Measuring and modeling the gravitropic response of oat shoots (Avena sativa)

Author

Ari Kornfeld

Graduation Date

2006

Document Type

Thesis

Program

Other

Program

Thesis (M.S.)--Humboldt State University, Environmental Systems, Mathematical Modeling, 2006

Committee Chair Name

Borbala Mazzag

Committee Chair Affiliation

HSU Faculty or Staff

Keywords

Gravitropism, Humboldt State University -- Theses -- Mathematical Modeling, Mathematical modeling

Abstract

Plants orient themselves in a gravitational field through a process known as gravitropism. In cereal grasses, for example, gravitropic bending raises the seed heads in crops that have been knocked down, thus protecting the seeds from damage. Many details of gravitropism, however, continue to elude the research community despite over 100 years of active research. Because we believe that growth rates hold important clues about gravitropism, we designed a new method for measuring gravitropism in oat (Avena sativa L.) shoot segments. Oat shoot segments, enclosed in CD jewel cases, are placed into vertically-oriented scanners programmed to capture images at regular intervals. We measure the bending angles using custom image processing software and then compute bending rates by differentiating numerically. Using a geometrical model, together with statistical analysis, we show that these bending rates are proportional to growth rates. Finally, by comparing the measured data against mathematical models of the physiology, we show that the gravitropic reaction in pulvini (the graviresponding organs in oats) most likely results from a single pulse of growth factor that is subsequently consumed. If true, then pulvini represent an important exception to the standard feedback model of gravitropism and may therefore be a useful tool for teasing apart the gravitropic process. We believe that our research will provide an important contribution to solving the longstanding puzzle of how plants detect and react to gravity.

https://scholarworks.calstate.edu/concern/theses/6395w932n

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