The Effect of Stress on the Height of Phaseolus vulgaris By Lily Aloe Teacher: Mrs. Atomic Class: Advanced Chemistry December 8, 2008

Background Japanese farmers routinely subject plants to stress before transplanting them from the greenhouse to the field. They pull on plants and hit them with straw rakes. A study done in 2006 showed a statistical difference in the growth and production of rice between stressed and unstressed rice plants (Osaki 57).

Statement of Problem Rationale Purpose Results of this research can be applied to improvement of crop yield. Purpose The purpose of this experiment was to determine if stressing bean plants will increase the height of the plant.

Experimental Design Hypothesis Statement: If stressing plants causes increased mitosis of the stem and one group of bean plants are pulled once a day for 15 days before transplanting, a second group is pulled twice a day and a third group is not pulled; then 30 days after transplant, the mean height of the plants stressed twice daily will be greater than the mean height of the other groups IV: Amount of stress to plants by pulling Levels No stress Stressed once daily Stressed twice Trials 10 plants DV: Height of bean plants, health of bean plants (color scale) Constants: type of bean plant, pots, soil, watering schedule, lighting, transplanting time, growth time

Materials 20 bean seedlings (Phaseolus vulgaris) Scott’s potting soil 20 pots (6 inch) Water Garden area for transplanting Shovel (obviously you would have more) Photo of your materials

Methods Each bean seedling was planted in a 6-inch pot with potting soil. Markers were placed in the plants to be stressed. Plants were set in the same area of the greenhouse. Plants were watered when the top ½ inch was dry. For the 20 plants to be stressed, each plant was pulled on 3 times daily at 8:00 am and one group of 10 was pulled again at 4:00 pm. After 15 days, all plants were transplanted to the garden, being sure to keep the plants marked. The plants were allowed to grow, without pulling any plants, for 30 more days. The height of each bean plant was measured in centimeters and the health was rated with a color scale.

Data (should be your photos) Transplanting bean seedlings to garden (Oct 30) Watering plants Measuring height of bean plants Weeding garden

Plants Stressed Twice Daily Plants Stressed Once Daily Effect of Stress on the Mean Height of Phaseolus vulgaris After 30 Days Plants Stressed Twice Daily Plants Stressed Once Daily Unstressed group Mean Standard deviation 1SD 2SD Number 78.88 cm 10.75 cm 68.13 – 89.63 cm 57.38 – 78.88 cm 10 60.13 cm 6.75 cm 53.38 – 66.88 cm 46.63 – 73.63 cm 56.12 cm 7.27 cm 48.85 – 63.39 cm 41.58 – 70.66 cm F: 20.70 Numerator df: 2 (between groups) Denominator df: 27 (within groups) F of 20.70 > 3.35 p = 3.55 X 10 -6

Results Effects of stress on the height of Phaseolus vulgaris plants are summarized in the previous charts and graph. Plants stressed twice daily exhibited a greater mean height (78.88 cm) than plants stressed once daily (60.13 cm) and non-stressed plants (56.12 cm). Variation within the group of plants stressed twice daily was greater than the other two groups of plants. This is shown by a standard deviation of 10.75cm for the plants stressed twice daily compared to a standard deviation of 6.75cm for plants stressed once daily and 7.27cm for plants not stressed. The ANOVA test was used to test the following null hypothesis at the 0.05 level of significance: The mean heights of plants stressed twice daily, plants stressed once daily and plants not stressed are not significantly different. The null hypothesis was rejected (F = 20.70 > 3.35; p = 0.00) The data did support the research hypothesis that the mean heights of Phaseolus vulgaris plants exposed to two stress treatments and those not exposed to stress would be different

Conclusions The effect of stress on the growth of Phaseolus vulgaris plants was investigated by comparing the height of three groups of plants exposed to varying levels of stress. One group of ten plants was not stressed, a second group of ten plants was stressed once daily, and a third group of ten plants was stressed twice daily. There was a significant difference between the mean heights of plants stressed once daily, plants stressed twice daily, and unstressed plants 30 days after transplanting.

Conclusions The research hypothesis that there would be a difference in the mean heights of Phaseolus vulgaris plants stressed once daily, twice daily and unstressed was supported. The mean height of plants stressed twice daily is much greater than the mean heights of the other two groups, but the mean height of plants stressed once daily is very similar to the mean height of unstressed plants. Further statistical tests are needed to determine if there is a significant difference between the plants stressed once daily and the unstressed plants. Similarly, Japanese farmers found that hitting and pulling rice plants were beneficial (Osaki 57). The type of stress (pulling of plants) used in this experiment was the same as in the Osaki experiment. The results were similar, even though the Phaseolus vulgaris plant is a dicot and the rice plants used in the Osaki experiment are monocots.

Further Investigations Additional investigations using various sources of stress at more frequent intervals with both monocots and dicots should be conducted. Improved experimental design techniques should be implemented, including a larger sample size, more frequent measurement, and a longer growing period. Measurements of flowering and fruiting should be made in addition to plant height and plant health.

Acknowledgments I would like to thank Mrs. Polly Atomic, who helped with the design of the experiment, gave me guidance throughout the project and explained the statistics. I would also like to thank Mr. B. Green for the use of his greenhouse. A special thanks to my mother for helping me purchase the materials and providing space in her garden.

Works Cited Freeman, Scott. Biological Science. Upper Saddle River, NJ: Pearson Education, Inc, 2005. Moore, Thomas C. Biochemistry and physiology of plant hormones. New York: Springer New York Inc., 2003. Osaki, Yoko. “Improving rice yields by stressing plants.” Journal of Agricultural Science 10 Dec 2006: 50-67. Plants database. 24 Nov 2008. United States Department of Agriculture. 28 Nov 2008 <http://plants.usda.gov/. Senaratna, Tissa, Darren Touchell, Eric Bunn, and Kingsley Dixon. “Acetyl salicylic acid (Aspirin) and salicylic acid induce multiple stress tolerance in bean and tomato plants.” Plant Growth Regulation Feb 2000: 157-161.