Abstract
Drought and heat are major abiotic stresses that usually occur simultaneously and cause significant yield losses in cereal crops including maize (Zea mays L.). First, ten genotypes of maize were screened using root length stress tolerance indices under heat (40 °C for 2, 4 and 6 h) and drought (−0.2, −0.4, and −0.6 MPa) stress. Two tolerant and two sensitive genotypes were selected and their growth and different biochemical traits were analyzed under drought stress (60% field capacity), heat stress (one cycle of 40 °C for 6 hours) and combined drought and heat stress. The results showed that drought stress had a predominant effect over heat stress, whereas combined drought and heat stress caused significant adverse effects on all parameters. The biochemical attributes such as total soluble sugars (TSS), proline, and total free amino acids (TFAA) were increased, whereas total soluble proteins (TSP) and nitrate reductase activity were decreased as compared to controls under all stress treatments. Biomass was positively correlated with the transpiration rate and TSP, while negatively related to leaf temperature and TFAA. The tolerant genotypes maintained higher proline, TSP, TSS, and TFAA contents and could be used for breeding for the adaptation to drought and heat under climate change.