Salt acclimation induced salt tolerance in wild-type and chlorophyl b-deficient mutant wheat

Salt acclimation can promote the tolerance of wheat plants to the subsequent salt stress, which may be related to the responses of the photosynthetic apparatus. The chlorophyl (Chl) b-deficient mutant wheat ANK 32B and its wild type (WT) were firstly saltly acclimated with 30 mmol NaCl for 12 days, then subsequently subjected to 6-day salt stress (500 mmol NaCl). The ANK 32B mutant plants had lower Chl b concentration, which was manifested in the lower total Chl concentration, higher ratio of Chl a/b and in reduced photosynthetic activity (P_n). The effect of salt acclimation was manifested mainly after salt stress. Compared to non-acclimated plants, the salt acclimation increased the leaf water potential, osmotic potential (Ψ_o) and K concentration, while decreased the amount of Na⁺ and H₂O₂ in WT and ANK 32B under salt stress, except for Ψ_o in ANK 32B. In addition, the salt acclimation enhanced the APX (ascorbate peroxidase) activity by 10.55% and 33.69% in WT and ANK 32B under salt stress, respectively. Compared to the genotypes, under salt stress, the Ψ_o, F_v/F_m, P_n and g_s of mutant plants were 5.60, 17.62, 46.73 and 26.41% lower than that of WT, respectively. These results indicated that although the salt acclimation could alleviate the negative consequences of salt stress, it is mainly manifested in the WT, and the ANK 32B plants had lower salt tolerance than WT plants, suggesting that lower Chl b concentration has a negative effect on the salt acclimation induced salt tolerance in wheat.

Salt acclimation induced salt tolerance in wild-type and abscisic acid-deficient mutant barley

Salt acclimation is a process to enhance salt tolerance in plants. The salt acclimation induced salt tolerance was investigated in a spring barley (Hordeum vulgare L.) cv. Steptoe (wild type, WT) and its abscisic acid (ABA)-deficient mutant Az34. Endogenesis ABA concentration in leaf was significantly increased by salt stress in WT, while it was not affected in Az34. Under salt stress, the salt acclimated Az34 plants had 14.8% lower total soluble sugar concentration and 93.7% higher sodium (Na) concentration in leaf, compared with salt acclimated WT plants. The acclimated plants had significantly higher leaf water potential and osmotic potential than non-acclimated plants in both WT and Az34 under salt stress. The salt acclimation enhanced the net photosynthetic rate (by 22.9% and 12.3%) and the maximum quantum yield of PS II (22.7% and 22.0%) in WT and Az34 under salt stress. However, the stomatal conductance in salt acclimated Az34 plants was 28.9% lower than WT under salt stress. Besides, the guard cell pair width was significantly higher in salt acclimated Az34 plants than that in WT plants. The results indicated that the salt acclimated WT plants showed a higher salt tolerance than Az34 plants, suggesting that ABA deficiency has a negative effect on the salt acclimation induced salt tolerance in barley.

Salt acclimation induced salt tolerance is enhanced by abscisic acid priming in wheat

High salt stress significantly depresses carbon assimilation and plant growth in wheat (Triticum aestivum L.). Salt acclimation can enhance the tolerance of wheat plants to salt stress. Priming with abscisic acid (1 mmol ABA) was applied during the salt acclimation (30 mmol NaCl) process to investigate its effects on the tolerance of wheat to subsequent salt stress (500 mmol NaCl). The results showed that priming with ABA modulated the leaf ABA concentration to maintain better water status in salt acclimated wheat plants. Also, the ABA priming drove the antioxidant systems to protect photosynthetic electron transport in salt acclimated plants against subsequent salt stress, hence improving the carbon assimilation in wheat. It suggested that salt acclimation induced salt tolerance could be improved by abscisic acid priming in wheat.