Abstract
Root Exudate (RX) is a general term for a series of complex organic substances that are released by plants through the root system into the inter-root soil as part of their photosynthetic products and their own nutrients under certain soil conditions. Root exudate mainly comes from the accumulation of photosynthesis and the decomposition and absorption of nutrients carried out by plants, accounting for about 5% to 30% of photosynthetic products. Its secretion process to the soil is mainly divided into two ways, the first is through the concentration gradient between the plant root cells and the soil solution, and the secretion is passively released to the soil along the concentration gradient; the other is actively secreted by the plant body under various kinds of stresses (drought stress, heavy metal stress) and interactions with the inter-root microorganisms. The number, type and amount of root secretions are influenced by many factors (mycorrhiza formation, soil organic matter content and temperature).