Tyler Hacking, Jonathan Wasden and Dr. Michael Stevens (Utah Valley University)
Faculty Advisor: Stevens, Michael (Science, Biology)
Abstract:
Plant growth can be affected by both genes and the environment. To test genetic effects on growth we used two varieties of lettuce. To test environmental effects on growth, we used four different water treatments. We were interested in the main effects of genes and the environment and also in their interaction. In other words, is the effect of water treatment different across two lettuce varieties? Two varieties of Lactuca sativa were cultivated in a growth chamber in pots using vermiculite as the growth medium. The two varieties were treated with four types of water: tap, tap-aerated, reverse osmosis, and reverse-osmosis-aerated throughout the experiment. Aeration was accomplished using both surface aeration (waterfall and vortex) and sub-surface aeration using submerged waterstones. All plants were fertilized using 8-15-36 (N-P-K) water-soluble lettuce fertilizer powder plus trace minerals by Greenway Biotech, Inc. The plants were harvested and dried to a constant weight for analysis of biomass. We observed varietal differences in growth with the Buttercrunch variety producing 145% more biomass than the Butterhead variety (p < 0.001). The water treatments affected growth, with the plants watered with tap water producing 31% more biomass than the plants watered with reverse-osmosis water (p < 0.001). The other two water treatments (tap-aerated and reverse-osmosis-aerated) were intermediate between the tap-watered plants and the reverse-osmosis-watered plants in terms of biomass. Finally, we observed a variety-by-environment interaction such that the Buttercrunch showed a marked response to water treatment whereas the Butterhead was only minimally affected by water treatment (p < 0.001). The Buttercrunch produced more biomass than the Butterhead because of its shorter life cycle. By the end of the experiment, the Buttercrunch plants were already bolting and producing flowers. This could also explain why the Buttercrunch was more responsive to differences in water treatments.