RELATIONSHIPS BETWEEN MYCORRHIZAE AND ROOT HAIRS

Abstract

Mycorrhizal extraradical hyphae and root hairs coexist on the root surface and are responsible for water and nutrient absorption from the soil. Root hairs generally are a preferential adhesion point colonized by ectomycorrhizal hyphae, and eventually are suppressed or incorporated in the fungal mantle. However, arbuscular mycorrhizal (AM) fungi occasionally penetrate root hairs of host plants. A root hair feature is not a reliable indicator of mycorrhizal dependency in plants, as well a mycorrhizal growth response. AM fungal inoculation has increased and reduced effects on root-hair growth (including length, density, and diameter), which is related mainly with auxin and some potential factors (i.e. P and glucose). Such AM effects on root hair can be regulated by substrate P and soil water levels. Root hairs have the preponderant role in soil adhesion under sand or semi-arid conditions, in comparison with extraradical hyphae. In addition, root hairs have higher effectiveness in P acquisition and utilization in biomass production than extraradical hyphae under P-deficient conditions. Under drought stress, AM fungi almost replace the absence of root hairs to enhance plant tolerance through alternative pathways.