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.

The aim of the study was to assess the impact of plant extracts from hemp inflorescences (H10-10% and H20-20%), as well as a mixture of extracts from hemp inflorescences, sage, and tansy leaves (M10-10% and M20-20%) on phytotoxicity and selected physiological and biometric parameters of wheat seedlings, as well as the biological activity of soil in a growth chamber experiment. In all experimental combinations, a low phytotoxicity of the extracts was observed in the form of leaf tip yellowing, classified as first-degree damage or its complete absence. The plant extracts and their mixtures, except for the H20 extract, had an inhibitory effect on the development of fungal pathogens, especially Fusarium spp. The H20 extract increased the fresh and dry weight of root seedlings. The tested extracts also had a positive effect on the chlorophyll content in seedlings. The highest chlorophyll concentrations were recorded for the seedlings sprayed with the M20 extract mixture. The applied plant extracts influenced the activity of soil enzymes. The highest activity of catalase and dehydrogenases was observed after spraying seedlings with M20, while the lowest was recorded after applying H10. Of all the tested groups of soil environment compounds included in the Biolog EcoPlates test, carbohydrates and carboxylic acids were most actively utilized. Conversely, amines and amides constituted the group of compounds utilized the least frequently. The present study demonstrated the high effectiveness of plant extracts on wheat seedlings due to their biocidal action against phytopathogenic fungi and increased biological activity of the soil. This research serves as an initial phase of work, which will aim to verify the results obtained under field conditions, as well as assess the biological stability of the extracts.