Characterization of contrasting genotypes reveals general physiological and molecular mechanisms of heat-stress adaptation in maize (Zea mays L.)

In order to dissect the adaptation response of maize to heat-stress, we characterized and juxtaposed different physio-biochemical parameters for two contrasting genotypes, namely DTPYC9F119 (heat-stress tolerant) and K64R (heat-stress susceptible) under 6 days heat treatment (38/28 °C). Chlorophyll a and b content was found to be reduced under high temperature in both the genotypes, but, it was reduced more prominently in the susceptible genotype (K64R). Net photosynthetic rate was significantly reduced under high temperature in K64R but this reduction was relatively lower in case of DTPYC9F119. Stomatal conductance was increased under stress treatment in both the genotypes but the rate of increase was lower in tolerant one (DTPYC9F119). Activity of anti-oxidant enzymes (viz. catalase, peroxidase and superoxide dismutase) and their gene expression was increased in both the genotypes under heat-stress condition. Thus, the heat-stress tolerant genotype has evolved some strategies like modulation of anti-oxidant gene expression, lower transpiration rate, lower increase of internal CO2 concentration which could make sustain a basic level of photosynthesis even under high temperature stress, etc. that may contribute to its tolerance trait.