Starch contents in alfalfa nodules with effective and ineffective symbiotic responses

Rhizobium meliloti auxotrophic and ineffective mutants induced nodules containing: 9.35 microg of starch per mg of the plant tissue (wet wt.) in the case of strain his-240 which did not occupy host cells and 2.7 to 3.5 microg of starch in strains: arg-55, cys-243, cys-244 and cys-246 which occupied part of the host cells (bacteroidal zone). Nodules induced by prototrophic and effective strains i.e. L5-30 (wilde type) and prototrophic transductants of arg-55 and his-240 mutants contained 0.13 to 0.06 microg of starch per mg of the plant tissue (wet wt.). These results indicate that iodometric estimation of starch contents in the nodules may by used as a simple test showing the quantity of plant cells infected by rhizobia.