EFFECT OF HEAT-STRESS ON SUBSEQUENT GERMINATION AND VIABILITY OF WILDSORGHUM (SORGHUM-ARUNDINACEUM (DEW) STAPF) SEEDS

The first indication of seed damage by heat stress was a delay in germ ination. Exposing unimbibed Sorghum arundinaceum seeds to 60-degrees-C for 24 hrs had no adverse effect on their viability. Viability was, h owever, reduced under moist conditions in the incubator or water bath at 45-degrees-C - 60-degrees-C. At these temperatures, it was found th at the higher the temperature and/or the longer the exposure period th e greater was the reduction in seed viability. Seeds with and without glumes which were previously imbibed at 30-degrees-C were more suscept ible to a 3 hrs exposure at 60-degrees-C in a water bath than previous ly unimbibed ones. Viability of seeds without glumes followed the same trend but were apparently more sensitive to heat stress. Splitting th e heat exposure period into one or two splits was more deleterious tha n a single exposure. The results are briefly discussed in relation to solarization.