Varietal difference in the correlation between leaf nitrogen content and photosynthesis in rice (Oryza sativa L.) plants is related to specific leaf weight
Xi LIU | Yong LI
Increasing leaf photosynthesis per area (A) is of great importance to achieve yield further improvement. The aim of this study was to exploit varietal difference in A and its correlation with specific leaf weight (SLW). Twelve rice cultivars, including 6 indica and 6 japonica varieties, were pot-grown under two N treatments, low N (LN) and sufficient N (SN). Leaf photosynthesis and related parameters were measured at tillering stage. Compared with LN treatment, A, stomatal conductance (gs), mesophyll conductance (gm), leaf N content (Narea), and chlorophyll content were significantly improved under SN treatment, while SLW and photosynthetic N use efficiency (PNUE) were generally decreased. Varietal difference in A was positively related to both gs and gm, but not related to Narea. This resulted in a low PNUE in high Narea leaves. Varietal difference in PNUE was generally negatively related to SLW. Response of PNUE to N supply varied among different rice cultivars, and interestingly, the decrease in PNUE under SN was negatively related to the decrease in SLW. With a higher Narea, japonica rice cultivars did not show a higher A than indica rice cultivars because of possession of high-SLW leaves. Therefore, varietal difference in A was not related to Narea, and SLW can substantially interfere with the correlation between A and Narea. These findings may provide useful information for rice breeders to maximize A and PNUE, rather than over reliance on Narea as an indicator of photosynthetic performance.
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