Abstract: There is a lack of knowledge about factors contributing to the chilling-induced alleviatory effects on growth of plants under salt stress. Thus, the primary objective of the study was to determine whether chilling-induced changes in endogenous hormones, ionic partitioning within shoots and roots and/or gaseous exchange characteristics is involved in salt tolerance of two genetically diverses of wheat crops. For this purpose, the seeds of two spring wheat (Triticum aestivum) cultivars, MH-97 (salt intolerant) and Inqlab-91 (salt tolerant) were chilled at 3°C for 2 weeks. The chilled, hydroprimed and non-primed (control) seeds of the two wheat cultivars were sown in both Petri dishes in a growth room and in the field after treatment with 15 dS mâ1 NaCl salinity. Chilling was very effective in increasing germination rate and subsequent growth when compared with hydropriming and control under salt stress. Results from field experiments clearly indicated the efficacy of chilling over hydropriming in improving shoot dry biomass and grain yield in either cultivar, particularly under salt stress. This increase in growth and yield was related to increased net photosynthetic rate, greater potential to uptake and accumulate the beneficial mineral elements (K+ and Ca2+) in the roots and reduced uptake and accumulation of toxic mineral element (Na+) in the shoots of both wheat cultivars when grown under salt stress. Salt-stressed plants of both wheat cultivars raised from chilled seed had greater concentrations of indoleacetic acid, abscisic acid, salicylic acid and spermine when compared with hydropriming and control. Therefore, induction of salt tolerance by pre-sowing chilling treatment in wheat could be attributed to its beneficial effects on ionic homeostasis and hormonal balance. The results presented are also helpful to understand the chilling-induced cross adaptation of plants in natural environments. Moreover, efficacy of pre-sowing chilling treatment over hydropriming suggested its commercial utilization as a low risk priming treatment for better wheat crop production under stressful environments.
Abstract: In order to elucidate the GA3-priming-induced physiochemical changes responsible for induction of salt tolerance in wheat, the primed and non-primed seeds of two spring wheat (Triticum aestivum L.) cultivars, namely, MH-97 (salt intolerant) and Inqlab-91 (salt tolerant) were sown in a field treated with 15 dS mâ1 NaCl salinity. Although all the three concentrations (100, 150 and 200 mg Lâ1) of GA3 were effective in improving grain yield in both cultivars, the effect of 150 mg Lâ1 GA3 was much pronounced particularly in the salt intolerant cultivar when under salt stress. Seed priming with GA3 altered the pattern of accumulation of different ions between shoots and roots in the adult plants of wheat under saline conditions. Treatment with GA3 (150 mg Lâ1) decreased Na+ concentrations both in the shoots and roots and increased Ca2+ and K+ concentrations in the roots of both wheat cultivars. GA3-priming did not show consistent effect on gaseous exchange characteristics and the concentrations of auxins in the salt stressed plants of both wheat cultivars. However, all concentrations of GA3 reduced leaf free ABA levels in the salt intolerant, while reverse was true in the salt tolerant cultivar under saline conditions. Priming with GA3 (150 mg Lâ1) was very effective in enhancing salicylic acid (SA) concentration in both wheat cultivars when under salt stress. Treatment with GA3 (100â150 mg Lâ1) lowered leaf free putrescine (Put) and spermidine (Spd) concentrations in the plants of both wheat cultivars. The decrease in polyamines (Put and Spd) and ABA concentrations in the salt stressed plants of the salt intolerant cultivar treated with GA3 suggested that these plants might have faced less stress compared with control. Thus, physiologically, GA3-priming-induced increase in grain yield was attributed to the GA3-priming-induced modulation of ions uptake and partitioning (within shoots and roots) and hormones homeostasis under saline conditions.
