Antonio Ocaña

Salinity effects on growth analysis and nutrient composition in four grain legumes. Rhizobium symbiosis

Abstract The effect of salinity on growth response, nitrogen (N) fixation and tissue mineral content was investigated for four legumes: faba bean (Vicia faba L), pea (Pisum sativum L), soybean (Glycine max L), and common bean (Phaseolus vulgaris L). Plants were grown in a vermiculite culture system supplied with a N‐free nutrient solution with the addition of 0, 50, and 100 mM NaCl. Plants were harvested at the beginning of the flowering period and the dry weights of shoots and roots and acetylene reduction activity (ARA) were evaluated at the same time plant tissues were analysed for N, potassium (K), calcium (Ca), magnesium (Mg), and sodium (Na) contents. The depressive effect of saline stress on ARA of nodules was directely related to the salt induced decline in dry weight and N content in shoots. Growth inhibition by NaCl treatments was greater for the pea than for other legumes, whereas the soybean was the most salt‐tolerant Saline stress also affected the N content in shoots and roots. In general th...

Effects of salinity on protein and lipopolysaccharide pattern in a salt-tolerant strain of Mesorhizobium ciceri

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 profiles, as well as determining the accumulation of amino acids, glutamate and proline.

Growth and macronutrient contents of faba bean plants: Effects of salinity and nitrate nutrition

Abstract The effects of the interaction between sodium chloride, nitrate, and concentrations on growth and internal ion content of faba bean (Vicia faba L.) plants were studied, to understand the relationship between the above parameters and salt tolerance. Increased salinity substantially reduced the dry weight of roots and shoots and increased the root/shoot biomass ratio. Additional nitrate‐N considerably moderated the salinity effects on these parameters. The promotive effects of nitrate‐N were more pronounced on shoot dry weight. These results suggest that an exogenous supply of nitrate‐N would improve the vegetative growth of V. faba plants by moderating the suppresive effects of salinity. The evolution of the root and shoot content in potassium (K), sodium (Na), magnesium (Mg), calcium (Ca), and nitrogen (N) was monitored during vegetative growth. A high correspondence between total N and Ca content was found. The acquisition of Ca and K in response to salt and nitrate was similar in shoots and roo...

Growth and symbiotic performance of faba bean inoculated with Rhizobium leguminosarum biovar. viciae strains tolerant to salt

Abstract Strain GRA19 of Rhizobium leguminosarum biovar. viciae was found to be tolerant to low levels of salt (50 mM) by comparing growth under stress conditions to that in the absence of stress. Growth and symbiotic N2 fixation (acetylene reduction activity) under saline conditions of the faba bean (Vicia faba L.) cultivar Alameda inoculated with GRA19 were reduced. Salinity significantly decreased shoot and root dry weight, nodule dry weight, and average individual nodule dry weight. Nitrogen fixation was more severely affected by salinity than plant growth and nodulation. Evidence presented here suggests the need for selecting faba bean cultivars that are tolerant to salt stress for breeding programs in order to improve the symbiotic performance of R. leguminosarum biovar. viciae.

Effect of phosphorous on nodulation and nitrogen fixation by Phaseolus vulgaris

The impact of phosphorous on plant growth and symbiotic N2 fixation in common bean (P. vulgaris) plants was investigated. Plants inoculated with R. tropici CIAT899 were grown with six P dosage. The P increased plant growth, nodule mass, nitrogenase activity (ARA) and P content, and decreased amino acids and total soluble sugars in the vegetative organs (root, shoot and nodule). The root growth proved less sensitive to P deficiency than did shoot growth, and the leaf area was inhibited at low P. The optimal amount for this symbiosis was 1.5 mM P, this treatment augmented nodule ARA some 20-fold and plant ARA some 70-fold with respect to control.

NITROGEN FIXATION AND CARBON METABOLISM IN VICIA FABA ROOT NODULES OVER ONTOGENY

The evolution of growth, nodulation, nitrogen fixation, and activities of root-nodule enzymes related to sucrose breakdown (sucrose synthase, alkaline invertase), pentose phosphate pathway (glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase), malate dehydrogenase, phosphoenolpyruvate carboxylase, and NADP-dependent isocitrate dehydrogenase, were followed over the complete life-cycle of faba bean in a growth chamber. The aim was to study the ontogenic changes of these parameters to obtain information on the carbon metabolism in nodules of Vicia faba , an amide-exporting legume. The maximum values of the relative growth rate and the specific acetylene-reducing activity were registered during the vegetative period. At pod-filling, the specific and total acetylene-reducing activity per plant declined in parallel with the enzyme activities of carbon metabolism. Contrary to reports for other legume species, in V. faba root nodule activity of sucrose synthase exceeded alkaline invertase values by 2-fold or more during the vegetative period. The activity of the two enzymes was similar at flowering and pod formation. The enzymes of carbon metabolism registered two maxima, one before and one after a trough (day 32), which marked the change from the vegetative to the reproductive period.

Comparative Study of Rhizobium Isogenic Strains in Symbiosis with Phaseolus Vulgaris under Saline Stress

Salinity of soils may adversely affect the formation of effective symbioses between Rhizobium and Phaseolus vulgaris. This legume is considered very sensitive to salinity, whereas there is a great variability of responses to different NaCl concentrations by free-living Rhizobium. Whereas many studies have used tolerant and non-tolerant strains to reveal the importance of Rhizobium tolerance to NaCl for the outcome of the symbiosis, few studies have made use of isogenic strains to actually verify this point.