Ground-based studies and space experiment with potato leaf explants.

This article details the extensive preflight research required to make a plant experiment conform to the constraints imposed by the spaceflight system. Potato explants, each consisting of a leaf, an axillary bud, and small stem section, were flown on USML-2 in the ASTROCULTURE (TM) flight hardware to study tuber formation from the axillary bud during the 16 days of flight. To obtain acceptable explant materials: 1) parent plants had to be grown under reduced light (150 micromoles m-2 s-1 PPF) to ensure uniform bud and tuber development, 2) leaves had to be trimmed to fit the small size of the flight growth chamber, and 3) only young, fully expanded leaves from plants 5-7 weeks old could be used. After six scrubs, the experiment was flown successfully October 20 to November 5 and produced tubers and accumulated starch similar to that produced on ground controls.