GROUND-BASED STUDIES WITH SUPER-DWARF WHEAT IN PREPARATION FOR SPACE-FLIGHT

Several experiments were carried out to test. responses of a Super-Dwa rf cultivar of wheat (Triticum aestivum L.) to various environmental p arameters that were anticipated to be present in our attempts to grow the wheat in a small growth chamber on the Russian Space Station, Mir, or that proved to be present in a 1995 trial space experiment. Under low photosynthetic photon flux (40-400 mu mol.m(-2).s(-1) PPF), develo pment (e.g. anthesis) was retarded, bur heads (often sterile) always f ormed, even if light was so low that plants died before the heads coul d mature. Longer photoperiods promoted flowering, but night interrupti ons combined with short days did not provoke a long-day response as oc curs with true long-day plants. The long-day effect could prove to be a summation of photosynthetic products. Heat stress (40 degrees C for 1-24 h) did not influence flowering but killed plants that were 13-16- day-old (no effect on younger plants). Concentrations of iodine or sil ver-fluoride disinfectants present in the water used for plants on Mir (1.0-4.0 mg.L-1) did not affect plant growth although higher concentr ations (8.0-1.6 mg.L-1) were inhibitory. GA(3) or indoleacetic acid ap plied every other day at concentrations from 1.0 x 10(-6) mg.L-1 to 3. 162 x 10(-4) mg.L-1 did not change the height of Super-Dwarf wheat, su ggesting that this cultivar is not a gibberellin mutant.