![]() ![]() This may result from an inherently low nutrient status of soil, low mobility of nutrients within soil, poor solubility of the given chemical form of the nutrient, or the soil-microbe-plant interactions (eg. Plants suffer nutrient deficiency stress when availability of soil nutrients, and/or the amount of nutrients taken up, is below that required for sustaining metabolic processes in a particular growth stage. Biofortification (Olsen and Palmgren, 2014 Vaz Patto et al., 2015) via agronomic means is becoming wide-spread (especially in case of Zn, Olsen and Palmgren, 2014 Tan et al., 2015) and is dependent on the interactions of numerous soil and plant factors, some of which will be covered in this paper. This fact has been brought into sharp focus in the last decade because of a large proportion of people being deficient in micronutrients (particularly Fe and Zn). Micronutrient-deficient soils are widespread many millions of hectares of arable land worldwide are deficient in one or more micronutrient elements. Keywords: Exudation, manganese, microflora, micronutrients, rhizosphere, zinc The interactions between microorganisms and plants at the soil-root interface are particularly important as well obscure. Our understanding of the physiological processes governing exudation and the soil-plant-microbe interactions in the rhizosphere is currently inadequate, especially in terms of spatial and temporal variability in root exudation as well as the fate and effectiveness of organic and inorganic compounds in increasing availability of soil micronutrients and undesirable trace elements. In addition, micronutrient-efficient crops and genotypes can increase an available nutrient fraction and hence increase micronutrient uptake. Fertilisation with micronutrients (more so in case of Zn than Fe) can be effective in increasing the concentration of micronutrients at the soil-root interface. for Zn, 100-fold increase in solubility for each unit of pH decrease).įor diffusion-supplied micronutrients, the uptake rate is governed by the soil nutrient supply. Acidification of the rhizosphere soil increases mobilization of micronutrients (eg. Increased availability may result from solubilization and mobilization by short-chain organic acid anions, amino acids and other low-molecular-weight organic compounds. Plants exude a variety of organic compounds (carboxylate anions, phenolics, carbohydrates, amino acids, enzymes, etc.) and inorganic ions (protons, phosphate, etc.) to change chemistry and biology of the rhizosphere and increase micronutrient availability. Micronutrient availability in the rhizosphere is controlled by soil and plant properties, and interactions of roots with microorganisms and the surrounding soil. The emphasis is placed on Zn and Mn, but Fe is also covered to some extent. *Corresponding author: review paper critically assesses the literature on soil-microbe-plant interactions influencing availability of micronutrients in the rhizosphere. Nevertheless, there are cases of acute and chronic Zn poisoning.Availability of Mn, Zn and Fe in the rhizosphereġSoil Science and Plant Nutrition, Faculty of Science, The University of Western Australia, 35 Stirling Highway, Perth WA 6000, Australia. Zinc is not stored in the body and excess intakes result in reduced absorption and increased excretion. Physiological supplementation of Zn in ageing and in age-related degenerative diseases corrects immune defects, reduces infection relapse and prevents ageing. Metallothioneins play a key role in Zn-related cell homeostasis due to their high affinity for Zn, which is in turn relevant against oxidative stress and immune responses, including natural killer (NK) cell activity and ageing, since NK activity and Zn ion bioavailability decrease in ageing. Zinc-binding proteins (metallothioneins, MTs), are protective in situations of stress and in situations of exposure to toxic metals, infections and low Zn nutrition. It is involved in homeostasis, in immune responses, in oxidative stress, in apoptosis and in ageing. Zinc (Zn) is one of the most important trace elements in the body and it is essential as a catalytic, structural and regulatory ion. ![]()
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