Response to Light Stimulus Phototropic Transients (FOTRAN)

Plant biology

Triticum aestivum (wheat) seedlings
Flight seedlings: 144

Clinostat, preflight and postflight asynchronous control using flight hardware

Gravitational Plant Physiology Facility, Middeck Ambient Stowage Insert, Plant Carry-On Container

The objective of the FOTRAN experiment was to determine the time course of plant seedling curvature induced by phototropic stimulations in a microgravity environment. The experiment was designed to provide data on discrete physiological responses of growing wheat coleoptiles and the effect of microgravity in modifying these responses. The purpose of this experiment was fourfold: 1) To determine whether seedling curvature proceeds in the same direction and rate in microgravity as on earth; 2) To determine whether the degree of extent of seed curvature is the same in microgravity as on Earth; 3) To see if seedling curvature reverses (autotropism) or oscillates (circumnutation) in microgravity; and 4) To determine the phototrophic dose-response relationship in plants in microgravity.

In orbit, plants were held in a 1-G-simulated environment to allow for normal plant development until the start of the experiment. Plants were then moved to the recording and stimulus chamber (REST) where they were held at microgravity and time-lapse videos were taken for 5 hours before photostimulus occurred. Plants were then exposed to various lengths of photostimulation, ranging from 3 seconds to 33 minutes 18 seconds. After completion of photostimulus, time-lapse video records were taken until the end of the experiment, approximately 7 hours. This process was repeated for subsequent batches of seedlings. Some batches were fixed inflight at the end of the experiment. Batches that were not fixed inflight were examined, photographed, measured, weighed, and fixed postflight. Any non-germinating seeds were cultured.

The curvature response to photostimulus in flight was not significantly different than the ground controls except in groups that received 6- and 9-second stimuli. Measurements of seedling curvature show a relationship between stimulus and curvature response. The dose response curve of wheat seedling phototropism shows that for the majority of stimulus durations the mean response in 0 G was not statistically different than the ground controls. Autotropic reversal of curvature and circumnutation was seen in flight data. Circumnutation was seen in half of the flight seedlings. Rhythmicities were also observed in groups that were not photostimulated.

Brown, A. et al.: Plants' Tropistic Responses in Zero Gravity. 29th Plenary Meeting of COSPAR, 1992, p. 530.

Chapman, D.K. et al.: Detection of Apparent Autotropic Responses of Seedlings under Microgravity Conditions on IML-1. American Society for Gravitational and Space Biology Bulletin, vol. 6(1), Oct 1992, p. 59.

Heathcote, D.G and B.W. Bircher: Enhancement of Phototropic Response to a Range of Light Doses in Triticum aestivum Coleoptiles in Clinostat-Simulated Microgravity. Planta, vol. 170, 1987, pp. 249–256.†

Heathcote, D.G. et al.: The Phototropic Response to Triticum aestivum Coleoptiles under Conditions of Low Gravity. Plant Cell and Environment, vol. 18(1), 1995, pp. 53–60.

Heathcote, D.G. et al.: The Occurrence of Spontaneous Growth Curvatures in Wheat Coleoptiles Grown at 0 G on the IML Mission (abstract). American Society for Gravitational and Space Biology Bulletin, vol. 6(1), Oct 1992, p. 50.

Heathcote, D.G. et al.: Evidence of Circumnutation in Wheat Coleoptiles under Microgravity Conditions on the IML-1 Mission. American Society for Gravitational and Space Biology Bulletin, vol. 6(1), Oct 1992, p. 88.

Heathcote, D.G. et al.: FOTRAN: An Experiment to Investigate the Effects of Phototropic Stimulations on the Growth Movements of Wheat Seedlings Using the Gravitational Plant Physiology Facility on the IML-1 Spacelab Mission. American Society for Gravitational and Space Biology Bulletin, vol. 4(1), 1990, p. 56.

Heathcote, D.G. et al.: Nastic Curvatures of Wheat Coleoptiles That Develop in True Microgravity. Plant Cell and Environment, vol. 18(7), Jul 1995, pp. 818–822.

Heathcote, D.G. et al.: The Gravitational Plant Physiology Facility: Description of Equipment Developed for Biological Research in Spacelab. Microgravity Science and Technology, vol. 7(3), 1994, pp. 270–275.†

Johnson, C.F. et al.: Infrared Light-Emitting Diode Radiation Causes Gravitropic and Morphological Effects in Dark-Grown Oat Seedlings. Photochemistry and Photobiology, vol. 63(2), 1996, pp. 238–242.

Rudolph, I.L. et al.: Development of Space Flight Experiments: I. Biocompatibility Testing—the IML Experience (abstract). American Society for Gravitational and Space Biology Bulletin, vol. 6(1), Oct 1992, p. 47.†