Morphological and Symbiotic Root Modifications for Mineral Acquisition from Nutrient-Poor Soils

Abstract

Plants have the ability to form vast root systems with lengths measuring up to several kilometers and branch roots numbering in millions. These expansive root systems provide plants with a large surface area for water and nutrient uptake from the surrounding soil. Roots also have further equally important functions to fulfil such as vegetative reproduction, hormone biosynthesis, photoassimilate storage, and the establishment of symbiotic relationships with microorganisms. Root systems have evolved several adaptations to aid them in maximizing nutrient uptake. These adaptations can be morphological such as changes in the root architecture or formation of cluster roots or may be symbiotic associations with mycorrhizae or nitrogen-fixing bacteria. Improvement of nutrient acquisition and use by plants is imperative for economic, humanitarian, and environmental reasons, and a better understanding of the processes governing root adaptations would enable us to adapt fertilizer and pesticide programs. In this chapter, we will focus on both morphological (cluster roots) and symbiotic root adaptations (associations with ectomycorrhizae, arbuscular mycorrhizae, and nitrogen-fixing bacteria) to soil nutrient deficiencies.