Performance of Hevea brasiliensis under drought conditions on osmoregulation and antioxidant activity through evaluation of vacuolar invertase and reducing sugars

Abstract

Rubber tree cultivation is limited in many regions by abiotic factors such as drought. We investigated the biochemical mechanisms responsible for responses to, and recovery from, drought conditions during the establishment phase of four high latex producing rubber tree clones (RRIM600, IAC40, PR255 and GT1). Five-month-old plants were exposed to 32 days of water restriction, followed by 15 days of soil rehydration. Leaf area, as well as their osmolyte accumulations, saccharolytic enzyme activity, and oxidative stress markers, were accompanied. Although clones IAC40 and PR255 responded more precociously to drought conditions, halting leaf expansion before clones GT1 and RRIM600, they demonstrated slow recuperation after reestablishing irrigation. The greater tolerances of clones RRIM600 and GT1 to drought conditions were related to greater vacuolar invertase (VINV) activity in their leaves, which guaranteed more significant accumulations of vacuolar reducing sugars (RS). Similar to RS, glycine betaine accumulations were related to osmoprotection and to reducing oxidative damage (lipidic peroxidation) caused by water deficit conditions. The observed decreases in cytosol neutral invertase (AINV) and cell wall insoluble invertase (CWINV) activities, which resulted in cytosol hexose decreases, may be related to increases in antioxidant enzyme (superoxide dismutase and ascorbate peroxidase) activities in the leaves in response to water deficit conditions. As such, the introduction of specific sugars (RS) and the modulation of key carbon metabolism enzymes, such as VINV, are promising strategies for promoting drought tolerance in rubber tree clones.