Effects of Zn2+ and niflumic acid on photosynthesis in Glycine soja and Glycine max seedlings under NaCl stress

The effects of two anion/Cl− channel inhibitors, Zn2+ and niflumic acid (NA), on seedling photosynthetic and fluorescent parameters of two Glycine soja populations (salt-tolerant BB52; salt-sensitive N23227) and Glycine max cultivar (salt-tolerant Lee68) were studied and compared under salt stress. Treatments with Zn2+ and NA only (10, 20 μmol L−1) were also imposed for comparisons. Results showed that, there were non-toxic and non-nutritional effects of Zn2+ and NA treatments alone on seed germination and seedling growth of soybeans. Under 150 mmol L−1 NaCl for 6 d, leaf chlorophyll and carotenoid contents, net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO2 concentration (Ci), transpiration rate (Tr), and the maximum photochemical efficiency of photosystem II (PS II) (Fv/Fm) except the stomatal limitation (Ls) significantly decreased in three kinds of soybean seedlings when compared with their control plants. The NaCl stress plus additional 20 μmol L−1 Zn showed an obvious enhancement of leaf chlorophyll and carotenoid contents, Pn, Gs, Ci and Tr, especially for the G. max cultivar Lee68, but the supplementation of 20 μmol L−1 NA showed the reverse effects.