional sample may have had a lower or higher rate of photosynthesis than the previous. The sensors had to be switched multiple times because of misreading as well. For example, the relatively large positive slope of 1.9618 PPM/s should not have been the slope of the negative control. In theory, the slope should have been around zero because fake leaves should neither produce carbon dioxide (cellular respiration) nor consume carbon dioxide (photosynthesis). The large deviation could have occurred due to incorrect data collection; the sensors used to record carbon dioxide levels were too sensitive and old to be of good use. Multiple sensors were used to no avail which may have meant the box connecting the computer to the sensor or the program ran awry. Several samples had a recorded carbon dioxide value of 300,000 PPM which was nowhere near the 400-1000 PPM range of the others. Additionally, it is possible that changing the sensor changed the reading slightly, impacting the gathered data. Each sensor may have worked slightly differently than the last; not every trial had the same baseline as the others. Another possible problem may have been lack of water in the solution. Ina Vasilean found that “for light to be perceived by plant tissues, one of the major conditions was reported to be the presence of water” (Vasilean et al 2018). One or more of the colors may have had a higher rate of carbon dioxide consumption if water was inside the container.

While the experiment did include many errors, many other researchers had similar results for the effect of light’s wavelength on plants. Even though Ina Vasilean, along with other researchers, studied the effect of light wavelength (color) on the germination performance of three different types of legumes, it is important to understand the effect of light on more than just spinach leaves. Oftentimes, there are similarities, and the findings can be applied to other plants. For each plant, the accepted wavelength range varied, meaning some light led to more germination than others. Lentils grew best under violet light (405 nm) and the red light (700 nm) which is somewhat surprising because those wavelengths are relatively far apart. They found that “broad bean germination under light also presented a significant improvement of total protein content and antioxidant activity” (Vasilean et al 2018). There results highlight that increased rates of growth occur under different colors of light, and that each species has its own range of wavelengths it can observe.

Sofia Carvalho and Kevin M. Folta wrote about the effects of light wavelength (color) on a variety of species including spinach. The study found that “spinach biomass is increased when grown under blue-rich light sources, whereas repressed by monochromatic red” (Carvalho and Folta 2014). They also found that blue light combined with others led to increased biomass. This is similar to what was found experimentally in lab as well. Spinach appeared to produce carbon dioxide under red light (cellular respiration) while it consumed carbon dioxide under blue, green and white light. Within our experiment, the green light led to the highest rate of photosynthesis; however, it is possible that a mix of blue and some other color would have led to an even higher rate.

Undernourishment is a large problem globally, “reaching an estimated 821 million in 2017” (Fao.org 2018). Additionally, the population of the world is continuing to increase, leading to more people with about the same amount of food. To fix this problem of malnourishment and feeding a global population, plants should be grown in the conditions that promote nutritious, large crop yields. By understanding what each color of light does for the plants, a “balance between fast growth, nutritional value and human safety must be considered when designing optimal light conditions for spinach growth” (Carvalho and Folta 2014). Studies have found that “exposure to different light-emitting diodes (LED) wavelengths can induce the synthesis of bioactive compounds and antioxidants, which in turn can improve the nutritional quality of crops”; however, some dangerous chemicals are produced as well (Vasilean et al 2018). By knowing which lights induce which characteristics, a combination of wavelengths can be found to grow a variety of nutritional plants to decrease the rate of world hunger and feed mankind for generations to come.

Works Cited

1. Angilletta, Michael J., et al. ‘Photosynthesis.’ Laboratory Exercises for BIO 181 and 281
2. General Biolgoy I. Plymouth: MacMillan Learning, 2018. 67-80. Print.
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4. De Moraes, Consuelo M., Beth I. Johnson and Mark C. Mescher. ‘Manipulation of light spectral quality disrupts host location and attachment by parasitic plants in the genus Cuscuta.’ British Ecological Society 53.3 (2016). Web. https://besjournals-onlinelibrary-wiley-com.ezproxy1.lib.asu.edu/doi/full/10.1111/1365-2664.12627Fao.org. “SOFI 2018 – The State of Food Security and Nutrition in the World.”
5. International Rice Commission Newsletter Vol. 48, FAO of the UN, 2018, www.fao.org/state-of-food-security-nutrition/en/.
6. Vasilean, Ina, et al. ‘THE INFLUENCE OF LIGHT WAVELENGTH ON THE GERMINATION PERFORMANCE OF LEGUMES.’ The Annals of the University of Dunarea De Jos of Galati.Fascicle VI.Food Technology, vol. 42, no. 2, 2018, pp. 95-108. ProQuest, http://login.ezproxy1.lib.asu.edu/login?url=https://search-proquest-com.ezproxy1.lib.asu.edu/docview/2175256976?accountid=4485.
7. “Visible Light and the Eye’s Response.” The Physics Classroom, www.physicsclassroom.com/class/light/Lesson-2/Visible-Light-and-the-Eye-s-Response

Abstract

Photosynthesis is the solar energy- dependent process on which food production for human existence ultimately depends. Each day passes with 854 million people hungry and, for that reason, the United Nations Millennium Declaration committed the world’s nations to ‘eradicate extreme poverty and hunger’. Sixty percent of the world’s population lives in Asia, where each hectare of land used for rice production currently provides food for 27 people, but by 2050 that land will have to sup- port at least 43 people. In 2007, about 250 million tonnes of carbon will be fixed in rice grains; by 2050, fixation will have to rise to about 400 mil- lion tonnes. However, the elite rice cultivars, which dominate the food supply of the millions of poor people in Asia, have approached a yield barrier and growth in production is slowing. In this paper, the role of photosynthesis in solving some of the food and environmental problems of tomorrow’s world is discussed. In particular, the possibilities and constraints associated with producing a very large increase in yield, water-use efficiency and nitrogen-use efficiency by developing a C4 rice are examined.

Introduction

Agriculture is the indispensable base of human society and the nature and productivity of agricul- ture is determined by water, climate and agricultural research. Today, 75% of the world’s 6.6 billion people live in the developing world where most of the world’s existing poverty is concentrated. Currently, a billion people live on less than a dollar a day and spend half their income on food; 854 million people are hungry and each day about 25,000 people die from hunger-related causes. The United Nations Millennium Declaration, agreed in September 2000, commits the world’s nations to ‘eradicate extreme poverty and hunger’. Modeled percentage increases in rice yields required by 2050 resulting from population increases, the combination of increases in temperature and CO2, and extreme weather events in four Asian countries industry. Seventy percent of all water withdrawn is used for irrigation and in the most populated country in the world, China, agriculture accounts for more than 80% of all water consumption. Only 29% of the earth’s surface is land (15.3 B ha) and only a little over a third of that is suitable for agri- culture (crops 1.4 B ha; grass/rangeland 3.9 B ha); the rest is ice, desert, forest (4.8 B ha) or mountains and is unsuitable for farming (Costanza et al. 1997; Noble and Dirzo 1997; de Haan et al. 1997). More simply stated, only 10% of the surface of the earth has topographical and climatic conditions suit- able for producing the food requirements of the 9 billion people expected to inhabit the planet by the year 2050. In 1950, there were about 2ha of farmland available to meet the food requirements of each person on the planet by 2050 the avail- able farmland will have fallen to 0.6ha/person; assuming forests and wetlands are to remain free of agriculture. Furthermore, each hectare of land used for rice production in Asia currently provides food for 27 people, but by 2050 that land will have to support at least 43 people.

For humans, agriculture is about providing food in a manner that is economically, socially and envi- ronmentally sustainable. For scientists, rice pro- duction has to be about converting the maximum fraction of solar energy into the maximum amount of chemical energy in grain in the shortest possible time; that conversion should be achieved using the smallest amount of land, water, and fertilizer. In his acceptance speech for the Nobel Peace Prize in 1970, Norman Borlaug warned that if the frighten- ing power of human reproduction was not curbed the success of the Green Revolution would only be ephemeral. Since that speech, world population has already increased by 75% and is continuing to increase; in the 21st century the population of Asia will rise by about 50% to 5.6 billion. A second ‘Green Revolution’ will be required to feed Asia but it will have to be achieved with less water and fertilizer. Theoretical models suggest that for rice, an increase in yield of 50% accompanied by improvements in water and nitrogen use efficien- cies can be achieved only by converting rice from a C3 to a C4 plant. Such a feat will require the integration that problem as it exists now is sufficiently challenging, but what makes it even more daunting is that the problem is being magnified by a number of dynamic, aggravating features (Table 1). Over the next 50 years, the population of the world will increase by about 50%, climate change will likely result in more extreme variations in weather and cause adverse shifts in the world’s existing climatic patterns. Water scarcity will grow; the increasing demand for biofuels will result in competition between grain for fuel and grain for food resulting in price increases. Furthermore, more than 75% of the world’s people will live in cities, the popula- tions of which will need to be largely supported by a continuous chain of intensive food production and delivery. All of these adverse factors are growing now, at a time when the developed nations are both reducing their investments in agricultural research and turning their remaining research investments away from productivity gains (Pardey et al. 2006). If all of this was not bad enough the elite rice cultivars, which dominate the food supplies of the millions of poor people in Asia, have approached a yield barrier (Kropff et al. 1994) and the Green Revolution is slowing (Dawe 2007). Rice, wheat, maize, millet, and sorghum provide 70% of the calories and up to 90% of all protein consumed by the world’s population. About half the world’s population has rice as the staple cereal and almost all of the 600 million tons of rice produced each year are consumed directly by humans.

Ninety-seven percent of the water on the earth is sea water, 2% is ice and there is rising competition for the remaining 1% which is needed not only for agriculture and human consumption, but also for of efforts from those engaged in fundamental and applied research in many different countries; particularly those engaged in research concern- ing photosynthesis. All forms of research require funding, but funding mechanisms to both integrate and sustain the fundamental and applied research required to produce C4 rice, across national and disciplinary boundaries are almost non-existent.

The questions addressed in this paper are: (1) is it feasible to build a C4 rice using existing tech- nologies; (2) would it really deliver a simultaneous quantum increase in yield, water-use efficiency and nitrogen-use efficiency; and (3) what would be the cost-benefit ratio? Furthermore, I hope to demon- strate that it can be done on a time scale relevant to food security during the next half century. Failure, in this endeavor will mean a huge increase in human misery, a massive loss of natural environments and its associated negative impact on climate change.

The green revolution exhausted

The Green Revolution in Asia began at the International Rice Research Institute (IRRI) in the 1960s. It was based on the development of erect- leaved, semi-dwarf rice cultivars that had higher harvest indices and were much more fertilizer responsive than the traditional cultivars. The Green Revolution more than doubled food supply in Asia in 25 years, with an increase of only 4% in net cropped area (Lipton 2007; Rosegrant and Hazell 2000). Since the early eighties the impact of green revolution rice has been slowing down.

Sakamoto et al. (2006) suggested manipulat- ing brassinosteroid levels could improve erect leaf erectness and hence improve yield in elite rice. However, plant breeders have been selecting for canopy erectness for many years (Sheehy and Cooper 1973; Khush 2000). Measurements of the extinction coefficient (k) for photosynthetically active radiation in a rice canopy of the elite indica cultivar IR72 (Sheehy et al. 2007a) showed that k varies with solar elevation; the variation was more marked in clear conditions than overcast conditions. This means the apparent erectness of the canopy varies with solar elevation, appearing to be more prostrate earlier in the morning and more erect closer to noon. At noon, when the sun is directly overhead, the leaves of the IR72 rice canopy, when calculated from the k values, have an inclination of about 79° to the horizontal. It must be remembered that structures other than leaves intercept light so, in the calculation of k, the leaves appear to be more prostrate to compensate for the interception by those structures. Canopy ‘gross’ photosynthesis (Pc) can be calculated using the equation of France and Thornley (1984).

The maximum yields and radiation-use effi- ciencies of rice and maize growing unrestricted by water and nutrients in the dry season in the tropics were measured concurrently (Sheehy et al. 2007a). The radiation use efficiencies of maize and rice were 4.4g DW MJ−1 and 2.9g DW MJ−1 respectively; the ratio of the values was 1.52. At 14% moisture content the grain yield for maize was 13.9t ha−1 and for rice was 8.3t ha−1. Rice growing unrestricted by water and nutrients reached a yield limit set by canopy photosynthesis that was about 60% of that achieved by maize.

The results presented here suggests that the gains made from the original Green Revolution technologies centered on canopy architecture and crop nutrition have been fully exploited (Dawe 2007; Sheehy et al. 2007a).

Powering a second green revolution

Significant future yield improvements in rice must come from increases in canopy photosynthesis of a magnitude comparable to a change from C3 to C4 photosynthesis. The C4 system is seen as an addition to the C3 system and the repeated evolu- tion of C4 photosynthesis indicates it should be possible to create C rice by engineering C genes are not as rigidly separated as once thought. There is a well developed C4 pathway in green tissue around vascular bundles and rice spikelets and in the opposite direction in maize there patches of C3 tissue wherever a mesophyll cell is not adjacent to a bundle sheath cell. The culms of Eleocharis vivipara switch from C3 when submerged to C4 with Kranz anatomy when they are terrestrial and the cells of Hydrilla verticillata switch between C3 and C4 modes of photosynthesis depending on environmental conditions

Currently, it is not clear whether a single-cell system of C4 photosynthesis, a non-C4 method or a full Kranz C4 system will be sufficient to power the yields required later this century; each approach is discussed in Sheehy et al. (2007b). However, it is worth remembering that the full C4 system brings with it not only high yields, but also better use of water and nitrogen fertilizer.

Constraints on progress towards C4 rice

In the absence of evidence to the contrary, it is easy to suggest that the construction of C4 rice would be difficult and the cost would be unusually high for agricultural research. However, the required knowledge is available, or becoming available and essential techniques in genetic engineering are advancing rapidly. The various strategies to be adopted to make C4 rice a reality over the next 10–15 years are discussed by an international group of scientists in Sheehy et al. (2007b).

There are a number of initial hurdles to be overcome in constructing a truly international collaborative program with the aim of producing C4 rice. The immediate challenge is to establish a funding bridge that enables researchers to come together as a functioning team. That team can then provide the proof of concept required to facilitate the large investment necessary for the production of C4 rice. It is constructive to compare scientific challenges of a comparable magnitude in the life sciences in terms of their impact on humanitarian problems and the funding available to solve those problems. Table 2 shows that the money spent annually on research aimed at curing malaria or HIV/AIDS far exceeds that spent on C4 rice; it is clear that the major funding obstacle to producing C4 rice is the small scale of funding available for research in the agricultural sciences. The economic benefits that would flow from a C4 rice are sub- stantial, the benefits accruing from increases in yield, water and nitrogen fertilizer savings would amount to many billions of dollars annually. The likely cost of constructing a C4 rice is of the order of hundreds of millions of dollars; the cost-benefit ratio is enormous.

The imperative for converting the photosyn- thetic system in rice from C3 to C4 is necessity rather than curiosity. It is not good enough to be optimistic that ‘business as usual’ will solve the problem of increasing rice yield. New and possibly radical approaches need to be explored urgently.

References

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Photosynthesis and cellular respiration are connected in a way that one cannot take place if the other is not performed. They need each other’s existence, basically. It’s like they are made to be soulmates; they co-exist. Light + 6CO2 + 6H2O → C6H12O6 + 6O2. Photosynthesis, with the help of light, 6CO2 (6 carbon dioxide molecules), and 6H2O (6 water molecules), produces C6H12O6 (glucose) and 6O2 (6 oxygen molecules). C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP. On the other hand, cellular respiration, using C6H12O2 and 6O2, produces ATP (adenosine triphosphate), 6CO2, and 6H2O. They are not completely the exact opposite of each other’s chemical equation, because of light and ATP, but they both give off energy.

Carbon dioxide needed by photoautotrophs that get converted into glucose along with other components in the Calvin cycle is released by humans and/or animals as a product of cellular respiration. Water broken down to make oxygen during photosynthesis is produced at the electron transport chain (ETC) of cellular respiration by combining oxygen inhaled by animals and/or humans that is produced by plants with hydrogen. We can conclude that one’s reactant is another’s product. That is another way of them being essential to each other.

Exposure to too much carbon dioxide results in short and long-term term health issues. It may cause short-term suffocation, unconsciousness, headaches, vertigo, tinnitus, and seizures. Breathing in so much carbon dioxide emissions might be life-threatening. It causes changes in our bone calcium and body metabolism in the long run.

Lack of oxygen intake causes poor blood circulation and low oxygen level in our blood results to hypoxemia, and it also results to limited and poor ATP production, which means low energy.

Of course, photosynthesis produces vegetables, sustain the animals, and gives us and them oxygen, which gives me meat and vegetables. The carbon dioxide that we and the animals produce supplies and continues photosynthesis, and vice versa. We can conclude that photosynthesis and cellular respiration can affect me in a positive and negative way.

Oxygen and carbon dioxide has that ‘perfect’ ratio that comes with balance to produce and intake carbon dioxide and oxygen. The higher the oxygen level, the higher the carbon dioxide concentration gets, as well, but as any other ‘perfect’ ratio, too much of something will lead to less of the other. Nowadays, air pollution and high carbon dioxide emission are problems that has solution but cannot be applied, because of our growing population with less plants and trees due to deforestation, for example. This will cause the greenhouse effect, and with less photoautotrophs to maintain that balance, photosynthesis gets affected. More carbon dioxide, the faster the rate of photosynthesis gets at a certain limit. Too much carbon dioxide will yield to the inefficiency of the plant, and in the long run will cause the plant to die. If photosynthesis is poor, so will be cellular respiration. Less oxygen intake will result to those mentioned above.

References

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ABSTRACT

Study on the temperature effect on plant photosynthesis is essential for proper understanding of physiology of plants as well as designing of crops that are able to cope-up with temperatures greater as well as lower than optimum growth temperatures. Any fluctuation in temperatures from the optimum temperature affects the overall growth and productivity of plants. Any temperature fluctuation from permissible values have known to affect the PSII, OEC, PQ, PSI, Cytochrome b559 as well as he primary enzyme of dark reaction Rubisco and Rubisco activase. Production of ROS, HSP generation and production of secondary metabolites are the results of temperature stress in plants. In this review I aim to discuss the physiological, biochemical and molecular changes in the photosynthetic apparatus during temperature stress as well as the protective mechanism devised by plants against it.

INTRODUCTION

Any adverse environmental factor affecting the normal growth and yield and productivity of the plant is known as stress. Several abiotic stress factors like temperature, drought, light intensity, salinity and heavy metal accumulation, tend to reduce the plant productivity and growth by reducing the photosynthetic rate and accumulation of ROS.

Among the abiotic factors, temperature stress plays an important part in the functioning of photosynthetic machinery. Temperatures above and below the optimum levels are known to cause heat and cold stress in plants. In nature, there no particular ideal temperature that prevails throughout the life cycle of plants. There are fluctuations in temperature throughout the growth period of plants. Since plants are sessile and unlike other mobile living organisms they have to endure as well as devise certain adoptive measures that helps them to adopt to the situation. The plant productivity is affected in a number of ways by high temperature stress. Several physiological, biochemical, and molecular processes contribute towards the plant growth with photosynthesis being the central pathway contributing towards crop yield and productivity. High temperature stress primarily inhibits the plant photosynthesis before impairing any other cell functions. Low temperature and freezing stress also limits the plant productivity of the plants belonging to majorly tropical and sub-tropical regions where the plants are generally adapted to grow in relatively higher temperatures

In order to to adapt to the temperature fluctuations, there is increased synthesis of antioxidants for the mitigation of ROS produced during the stress. Along with the production of antioxidants there is also increased synthesis of HSP, modifications in the photosynthetic antennae complex and electron transfer rates.

HIGH TEMPERATURE STRESS

Temperatures more than 35 degrees are known to cause inhibitory effects on plant photosynthesic chemical reactions as well as affects the structural organisation. High temperature stress leads to the overproduction and accumulation of reactive oxygen species (ROS) that in turn leads to lipid peroxidation and accumulation of malondialdehyde (MDA). Along with it, there is also reduction or inhibition of photosynthesis, protein denaturation, and accumulation of compatible solutes. some of the effects of high temperature stress on plants are summarised below.

Effect on High temperature stress on the photosynthetic pigments

Plant chloroplast pigments play an important role in capturing the light energy as well as electron excitation leading to the photochemical reactions and photolysis of water that mainly drives photosynthesis. Pigments constitute an important constituent in the LHC complexes as well as RC of the photosystems. High temperature stress induced plants have known to show a reduction in the chlorophyll biosynthesis. Decrease in chlorophyll biosynthesis due to high temperature stress is the result of the inactivation of chlorophyll biosynthesic enzymes like ALAD under high temperature stress. 5-aminolevulinate dehydratase (ALAD) is the first enzyme involved in pyrrole synthesis. Also, in response to high temperature there is decrease in 18% of total chlorophyll content, 7% decrease in chlorophyll a content, 3% decrease in chlorophyll a/b ratio, 9% decrease in sucrose content, along with an increase in 47% and 36% of soluble sugar content and leaf soluble sugar content respectively in soyabean. The decrease in the amount in chlorophyll pigments was due to the increased production of ROS, thereby indirectly representing the heat stress level in plants. while there was an increased action of Carotenoids along with APX and CAT that function as major antioxidants for the scavenging of H2O2 produced during the heat stress. Carotenoids not only acts as an accessory light-harvesting pigment but also helps in protecting the photosynthetic systems as nonenzymatic mediated antioxidant against reactive oxygen species generated during heat or high temperature stress.

Effect of High temperature stress on PSII structure and function

Higher temperature affects the thylakoid membrane fluidity changing its physiochemical properties and functional organisation. Among the two photosystems, PSII is most sensitive to high temperature stress. Depending on the type of photoautotrophic plant cell (cyanobacteria, monocot, dicot), the sensitivity of PSII varies. Variations among acclimation of PSII to high temperature stress also varies among organisms. PSII reaction centre and light harvesting complexes are primarily damaged by high temperature or heat stress. The organisation and composition of PSII subunits and cofactors are equal in higher plants and cyanobacteria. Photosystems constitute both LHC and Core complex proteins. The intrinsic light-harvesting proteins of PSII are LHCII, LHCb4 (CP29), LHCb5 (CP26), and LHCb6 (CP24). The core complex has four intrinsic subunits namely, D1(PsbA), D2 (PsbD), CP43 (PsbC) and CP47 (PsbB). Among these, D1 and D2 constitute the Reaction Centre of PSII contributing towards charge separation and photochemical electron transfer while the rest two contribute in the transfer of light energy from peripheral antenna molecules to the Reaction Centre. The Reaction Centre is also surrounded by 12 low molecular mass subunits namely PsbE, PsbF, PsbH, PsbI, PsbJ, PsbK, PsbL, Psb M, PsbTc, PsbW, PsbX, and PsbZ. These subunits help in dimerization and stabilization of the core complex, association of the core complex with the peripheral antenna complex and binding of cytochrome b-559 in order to protect PSII complex from the photo-damage. PsbO, PsbP, PsbQ. PsbR, PsbU and PsbV are the associated extrinsic proteins of the PSII. High temperature stress results in the loss of cofactors as well as the dissociation of PsbO, PsbQ and PsbP subunits. Likewise, there is also damage to the D1 protein leading to photoinhibition and production of ROS during high temperature stress. It is well known that high temperature stress increases membrane fluidity of plastids as well as cause granal de-stacking. High temperature stress also affects the phosphorylation of proteins. One such example being the phosphorylation of D1 protein in PSII that is cleaved by FtsH activity. FtsH is initially located in the stromal region of thylakoid and after high temperature stress degrades the D1 protein. Migration of phosphorylated LHCII from PSII towards PSI is reported in plants under elevated temperatures. Heat stress also affects the electron transfer from QA to QB as a result of the damage to the intrinsic proteins D1 and D2. These processes may further contribute to decreased Quantum efficiency of PSII.

Effect of High temperature stress on Oxygen Evolving Complex

The OEC contains three protein subunits, PsbO, PsbP and PsbQ mainly. PsbO is present in every oxygen evolving organism and involved in the stabilization of the Mn complex of OEC. while PsbP and PsbQ are involved in optimizing the oxygen evolution at physical concentration of calcium and chloride ions. Manganese and Calcium binds to the core of the OEC, with the empirical formula for the inorganic core of Mn4Ca1OxCl1–2(HCO3)y. This cluster is coordinated by D1 and CP43 subunits. The peripheral membrane proteins help in the stabilization of the cluster as well. At temperatures around 47°C, there is the release of 18 kDa protein that is associated with the loss of Ca ion from the Mn4Ca complex.

Cytochrome b559 (Cytb559) is an iron containing compound linked to PSII whose c terminus had a 33KDa protein that stabilizes Mn atoms. During Heat stress, the 33 KDa Mn-stabilizing protein dissociates from the reaction centre of PSII followed by the release of Mn atoms that might cause the thermal inactivation of OEC. Cytb559 is present in two forms, a dominant high potential form and other low potential form. Studies have shown that, mild temperature stress causes rapid interconversion of HP to LP form. Under high temperature stress, there is complete absence of HP form of cytb559. Heat stress may cause CEF around PSII involving the cytb559. Photosynthetic action is halted when the OEC gets damaged due to heat. Under such conditions the electron is donated from PSII acceptor side through the CEF to P680+ or Yz ox. This way the normal photochemical activity can be carried on without any halt. Two redox active tyrosines, YD and YZ, with different functions are present in PSII. These tyrosine residues Yz and Yd are found in D1 and D2 polypeptide in 161 and 160 positions of PSII respectively. Yd tyrosine is involved in the OEC assembly and is oxidised via p680+. According to some authors, the Redox state of Yd can be used to determine the damage amount caused in the PS due to high temperature stress since the electron donation from YD to P+680 increases under high temperature stress.

Chlorophyll a fluorescence of PSII indicates the heat stress amount experienced by a plant. Plants grown under normal growth temperatures 25°C displayed OJIP fluorescence transient curves. While in plants under heat stress, there was an additional k step (OKJIP fluorescence transient). The K step only occurs due to the high temperature stress and indicated that the OEC is damaged completely and at 45 °C. During a strong heat stress, the OEC is blocked and its efficiency decreases. This marks an additional step K-step in the fluorescence transient (now OKJIP). We can conclude from this that the high temperature stress induces the K step since the OEC is unable to donate electron efficiently to the RC of PSII. It is also known that the K step arises due to the imbalance in the electron acceptor and donor sides. There is increase in electron pressure on the acceptor side of the PSII but the donor side is not able to cope up with this flow. This irregularity leads to the oxidation of RC. There is also evidence that the K step also arises due to the inhibition of electron transport from Phaeophytin PQ. From the fluorescence analysis there is decrease in the antenna size, Fm value and Fv/Fm ratio. While the value of Fo increased. These are the common fluorescence values seen in the stressed plants. There is also increase in energy dissipation in the form of heat when plants were exposed above 35°C temperature. This form of non-photochemical chlorophyll a fluorescence quenching led to decreased photochemical efficiency since there was less energy available for photochemistry. Plastohydroquinol (PQH2) oxidation site in the cytb6/f complex is also reported to be inhibited during heat stress.

Effect High Temperature stress on the PQ pool

In oxygenic photosynthesis, both PSI and PSII function in tandem. The electron flow through electron transport chain (ETC) following the path from PSII → PQ → b6f → Pc → PSI and finally to NADP+, the terminal electron acceptor of PSI. Similar form of electron transport is seen in higher as well as lower plants. Phycobilisomes (PBS) are the mobile antenna found in synechococcus. Because of its mobile character, it is not bound tightly to RC of Photosystems. During the state transitions, the association or dissociation of PBS with the two photosystems depend on the Redox poise of PQ. Oxidised PQ pool is known to induce PBS to associate with PSII (State1) in order to increase the rate of electron flow. While the reduced pool of PQ induces the PBS to associate with PS1(state2), initiating the withdrawal of electrons from ETS. In the dark condition also, the PBS is associated with PSI since there is reduction of PQ pool due to the operation of respiratory electron flow. Along with the state-transitions, PQ also takes part in the biosynthesis of chlorophyll, LHC accumulation, protein synthesis rate of photosystems and the balance in the photosystem stoichiometry. During high temperature stress the PQ pool is in more reduced form Over reduction of PQ pool causes double reduction of QA to QA2− in the PSII reaction centre, triplet 3P680 and ion-radical pair [_680 + Pheo−] formation. Longer Excited states of chlorophyll can damage the photosystem proteins by the formation of ROS. Reduced PQ are known to counteract ROS by scavenging them around PSII through the oxidation of plastoquinol. Similar mechanism is also observed around PSI in which superoxide anion radical is scavenged through oxidation of plastoquinol. Scavenging of ROS through plastoquinol oxidation around both PS can help in faster replenishment of PQ molecules. It is also well known that the reduced PQ pool triggers the CEF around PSI for efficient photosynthesis.

Effect on High temperature stress on the Biological membrane dynamics and functions

Higher temperatures affect the fluidity and permeability of membranes, through changes in the lipid composition and interactions between lipids and specific membrane proteins. Higher temperatures also tend to decrease the hydrophilic interactions between LHC with PSII along with increase in the hydrophilic interactions leading to the increased affinity of pigment-protein complexes towards lipids, leading to their dissociation. There is also increase in the content of saturated and monounsaturated fatty acid during increase in temperatures. Increased ROS production during high temperature stress is known to cause oxidative stress to plants with inhibition of protein synthesis, oxidation of saturated fatty acids and decrease in fatty acid saturation in thylakoid membranes, destabilizing the PSII structure. High temperature stress is also known to cause structural changes in the thylakoid membrane stacking. Temperatures ranging from 35°C-45°C caused unstacking of thylakoid grana membranes. Bleaching experiments demonstrated the disruption of chlorophyll-protein complexes of PS due to temperature induced destacking of thylakoid membranes.

High temperature stress induced changes in the PSII heterogeneity

The heterogeneity of PSII is due to its diverse structure as well as function. The heterogeneity is mainly due to its differences in antenna size as well as the reducing side. Three types of antenna namely, PS II alpha, PS II beta and PS II gamma are present depending on the size of the antenna. QB-reducing and QB-non-reducing centers are proposed due to acceptor/reducing side function. Grana stacking and unstacking is another form of structural heterogeneity found in PSII. This form of heterogeneity depends on the distribution of PSII in grana and stroma lamellar regions of thylakoid membrane. During high temperature stress, alpha centres of PSII declined while there was an increase in the other antenna types. This change in the antenna types during the shift from 25°C to 45°C could be due to the interconversion of alpha to beta and gamma types during onset of high temperature stress. There are also reports in the decrease in the connectivity between antenna molecules at around 40°C. while a rise in 5°C caused complete ungrouping of the antenna molecules in wheat. During the fluorescence kinetics measurements, the heat-treated leaves of apple showed positive L step depicting the ungrouped nature of PSII units. Lowering in the cooperativity during the heat stress indicates the lower stability of PSII units. There was a marked effect of high temperature stress (45°C) on QB non reducing centres. Upon treatment with higher temperatures (45°C) there was an increase in the proportion of QB non reducing centres with respect to growth temperatures. This increase can be related to the inactivation of active QB reducing centres due to heat stress.

Effect of High temperature stress on PSI function.

Unlike PSII, PSI is more resistive to the heat stress in dark. 2.8 Å resolution structure of plant PSI reveals 12 core subunits and 4 LHC proteins (LHCa1, LHCa2, LHCa3, and LHCa4). The prosthetic groups of the complex including the number of chlorophyll molecules, carotenoids and lipids varies from cyanobacteria to higher plants. There is presence of 12 protein subunits, 96 chlorophyll a molecules, 22 carotenoids, three [4Fe4S] clusters and 2 Phylloquinones in the PSI structure of cyanobacteria Synechococcus elongatus. PSI structure of thermophilic cyanobacteria, Thermosynechococcus elongatus is a trimer while the structure of PSI in plants at 4.4 ˚A resolution, is a monomeric unit having 16 protein subunits, 167 Chl, 2 phylloquinones, and 3 Fe4S4 Clusters.

For a proper and efficient way of electron transfer during photosynthesis, the two PS must work in a coordinated way. Electrons can be transferred either through linear electron flow (non-cyclic way LEF) or through cyclic electron flow (CEF). LEF includes PSII, cytochrome b6f and PSI. CEF can occur through PGR5–PGRL1 pathway or through NAD(P)H dehydrogenase (NDH) pathway. There are evidences that, moderate increase in temperature activates PSI activity along with increase in CEF of PSI and thylakoid proton conductance. Similar evidences of increased PSI mediated CEF under high temperature stress is reported from plants like pea, tobacco, Arabidopsis, Symbiodinium and grapes. NDH complex lacking transformants of tobacco that were unable to balance the NADPH/ATP ratio during high temperature stress, generated greater amounts of ROS generation. Non photochemical or dark reduction of PQ is reported to be increased during the heat stress. Studies have also shown that during the mild temperature stress, the ATP demand for plant increases due to photorespiration as well as Rubisco activase. Increase in the efficiency of P700+ could be due to high temperature induced structural modifications of PSI, increasing the PSI absorption cross-section.

Photosynthesis is a concept that most people have heard about from a very young age. We all know that plants use sunlight and convert it into energy, but this is really just the basics of what happens during photosynthesis. Thus, in my essay, I’m going to dig deeper into it.

First of all, it should be noted that there are two types of photosynthesis: oxygenic photosynthesis and anoxygenic photosynthesis. Oxygenic photosynthesis produces oxygen and is used by plants and algae to convert photons from sunlight into chemical energy. In this process, energy from the sunlight transfers electrons from water into carbon dioxide. This ultimately produces carbohydrates, which is what makes the plant grow, and oxygen. In this process, CO2 gains electrons while oxygen loses electrons and becomes oxidized. The process of oxygenic photosynthesis acts as a counterbalance to another process that plants go through, called respiration. It balances out respiration by taking all the carbon dioxide that is produced by other living organisms and putting oxygen into the air. The process of oxygenic photosynthesis can be written as a chemical equation. It is written as shown: 6CO2 + 12H2O + Light Energy → C6H12O6 + 6O2 + 6H2O. This means that six molecules of carbon dioxide combined with 12 molecules of water and the use of light energy are converted into a carbohydrate and six molecules of oxygen and water are released into the air (Vidyasagar, 2018).

There are three basic segments in the process of photosynthesis: carbon fixation, reduction, and regeneration. In carbon fixation, six molecules of CO2 are put into the cycle. Then, it is split into two 3PGAs. Subsequently, 6ATP is converted into 6ADP and 6NADPH is changed into 6NADP+. Next, the process of reduction is started. One molecule of G3P goes to make sucrose or other sugars. The remaining 5G3P are recycled and go back through the process. In the process of regeneration, there are 3RU5P, and 3APT is converted to 3ADP, and the process starts again.

Parts of photosynthesis are reliant on sunlight, and some are not. Both light-dependent and light-independent reactions happen in the chloroplasts of plants. But more specifically, light-dependent reactions happen in the thylakoid and light-independent reactions occur in the stroma. Light-dependent reactions are dependent on light, unlike light-independent reactions, which don’t need light. This gives a false pretense that light-independent reactions happen in the dark, but that is incorrect. Both reactions happen in the light. Light-dependent reactions happen when a photon from sunlight hits a reaction center in a chloroplast, and chlorophyll or another pigment releases an electron. The electron that was released in this process travels through the electron transport chain. This is needed to create ATP and NADPH. The hole that was left by the released electron is filled with an electron that is stolen from the water. As a result of this process, oxygen is released into the air. The reason that this is called a light-dependent reaction is that the energy of light, or photon, is needed for the cycle to begin. Light-independent reactions happen when CO2 is reduced and carbohydrates are produced. This action needs ATP to happen and is taken for the electron transport chain.

PSⅠ and PSⅡ are different photosystems. Different photosystems, like these, contain different kinds of chlorophyll in their reaction centers. In photosystem I (PSI), chlorophyll has a maximum absorption of 700nm, while in photosystem II (PSII) the maximum absorption is 680nm. The main function of these photosystems is to collect and trap solar energy and convert it into ATP. To achieve this, they have to work together. The process of the electron transport chain in photosynthesis starts when PSII absorbs light (energy) and passes it on to its reaction center. When it absorbs light, an electron is lost. This makes it oxidized, and because of this, the water molecule splits into oxygen and hydrogen, and the oxygen is released into the air. In the procedure of water splitting, electrons are made that replace the lost electron from the reaction center. These electrons are passed to the reaction center of PSI, through the electron transport chain. During this process, ATP is formed and stored. The same process happens to create NADPH, except in PSI electrons are borrowed from PSII.

Photosynthesis has many different essential parts that influence the rate at which the process happens: light intensity, temperature, carbon dioxide, water, minerals, and other internal factors (Bassham & Lambers, 2019). Light intensity and temperature affect photosynthesis because the amount of light intensity determines how quickly it goes. It is relatively independent of temperature, but temperature also plays a small role in how quickly it goes. As the light intensity increases, the rate becomes saturated. If there is too much light intensity, stages in the light-independent reaction are affected and can’t go as quickly. There has to be just the right amount of light intensity, otherwise other stages of the operation will be affected. Carbon dioxide is also an important factor in how photosynthesis occurs. CO2 affects the dark stages (light-independent stages) because it promotes the creation of organic compounds. An increase in carbon dioxide in the air could affect plant growth because it increases global temperatures, causing less precipitation. This will affect photosynthesis because it will make fewer water molecules for the plant to get food. Water affects the rate of photosynthesis more indirectly than the rest of these elements. If there is no water in the soil, the plant can’t absorb CO2 from the air, putting a damper on photosynthesis. Minerals like manganese and copper change the rate of photosynthesis because they are components of chlorophyll and other pigments. Increasing or decreasing these minerals slows down or quickens the rate based on the amount of each. Every plant is adapted to external climate and environmental factors. The plant is adapted to the normal conditions of the surrounding habitat. Certain enzymes and amounts of chemicals are balanced to fit the environment. Changes in the environment affect the internal factors of the plant. For example, if the amount of carbon dioxide in the air was doubled, the plant would increase the rate of photosynthesis, but after a few days, it would drop back down to the original rate or lower. This would be because the plant produced more sugar than it needed. Another factor that could influence the rate of photosynthesis would be electricity. Similar to how heat can affect the rate of photosynthesis, adding electricity may also speed up the rate of photosynthesis. Research reported in the journal Nature has shown that chemical reactions can be quickened using electricity (2016). Photosynthesis, being a chemical reaction, also may be able to be sped up using electricity if this is true.

Photosynthesis is a very complex reaction that is dependent on many different factors that help a plant grow. Photosynthesis itself is only a part of how a plant grows and functions. Photosynthesis is a process that helps plants grow, more or less keeping them alive. It is an important procedure that has to happen. But it takes time.

Photosynthesis is a concept that most people have heard about from a very young age. We all know that plants use sunlight and convert it into energy, but this is really just the basics of what happens during photosynthesis. Thus, in my essay, I’m going to dig deeper into it.

First of all, it should be noted that there are two types of photosynthesis: oxygenic photosynthesis and anoxygenic photosynthesis. Oxygenic photosynthesis produces oxygen and is used by plants and algae to convert photons from sunlight into chemical energy. In this process, energy from the sunlight transfers electrons from water into carbon dioxide. This ultimately produces carbohydrates, which is what makes the plant grow, and oxygen. In this process, CO2 gains electrons while oxygen loses electrons and becomes oxidized. The process of oxygenic photosynthesis acts as a counterbalance to another process that plants go through, called respiration. It balances out respiration by taking all the carbon dioxide that is produced by other living organisms and putting oxygen into the air. The process of oxygenic photosynthesis can be written as a chemical equation. It is written as shown: 6CO2 + 12H2O + Light Energy → C6H12O6 + 6O2 + 6H2O. This means that six molecules of carbon dioxide combined with 12 molecules of water and the use of light energy are converted into a carbohydrate and six molecules of oxygen and water are released into the air (Vidyasagar, 2018).

There are three basic segments in the process of photosynthesis: carbon fixation, reduction, and regeneration. In carbon fixation, six molecules of CO2 are put into the cycle. Then, it is split into two 3PGAs. Subsequently, 6ATP is converted into 6ADP and 6NADPH is changed into 6NADP+. Next, the process of reduction is started. One molecule of G3P goes to make sucrose or other sugars. The remaining 5G3P are recycled and go back through the process. In the process of regeneration, there are 3RU5P, and 3APT is converted to 3ADP, and the process starts again.

Parts of photosynthesis are reliant on sunlight, and some are not. Both light-dependent and light-independent reactions happen in the chloroplasts of plants. But more specifically, light-dependent reactions happen in the thylakoid and light-independent reactions occur in the stroma. Light-dependent reactions are dependent on light, unlike light-independent reactions, which don’t need light. This gives a false pretense that light-independent reactions happen in the dark, but that is incorrect. Both reactions happen in the light. Light-dependent reactions happen when a photon from sunlight hits a reaction center in a chloroplast, and chlorophyll or another pigment releases an electron. The electron that was released in this process travels through the electron transport chain. This is needed to create ATP and NADPH. The hole that was left by the released electron is filled with an electron that is stolen from the water. As a result of this process, oxygen is released into the air. The reason that this is called a light-dependent reaction is that the energy of light, or photon, is needed for the cycle to begin. Light-independent reactions happen when CO2 is reduced and carbohydrates are produced. This action needs ATP to happen and is taken for the electron transport chain.

PSⅠ and PSⅡ are different photosystems. Different photosystems, like these, contain different kinds of chlorophyll in their reaction centers. In photosystem I (PSI), chlorophyll has a maximum absorption of 700nm, while in photosystem II (PSII) the maximum absorption is 680nm. The main function of these photosystems is to collect and trap solar energy and convert it into ATP. To achieve this, they have to work together. The process of the electron transport chain in photosynthesis starts when PSII absorbs light (energy) and passes it on to its reaction center. When it absorbs light, an electron is lost. This makes it oxidized, and because of this, the water molecule splits into oxygen and hydrogen, and the oxygen is released into the air. In the procedure of water splitting, electrons are made that replace the lost electron from the reaction center. These electrons are passed to the reaction center of PSI, through the electron transport chain. During this process, ATP is formed and stored. The same process happens to create NADPH, except in PSI electrons are borrowed from PSII.

Photosynthesis has many different essential parts that influence the rate at which the process happens: light intensity, temperature, carbon dioxide, water, minerals, and other internal factors (Bassham & Lambers, 2019). Light intensity and temperature affect photosynthesis because the amount of light intensity determines how quickly it goes. It is relatively independent of temperature, but temperature also plays a small role in how quickly it goes. As the light intensity increases, the rate becomes saturated. If there is too much light intensity, stages in the light-independent reaction are affected and can’t go as quickly. There has to be just the right amount of light intensity, otherwise other stages of the operation will be affected. Carbon dioxide is also an important factor in how photosynthesis occurs. CO2 affects the dark stages (light-independent stages) because it promotes the creation of organic compounds. An increase in carbon dioxide in the air could affect plant growth because it increases global temperatures, causing less precipitation. This will affect photosynthesis because it will make fewer water molecules for the plant to get food. Water affects the rate of photosynthesis more indirectly than the rest of these elements. If there is no water in the soil, the plant can’t absorb CO2 from the air, putting a damper on photosynthesis. Minerals like manganese and copper change the rate of photosynthesis because they are components of chlorophyll and other pigments. Increasing or decreasing these minerals slows down or quickens the rate based on the amount of each. Every plant is adapted to external climate and environmental factors. The plant is adapted to the normal conditions of the surrounding habitat. Certain enzymes and amounts of chemicals are balanced to fit the environment. Changes in the environment affect the internal factors of the plant. For example, if the amount of carbon dioxide in the air was doubled, the plant would increase the rate of photosynthesis, but after a few days, it would drop back down to the original rate or lower. This would be because the plant produced more sugar than it needed. Another factor that could influence the rate of photosynthesis would be electricity. Similar to how heat can affect the rate of photosynthesis, adding electricity may also speed up the rate of photosynthesis. Research reported in the journal Nature has shown that chemical reactions can be quickened using electricity (2016). Photosynthesis, being a chemical reaction, also may be able to be sped up using electricity if this is true.

Photosynthesis is a very complex reaction that is dependent on many different factors that help a plant grow. Photosynthesis itself is only a part of how a plant grows and functions. Photosynthesis is a process that helps plants grow, more or less keeping them alive. It is an important procedure that has to happen. But it takes time.

Introduction: Main theme and concept of the article

The article under analysis called Why Study Photosynthesis? is written by Devens Gust, the doctor of philosophy at the Department of Chemistry and Biochemistry. The paper considers the significance of such biological process as photosynthesis, its actual process, and its connection with the economic policy. The author emphasizes major reasons of understanding process. Further, the paper enlarges upon the connection of this biological phenomenon with agriculture, industry, medical sphere and the ecological situation in the world.

Main body

The research reveals that the study of nature is important because understanding the basis principles of photosynthesis are crucial. Due to the fact that people cannot control natural processes but the knowledge enables them to use them in the appropriate way. By revealing the information about the details of photosynthesis, Gust encourages people to investigate and to develop the innovated techniques thus applying them to the problem solution in the different spheres of life. The detailed description shows how people can benefit from this information and apply this natural process for the well-being of people.

The arguments presented by the author are logical and consistent based on variable sources. His interpretation of this process as transition from one type of energy into another is rather evidence-based. The ideas about connection of photosynthesis and metabolism are proved by its comparison with hydro carbonates conversion into cellulose. Author manages to show the connection between photosynthetic processes and production of photosynthetic products. The second part of the article explains the previous arguments about the results of photosynthesis. His ideas also explain why biology is closely connected with chemistry.

In the article, there are some points that contradict one another. On the one hand, Gust describes photosynthesis as the most crucial biological process that serves as the basis for other natural processes. On the other hand, he points out that “photosynthesis is relatively inefficient” (Gust 1996) so that it requires the invention of more advanced method of production. This controversy generates other discussions about photosynthetic functions. Hence, Castelvecchi (2007) believes that photosynthesis has a deeper meaning and a wider range of functions. He insists on how the connection of this process with quantum physics explains the extraordinary efficiency of solar energy and water. Moreover, he proves that 90 % of light is used for the plant to generate oxygen. As Gust gives little importance of photosynthesis as the source of life, it is necessary to consider it as primary function, because no other biological processes could be more significant (Koh et al. 2007). Finally, there is an assumption that it is possible to create some artificial models of oxygen reproduction in future so that people could use it without applying the solar energy. To do that, it is obligatory to study carefully the natural process (Ort et al. 2000).

Conclusion: personal opinion

In general, the author managed to discover mostly all aspects of the photosynthesis and its significance in biochemistry and chemistry. Despite some trifle divergences, the article is rather comprehensive and profound as touches upon the most significant problems at the international level. The article is of great value for current society to understand why these biological principles are so crucial for the environment as well as for the economic development. In addition, the author proved the photosynthesis is the basis and the model for creating the alternative method of energy acquisition.

Reference List

Castelvecchi, D. (2007). Quantum Capture: Photosynthesis Tries Many Paths at Once. Science News, 171, 229.

Gust, D. (1996). “Why study photosynthesis”. Center of Bioenergy and Photosynthesis.

Koh, T. and Lee (2007). Biology ‘O’ level. Asia: Pearson Education South Asia.

Ort, D., Yocum, C., Heichel, I. (2000). Oxygenic Photosynthesis: the light reactions.

The genus Aesculus consists of (depending on classifications) 13-19 plant species named after the territories in which they are distributed. All of these species are trees with green leaves. At the flowering time, pink, red, or yellow flowers appear on the trees, depending on the species. For example, typical in eastern Asia, Aesculus Indica (Indian horse chestnut) has pale pink flowers. Aesculus Pavia (red buckeye) has bright red, catchy flowers; the inflorescences later give brown fruits called chestnuts.

The most common (broad area of distribution) and known to all is the horse chestnut or Aesculus hippocastanum. This species is expected in the Balkans, Europe, and North America. Other species are common in eastern Asia (China, Japan) and differ from western species in their inflorescences and leaves. These trees are common in urban environments: they grow along roads, and alleys and interact closely with cars. Often the health of these trees deteriorates due to a large amount of exhaust from vehicles (Ianovici, Latis, & Radac, 2017, pp. 12406-12408). These trees need constant supervision by botanists; otherwise, their photosynthetic abilities decline.

Aesculus hippocastanum is not picky about food and can grow for a long time in the shade and on sub-hourly soils. Clay soils are also suitable for it, “grow in different site conditions, both soil and microclimatic” (Swoczyna & Latocha, 2020, p. 575). It can tolerate steppe soils well, although excessive acidity of the earth can harm the roots. Broad leaves are well photosynthesized until they get sick and take on the color of rust instead of green (until the amount of chlorophyll A and B pigment in the leaf drops). In addition, green leaves contain xanthophyll pigment (localized in the inner membranes of chloroplasts). They photosynthesize as C3, and this process is bypassed in one stage. Chloroplast organelles store solar energy, subsequently combining ATP and NADP; at the exit, the plant receives a sugar molecule.

References

Ianovici, N., Latis, A. A., & Radac, A. I. (2017). Foliar traits of Juglans regia, Aesculus hippocastanum and Tilia platyphyllos in urban habitat. Romanian Biotechnological Letters, 22(2), 12400-12408.

Swoczyna, T., & Latocha, P. (2020). Monitoring seasonal damage of photosynthetic apparatus in mature street trees exposed to roadside salinity caused by heavy traffic. Photosynthetica, 58(SPECIAL ISSUE), 573-584.