Effect of plant nutrient supply on nodule effectiveness and rhizobium strain competition for nodulation ofLotus pedunculatus
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- Pankhurst, C.E. Plant Soil (1981) 60: 325. doi:10.1007/BF02149629
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The effect of nutrient supply on nodule formation and competition between Rhizobium strains for nodulation ofLotus pedunculatus was studied. Limiting plant growth by decreasing the supply of nutrients in an otherwise nitrogen-free medium, increased the size but decreased the number and the nitrogenase activity of nodules formed by a fast-growing strain of Lotus Rhizobium (NZP2037). In contrast decreasing nutrient supply caused only a small decline in the size, number and nitrogenase activity of nodules formed by a slow-growing strain (CC814s). Providing small quantities of NH4NO3 (50 to 250 μg N) to plants grown with a normal supply of other nutrients stimulated nodule development by both Rhizobium strains and increased the nitrogenase activity of the NZP2037 nodules. Differences in the level of effectiveness (nitrogen-fixing ability) of nodules formed by different Rhizobium strains on plants grown with a normal supply of nutrients were less apparent when the plants were grown with decreased nutrient supply or when the plants were supplied with low levels of inorganic N.
Inter-strain competition for nodulation ofL. pedunculatus between the highly effective slow-growing strain CC814s and 7 other fast- and slow-growing strains, showed CC814s to form 42 to 100% of the nodules in all associations. The greater nodulating competitiveness of strain CC814s prevailed despite changes in the nutrient supply to the host plant. A tendency was observed for partially effective Lotus Rhizobium strains to become more competitive in nodule formation when plant growth was supplemented with low levels of inorganic nitrogen.