Effect of pH on the growth of Medicago sativa and Lotus tenuis

CORREA OLGA SUSANA; ARANDA RICKERT ADRIANA; BARNEIX ATILIO

Lotus Newsletter

P.R. Beuselinck USDA-Agricultural Research Service

Lugar: Columbia; Año: 1995 vol. 16 p. 25 - 26

0316-0106

Low soil pH limits the legume culture by effects on the plant, on the bacterium and on nodule formation and function. The purpose of this work was to determine the effect of pH on the growth of Medicago sativa and Lotus tenuis uninoculated and inoculated with appropriate rhizobia. Rhizobium meliloti strains multiplied readily at high pH values, but multiplication failed at low pH values. In contrast, R. loti strains showed no significative differences in growth at both pH. These results indicate that in liquid culture, loti rhizobia are tolerant to acidity at least at pH 4.0, whereas meliloti rhizobia are significantly affected by low pH stress. On the other hand, the growth of M. sativa uninoculated plants was markedly affected by low pH conditions. For the plants inoculated with their symbiotic bacteria the growth decreased at pH values bellow 6.0. In contrast, uninoculated L. tenuis showed no significant difference in its growth at all pH assayed. Under inoculated conditions, the growth of L. tenuis depended upon the strain used. The highest tolerant strain grew at pH 4.0 or 7.0 without significative differences. In conclusion, in alfalfa-R. meliloti symbiosis both the plant and the bacteria show a sensitivity to low pH, whereas in the L. tenuis-R. loti symbiosis, both plant and bacteria seem to have developed acid pH tolerance.