Physiological and biochemical characteristics of two contrasting clones of Hevea brasiliensis under cold stress

Abstract

Physiological and biochemical responses of two Hevea clones, differing in cold tolerance potential, namely, RRII 105 (susceptible) and SCATC 88/13 (tolerant) were assessed under low temperature exposure. They were accustomed under controlled conditions (30°C/22°C day/night) for one week before the actual low temperature treatment (15°C/7°C day/night) for two weeks and then allowed for a recovery period (30°C/22°C day/night) of three days. The objective of the experiment was to evaluate the changes in physiological and biochemical characteristics and to determine the ability of the genotypes to recover from cold injury upon exposure to subsequent normal temperature. Photosynthetic pigment contents were more sensitive to cold stress induced photo-oxidation; however, the clone SCATC 88/13 could maintain better level of pigments and remained green with less level of leaf yellowing even after two weeks of stress imposition. A fast recovery of growth on re-warming was noticed in this clone than RRII 105. Cold stress induced leaf injury resulted in significant inhibition of photochemical efficiency (Fv/Fm) and effective quantum yield (O PS II) of PS II in both the clones but the decline was comparatively lesser in SCATC 88/13. During stress recovery periods the rate of PS II repairing was better in SCATC 88/13 than susceptible clone. Comparatively the level of antioxidant, glutathione and rate of antioxidant enzymes activities such as total peroxidase and SOD were high during stress and recovery periods in SCATC 88/13 than RRII 105. The clone SCATC 88/13 maintained a low level of lipid peroxidation during all the phases. Low temperature stress could impair different physiological activities such as antioxidant defense systems and photochemical reactions of photosynthesis and enhance the rate of lipid peroxidation, pigments degradation and photo-inhibition. The results obtained indicate lesser cold injury and faster stress recovery on re-warming in clone SCATC 88/13.