Mineral Solubilization and Enhanced Nutrient Uptake
Soil nutrient content is an significant factor that influences the proliferation and bioactivity of plant emergence promoting fungi. Growth promotion has been observed to be greatest in soils where alimentary and/or mineral contentedness is depleted. In several instances it was determined that the limiting factor in crop render was nitrogen. In a field trial on corn, T. harzianum T22-treated plants were perceptibly green and larger than control plants. The number of ears increased from 1447 to 1995 twelve ears/ha and yields increased from 4940 to 7184 kg/ha ( Harman and Bjorkman, 2005 ). The mechanism of this plant growth promotion was deemed to be enhanced uptake of minerals and ammonia water nitrogen by the roots. Research has shown that corn roots colonized by T. harzianum T22 require 40 % less nitrogen fertilizer than corn with roots lacking the fungus. Since there is likely to be restrictions placed on the practice of nitrogen fertilizers in many countries, this attribute shown by many Trichoderma species, may provide farmers with an alternate management exercise to maintain high gear agricultural productivity.
It has besides been reported that T22 can solubilize a range of plant nutrients such as rock phosphate, Fe3+, Cu2+, Mn4+ and Zn0 that may be unavailable to plants in certain soils ( Altomare et al., 1999 ; Harman et al., 2004b ). similarly, T. harzianum 1295-27 was shown to solubilize phosphate and micronutrients that could then be made available for establish growth ( Altomare et al., 1999 ; Whipps, 2001 ). The Trichoderma was shown to be able to reduce insoluble Mn4+ to soluble Mn2+, Cu2+ to Cu1+, and Fe3+ to Fe2+. Benitez et aluminum. ( 2004 ), reported that Trichoderma can produce organic acids such as citric, gluconic or fumaric acids that lower land ph and thereby permit the solubilization of phosphates. When Trichoderma GT2-1-colonized barley grains were incorporated in brown loam dirt, 4-week-old wheat seedlings had enhanced uptake of inorganic minerals in Trichoderma-treated pots compared with the master ( e.g. P 17.13 μg/kg compared with 11.76, K 70.53 μg/g compared with 46.47 ) ( Shivanna et al., 1994, 1995, 1996 ). Trichoderma harzianum 25-92 ( conidium 108 g−1 mixed into the dirt before planting ) importantly increased newly and dry weights of chickpea by 50–63 % and 24–42 %, respectively, and besides increased root length by 25 %. The number of etymon tips increased by 30–95 % and there was a significant increase in chlorophyll content of leaves ( 33.25 spad units compared with 26.6 in the manipulate ). The authors postulated that the underlying mechanism was related to increased uptake of phosphorus and other minerals ( Jyotsna et al., 2008 ).
These examples show that Trichoderma species have across-the-board ranging abilities to solubilize plant nutrients such as phosphorus and micronutrients including copper, iron, manganese and zinc, thereby making them available to plants for enhanced growth capability.