Ashley Goodman with Chris Schwartz Ph.D. and Professor Rick Amasino Ph.D.

UW-Madison Department of Biochemistry

The purpose of this study is to determine the effects of three variables on the flowering time of Arabidopsis thaliana; vernalization, far-red light, and the plant hormone gibberellic acid (GA). All three variables generally accelerate flowering and are part of biological pathways that promote the transition from vegetative to reproductive growth (flowering). Ten natural Arabidopsis accessions were chosen based upon flowering behavior and geographic location. Two blocks of 3 plants each were grown in the different experimental conditions, and flowering was recorded as the number of leaves present when the plant had produced a reproductive stem (bolt) of 1cm. Vernalization is an extended cold treatment that renders a plant capable of flowering upon a return to warm conditions. Plants were subjected to varying times of cold (10, 15, 20, 40, or 60 days); some accessions required only a short cold treatment, while others required an extended cold treatment. Far-red light, is used to mimic the effects of shading on plants and competition for sunlight. Some accessions flowered rapidly under far-red light, while others were insensitive to its effects. We examined the effects of GA, an endogenous plant hormone, on flowering time. After a certain accumulation of GA, Arabidopsis plants will flower. Variable responses to the GA treatment indicated that accessions had different GA sensitivity levels. Unlike the vernalization and far-red treatments, where some accessions had no response, all displayed a decrease in flowering time when GA was added. As a control, two flats were grown under long day conditions without any treatments. The majority of these accessions did not flower, demonstrating the substantial effect that each treatment has on promoting flowering.