To elucidate the mechanism underlying the enhancement of salinity tolerance by tea polyphenols (TPs), we employed seedlings of the wheat cultivar Longchun 30 to explore the individual and combined effects of 150 mM sodium chloride (NaCl) and 25 mg L-1 (25) or 100 mg L-1 (100) TPs on growth parameters, element absorption and transport, as well as polyphenols including anthocyanin metabolism. Compared to the control, treatment with NaCl significantly reduced plant biomass, relative growth rate (by 62%), leaf area (by 61%), AS(K)(+), Na+ levels (by 38%), and AS(Ca2)(+), Na+ levels (by 54%) in wheat seedlings. Conversely, it led to an increase in TSK+, Na+ (by 88%) and TSCa2+, Na+ levels (by 257%). Moreover, the NaCl treatment diminished the antioxidant activity in the in vitro leaf extract, resulting in enhanced reactive oxygen species levels and oxidative damage in wheat leaves. Furthermore, the levels of total polyphenols (by 27%), flavonoids (by 31%), and anthocyanins (by 27%) in wheat leaves were markedly reduced under salt stress. This was accompanied by the down-regulation of the activities of 4-coumaroyl: CoA ligase (4CL), chalcone synthase, chalcone isomerase (CHI), flavanone-3-dioxygenase (F3H), dihydroflavonol reductase (DFR), and anthocyanidin synthase, along with the down-regulation of their gene expression. In contrast, individual TPs exposure resulted in weak, ineffective, or even opposite effects on most of these parameters. More importantly, the addition of TPs partly counteracted salinity-induced changes in these parameters, particularly by increasing total polyphenols, flavonoids, and anthocyanins levels, upregulating the activities of the aforementioned six enzymes, and enhancing the expression of Ta4CL, TaCHI, TaF3H, and TaDFR in wheat leaves under salinity stress. Additionally, the growth-promoting effect of 100 mg L-1 TPs on salinity-stressed seedlings was stronger than that of 25 mg L-1 TPs. Overall, TPs application significantly enhanced the growth of salinity-stressed wheat seedlings by improving K+ and Ca2+ absorption and elevating polyphenols, including flavonoids and anthocyanins levels. Moreover, the accumulation of anthocyanins in salinity-stressed wheat leaves induced by TPs was attributed to the up-regulation of the activities and gene expression of synthesis-related enzymes.

来源平台：JOURNAL OF PLANT GROWTH REGULATION