Photosynthetic acclimation to elevated CO2 in wheat cultivars

Abstract

Wheat (T. aestivum) cvs. Kalyansona and Kundan grown under atmospheric (CA) and elevated CO2 concentrations (650±50 cm3 m-3 - CE) in open top chambers were examined for net photosynthetic rate (P(N)), stomatal limitation (l(S)) of P(N), ribulose-1,5-bisphosphate carboxylase (RuBPC) activity, and saccharide content of the leaves. The P(N) values of both CA- and CE-grown plants compared at the same CO2 concentration showed a down regulation under CE at the post-anthesis stage. The negative acclimation of P(N) appeared to be due to both stomatal and mesophyll components, and the RuBPC activity got also adjusted. There was a decrease in activation state of RuBPC under CE. In connection with this, an increased accumulation of saccharides in wheat leaf under CE was observed. Kalyansona, owing to its larger sink-potential in terms of the number of grains, showed a greater enhancement under CE in both post-ear emergence dry matter production and grain yield. Under CE, this cultivar also showed a lower down regulation of P(N) than Kundan.