Adaptive Importance of Mesocotyl and Coleoptile Growth in Rice Under Different Moisture Regimes.

Abstract

The lengths of mesocotyls (first internodes) and coleoptiles of rice varied greatly with the moisture content of the seed-bed. The optimum moisture content in most Indica cultivars was much higher for coleoptile than for mesocotyl growth, but not in some Japonica cultivars because the mesocotyl growth was not vigorous and did not vary with water content. Under submerged conditions, coleoptile growth was markedly stimulated, particularly in Japonica cultivars but there was no mesocotyl elongation in either cultivar. The plastic variability in the growth of coleoptile, leaves, mesocotyl and other internodes may be an adaptive response of rice to the water tension of the soil. Endogenous ethylene formation and effects of ethylene and carbon dioxide were also studied.