Mineral elements and nutrients are absorbed by the plants in specific chemical forms i.e. roots absorb Fe and Zn in their cationic forms. For successful biofortification, the mechanisms of mineral nutrients absorption by plant roots should be well known. The limiting factors which reduce the phytoavailability and supply of micronutrients in rhizospheric solution should be given special considerations. Mineral elements makeup greatly affects their uptake and translocation by the plants.
Reduced Solubility of Minerals in Rhizosphere
The reduced solubility in the rhizosphere ultimately reduces the accumulation of mineral nutrients in edible plant parts. So some alternatives have to be developed to reduce the risk of malnutrition on a sustainable basis.The Phytoavailability of mineral elements in plants is greatly affected by the physicochemical and biological properties of soil.
Factors Affecting Uptake of Mineral Elements and Nutrients by Plants
The mineral elements in the soil are either freely present in soil solution as free ions or they are adsorbed on the organic and mineral surfaces of soil as precipitates or dissolved compounds or as a part of crystal lattice structures within soil biota. Microbial activities, redox potential, soil pH, cation exchange capacity, soil structure, water contents, and organic matter contents in soil greatly affect the solubility and bioavailability of mineral nutrients in the soil.
Improving Soil Properties to Enhance Uptake of Mineral Elements and Nutrients
Indeed the greatest concentration of Fe and Zn is present in various soils but the phytoavailability of these elements is often restricted by soil properties. Cationic concentrations of Fe and Zn in rhizospheric solution are greatly determined by complex formation, adsorption reactions, and soil-specific precipitation. Moreover, mineral elements makeup soil physical properties, and chemical properties of soil greatly affects the transport and translocation of Zn and Fe in plants. https://soilplantfood.com/food-security-improvement-by-biofortification-of-chickpea-wheat-rice-and-cereals/
Effects of pH
High soil pH is a major limiting factor for the reduced phytoavailability of these micronutrients in the soil. These soil properties can be used for the predetermination of proper utilization of land by genetic and agricultural use. In India and Turkey half of the soils, a third of the soils in China, and most of the soils in Western Australia lack phytoavailable zinc.
Effects of Diffusion Coefficients
Due to small diffusion coefficients and low concentrations in soil solution, Zn2+ has limited mobility in soil solution. Exudation of protons, organic acids, and phytosiderophores by roots generally increases the concentration of Zn and Fe in crop plants. The presence of mineral trace elements and properties of soil are significantly helpful from diffusion point of view.
Use of Synthetic Fertilizers to Improve Phytoavailability of Mineral Elements and Nutrients
Most of the strategies for biofortification of crops depend upon increased acquisition of mineral nutrients from the soil. But when the soil contains insufficient amounts of these nutrients then they must be provided by artificial fertilizers. Then the second most important focus is their increased supply and phytoavailability in the rhizosphere.
Increasing Mineral Concentration in Edible Plant Tissues
Their uptake by roots and redistribution to edible plant parts to make biofortification effective is dependent on their solubility and bioavailability to plants. To increase the mineral concentration in edible tissues, without compromising the yield the uptake of mineral nutrients by roots and leaves should be increased. https://soilplantfood.com/reducing-hidden-hunger-by-fertilization-of-edible-plants/
Effecient Exploitation of Mineral Fertilizers
If Fe and Zn are phytoavailable in soil then their concentration is good enough to support dense and healthy vegetation. So there is a need to develop an effective management system by which the soil and fertilizer sources of mineral elements can be exploited in a much better way in the soils with low fertility.
Mobility of Mineral Elements and Nutrients from Soil to Plants
The acquisition of Fe and Zn which have restricted mobility from soil can be improved by the investment of more biomass in the root system. With the spread of a greater number of roots and by the establishment of a greater root system with more root hairs and thin and longer roots these nutrients can be absorbed easily from soil.
Zinc Uptake and Translocation to Plants
Zn is transported by symplast movement from root to xylem and a substantial fraction is transversed by root to xylem via apoplast. Zinc is transported across the plasma membrane of root cells by as Zn-phytosiderophores complex or as Zn2+.
Its transportation is conducted by xylem as Zn2+ or in the form of organic acid complex such as histidine or nicotinamine. So the plant system should be efficient enough for the transportation of Zn from soil to plants and then to the edible tissues. https://soilplantfood.com/role-of-zn-for-life-and-zn-deficiency-across-the-globe/
Improving Zinc and Iron Uptake by Organic Acid Efflux
Zn and Fe acquisition can also be increased by the organic acids efflux by the displacement of cations from binding sites in soil and enzymatic secretions which degrade the organic compounds and cause cationic chelations. Crop rotation and intercropping can also help the plants to attain the mineral elements with low solubility and bioavailability.
Role of Soil Microorganisms and Biodiversity to Improve Mineral Bioavailability
Soil microorganisms increase the volume of soil explored by the plants and also increase the bioavailability of mineral elements from soil. Proper management of mycorrhizal fungi in agricultural lands can increase the mineral concentration in edible plant portions and their delivery to the human diet can be easily increased.
Incoculations with Growth Promoting Rhizobacteria
But in the well-fertilized soils, the yields may be reduced due to symbiotic relationships. Inoculation by growth-promoting rhizobacteria can also increase Fe and Zn acquisition from the soil, increase the mineral concentrations in edible tissues, and enhances the growth and yield by exerting beneficial effects on plant metabolic functions.
Ensuring Normal Supplies of Fertilizers in Soils
Although Fe and Zn are abundant in many soils yet the plants cannot acquire it easily from the soil. Fe and Zn absorption and translocation by plants is the highly coordinated and regulated process for execution of normal supply of Fe for plant growth and development.
Recenet Advanvces for Improving Phytoavailability of Mineral Elements and Nutrients
Recent advancement has studied the absorption and translocation of mineral elements into edible plant parts. However, there is a significant gap to understand the mineral transportation and allocation to edible plant portions. Despite the various efforts by different organizations the potential of crop biofortification is not yet achieved.
Malnutrition universal screening tool is also helpful to identify the malnutrition and problems associated with undernutrition. So precisely controlled studies are required to get success in this perspective. An integrated approach can tackle the malnutrition problem by the development of biofortified food crops. https://soilplantfood.com/threat-level-due-to-micronutrient-malnutrition-and-possible-remediation-measures/