Remote sensing of physiological traits associated with rice yield potential and its application to screening of genotypes.

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The objectives were (i) to identify yield determination processes of rice and the associated traits, (ii) to develop method to evaluate the traits by remote-sensing under field conditions, and (iii) to clarify the applicability of the remote-sensing method for screening of high-yielding genotypes. On the basis of field experiments on widely different 10 genotypes conducted in 3 years, the following results. were obtained :(1). It was confirmed from the field experiments conducted under widely different environments that genotypic difference in yielding ability is related to that in crop growth rate (CGR) during 2-week period preceding heading. The mechanism through which the CGR during 2-week period determine rice yield potential was hypothesized based on the review of previous studies.(2). The genotypic difference in the CGR during 2-week period preceding heading could well be explained by the difference in the canopy diffusive conductance.(3). We developed a method to estimate canopy diffusive conductance by incorporation of simultaneously remote-sensed sunlit and suddenly shared canopy temperatures and micro-climatic data into energy budget equations of rice canopy. The canopy conductance thus estimated showed close relationships with stomatal conductance, and the CGR over different genotypes.(4). The results above suggest that the remote-sensing system here developed can be useful tool for rapid evaluation of yield potential of rice genotypes under field conditions.