Regulation Mechanism Of Rho-Hydroxybenzoic Acid On Grapevine Root Secretion Characteristics

rho-Hydroxybenzoic acid (4-HBA) is a major autotoxin that can regulate grapevine secretion characteristics and cause replant disease. In our study, we aimed to investigate the involvement of various signal transduction pathways (calcium, Ca2+ and reactive oxygen species) in 4-HBA-induced grapevine root secretions. The roots of grapevine seedlings were treated with specific calcium channel inhibitor (Verapamil, Vp), and inhibitors of superoxide dismutase (SOD) (diethyldithiocarbamate, DETC) and NADPH oxidase (diphenylene iodonium, DPI). The distribution of Ca2+ in the root tip tissues was observed, and the phenylalanine ammonia-lyase (PAL) activity and phenolic acid content (rho-Hydroxybenzoic acid and salicylic acid) in the secretions were measured. The results showed that 1000 mu M of 4-HBA had a significant allelopathic effect on seedling growth, leading to Ca2+ flow from the cell wall to the cytoplasm, and that Vp hindered this process. The treatments with Vp and 4-HBA or DETC and 4-HBA decreased the PAL activity of roots and 4-HBA content in root exudates compared to the 4-HBA treatment. The salicylic acid (SA) content in root exudates decreased after co-treating with Vp and 4-HBA, DPI and 4-HBA. This result indicates that Ca2+ and SOD play major roles in 4-HBA induced root secretions.