| Summary: | Penicillium bilaii (ATCC strain no. 20851) is a rhizospheric fungus sold commercially in western Canada to improve phosphate (P) uptake of various crops. The objective of our research was to determine if the stimulation of P uptake in pea (Pisum sativum L.) treated with P. bilaii is the result of increased root surface area for P absorption. In addition, we examined the effect of P. bilaii and P concentration on root architecture of pea. Under controlled conditions, treatment of peas with P. bilaii resulted in increased root and shoot P concentration and accumulation when no P fertilizer was added, or when rock phosphate fertilizer was applied. This stimulation of P uptake was not a result of increased root growth. Inoculation with P. bilaii resulted in a reduction in root length and had no effect on P concentration, accumulation, or dry matter effect. Penicillium bilaii inoculated plants, when no P fertilizer was added, had greater mean root diameters. Under field conditions, when no P fertilizer was applied, P. bilaii treatment resulted in a 48% increase in upper root length, and roots were significantly finer in the sample core (an area 15 cm in depth, and 6.5 cm in diameter around the stem base). This increase in root length may have contributed to the 13% increase in shoot P concentration of inoculated plants. It proposed that P. bilaii increased the availability of soi P in the sampled area, resulting in the proliferation of plant roots. Under controlled conditions, using growth pouches, P concentration in the nutrient solution had a greater effect on branching patterns of pea than P. bilaii. P. bilaii treatment resulted in a reduction in root length, and increased average root diameter at the intermediate P levels. (Abstract shortened by UMI.)
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