DROUGHT RESISTANCE OF SORGHUM BICOLOR L. MOENCH. 3. SEED GERMINATION UNDER OSMOTIC STRESS

Abstract

The germination characteristics of two cultivars, NK300 and M35, of Sorghum bicolor were studied under situations of different water potential. When seeds were germinated either in soil with low water content or in the osmotica D-mannitol, sucrose and polyethylene glycols 6000 and 20 000, the cultivar NK300 gave a faster rate and higher percentage germination than the cultivar M35. Germination in osmotica can predict only the relative ability of a cultivar to germinate in soil of low water content. The cultivar NK300 was less inhibited in germination by the growth regulator abscisic acid than M35. Under conditions of osmotic stress, the growth regulator gibberellic acid increased the germination of M35 seed but not of NK300. Osmotic stress inhibition of germination is not due to decreased water uptake but rather appears to be due to an inhibition of metabolism in cells which have sufficient turgor potential to permit cell expansion.