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

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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 growth. For those interested in harvesting duckweed, future studies can focus in determining the amount of light needed for optimal growth.

Introduction Plants are able to convert light energy into chemical energy through the process of photosynthesis (Campbell & Reese, 2005). This process is dependent on both abiotic and biotic factors. Since plants are autotrophs, the most vital are abiotic factors such as light, temperature, wind, water, and atmospheric gases (Campbell & Reese, 2005).
The plant of interest in this study is Lemna minor. Duckweed is a small aquatic watering plant that inhabits fresh water environments and exists in clusters of 3-4 leaves that are approximately 2-4 mm in size (Galt et al, 2005). Duckweed was chosen for this experiment because it can be manipulated easily within a laboratory setting. This experiment was designed to test the hypothesis that altering the amount of light received by the Duckweed will alter its photosynthetic rate. Plants that receive more light are predicted to exhibit a higher rate of per capita growth because light is a necessary to carry out the process of photosynthesis. Plants that receive more light are also predicted to reach their carrying capacity sooner because of



Cited: 1) Brun, F.G., Olive, I., Perez-Llorens, J.L., and J.J. Vergara. 2007. Effects of Light and Biomass Partitioning on Growth, Photosynthesis and Carbohydrate Content of the Seagrass Zostera noltii Hornem. Journal of Experimental Marine Biology and Ecology. Vol. 345(2): 90-100. 2) Campbell, N.A., & Reese, J.B. 2005. “Population Ecology”. Biology. 7th Edition. San Francisco, Pearson Education Inc., 1143-1147 pp. 3) Galt, C., D. Huckaby, T. Stanton, P. Baker. 2005. “Ecology”. Laboratory Manual for Biological Sciences II. 6th Edition. CSULB Bookstore, Long Beach, 105-110 pp. 4) Nedbal, L. and U. Rascher. 2006. Dynamics of Photosynthesis in Fluctuating Light. Current Opinion in Plant Biology. Vol. 9(6): 671-678.

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