1 Population and Community Ecology, Butler University, Indianapolis, Indiana 46208, USA
For this experiment, we set out to find if density and time had an effect on growth of mung bean plants. We decided to test evidence of growth by measuring plant biomass. We measured the biomass each week for four weeks of plants grown at different densities. We found that density had an overall effect on plant growth, but density only had an effect after the first two weeks of growth. INTRODUCTION
Successful growth of plants has been important ever since agriculture began playing a part in human survival. Understanding what facilitates or inhibits growth of these types of plants can provide information on how to better grow them. For example, factors such as disease, climate, density, or competition can cause facilitation or inhibition of growth. For this article we focus on how density might affect plant growth. Density is one of the biggest factors farmers must deal with when planting a crop to ensure maximum production (Sangoi, 2001). More specifically, this can be seen in corn. In this case density can effect growth and development, nutritional output, and overall structure of the plant (Casal, 1985).
Observing the effect of density in mung bean plants (Vigna radiata) allows the effect to be seen occurring in dicot plant, rather than a monocot plant such as corn. Mung bean is most commonly used as a food source for the sprouts they produce. When grown as a crop, these plants can grow anywhere between twenty four and thirty inches tall, and they can flower after about fifty days (Myers, 2000).
Based upon previous research on plant density affecting growth, mung beans should also be affected when grown in higher densities. In this experiment we attempted to determine the effect that density and time have on the growth of mung bean plants. MATERIALS AND METHODS
Growing the Plants
We used densities of one plant, two plants, four plants, and eight plants in separate blocks to observe where density has the most obvious effect. Each density was planted four times. Biomass was observed for four weeks. After each week we cut plants off at the stem. We duplicated the process to show replication. The results from five other groups were observed, giving us ten trials total. It is important to note that we put in extra seeds according to the germination rate. Extra plants were killed off after germination. Measuring Biomass
Biomass of the stems without water was measured in grams. The mung bean stems from each density were placed in separate envelopes and dried in an oven for about a day. We weighed the biomass of each density for both trials for four weeks. Testing the Biomass Results
We ran statistical tests on our observations. All together we conducted eight ANOVA tests. First we ran an ANOVA test for average biomasses of plants grown with one plant, two plants, four plants, and eight plants. This accounted for the first four ANOVA tests. For the other four ANOVA tests we tested for each week. This allowed us to see if density has an effect for each week separately. RESULTS
The data we collected for biomass for every trial can be seen in Table 1. The average biomass of all the trials for each density can be seen in Figure 1.
For the first ANOVA test for plants grown with a one plant density we observed a P-value of 0.018438215, two plant density had a P-value of 0.049989373, four plant density had a P-value of 0.016515281, and eight plant density had a P-value of 0.001071732. The ANOVA test for week one had a P-value of 0.939796889, week two had a P-value of 0.418632954, week three had a P-value of 0.022695801, and week four had a P-value of 0.019452439. DISCUSSION
Based on the results of the P-values from the ANOVA tests, we can determine whether or not density...