Effects of water deficit on osmotic adjustment, photosynthesis and dry matter production of rice (Oryza sativa L.) genotypes

Abstract

Three genotypes of upland and one genotype of lowland rice (Oryza sativa L.) were transplanted in pots, and were exposed to gradually developed long-term, and rapidly developed short-term water deficits. Genotypical difference in osmotic adjustment varied with the development of stress. Under long-term water deficits, the three upland rice genotypes showed the higher degree of osmotic adjustment, and thus maintained higher turgor, than that of lowland genotype. With short-term water deficit, upland rice genotypes 4652 and Genta, and lowland rice genotype Taichung 65 showed the higher degree of osmotic adjustment than that of upland genotype 4621. Upland rice genotypes with high degree of osmotic adjustment showed high values of leaf conductance, net photosynthetic rate, leaf area and dry matter under long-term condition with severe water deficit, and also showed high values of leaf conductance and net photosynthetic rate under short-term water deficit. It appeared that under long-term with severe water deficit, the leaf area is more important than the photosynthetic rate in determining the dry matter production. Besides, under short-term water deficit, the lowland genotype, Taichung 65, showed an osmotic adjustment as high as those in upland genotypes 4652 and Genta, but it could not maintain its photosynthetic rate and leaf conductance as high as 4652 and Genta when soil water potential decreased.