Exogenous boron alleviates growth inhibition by NaCl stress by reducing Cl− uptake in sugar beet (Beta vulgaris).

Aims: This study aimed to better understanding the mechanism underlying the interaction between boron and NaCl and may provide methods to improve sugar beet production in saline soils. Methods: Sugar beet seedlings were treated with different concentrations of boron and NaCl. The flame photometer and ion chromatography were used to determine the ion content. And the uptake of Cl⁻ by beet roots, was measured by non-invasive micro-test technology (NMT) and in vivo uptake system. The qPCR was used to measure the relative expression of the genes encoding ion transporters. Results: In this study, we demonstrate that application of 750 µM boron markedly mitigated the growth inhibition of sugar beet seedlings caused by 300 mM NaCl, as reflected in dry and fresh weight, leaf area, chlorophyll content, and net photosynthetic rates. Both Na⁺ and K⁺ in the plants were not affected by treatment with boron. However, boron markedly reduced the Cl⁻ content of sugar beet seedlings. Boron profoundly upregulated the expression of CLC-b, CLC-c, CLC-f and downregulated the expression of NIP5, NIP6 and AKT1 under NaCl stress. Conclusions: Our results indicate that exogenous boron reduced Cl⁻ content of sugar beet seedlings by regulation of Cl⁻ transport under NaCl stress, which is possibly involved in upregulation of BvCLC-b, BvCLC-c and BvCLC-f genes encoding Cl⁻ transporters in a cell wall-dependent Ca²⁺ signal transduction process. [ABSTRACT FROM AUTHOR]