Review on Arbuscular Mycorrhizal Fungi: An Approach to Overcome Drought Adversities in Plants

Abstract

The ever changing environmental conditions have been faced by plants through evolutionary time, among which drought is considered as the most common having an adverse effect on growth and development of the plants which is one of the major constraints on plant productivity worldwide and is expected to increase with climatic changes. The symbiotic relationship between arbuscular mycorrhizal (AM) fungi and the roots of higher plants is widespread in nature. Several ecophysiological studies have demonstrated that AM symbiosis is a key component in helping plants to cope with water stress and in increasing drought resistance by bringing about various changes in the host plant at the morphological level like alterations in root morphology to form a direct pathway of water uptake by extra radical hyphae. Whereas, the physiological mechanisms promoting enhanced drought tolerance of the host plant by AM inoculation include increased photosynthetic rate and nutrient mobilization followed by their rapid uptake under drought conditions. The biochemical mechanisms promoting drought tolerance in AM inoculated plants include accumulation of osmoprotectants like proline, sugars and trehalose and a rapid enhancement in the concentration of different enzymatic and non- enzymatic antioxidants which reduce the risk of free radical attack on the plant cell membrane which has been evidenced in terms of reduced electrolyte leakage and malondialdehyde (MDA) content of drought stressed plant tissues in various studies. Introduction