Maria del Pilar Cordovilla

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...

Influence of host genotypes on growth, symbiotic performance and nitrogen assimilation in faba bean (Vicia faba L.) under salt stress

Fifteen genotypes of faba bean (Vicia faba L.) were inoculated with salt-tolerant Rhizobium leguminosarum biovar. viciae strain GRA 19 in solution culture with 0 (control) and 75 mM NaCl added immediately after transplanting. Genotypes varied in their tolerance of high levels of NaCl. Physiological parameters (dry weight of shoot and root, number and dry weight of nodules) were not affected by salinity in lines VF46, VF64 and VF112. Faba bean line VF60 was sensitive to salt stress. Host tolearance appeared to be a major requisite for nodulation and N2 fixation under salt stress. Tolerant line VF112 sustained nitrogen fixation under saline conditions. Activity of the ammonium assimilation enzymes glutamine synthetase and glutamate synthase, and soluble protein content, were reduced by salinity in all genotypes tested. Evidence presented here suggests a need to select faba bean genotypes that are tolerant to salt stress.

Effects of NaCl on growth and nitrogen fixation and assimilation of inoculated and KNO3 fertilized Vicia faba L. and Pisum sativum L. plants

Faba bean (Vicia faba L. var. minor cv. Alborea) and pea (Pisum sativum L. cv. Lincoln) plants, inoculated with Rhizobium leguminosarum biovar. viciae strain GRA19, were treated with salt (100 mM NaCl) and/or nitrate (8 mM KNO3) to test whether plants grown with inorganic-nitrogen are more tolerant to salinity than plants entirely reliant upon fixed nitrogen. According to the growth inhibition recorded, pea plants dependent on dinitrogen fixation proved more tolerant to salt stress than those N-fertilized, in contrast to results obtained for faba bean plants. This study therefore confirms that plants dependent on nitrogen fixation are not always more sensitive to salinity than are N-fertilized plants. Nitrate addition did not reduce the specific nitrogenase activity in pea, but did in faba bean. However, nodulation was inhibited in both legumes. The specific nitrogenase activity was more affected by salt treatment in N-fertilized plants for both legumes. The activity of the enzymes mediating ammonium assimilation in nodules (GS, NADH-GOGAT) was inhibited by salt stress both in N-fixing and in N-fertilized pea and faba bean plants.

Rhizobium Strain Effects on the Growth and Nitrogen Assimilation in Pisum sativum and Vicia faba Plant Growth under Salt Stress

Summary The present study was designed to investigate the differences in responses to salt stress between pea (Pisum sativum) and faba bean (Vicia faba) plants inoculated with the same salt-tolerant (GRA19) or saltsensitive (GRL19) Rhizobium leguminosarum strain. After 12 days of growth, the nutrient solution was supplemented progressively with salt until reaching the final concentration (100 mmol/L NaCl) on day 18. This level of NaCl was maintained until harvesting at the beginning of flowering. The growth of pea plants was reduced only in plants inoculated with GRL 19 strain, while the growth of faba bean plants was inhibited regardless of the Rhizobium strain used. Under salt stress, pea plants showed higher levels of nodule mass and nitrogen fixation than faba bean plants. In nodules, nitrogenase and glutamate synthase activities proved more sensitive to salinity than did glutamine synthetase.

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 Organic Agriculture and Soil Forming Factors on Soil Quality and Physiology of Olive Trees

We studied the soil quality and the response of olive trees (Olea europaea L.) to organic agriculture. Three factors were considered: management (organic and conventional), soil parent material (calcareous colluvium and marl), and slope (upper, middle, and lower). An increase in soil quality was observed in organic plots and colluvial soils. Moreover, we noticed an increase in the assimilation rate of CO2 and lower water deficit in leaves of trees under organic management, which are of great importance in semi-arid environments. These results indicate a relationship between soil quality and physiological responses of olive trees that should be taken into account by agronomists and policymakers.

Partial purification and characterization of NADH-glutamate synthase from faba bean (Vicia faba) root nodules.

The NADH-dependent glutamate synthase (EC 1.4.1.14) from the plant fraction of N2-fixing faba bean (Vicia faba) nodules has been purified 74-fold to a specific activity of about 3 mmol min 1 mg protein 1 with a final yield of 32%. The NADH-GOGAT activity was associated with a single form of the enzyme that behaved as a monomeric protein with a subunit molecular weight of 195 kDa and a native molecular weight from 222 to 236 kDa estimated by gel filtration or PAGE, respectively. The NADH-GOGAT band on SDS-PAGE was cut out and used to produce antibodies. Western blots of SDS-PAGE of crude nodule proteins revealed a 195 kDa polypeptide in root extracts but not in those of leaves or bacteroids. The antiserum also cross-reacted with a polypeptide of camparable molecular weight (195 kDa) from both amide and ureide transporting species legume nodules, indicating that some antigenic epitopes have been conserved between nodule NADH-GOGAT of different species.