![]() ![]() ![]() Extracellular enzymes release P from organic compounds, and several types of molecules increase iron availability through chelation. Plants growing in low-nutrient environments also employ root exudates in ways other than as symbiotic signals to soil microbes involved in nutrient procurement. Some of the same compounds affect development of mycorrhizal fungi that are crucial for phosphate uptake. Phenolics and aldonic acids exuded directly by roots of N2-fixing legumes serve as major signals to Rhizobiaceae bacteria which form root nodules where N2 is reduced to ammonia. ![]() –, OH–, H+), gaseous molecules (CO2, H2), enzymes and root border cells which have major direct or indirect effects on the acquisition of mineral nutrients required for plant growth. Plant root exudates consist of a complex mixture of organic acid anions, phytosiderophores, sugars, vitamins, amino acids, purines, nucleosides, inorganic ions (e.g. Plants take up most mineral nutrients through the rhizosphere where micro-organisms interact with plant products in root exudates. Thus, the availability of nutrient elements can be a major constraint to plant growth in many environments of the world, especially the tropics where soils are extremely low in nutrients. Plant developmental processes are controlled by internal signals that depend on the adequate supply of mineral nutrients by soil to roots. ![]()
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February 2023
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