The Duckweed Experiment: Effects of Lowering Light Intensity on the Rate of Per Capita Growth of Lemna Minor

1545 words 7 pages
Abstract

Duckweed is a small aquatic plant that is able to grow rapidly, making it the ideal specimen for our experiment. It is hypothesized that altering the amount of light received by duckweed will alter its photosynthetic rate. It is predicted that a lower light intensity will lower the rate of growth in duckweed.
Two treatment groups were covered with a screen in order to reduce light intensity. Both groups were kept under a controlled light source for fourteen days and plant counts were taken at regular intervals.
The ravg for the experimental group was 0.1613 and the ravg for the control group was 0.2047. The results indicated that our predictions were correct; duckweed that received less light exhibited a lower rate of
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The results in Figure 1 illustrate that the population size of duckweed exposed to light with a screen was much smaller than that of duckweed exposed to light without a screen throughout the fourteen day period.

Figure 1: Average population of duckweed when exposed to light in the presence/absence of a screen over a 14 day period

The duckweed was also observed qualitatively for overall health. Those in the control group had larger clusters and longer roots than those in the treatment group. Also, the leaf color of the treatment group was a yellow/green while the leaf color of the control group was bright green.
Discussion
The purpose of this experiment was to test our hypothesis, which stated that varying levels of light would alter the photosynthetic rate of duckweed. We predicted that lowering light intensity would decrease the rate of growth in duckweed. Based on the results of this experiment, this hypothesis was proven correct. The results show that the average population size and the growth rate of duckweed in the treatment groups were lower than that of the control groups.
The second prediction stated that duckweed exposed to more light will reach carrying capacity sooner. Conclusions were not reached on

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