MOBILIZATION AND UTILIZATION OF STRUCTURAL POTASSIUM IN PHLOGOPITE AS AFFECTED BY PLANT SPECIES

The weathering of a tricotahedral mica (phlogopite, 0.25mm particle size) was investigated in the rhizophere of radish and pak choi. When phlogopite was the sole source of K for the plants under P-deficiency, total K uptake of both plants were significantly higher than that in the normal P conditions, 14.96mgpot-1 versus 11.90mgpot-1 for radish and 12.88mgpot-1 versus 9.57mgpot-1 for pak-choi, and corresponding numbers for net release of mineral K were 6.22mgpot-1 versus 3.72mgpot-1 for radish and 4.32mgpot-1 versus 3.07mgpot-1 for pak choi. The X-diffractometry showed a strong vermiculitization of the phlogopite. In contrast to the normal growth conditions, the degree of vermiculitization was much stronger induced by two species under P deficiency. That suggests that P-starvation led to a significant increase in the amount of K released from mineral K pool. The enhanced mobilization of mineral K might be attributed to the release of organic acids from the plant roots.