Variability in drought response among the plus tree accessions of Tectona grandis (Linn f.) from the provenances of Kerala, South India

Moisture stress is one of the major impediments in establishment of plantations since the seedlings are susceptible to moisture stress. Rapid recovery from the drought stress is as important as stress tolerance of tree seedlings. Present study evaluated the physiological and biochemical responses related with stress tolerance and recovery in plus trees of teak from different provenances. One-and-a-half-year-old ramets of eleven plus trees of teak from different provenance of Kerala were exposed to two consecutive drought treatments, till most of leaves exhibited symptoms of wilting with an intervening period of stress relief through rehydration for six days in green house nursery. During the second cycle of drought stress and recovery, physiological parameters like relative water content, canopy air temperature, photosynthesis, stomatal conductance, transpiration, chlorophyll content, chlorophyll stability index and cell membrane stability index were determined. The biochemical constituents like total soluble protein, nitrate reductase, free amino acid, proline, glycine betaine, soluble sugar, super oxide dismutase, peroxidase and malondialdehyde were also recorded in addition to leaf numbers before and after stress. The results showed that physiological and biochemical parameters are crucial to maintain seedling functions during drought and to rapidly recover after re-watering during early vegetative stage. During stress and after rehydration, accessions exhibited variation between full and partial recovery in which both genetic and epigenetic factors may play crucial role. Combinations of photo-protection, osmoregulants and antioxidants measures are employed by teak to combat drought stress. Our results also suggest considerable variation that both drought stress and recovery among the plus trees that were originally selected for growth and wood quality and the potential to use them for further breeding.