The impact of phosphorous nutrition on plant growth, symbiotic N 2 fixation, ammonium assimilation, carbohydrate and aminoacid accumulation, as well as on nitrogen, phosphorus and ATP content in tissues in common bean (Phaseolus vulgaris) plants was investigated. Plants inoculated with Rhizobium tropici CIAT899 were grown in Leonard jars under controlled conditions, with P-deficient (0 and 0.1 mM), P-medium (0.5, 1 and 1.5 mM) and P-high (2mM) conditions in a N-free nutrient solution. The P application, increased leaf area, whole plant DW (67%), nodule biomass (4-fold), and shoot and root P content (4-and 6-fold, respectively) in plant harvested at the onset of flowering (28-days-old). However, P treatments decreased the total soluble sugar and amino acid content in vegetative organs (leaf, root and nodules). The root growth proved less sensitive to P deficiency than did shoot growth, and the leaf area was significantly reduced at low P-application. The absence of a relationship between shoot N content, and P levels in the growth medium could indicate that nitrogen fixation requires more P than does plant growth. The optimal amount for the P. vulgaris-R. tropici CIAT899 symbiosis was 1.5 mM P, this treatment augmented nodule-ARA 20-fold, and ARA per plant 70-fold compared with plants without P application.

utes is more a consequence of damage produced by salt stress than of a protective strategy. Plants of chick-pea (Cicer arietinum L. cv. ILC1919) inoculated with Mesorhizobium ciceri strain ch-191 Key words: Chick-pea, salt stress, nitrogen fixation, photowere grown in a controlled environmental chamber, synthesis, ammonium assimilation. and were administered salt (0, 50, 75, and 100 mM NaCl) during the vegetative period. Four harvests (4, 7, 11, and 14 d after treatment) were analysed. The

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Aims: To characterize the physiological and metabolic responses of Mesorhizobium ciceri strain ch-191 to salt stress, investigating the changes induced by salinity in protein and lipopolysaccharide pro®les, as well as determining the accumulation of amino acids, glutamate and proline. Methods and Results: Strain ch-191 of M. ciceri was grown with different NaCl concentrations. Protein and lipopolysaccharide patterns were determined by electrophoresis. The strain ch-191 tolerated up to 200 mmol l )1 NaCl, although higher salt dosages limited its growth and induced changes in the protein pro®le. The most noteworthy change in the LPS-I pattern was the decrease in the slowest band and the appearance of an intermediate mobility band. The accumulation of proline in response to salt stress surpassed that of glutamate. Conclusions: The protein pro®le showed major alterations at salinity levels which inhibited growth. However, the alterations in the LPS pro®le and accumulation of compatible solutes were evident from the lowest levels, suggesting that these changes may constitute adaptative responses to salt, allowing normal growth. Signi®cance and Impact of the Study: The selection and characterization of salt-tolerant strains, which also show ef®cient symbiotic performance under salinity, may constitute a strategy for improving Cicer arietinum±Mesorhizobium ciceri symbiosis in adverse environments.