Salt stressis a main factor restricting the growth and grain yield of wheat grown in the salinized soils. Understanding the mechanism of salt resistance of wheat cultivars is of importance to wheat production and breeding. The endogenous hormones contents and their balance have close link to growth and development in wheat plant. However, limited knowledge exists on the relationship between endogenous hormone and salt resistance of wheat subject to salt stress. The objective of this research, therefore, is to determine the responses of endogenous hormone contents and their balance to salt stress in two wheat cultivars contrasting in salt resistance. The results will help to recognize the mechanism of salt resistance and to offer valuable information in salt resistance breeding of wheat.
The experiment was conducted with two wheat cultivars, DK961 (salt-resistant) and TS9818 (salt-sensitive). The seeds of each cultivar ware water-cultivated in three salt concentrations, 0(CK), 100(S100) mmol/LNaCl, and 200(S200) mmol/LNaCl. The seedlings of each treatment were sampled after having been cultivated for 5, 7, 9, 11, and 13 d, respectively, for determining the growth and endogenous hormone contents of seedlings. The results showed that salt stress had obviously inhibitory effects on seedlings growth, especially, of TS9818.ABA contents of the seedlings increased with salt concentration and the increased magnitude due to salt stress in TS9818 were markedly higher than those in DK961. Salt stress caused the decrease of IAA contents of seedlings in both cultivars. However, the comparison of two cultivars showed that IAA contents of seedlings in DK961were over those in TS9818 under salt stress environment, indicating that the salt-resistant cultivar has a higher potential to synthesize IAA for adapting salt stress. GA3 content of seedlings of both cultivars varied with salt concentration. The increased GA3 contents in shoots of salt-resistant cultivar DK961was found under the lower salt stress of 100 mmol/LNaCl, which was beneficial to the seedling growth. However, the GA3 contents declined significantly in seedlings of both cultivars grown in the higher salt stress of 200 mmol/LNaCl. The contents ZR in shoot of both cultivars rose as the salt concentration increased, and ZR content in shoot of DK961was higher than that in TS9818, and the latter had a higher ZR content in root than the former. Based on the results above, we considered that salt stress stimulated the translation of ZR from root to shoot for maintaining seedling growth under salt stress environment. The ratios of IAA to ABA and GA3to ABA showed dropping trend with increased salt concentration and the prolongation of salt stress duration in both cultivars.However, the ratios of IAA to ABA in DK961were higher than those in TS9818 subject to salt stress. Those results mentioned above suggested that salt resistant cultivar has stronger ability to regulate endogenous hormone contents of seedlings for adapting salt stress, which was an important reason why seedlings growth of salt resistant cultivar was less inhibited than salt-sensitive cultivar by salt stress.