Soil microbe mediated zinc uptake in soy bean: A review

Abstract

The availability of the nutrients to plants depends on the inherent and derived mechanisms to access these nutrients. More attention has been given to macronutrients which are more accessible, easily replenished and utilized by plants for growth. Macronutrients are crucial and improve yield but compromise quality of the crop, leading to a phenomenon termed as 'the empty harvest'. The soil nutrient cycle processes are mediated by both biotic and abiotic factors with nutrients available in gaseous and in soil solution. Roots play a major role in the uptake of nutrients from the soils. The rhizosphere and rhizoplane of roots is rich with soil biota, amongst them microorganisms, which play a major role in nutrient availability, accessibility and translocation. Nutrient uptake can be enhanced by microorganisms through direct and indirect processes. There is sufficient evidence for nitrogen, phosphorus and micronutrient uptake and availability mediated by microorganisms. The uptake of micronutrients such as zinc depends on that of phosphorus. A large proportion of the world population has shortcomings from a nutrition perspective of being low in zinc and other essential nutrients. There is widespread zinc deficiency in diets causing zinc deficiency diseases. This is combated through pharmaceutical supplements, industrial fortification and most recently biofortification through agriculture. Biofortification has taken highest priority in guaranteeing quality of crops. However, soils exploitation for micronutrients can be enhanced by biological interventions to guarantee adequate uptake by plants and improve crop quality. Microbiological interventions that increase root growth, the availability and transfer of Zn from soil to plants are, therefore, crucial. This article reviews promising microbiological interventions for zinc uptake and gives an overview of microbiological interventions for nitrogen and for phosphorus that are directly linked with zinc uptake. Soya bean is taken as a model plant in this review to elucidate the mechanism of Zn mobilization.