<b>Effects of Inoculation and Fertilizers on</b>Desmodium Intortum<b>at Serere, Uganda</b>

Wendt, W.

doi:10.1080/00128325.1971.11662479

Cited by 6 publications

(1 citation statement)

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“…Colonization of the rhizosphere and nodule initiation are growth rate dependent (4), and growth reduction by low levels of P could be critical. A beneficial effect of P on nodulation in greenhouse and field trials has been shown with several species and is probably not due entirely to increased plant vigor (5,12).…”

Section: Discussionmentioning

confidence: 96%

Phosphate Nutrition of Rhizobium spp

Beck

Munns

1984

Appl Environ Microbiol

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This study was conducted to determine the behavior of 40 strains from six species of Rhizobium in liquid defined media containing orthophosphate at levels likely to be encountered naturally, ranging from the high concentrations expected in nodules and artificial media to the low concentrations of soil solutions. Storage capacity in strains with high levels (2 mM) of P and ability to utilize this stored P for growth after transfer to low levels (0.06 F.M) of P varied with each strain. Storage varied from about 1 to 2% P (dry weight) for all strains, with the number of generations supported dependent on the quantity of P stored and on the utilization efficiency. The ability to store P at high levels is probably less important than the uptake and utilization efficiency of P supplied at low levels. Strains varied greatly in tolerance to low levels of P maintained in solution by an iron oxide buffering system. Differences in growth rate at low levels of P were large enough to be agronomically important. Successful rhizobia must be able to spread and persist in soils and rapidly colonize the host root (8) under extremely diverse P environments. The P gradient from rhizosphere to nodule may be as much as five orders of magnitude (1). Nodule tissue, which may contain concentrations of 10-4 to 10-2 M dissolved Pi (6), probably provides the same luxury P conditions as conventional laboratory media. Soil solutions commonly range from 10-5 to 10-7 M P in solution (9), and rhizospheres may reach concentrations of 10-8 M P (7). To deal with this variation, a P-efficient strain has three mechanisms: (i) ability to store large quantities of P, (ii) utilization efficiency of internal P, and (iii) uptake efficiency at low external concentrations. Mechanisms (i) and (ii) would be most important when rhizobia move from nodules or artificial media into soil. Mechanism (iii) would be most important for long-term growth and persistence in the soil. Recent work on the performance of Rhizobium japonicum under various phosphate regimes has shown considerable strain-to-strain differences in growth at low levels of P (2, 3). The purpose of this work was to determine the scope of strain variability in response to P stress.

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Section: Discussionmentioning

confidence: 96%