Nitrogen application enhanced the expression of developmental plasticity of root systems triggered by mild drought stress in rice

Abstract

Background: The promoted root growth under developmental plasticity triggered specifically by mild drought stress (MDS) is known to contribute to maintained water uptake and dry matter production (DMP). Aims: To examine whether the expression of developmental plasticity of root systems and its contribution to DMP would be affected by the levels of nitrogen (N) application. Methods: Two genotypes (CSSL50 derived from Nipponbare/Kasalath cross and Nipponbare) were grown under soil moisture gradients with a line source sprinkler system. Three N fertilizer treatments were used; 25 (low), 75 (standard) and 150 kg N ha-1 (high) in 2009 and 60 (low), 120 (standard) and 180 kg N ha-1 (high) in 2011. Results: Across varying N level treatments, there were no significant differences in any of the traits examined between the two genotypes under well-watered and severe drought stress conditions. In contrast, under MDS conditions (15-25 % w/w of soil moisture content (SMC) in 2009 and 17-25 % w/w of SMC in 2011), CSSL50 showed greater DMP than Nipponbare. The difference, however, varied with N level treatments since CSSL50's greater root system development under MDS, was more pronounced at standard and high N levels than at low N level than it was for Nipponbare. Conclusions: N application enhanced the expression of plasticity in root system development at standard and high N levels as compared with low N level under MDS conditions, which contributed to the maintenance of DMP. © 2014 Springer Science+Business Media Dordrecht.