Genotypic Responses And Physiological Mechanisms Of Maize (Zea Mays L.) To High Temperature Stress During Flowering

As greenhouse effect is worsening and extreme high temperatureevents frequently happening, high temperature has become one of the main abioticstresses that constrain agricultural productivity. It is important to elucidate grain yield,grain quality and photosynthesis responses to high temperature treatments duringflowering of different maize genotypes. The effects of high temperature treatmentsduring flowering (0–8d before silking and0–8d after silking) on yield andphysiological response were investigated using heat-tolerant maize genotype Xundan20and heat-sensitive maize genotype Zhuyu309. The main results were as follows:1. Effect of high temperature during flowering on grain yield and quality ofmaize. Under high temperature treatment, the heat-sensitive genotype had asignificant reduction in grain yield with a longer reduction rate under the treatmentafter flowering than before flowering, which was less affected for heat-tolerantgenotype. High temperature treatment significantly reduced pollen fertility rate inheat-sensitive genotype, but the effect was similar to that of control in heat-tolerantgenotype. High temperature reduced ATPase activity in kernels for both theheat-sensitive and heat-tolerant genotypes, but the decrease was not significant for theheat-tolerant genotype. These results suggested that higher pollen fertility rate, higherATPase activity in kernels would be important physiological traits leading to a highergrain yield for a heat-tolerant maize genotype.2. Simulation on Shoot Dry Matter of maize under high temperature duringflowering:The results showed that it was less affected for heat-tolerant genotype.SPAD, netphotosynthetic rate(Pn), stomatal conductance (Gs), primarily photochemicalefficiency (Fv/Fm), actual photochemical efficiency (PSII), photochemical quenching (qP), PEPCase and RuBPCase activities of ear-leaves were reduced. Butintercellular CO2concentration (Ci), non-photochemical quenching (qN) wereincreased; The results showed that there were significant effects of high temperaturetreatments during flowering on photosynthetic characteristics of summer maize, andthe yield were significantly decreased. The heat-tolerant maize genotype has morephotosynthesizing capacity and chlorophyll content than the heat-sensitive maizegenotype.The heat-stress treatment significantly increased the activities of enzymes for theleaves for the heat-tolerant genotype, while decreased the activities of enzymesinvolved in antioxidant system in heat-sensitive genotype. High temperature increasedmalondialdehyde content in ear leaves.3. Root activity of maize under high temperature during flowering:High temperature treatment significantly reduced root activity for heat-sensitivegenotype. However, root activity of heat-tolerant genotypes increased significantlyunder high temperature.