Photosynthetic gas exchange in leaves of wheat plants supplied with silicon and infected with Pyricularia oryzae

Photosynthetic gas exchange in the leaves of wheat plants growing in a nutrient solution containing 0 or 2 mM silicon (Si) and inoculated with Pyricularia oryzae was investigated. The blast severity, the gas exchange parameters such as net carbon assimilation rate (A), stomatal conductance to water vapor (g (s)), internal CO2 concentration (C (i)) and transpiration rate (E) and the concentration of pigments (chlorophyll a, chlorophyll b and carotenoids) were determined. The blast severity was reduced by 67.66 % on +Si plants compared with the -Si plants. There were significant increases of 29.3, 17.7 and 45 % for A at 48, 72 and 96 h after inoculation (hai); 26.7 and 49 % for g (s) at 48 and 96 hai; and 25.2 and 31.4 % for E at 48 and 96 hai, respectively, for +Si inoculated plants when compared with the -Si inoculated plants. The C (i) was significantly lower for +Si inoculated plants than for -Si inoculated plants at 48, 72 and 96 hai. For inoculated plants, the concentrations of chlorophyll a and chlorophyll b were significantly higher for the +Si plants compared with the -Si plants at 72 and 96 hai. The results of this study clearly demonstrated that the supply of Si to the wheat plants was associated with lower blast severity in parallel with improved gas exchange performance, resulting in higher energy for mounting successful defense strategies against P. oryzae infection.