Collection of 1g Reference Data for ISS Experiments

Students: Allyson Wojnosky, Meka George, and Rachael Quick
Mentor: Chris Wolverton (Department of Botany-Microbiology)

Data will be collected as a control and used as a “1g” comparison for data to be collected aboard the International Space Station at fractional gravity. Differences in gravity responses were observed via the analysis of timelapse photography of wild type Arabidopsis thaliana, a Eurasian weed, and starchless mutant Arabidopsis thaliana plants.

Plants grow and develop through an adaptive process by which numerous inputs from the environment are detected and acted upon to determine the final shape of the plant body. Upon displacement from vertical, primary roots respond to gravity at a rate that varies depending on the angle of stimulation, a process which relies on the sedimentation of starch-filled plastids called statoliths. We have previously shown that roots lacking statoliths show reduced gravitropic response and rates of differential growth that do not vary with the angle of stimulation. These results suggest an alternate mechanism of gravity perception not involving plastid sedimentation. We are planning to probe this alternate mechanism by applying fractional g treatments to wild type and starchless mutants using centrifugation in the EMCS facility aboard the ISS.

As part of Flight Definition, we have investigated a number of parameters in order to optimize seedling growth in flight hardware. All of our previous work on root gravitropism has been carried out with primary roots between 4 and 5 d old growing on agar-based nutrient media containing 1% sucrose. Agar-based substrates differ significantly from the growth environment in the Seed Cassettes designed for the EMCS, in which seedlings grow along the surface of a polyethersulfone (PES) membrane. One objective here was to compare growth and gravity response of roots growing along the surface of membranes with those of roots on agar. Results thus far suggest that roots growing on membranes elongate and respond to gravity consistently and at a lower rate than in previous experiments on agar media. These data will be used to develop a model of gravitropic response rates for use in interpreting the fractional g flight treatments. Supported by NASA grant NNX15AG55G.