Mycorrhiza: An alliance for the nutrient management in plants

Abstract

Mycorrhizal fungi are a wide ranging group of heterogeneous fungal taxa found to be allied with the roots of over 90% of all plant species. Among several types of mycorrhizal associations, two types are of high ecological and economic importance, i.e. arbuscular and ectotrophic mycorrhizal interactions. We have given a brief account on habitat, host specificity, and structural components of these mycorrhizal groups. An elaborated discussion on mineral absorption, different absorption pathways and the mechanisms involved has been presented in this chapter. Besides improving plant uptake of mineral nutrients already present in soil, many mycorrhizal fungi play a significant role in mobilizing nutrients either from organic substrate, mineral particles or rock surface. Mycorrhizal fungi take on several mechanisms to accomplish the function successfully, such as enhanced absorbing area of plant roots, release of biochemicals and consortium with other microorganisms. In addition to mobilizing nutrients, mycorrhizal fungi also serves as an important C sink in the soil, thus having an important influence on the cycling of these elements. The contributions of each partner in a mycorrhizal association are starting to be revealed by the use of molecular and genetic tools, coupled to high-throughput sequencing and advanced microscopy. Signalling pathways between plants and fungi have now been marked out, and the recognition of various novel nutrient transporters has unveiled some of the cellular processes that are fundamental to the mycorrhizal symbiosis. Different transporters, especially proton-coupled phosphate transporters, have been recognized on both the plant and fungal membranes and contribute to delivering phosphate from fungi to plants. Although much work has been previously done on several aspects of such symbioses, the extent to which they are functionally important in agriculture remains unclear. We are in urgent need to focus on the questions, the answers of which will give the new perspectives on mycorrhizal function.