Relative Contribution of Hetero- and Auto-trophic Growth to Genotypic Variation of Seedling Vigor in Rice (Oryza sativa L.)

抄録

To elucidate the major physiological process to cause genotypic variation in the seedling vigor of rice, we analyzed the dry matter accumulation in the seedling for diverse cultivars distinguishing hetero- and auto-trophic growth. Four cultivars in Exp. 1 and 63 cultivars in Exp. 2 were grown in a glasshouse by hydroponics for about three weeks. In Exp. 1, heterotrophic dry weight (DW_h) was regressed against thermal time (T,°C d) by logistic functions, in which the final heterotrophic dry weight (DW_h.Max) was considered the primary determinant of heterotrophic growth rate. The increase of autotrophic dry weight (DW_a, DW_t (total DW)-DW_h) was regressed to the exponential function of T with a fairly stable parameter, relative growth rate (RGR). The variation of DW_t among cultivars and seed-sizes was well represented by combining the DW_h and DW_a models. In Exp. 2, DW_t varied among cultivars from 51 to 116 mg pl^-1. The effects of cultivar-specific parameters, DW_h.Max (final DW_h) and RGR, were evaluated by calculating the standard DW_t with the mean DW_h.Max and RGR, and then substituting one of the two cultivar-specific parameters for every cultivar. The results showed that those cultivars whose superior DW_t was attributable to DW_h.Max were limited to very large-seed cultivars. If they were excluded, the estimated effect of RGR (autotrophic process) on DW_t was evidently greater than that of DW_h.Max (heterotrophic process).