ABSTRACT
Approximately, 46, 14 and 40% fungi are free-living decomposers, symbionts and parasites, respectively. Unlike animals, fungi digest their food by external digestion. The need for economization of externally released digestive enzymes has driven 54% fungi toward endosymbiosis and endoparasitism. On land, the estimated quanta of decomposed plants amounts to 38 t carbon/ha/yr . The standing biomass of decomposing fungi constitute 1,070 g/m2, in comparison to 270, 80 and 11 g/m2 for bacteria, earthworms and protozoans, respectively. The ability of fungi to sustain decomposition at water potential on such low water containing substrates is far higher at – 4.0 Mpa, against – 4.0 and – 1.5 Mpa for bacteria and protozoans. As symbionts with > 99% terrestrial plants, the arbuscular mycorrhizas enhance direct water uptake along with minerals and indirect uptake of nitrogen. Parasitism is more prevalent among the 23,375 speciose Basidiomycota than among the 78,532 speciose Ascomycota. However, the latter have developed an immune system in 4,570 animal parasitic species, as compared to only 350 animal parasitic species in the former.
