Interaction among rhizospheric microbes, soil, and plant roots: Influence on micronutrient uptake and bioavailability

Abstract

Soils resulting in micronutrient deficiency in agricultural land and pastureland are increasing globally. Such micronutrient deficiency is due to lower nutrient availability, lower nutrient mobility, and lower capacity of plants to take up nutrients from the rhizosphere. The rhizosphere extends up to a few millimeters from the root surface into the surrounding soil and is rich in microbial activity and diversity. The activity and types of microbes and the soil characteristics influence the uptake and transport of micronutrients in the roots. From the root zone, mobilization of micronutrients in the edible part of plants and their bioavailability is another question. The availability and uptake of various micronutrients in the rhizosphere is again influenced by soil properties and plant root exudates, and depends on microbial interactions with plant roots. The micronutrient transfer dynamics from the microbial cell to the plant cell is also influenced by the physiology of plant-microbe interactions. For diffusion-supplied micronutrients, if a large diffusion gradient exists between the root surfaces and the soil, a large amount could be shipped toward the roots. Conversely, when the capacity of root cells to take up micronutrients exceeds the rate of nutrient replenishment in the root zone, the uptake rate is regulated by nutrient availability rather than the capacity of plant roots to absorb nutrients. Plants exude a wide range of organic compounds and inorganic ions into the rhizosphere, changing the micro-chemical and biological zone of the rhizosphere and enhancing acclimatization or modification toward a particular biotic and abiotic environment. Absolute understanding of the multifaceted and intricate interactions dominating the relationship among plants, microbes, and soil that influence the composition of root exudates is still far off. Understanding of the plant-microbe-soil interaction mechanism for the uptake and mobilization of micronutrients and their bioavailability in the edible part of plants will open an avenue in biological science which could help solve the problem of micronutrient deficiency in consumers.