ABA regulation of post-germination desiccation tolerance in wheat cultivars contrasting in drought tolerance

Abstract

Post-germination desiccation tolerance (DT) was studied in two wheat cultivars. Effect of pretreatment of abscisic acid (ABA)/ osmotic/ salt/ heat stress was also studied. One day (d)-old seedlings of wheat cultivars PBW 644 (drought tolerant) and PBW 343 (drought susceptible) were exposed to ABA/stress treatment for next 1 d, desiccated for 4 d and subsequently rehydrated for 4 d. Biomass, protein, water, protein carbonyls (oxidative toxicity) and nitric oxide (NO) levels were measured in 2 d (treated), 6 d (desiccated), 10 d (rehydrated) seedlings. Vegetative reactive oxygen species (ROS)/ NO-pathways were studied under normal condition and ABA supply by supplying ROS/NO scavengers. Desiccation caused water loss and increased oxidative toxicity. PBW 644 showed very low level of toxicity but higher loss of water under desiccation. ABA/ stress pretreatment further reduced water level under desiccation and reduced biomass upon rehydration in PBW 644 only. On the other hand, PBW 343 did not show higher decrease of water but showed high toxicity under desiccation where ABA/stress pretreatment improved this response by increasing biomass upon rehydration. This indicated that PBW 644 used metabolic arrest under desiccation for survival while PBW 343 used growth promotive mode. ABA/ROS/NO-pathways were operational in both cultivars.