The role of phytochelates in plant growth and productivity

Plants require minimal amounts of certain metals (Zn,Fe,Cu,etc) for optimal growth and productivity, but excess of these metals leads to cell death. When growth is limited by metal excess or metal deficiency plants respond by synthesizing nonproteinogenic chelating substances. Phytosiderophores are secreted by roots of iron deficient grasses and are important in providing sufficient Fe for normal growth. In response to growth-inhibitory levels of heavy metals plants synthesize metal-binding phytochelatins which detoxify excess metals. Biostimulants such as humic substances and oligomers of lactic acid have properties in common with both phytosiderophores and phytochelatins. The word phytochelates is proposed as a generic term to cover substances that affect plant growth by acting as chelating agents.