PHOTOPERIOD SHIFT EFFECTS ON YIELD CHARACTERISTICS OF RICE

Edible yield must be maximized for each crop species selected for incl usion in the Controlled Ecological Life-Support System (CELSS) propose d by NASA to support long-term manned space missions. In a greenhouse study aimed at increasing biomass partitioning to rice (Oryza sativa L .) grain, plants of the high yielding semi-dwarf rice cultivar Ai-Nan- Tsao were started in pots under 8-h photoperiods at a density of 212 p lants m(-2). After different periods of time under 8-h photoperiods, p ots were switched to continuous Light for the remainder of the croppin g cycle. Continuous Light did not delay time to first panicle emergenc e (60 d) or time to harvest (83 d). There was a positive correlation b etween the length of continuous Light treatments and nongrain biomass. Grain yield (1.6 +/- 0.2 g plant(-1)) did not increase in continuous light. Yield-efficiency rate (grain weight per length of cropping cycl e, canopy volume, and weight of nongrain shoot biomass) was used to co mpare treatments. Small Ai-Nan-Tsao rice canopies grown under 8-h phot operiods were more efficient producers of grain than canopies grown un der continuous light for a portion of the rice cropping cycle.