Studies on Agronomic Traits of African Rice (Oryza glaberrima Steud.) II. Dry matter increase and water use efficiency.

Abstract

To compare the time courses of dry matter increase and water consumption in the two cultivated rice species, Oryza sativa L. and O. glaberrima Steud., six strains each of O. glaberrima and O. sativa collected in West Africa and Nipponbare, a Japanese leading cultivar, were examined. The six strains of O. glaberrima showed a vigorous growth around the heading time but afterward the dry matter increase stopped promptly, while all strains of O. sativa showed a slower but longer dry matter increase. The decline of leaf area after heading was slower in strains of O. sativa than in those of O. glaberrima. The root/top weight ratio increased after ripening again in O. sativa, but no such phenomenon was observed in O. glaberrima. These differences between the two species are presumed to be caused by the genetic differences in their progenitors, i.e., whether they are perennial or annual. The water use efficiency (WUE) estimated on the basis of dry matter was smaller in O. glaberrima than in O. sativa, and decreased with the advance of growth stages. The decline was closely, correlated with the decrease in the leaf area ratio (LAR) which accompanies the advanced growth stages. Although vigorous leaf development is one of the characteristics of O. glaberrima, and this is resulted in a large water consumption, the leafy posture seemed to be beneficial for WUE. The ratio of panicle dry weigh to total transpiration was equal both in O. glaberrima and O. sativa.