Preconditioning of chickpea seedlings for terminal heat stress: understanding associated mechanism and HSP's expression
Chickpea (Cicer arietinium L.) is the second most important pulse crop grown worldwide. Changes in the cropping system, competition from other cash crops (wheat) and global warming are pushing chickpea to relatively warmer growing environment. In northern part of country chickpea come across with terminal high temperature stress during reproductive stage which lead to reduced grain yield. Therefore to prevent the plant from incoming heat stress, 11 day chickpea seedling were preconditioned with mild drought stress, then put on recovery for six days and then recovered seedlings were exposed to lethal stress (where temperature was increased step wise from 30?C to 36?C). This study revealed that % EL, Lipid peroxidation increased with the increase in temperature while percent TTC reduction and total protein content decreased with the increase in temperature. Antioxidative enzymes provide the major defence against the ROS generated during the abiotic stress, and it was found that activity of SOD, CAT and APX enzyme increased proportionately with the rising temperature. HSP's act as molecular chaperons and are over expressed at both mRNA and protein level in preconditioned seedlings exposed to high temperature stress as compared to non- preconditioned ones. To conclude the whole study, results obtained clearly reveal that preconditioning with drought stress has the ability to improve tolerance above ambient temperature (27?C 7?C), thereafter preconditioning did not have any influence in terms of the improvement in membrane damage and level of antioxidants. Higher expression of sHSP's is corroborated with the low expression of antioxidants.