Salicylic acid enhances sunflower seed germination under Zn2+ stress via involvement in Zn2+ metabolic balance and phytohormone interactions

Zinc (Zn2+) stress is an important abiotic constraint affecting crop seed germination and plant growth. It is vital to exploit and utilize zinc-polluted soil by exploring technologies for promoting seed germination under Zn2+ stress. This study aims to explore the effects of salicylic acid (SA) and 2-aminoindan-2-phosphonic acid (AIP, SA synthesis inhibitor) on the Zn2+ stress resistance of sunflower during seed germination. Zn2+ treatment significantly inhibited seed germination and seedling growth of sunflower. In addition, Zn2+ treatment increased Zn2+ and abscisic acid (ABA) contents, while decreased SA and gibberellins (GA) contents of sunflower seeds. Exogenous SA effectively alleviated the inhibition of Zn2+ stress on sunflower seed germination, promoted endogenous SA anabolism, and increased the expression of zinc transporter-related genes family (MTP and HMA), which leading to decreased Zn2+ accumulation. Moreover, exogenous SA increased GA content and decreased ABA content by regulating the gene expressions of metabolic related enzymes. On the contrary, AIP treatment further aggravated the inhibitory effect of Zn2+ stress on sunflower seed germination. This study demonstrated that exogenous SA could affect the Zn2+ metabolic balance in sunflower seeds by regulating the expression of Zn(2+ )transport-related gene (MTP and HMA), promote the biosynthesis of endogenous SA and GA, inhibit the accumulation of ABA content, and improve the germination ability of sunflower seed under zinc stress.

Automated summary

The study found that exogenous SA can effectively alleviate the inhibitory effect of Zn2+ stress on sunflower seed germination, promote the biosynthesis of endogenous SA and GA, increase the expression of zinc transporter-related genes family (MTP and HMA), leading to decreased Zn2+ accumulation. Exogenous SA also increased GA content and decreased ABA content by regulating the gene expressions of metabolic related enzymes. Conversely, AIP treatment further aggravated the inhibitory effect of Zn2+ stress on sunflower seed germination.