Altomare et al.(1999) found that T. harzianum strain T22 could produce soluble forms of manganese, metallic zinc and calcium phosphatein vitro, and also that the fungus produced metabolites that reduced ferric iron (III) to the ferrous form readily assimilated by plants. Studies by Jalal et al. (1986, 1987) showed that T. virensproduces the siderophores mono- and di-hydroxamates as mechanisms of Fe III chelation. According to these investigators, the conversion of metal oxides to soluble forms by
Trichodermaspp.