Ecology of arbuscular mycorrhizal fungi

Abstract

It is a well-established fact that arbuscular mycorrhizal (AM) fungi improve plant growth. The main effect of AM fungi in improving plant growth is through improved uptake of nutrients, especially phosphorus, which is due to exploration by the external hyphae of the soil beyond the root hair and phosphorus depletion zone. Fungal hyphae are also known to absorb phosphorus from lower concentrations compared to non-mycorrhizal roots. They also improve the uptake of minor elements like Zn, Cu, etc., and water. They also produce plnt hormones, increase the activity of beneficial soil organisms in the root zone and reduce the severity of disease caused by root pathogens. Thus the benefits the plant derives from mycorrhizal inoculation seem to be enormous. The ecology of these fungi, in tropics, is not fully understood. These fungi are geographically ubiquitous. An explanation for their remarkably wide spread distribution is that these fungi were disseminated inter-continentally prior to continental drift. Further, these fungi can grow actively, to a limited extent, spending their own energy. Passive dissemination can occur through biotic agents like earthworms, ants, wasps, etc. and abiotic agents like wind, water, etc. The various agricultural practices are known to influence the occurrence of these fungi qualitatively and quantitatively. The approaches in understanding the occurrence, dissemination, survival and persistence of these fungi in tropics is discussed.