Rice varietal differences in responses of stomatal gas exchange to supplemental nitrogen application

Abstract

In the field, supplemental application of N fertilizer to rice (Oryza sativa) shortly before the beginning of heading stage increases leaf N content and enhances photosynthesis during the grain-filling period. In search of varietal differences in leaf gas exchange in response to supplemental N application, we examined 13 rice varieties grown in the field during two successive years. The varieties included japonica and indica varieties, both of which are widely grown in Japan. The response to supplemental N application could not be separated clearly between variety groups; some of the japonica varieties, but none of the indica varieties, exhibited significant increase in stomatal conductance (g s ) after supplemental N application. Supplemental N was more effective to increase stomatal aperture in the varieties with inherently lower g s . Varieties that showed greater response of g s to supplemental N application might be able to adjust their stomatal aperture with appropriate N control. Although the internal-to-ambient CO 2 mole fraction ratio and the leaf carbon isotopic composition (δ 13 C) differed among varieties as a result of variations in stomatal aperture and the CO 2 requirement of mesophyll, supplemental N application barely influenced these parameters, because it only moderately affected stomatal aperture. Since δ 13 C tended to increase with increasing number of days from transplantation to heading stage in japonica varieties, δ 13 C values were more sensitive to differences in growth rate between years than to N application.

Is triose phosphate utilization involved in the feedback inhibition of photosynthesis in rice under conditions of sink limitation?

“…In our study, a supplemental dose of N fertilizer was applied just before heading stage. This might have maintained high stomatal conductance as previously shown in rice (Shimoda, 2012;Shimoda and Maruyama, 2014). Similar to another study evaluating short-term CO2 enrichment effects on mesophyll conductance (Tazoe et al, 2009), no PR and CO2 effect was observed on mesophyll conductance gm, a parameter known to be sensitive to environment and estimation method (Flexas et al, 2008;Pons et al, 2009;Singsaas et al, 2004;Sun et al, 2014).…”