Salt interferences to metabolite accumulation, flavonoid biosynthesis and photosynthetic activity in Tetrastigma hemsleyanum

This work mainly investigated the interferences of NaCl treatment to major metabolite accumulation, individual flavonoid biosynthesis and photosynthetic activity in Tetrastigma hemsleyanum. The results showed that the accumulation of phenolic acids, steroids and polysaccharides in T. hemsleyanum was significantly enhanced after the treatment of 50 or 100 mM NaCl for 12 days, and after 150 mM NaCl treatment for 3 days, the total content of flavonoids reached the highest value of 219.5 μg·g‐1−1 and was higher by 3.8 times in comparison with the control (CK). In addition, the salt stress would generally enhance the reaction selectivity of Path II (RPSII) to produce flavonol derivatives (Rut, IsoQ, Km3rut, Ast, Qu, Km) and reduce the reaction selectivity of Path I (RPSI) to produce flavone derivatives (IsoO, Or, Ap), and after the treatment of 150 mM NaCl for 3 days, the RPSII and the RPSI reached the highest level of 0.785 and the lowest level of 0.215, respectively. Moreover, salt stress demonstrated significant and diverse effects on photosynthetic characteristics of T. hemsleyanum. Compared with CK, the values of Pn, Cond, Tr, Fv/Fm, Y(Ⅱ) and qP increased first and then declined with increasing NaCl concentration and stress time, and the highest level of Pn, Fv/Fm and Y(II)occurred after 50 mM NaCl treatment. These findings clearly showed that 50 mM NaCl treatment results in favorable changes in photosynthesis and secondary metabolites accumulation in T. hemsleyanum.