No abstract

The utility of spraying some known N2-fixing microorganisms on rice leaves grown both in N-less sand culture and under field conditions was examined. The effect was compared with that of spraying a phyllosphere Nz-fixing isolate of Klebsiella, KUPBR 2, and application of nitrogenous fertilizers. All the growth parameters studied including dry weight and N-content were enhanced. Under field conditions number of tillers was increased by 26')/0 with Klebsiella pneumoniae M 5al and by 65')~, with Aphanothece. The dry weight of the plants was enhanced by 61-119%. The yield per 10 m 2 was almost doubled with Aphanothece, Beijerinckia 8007, Mycobacterium flavum, K. pneumoniae M5al and KUPBR 2. The increases observed with Streptomyces sp. G 12 though less spectacular was significant at 1~s level with respect to several growth parameters. K. pneumoniae M5al, M.flavum and Streptomyces sp. G 12 exhibited nitrogenase activity both in laboratory culture and in association with rice plants.

Soya bean, mung bean, Bengal gram and lentil grown in nitrogenless sand culture and sprayed with suspensions of different strains of Rhizobium showed increases in dry weight, chlorophyll and N-content. In a few cases the performance of Rhizobium applied to the phyllosphere was almost as good as a seed inoculation treatment. The beneficial effect of spraying Rhizobium strains was independent of the specificity of cross-inoculation groups. Nitrogenase activity as indicated by acetylene reduction by the Rhizobiitm-le&f association varied between 460 and 723 nniol/g leaf/h.

SUMMARYThe nature of the ectosymbiotic association between Rhizobium and such legume leaves as Bengal gram and mung bean was investigated using radioactively labelled compounds. About 8% of the 14CO2 fixed photosynthetically in the 70% ethanol soluble fraction was leached out within 1 h of contact with water. The 14C-compounds leached out include sucrose, serine glycine, glutamic acid, malate, alanine and succinate. A part of the 14C-activity was incorporated by Rhizobium cells sprayed on leaves. Association with rhizobia increased the rate of photosynthesis and leaching by 129–240% and 134–281%, respectively. Bacterial metabolites are translocated along the midribs and veins to different plant parts. The beneficial effects are not restricted to members of the same cross-inoculation group.

SUMMARYSoya bean, Bengal gram and lentil plants were grown under field conditions and sprayed with suspensions of different strains ofRhizobium. Irrespective of crossinoculation groups beneficial effects were similar to those observed in nitrogen-free sand culture with respect to dry weight, chlorophyll and N contents. The beneficial effects of sprayingRhizobiumstrains compared favourably with seed treatment by appropriateRhizobiumstrains and application of urea. Both an ineffective strain and a mutant strain ofR. japonicumshowed similar beneficial effects. Acetylene reduction by theRhizobium-leafassociation ranged from 497 to 890 nmol/g leaf/h. The ectosymbiotic association ofRhizobiumwith foliage of legumes, thus, may meet to a large extent the nitrogen requirement of such plants.