Kamaljit KaurKhushdeep Kaur2017-08-212017-08-212016http://krishikosh.egranth.ac.in/handle/1/5810029170The present investigation was undertaken to study the effect of nitric oxide on antioxidant defence system of spring maize (Zea mays L.) under high temperature stress (40˚C). For this study, two genotypes of maize viz., LM-11 (relatively susceptible to heat stress) and CML-32 (relatively tolerant to heat stress) were taken into consideration. High temperature stress reduced lengths and dry biomass of roots and shoots of seedlings of both the genotypes. However, priming of seeds with 75µM sodium nitroprusside (SNP) improved seedling growth in terms of their lengths and biomass, under stress conditions. 75µM SNP specifically enhanced CAT activity in seedlings of both the genotypes under high temperature stress. It also increased POX activity in the roots of CML-32 seedlings. This showed that SNP treatment increased the H2O2 scavanging efficiency of CML-32 genotype by enhancing the cumulative activation of CAT and POX in its roots. An increase in SOD activity was observed in roots and shoots of SNP treated LM-11 seedlings that might protect the seedlings against superoxide radicals. SNP decreased the contents of H2O2 and MDA in seedlings of both the genotypes indicating reduced membrane damage and lipid peroxidation. Proline content was also improved by SNP treatment in seedlings of both the genotypes. Thus, exogenous application of nitric oxide (by priming) improved seedling growth and antioxidant potential of maize seedlings exposed to high temperature stress.ennullThesis