Understanding the Effects of Quantity of Light on Plants Growth

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Table of Contents

Introduction
Observation
Hypothesis
Predictions
Experiment and Methods
Results
Discussion and Conclusion
Reference List

Introduction

The healthy growth of plants is inarguably limited by the factors existing in the macro-environment. Available literature reveals that one of the most fundamental factors in the external environment that affects every single aspect of plants is light (Doll, 2007). Without adequate light, a plant can neither grow nor reproduce. A multiplicity of other environmental factors, including soil composition, humidity and rainfall patterns inexorably constrains the healthy growth of plants if they become more or less than ideal (Hall & Rao, 1999). External factors are also known to be responsible for the physical distribution of plants. For instance, only plants adapted to certain amounts of acid concentrations in the soil and limited amounts of water can survive in deserts.

Light has three foremost aspects that influence plant growth and development – quantity, length, and quality. The term ‘light quantity’ is basically used to refer to the strength and concentration of sunlight, and fluctuates with seasons (Hall & Rao, 1999). In many regions across the world, the maximum concentration of sunlight is found during the summer season, while the minimum is present in winter. Maximum sunlight, up to a given point, gives plants an enhanced capacity to produce their food through a process known as photosynthesis.

Observation

Some flowering plants meant to decorate the researcher’s house had been placed in two separate rooms after being purchased from the market. One had been placed in a vase and left in the well-lit living room while the other had also been placed in a vase and taken to the dimly lit bedroom. The only source of light to the bedroom was only through a small window, which was left shut most of the times. However, tiny streaks of sunlight still penetrated through. After a few days, the researcher noticed that the plant placed in the bedroom had grown abnormally tall and tended to bend towards the window. However, the plant in the living room was growing normally, and in an upright position. What could have caused the plant in the bedroom to grow abnormally and bend towards the window? This formed the basis for the inquiry.

Hypothesis

A hypothesis can be described as a rationally testable justification for the observed phenomena. In devising an effective hypothesis, the researcher must endeavor to come up with preliminary suggestions aimed at clarifying the causes of the noted observations (Carter, 2004). This study was guided by the following hypothesis:

H1: The plant in the bedroom was in need of adequate sunlight to produce its food and therefore it had to grow extremely taller and bend towards the only source of light to have access to its only source of livelihood.

Predictions

Based on the stated hypothesis, my predictions for the experiment included:

If it is indeed true that plants react to the quantity of sunshine, then I should be able to observe significant changes in leaf color
If it is true that plants react to the quantity of sunlight, then the length and stem will continue to grow abnormally until such a time when the plant will have adequate light to generate enough food
If it true that plants react to the quantity of sunlight, then the plants in my experimental group will continue to bend towards the sources of light while those in the control group will continue to grow upwardly.

Experiment and Methods

To set up the experiment, the researcher went back to the market and bought six healthy plants more or less of equal height. However, he took a precautionary step to quantitatively measure the heights of individual plants and record the figures. According to the measurements, the smallest plant was 45 CM while the tallest was 46 CM, a difference of only one CM. Conventional approaches in the Scientific Method demand that two simultaneous groups – control and experimental – be involved in any scientific inquiry to effectually compare and contrast the observations between the groups. The two groups must be treated in equal terms except for the phenomena or variable under investigation for the sake of objectivity and generalization of the experiment’s results (Carter, 2004). In conceptualizing the variables for the experiment, the source of the light became the independent variable while the direction of bend, length of stem, and leaf colour became dependent variables for both the experimental and control group.

Four of the six plants were put in an enclosed structure and grown under precisely the same conditions. The remaining two formed the control group, and were also given the same treatment as the experimental group except for the fact that they were allowed adequate sunlight to satisfy their food demands. After 3 days, 2 of the plants in the enclosed structure were introduced to some light from the left while the other two from the right. All the other conditions were kept constant for a period of two weeks. On daily basis, the researcher collected data on the color of the leaves, the height of the plants, and the direction of bend in the two groups – experimental and control

Results

After two weeks, the two plants with light introduced from the left had already bended towards the left, while the other two with light introduced from the right similarly bended to the right. The control group growth was vertically inclined, the same way it was before the experiment. The sources of light in the experimental group did not affect the length of stems since all the four plants enlarged in length in just about the same quantities. However, plants from the experimental group were 4.7 to 4.9 CM taller than those in the control group after the experiment. The leaves of all plants retained their green color

Discussion and Conclusion

The hypothesis that ‘plants in my bedroom are bending towards the window to secure enough light for food generation through photosynthesis’ was proved right by the experiment. Two of the experiment’s prediction’s, increase in length of stem and bending towards the source of light were also confirmed. The prediction that quantity of light affected the colour of leaves was proved wrong since no significant change of leaf colour was noted. However, the leaves in the two sets of the experimental group turned straight towards the sources of light. It is therefore prudent to underscore the fact that the relationship between light and the capacity of plants to grow is an intricate one since plants completely depend on the light to generate their food. Further research is needed into how the colour of light affects plants growth.

Reference List

Carter, J.S. (2004). The scientific method. Web.

Doll, A. (2007). How colored light affects plant growth. Web.

Hall, D.O., & Rao, K. (1999). Photosynthesis. Cambridge University Press.

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