Alternate mild drought stress (20.1 MPa PEG) immunizes sensitive chickpea cultivar against lethal chilling by accentuating the defense mechanisms

Abstract

The changes in climate particularly, the rise in temperature and humidity affect the physiological functions of plants subsequently affecting crop productivity adversely. A strategy is required which can be directly implemented in fields to induce the tolerance in crop plants. In present study, two chickpea varieties with contrasting sensitivity PDG3 (Tolerant) and GPF2 (Sensitive) were raised hydroponically, preconditioned with mild drought stress (0.1 MPa PEG-6000) for 3 days (above 0.1 MPa is lethal) and subsequently recovered for double time (6 days) and finally exposed to lethal cold stress (4 °C) for 3 days. We hypothesize that preconditioning with non-lethal drought stress may immunize the plants to combat lethal cold stress. Membrane integrity improved in root and shoot, lipid peroxidation decreased to control level in preconditioned seedlings. Cellular respiration ability (% TTC reduction) increased in the preconditioned seedlings to almost 90 % in the shoot and 60 % in the root, concurrently it was 45 % in non-preconditioned seedlings. Proline content also increased in preconditioned seedlings, especially roots. Carbohydrate had a shift in terms of a high amount of total, reducing sugars and starch in non-preconditioned seedlings compared to preconditioned. Both PDG3 and GPF2 showed enhanced SOD, CAT and GPOX activity indicating tolerance against cold-induced oxidative stress and preconditioning induced improvement against lethal cold stress.