Water status and grain production of several Japonica rices under grain-filling stage drought.

Abstract

This study was designed to compare leaf water potential (LWP) and grain yield responses to drought imposed during the grain-filling stage in several Japonica dryland (upland) and wetland (paddy) rice cultivars (Oryza sativa L.). Six rice cultivars (5 dryland, one wetland) were each grown in two upland plots. The irrigation of the one plot was discontinued on August 15, while the remaining plot received irrigation as before. Heading occurred between 0 and 12 days after the cessation of irrigation. Thereafter, the LWP for both plots was monitored at midday. Traditional dryland cultivars had a higher ability of maintenance and recovery of LWP than improved dryland and wetland cultivars. The dry-matter production of the shoot and the grain of the main culm decreased with decreasing LWP in all the cultivars tested. Furthermore, there was a close correlation between the grain yield of the main culm and of the whole plant. The result therefore suggests that the maintenance of LWP may be one of the most important factors for the grain yield under drought during the grain-filling stage.