UPTAKE AND TRANSPORT OF PHOSPHORUS BY AGROSTIS-CAPILLARIS SEEDLINGS FROM RAPIDLY HYDROLYZED ORGANIC SOURCES EXTRACTED FROM P-32 LABELED BACTERIAL CULTURES

Cultures of the soil bacterium Serratia liquifaciens grimesii were gro wn with P-32 labelled phosphate, to produce a uniformly P-32 labelled source of microbial P. Extracts of the bacteria were prepared by sonic ation, dialysis and filtration to provide st clear sterile solution wh ich was characterised in terms of dissolved organic and condensed P (D OP and DCP) and molecular weight range. The extract was used as a sour ce of P to Agrostis capillaris L. seedlings in nutrient solution from which orthophosphate was omitted. In a time course experiment, root su rface phosphatase activity increased as soon as extract was added to t he root medium, DOP was rapidly hydrolysed and orthophosphate concentr ation increased rapidly. These processes were complete within about 8 h, after which phosphatase activity fell to its original level, and th e plants absorbed molybdate reactive P from the nutrient solution so t hat it reached its original concentration over 48 h. DCP concentration s did not change significantly throughout the experiment. This work cl early demonstrated that DOP but not DCP, as a component of a bacterial extract produced by a relatively straightforward method, was quickly hydrolysed and the P made available for plant uptake.