Genotypic Variation in Physiological Traits Under High Temperature Stress in Maize

Maize (Zea mays L.) is a major cereal crop in India and worldwide whose production and productivity are greatly affected by high temperature stress. Twenty-one maize genotypes were staggered sown and evaluated for the variations in different physiological traits under high temperature stress. Observations were recorded for net photosynthetic rate, transpiration rate, stomatal conductance, leaf temperature, canopy temperature, maximum quantum yield PSII photochemistry (Fv/Fm), SPAD, ASI, stover and grain yield. Meteorological data of cropping season for first and second date of sowings showed maximum and mean day time temperature of 37.6, 37.2 and 41.4, 37.5 °C, respectively, during reproductive stage. These temperatures were optimal for photosynthesis, fertilization and grain filling in early sown crop, while for the late sown crop, it was optimal for photosynthesis but above threshold and detrimental for fertilization and grain filling. Combined analysis of ANOVA showed that all the parameters were found significant with respect to genotypes (G), date of sowings (T) and their interaction (G * T) except leaf temperature. The high temperature stress increased the plant stover weight due to increased photosynthesis coupled with maximum quantum yield PSII photochemistry which may improve the total plant growth. Results revealed that high temperature promoted the growth of vegetative plant parts but affected yield-related parameters. Higher temperatures during vegetative growth improved net photosynthetic rate resulting in higher total stover yield (28 %) at maturity. It impacted pollen viability and source to sink supply of photosynthates leading to reduced grain yield (13 %) in all genotypes. © 2015, NAAS (National Academy of Agricultural Sciences).