Plant Growth: Artificial vs. Natural Light Effects on Solanum lycopersicum

1. Plant Growth: Artificial vs. Natural Light Effects on Solanumlycopersicum Cody Britton, Undergraduate Student (Fisheries Biology), Department of Biology, Tennessee Technological University, Cookeville, TN 38505

2. Introduction Various studies have been done on plant growth in the past. It is now known that different light intensities can have positive or adverse effects on plants (Hardy 1995). Some examples of other studies are the effects of dark and light cycles on tomato plants, which can alter their daily rhythm, thus stunting or accelerating growth (Highkin and Hanson 1954). It has even been proven that certain species of plants can be effectively grown with the utilization of super-bright light emitting diodes as the light source (Yanagi and Okamoto 1997). Some suggest that most plants exhibit better growth in natural light and conditions, however some studies show that plant growth can be maximized by using artificial light in a controlled environment where there are less uncontrollable variables (Murakami, et al 1997). Other studies have been done that accidentally led to conclusions about the best light source. The studies were not conducted to test light sources, but through their experiments it was clear that natural light was the most successful (Prescott, et al 2005). As we can see, there are a few conflicting ideas on which light source is the most effective. By reading these studies we can see that plants can indeed be grown under different sources of light. In my project, I will try to determine whether natural light or artificial light causes plants to grow the best. My objective is to learn the most effective light source for tomato plants. The results could help people maximize tomato growth, which would be very beneficial to both commercial farmers and small-scale gardeners. I hypothesize that tomato plants grow faster and larger in natural light than in artificial light. The null hypothesis is that plants grow faster and larger in artificial light than in natural light. Using the data I collect from my experiments, I expect that the null hypothesis will be rejected and the hypothesis will be accepted.

3. Introduction cont’d • Objective : To learn the most effect light source for plants. • Hypothesis: Plants grow faster and larger in natural light than in artificial light. • Null Hypothesis: Plants grow faster and larger in artificial light than in natural light. • Expected result is to reject the null hypothesis.

4. Methods and Materials • Experimental Design: There will be two groups of four small paper cups each. Each cup will be filled with top soil. In each group, one cup will be planted at a density of two seeds, one cup will be planted at a density of four seeds, one cup will be planted at a density of eight seeds, and one cup will be planted at a density of sixteen seeds. All cups will then be watered until the soil is adequately moist. One group of four cups will be placed outside in natural light. The other group will be placed inside under an artificial grow light. Both groups will receive water daily. After four weeks, data will be gathered on both the indoor group and the outdoor group. Height, weight, and number of leaves will be determined for each cup, and an indoor average and outdoor average will be determined (Highkin and Hanson 1954). The information will be interpreted using xy scatter plots and bar graphs, which together can show which light source was more effective in this experiment (Hardy 1995).

5. Experiment Pictures

6. Results After gathering my data, and interpreting the information, I found that the plants grown in artificial light actually had a higher average height than plants grown outside in natural light (Table 1). However, the plants grown outside in natural light had a higher average mass and a higher average number of leaves per plant (Table 1). There was not a huge difference in the two groups of plants as seen in figure 1, but it is still significant (Figure 1).

7. Results Table 1 shows the averages of the data taken for each group of plants.

8. Figure 1 shows a graph of the data collected.

9. Discussion Although the plants grown under an artificial light had a greater average height, the null hypothesis can still be rejected. The plants grown outside had a higher average mass and number of leaves. These two features account for a higher level of fitness in the plants (Yanagi and Okamoto 1997), which is interpreted to mean that these plants had better growth even though they were not as tall (Martin, et al 1993). This is on par with the findings of a study on pea plants that has been done (Prescott, et al 2005), however this contradicts other studies that have been done. One study suggested that plants grown in artificial light in a controlled environment grow better (Murakami, et al 1997). My initial predictions were correct, meaning that the null hypothesis can be rejected (Malarkey 1999).

10. Conclusions • Plants grown in artificial light had a higher average height. • Plants grown in natural light had a higher average weight and number of leaves. • The null hypothesis can be rejected.