3. Discussion
T. asperellum Q1 agents may be equipped with multiple mechanisms for plant growth promotion under salt stress because it possesses a variety of plant growth-promoting
properties, such as phosphate solubilization. The soluble P content in the medium depends on the solubilization of insoluble phosphate and the consumption of the solubilized
phosphate by the strain for its growth. In solubilizing processes of TCP and DCP, which are common forms of
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in pH accompanied with the release of phosphorous from DCP and TCP in culture supernatants. Moreover, three organic acids (oxalic acid, formic acid and lactic acid) were
detected in culture broth by the high performance liquid chromatography (HPLC) (data not shown). Although the peak of the reduction in pH was not coincided with the peak
of solubilization of phosphorus source (maybe it was caused by different growth rates of T. asperellum Q1 with various forms of phosphates), it still could be concluded that the solubilization of TCP and DCP was intimately linked to some organic acids produced by T. asperellum Q1. Extensive researches
have demonstrated that organic acids produced by bacteria and parts of fungal species such as Penicillium spp. are vital to solubilization of insoluble inorganic phosphates(Rashid et al. 2004). Moreover, the same three organic acids were also detected in culture broth inoculated with
another T. asperellum_ __ ______ ___ ___ ___ ____ ______
have just been published recently (Zhao and Wang 2014).
Phytate is the major organic phosphorus compounds
in soil which is not readily available to plants as a source
of phosphorus. To make this form of P available for plant
nutrition, it must be hydrolyzed to inorganic P. Mineralization
of most organic phosphorous compounds is carried