Elevated CO2 ameliorate the negative effects of high temperature on groundnut (Arachis hypogaea) - Studies under free-air temperature elevation

Four groundnut (Arachis hypogaea L.) genotypes- Narayani, Dharani, K-6 and K-9 were assessed for growth and yield responses at elevated temperature of 3.0 +/- 0.5 degrees C above ambient canopy temperature (eT) and its interaction with elevated CO2 of 550 +/- 50ppm (eT+eCO(2)) under Free Air Temperature Elevation (FATE) facility. The study revealed that eT significantly decreased photosynthetic rate (A(net)) of all groundnut genotypes whereas eT+eCO(2) condition ameliorated the ill effects of eT. The impact of eT on A(net), was higher than transpiration rate (Tr) and this reflected in decreased WUE with all genotypes. WUE improved significantly at eT+eCO(2) with increased A(ne)t and decreased Tr. Increase in canopy temperature (eT) resulted decreased relative water content (RWC), cell membrane stability and increased osmotic potential, Malondialdehyde (MDA) content and accumulation of proline. Elevated CO2 along with eT (eT+eCO(2)) facilitated these parameters to recover to that of ambient controls, revealing the ameliorative effect of eCO(2). Similar responses were recorded for biomass and yield parameters. Among the selected groundnut genotypes, superior performance for seed yield at high temperature of >40 degrees C by K-9 was due to ability to maintain better reproductive capacity and Dharani was responsive to elevated CO2 even at high temperature, indicating the genotypic variability.