HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Cassman, K. G. Articles by Beck, D. P. Search for Related Content PubMed Articles by Cassman, K. G. Articles by Beck, D. P. Agricola Articles by Cassman, K. G. Articles by Beck, D. P.

Growth of Rhizobium Strains at Low Concentrations of Phosphate¹

ABSTRACT

A technique was developed for assessing effects of P on growth, in defined liquid media at orthophosphate concentrations comparable to those in soil solutions. Phosphate was supplied in sorbed form on iron oxide (goethite) separated from the liquid medium by a dialysis membrane. Depending on the level of sorbed P, concentrations in solution were established in the range 0.05 to 30 µM. Analytical monitoring indicated that concentrations above 0.1 µM were buffered against depletion by cell growth until populations exceeded 10⁶ cells per ml.

The system was used to compare P responses of seven strains of soybean and cowpea rhizobia grown from P-depleted inocula at initial densities of 10⁴ cells per ml. Two P-efficient strains grew as rapidly at the lowest concentration (0.05 µM) as in a control medium at 2,000 µM. They would seem unlikely to be P-limited in the field. Other strains were less efficient. One strain could barely grow at P concentration below 1 µM; this strain could have difficulty colonizing P-deficient soils or normal rhizospheres.

Large differences in tolerance to low P among strains may be agronomically important. The technique could be simplified for routine screening of strains; and its operation at submicromolar concentrations could be improved for research on nutrition and requirements of P-efficient rhizobia and other organisms.

¹ Contribution from Dep. of Land, Air, and Water Resources, Univ. of California, Davis CA 95616.

² Postgraduate Research Scientist, Professor, and Graduate Research Assistant.

Received for publication August 22, 1980. Accepted for publication December 12, 1980.

This article has been cited by other articles:

				S. D. Bardin, R. T. Voegele, and T. M. Finan Phosphate Assimilation in Rhizobium (Sinorhizobium) meliloti: Identification of a pit-Like Gene J. Bacteriol., August 15, 1998; 180(16): 4219 - 4226. [Abstract] [Full Text]