Marilyn Deaner

Due 11/28/12

Section 008

Introduction

Duckweed is an aquatic plant used often in removing some nitrates from water.

In this lab we will be testing how it grows in different environments. Our group has

selected to look at how light affects the growth. Our hypothesis is that the duckweed

left in natural light for a week will yield more frond growth than those left in high or

low light.

Abstract:

In this lab we wanted to see how different levels of light affected the growth of

Duckweed. To do so, we had 2 samples placed in carrying levels of light. We used

natural light which was near the window, high light on a rack with constant light on

it, and for low light we put the samples in a drawer.

* There could be a confounding variable with the sampled placed in the drawer

because they could be exposed to less oxygen*

Methods:

We gathered six cups and filled each cup halfway with distilled water. We then

counted out twenty-five duckweed frons and put that amount in each cup. After that

we placed plastic wrap over each of the cups and poked ten holes in the plastic

wrap. We labeled all six cups, two cups for each light source we used (high light,

natural light, low light). Finally, we placed two cups in each of the light sources. The

high light cups were placed under a high light, the normal light cups were placed by

a window, and the low light cups were placed in a drawer.

Results

All cups placed in the environment began with 25 fronds.

After a week had passed the results were as follows:

Natural light: 45 and 47

High light: 43 and 43

Low light: 27 and 27

Natural Light initial

Natural Light After

Low light Initial

Low Light after

High light initial

High light after

0 5 10 15 20 25 30 35 40 45 50

Duckweed Frond Growth in Varying Light

Series2Sample 1

Conclusion

Before we conducted our experiment, we hypothesized that the natural light

environment would be the best place for fond growth. After observing the cups

from: natural light, high light, as well as low light environments, we conclude that

the amount of fronds supported our hypothesis. Although there was only a small

margin of increase between the natural light and high light, both fond amounts in

those environments dominated the amounts of fronds in the low light. The small

growth in the low light environment could have been due to lack of oxygen rather

than the lower levels of light. If the experiment were to be repeated, the low light

environment should be one with a more consistent availability of oxygen t the other

samples.