Mechanism of root exudates regulating plant responses to phosphorus deficiency

Phosphorus (P) is an essential nutrient for plant growth and development. Low phosphate (Pi) availability in soil largely limits crop yield. Due to long-term improper P fertilizer application, a lot of P accumulates to form a huge P pool in soil. However, most P are insoluble inorganic P and organic P, and are difficult to be directly absorbed by plants. Plants have evolved a set of adaptive strategies to low P stress. Among them, the mechanism of root exudates participating in P acquisition and utilization has always been a hot issue. In this review, advances in low P stress regulating synthesis and exudation of root exudates (organic acid and purple acid phosphatases) were summarized. Furthermore, the vital functions of root exudates in rhizosphere ecological system are discussed to elucidate mechanism of P efficiency enhancement in crops through root exudate regulation, which would provide some clues and theoretical bases for development of high P efficiency cultivar and optimization of Pi fertilizer management in fields.