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Manuel Sánchez-Díaz

Bio: Manuel Sánchez-Díaz is an academic researcher from University of Navarra. The author has contributed to research in topics: Photosynthesis & Medicine. The author has an hindex of 45, co-authored 102 publications receiving 4879 citations. Previous affiliations of Manuel Sánchez-Díaz include Spanish National Research Council.


Papers
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Journal ArticleDOI
TL;DR: The significantly lower contents of H( 2)O(2) and malondialdehyde in nodules with respect to those in leaves reveal that the above-mentioned bacteroid and cytosol enzymes act in an efficient and combined manner to preserve integrity of nodule cell membranes and to keep leghemoglobin active.
Abstract: Leaves and nodules (bacteroids and cytosol) of alfalfa (Medicago sativa L. cv Aragon) plants inoculated with Rhizobium meliloti strain 102F51 have been analyzed for the presence of the enzymes superoxide dismutase (SOD, EC 1.15.1.1), catalase (EC 1.11.1.6), and peroxidase (EC 1.11.1.7). All three fractions investigated (leaves, bacteroids, and nodular cytosol) show Cu,Zn-SOD activity. Besides, the bacteroids and cytosol of nodules possess CN−-insensitive SOD activities. Studies of SOD inactivation with H2O2 indicate that, very likely, a Mn-SOD is present in the bacteroids, and suggest that the cytosol contain both Mn-SOD and Fe-SOD. Bacteroids show high catalase activity but lack peroxidase. By contrast, the nodule cytosol exhibits an elevated peroxidase activity as compared with the foliar tissue; this activity was completely inhibited by 50 to 100 micromolar KCN. The significantly lower contents of H2O2 and malondialdehyde (a product of lipid peroxidation) in nodules with respect to those in leaves reveal that the above-mentioned bacteroid and cytosol enzymes act in an efficient and combined manner to preserve integrity of nodule cell membranes and to keep leghemoglobin active.

234 citations

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TL;DR: In this paper, a field experiment was carried out from 1998 to 2001, to investigate the effects of sewage sludge application to barley (Hordeum vulgare L.) var. Sunrise crops on the relationships between plant physiology and some soil properties.

192 citations

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TL;DR: The relationships found between these gas exchange parameters and the hormone concentrations in stressed alfalfa tissues suggest that microsymbionts have an important role in the control of gas exchange of the host plant through hormone production in roots and the ABA/cytokinin balance in leaves.
Abstract: The beneficial effect of mycorrhization on photosynthetic gas exchange of host plants under drought conditions could be related to factors other than changes in phosphorus nutrition and water uptake Our objective was to study the influence of drought on phytohormones and gas exchange parameters in Medicago sativa L cv Arag6n associated with or in the absence of arbuscular mycorrhizal (AM) fungi and/or nitrogen-fixing bacteria Four treatments were used: (1) plants inoculated with Glomus fasciculatum (Taxter sensu Gerd) Gerdemann and Trappe and Rhizobium meliloti 102 F51 strain (MR); (2) plants inoculated with only Rhizobium (R); (3) plants inoculated with only mycorrhizae (M); and (4) non-inoculated plants (N) When endophytes were well established, treatments received different levels of phosphorus and nitrogen in the nutrient solution in order to obtain plants similar in size Sixty days after planting, plants were subjected to two cycles of drought and recovery Midday leaf water potential (Ψ), CO 2 exchange rate (CER), leaf conductance (g w ) and transpiration (T), as well as leaf and root abscisic acid (ABA) and cytokinin concentrations were measured after the second drought period Gas exchange parameters were determined by infrared gas analysis Cytokinins and ABA levels in tissues were analysed by ELISA and HPLC, respectively Nodulated R and MR plants had the lowest ABA concentrations in roots under well-watered conditions Water stress increased ABA concentrations in leaves of N, R and MR plants, while ABA concentration in M plants did not change The highest production of ABA under water deficit was in the roots of non-mycorrhizal plants The ratio of ABA to cytokinin concentration strongly increased in leaves and roots of non-mycorrhizal plants under drought By contrast, this ratio was lowered in roots of M plants and remained unchanged in leaves and roots of MR plants when stress was imposed The highest leaf conductances and transpirational fluxes under well-watered conditions were those of nitrogen-fixing R and MR plants, but these results were not impaired with increased CO 2 exchange rates Photosynthesis, leaf conductance and transpiration rates decreased in all treatments when stress was imposed, with the strongest decrease occurring in non-mycorrhizal plants The relationships found between these gas exchange parameters and the hormone concentrations in stressed alfalfa tissues suggest that microsymbionts have an important role in the control of gas exchange of the host plant through hormone production in roots and the ABA/cytokinin balance in leaves The most relevant effect of mycorrhizal fungi was observed under drought conditions

156 citations

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TL;DR: Although total leaf respiration was not affected by the chilling treatment in either of the two cultivars, electron partitioning to the alternative pathway was significantly increased in the more stressed chilling-sensitive cv Penjalinan, suggesting that increased activity of theAlternative pathway is not related to the plant tolerance to chilling.
Abstract: Chilling effects on respiration during the recovery period were studied in two maize (Zea mays L.) cultivars differing in their tolerance to chilling: Penjalinan, a chilling-sensitive cultivar, and Z7, a chilling-tolerant cultivar. Both cultivars were exposed to 5°C for 5 d, after which measurements were taken at 25°C. Chlorophyll fluorescence analysis in dark-adapted leaves showed less damage in cv Z7 than in cv Penjalinan during recovery from the chilling treatment. Studies of the electron partitioning between the cytochrome and the alternative respiratory pathways during chilling recovery using the oxygen isotope fractionation technique showed that, although total leaf respiration was not affected by the chilling treatment in either of the two cultivars, electron partitioning to the alternative pathway was significantly increased in the more stressed chilling-sensitive cv Penjalinan, suggesting that increased activity of the alternative pathway is not related to the plant tolerance to chilling. These results suggest a possible role of the alternative pathway in plants under stress rather than specifically contributing to plant resistance to chilling.

141 citations

Journal ArticleDOI
TL;DR: In this article, the effect of drought on alfalfa leaves was investigated and the potential of the leaves to produce ethylene was shown to increase with the severity of the stress.
Abstract: Exchange rates of CO2 and H2O and metabolism of hydrogen peroxide have been measured in leaves of alfalfa ev. Aragon) under drought stress. The inhibitory effect of drought upon photosynthesis depended on the severity of the stress treatment. Leaf water potential (Ψleaf) down to,-2.8 MPa reduced CO2 availability due to stomatal closure and inhibited the rate of photosynthesis. Leaf water potential lower than,-2.8 MPa directly affected CO2 fixation, although CO2 was not limiting. Transpiration was more affected by stornatal closure than photosynthesis, which led to am apparent improvement in WUE (water use efficiency). Alfalfa leaves with Ψleaf lower than,-2.0 MPa had an increased quantum requirement, probably due to the severe stress effect on photoenergetic reactions. Ethylene evolution from alfalfa leaves increased when they were subjected to Ψleaf of,- 1.6 MPa. Under more severe stress, the leaves showed low or almost no ethylene production. In parallel with the increase in ethyiene production, alfalfa leaves exhibited an increased membrane lipid peroxidation index (maloridialdehyde content) and an increased peroxide content. Superoxide disinutase activity (SOD; EC 1.15.1.1) was not affected by drought stress. Catalase (EC 1.11.1.6) was inhibited at slight stress, but significantly increased at a Ψleaf of -2.0 MPa. Peroxidase (EC 1.11.1.7) was progressively inhibited as drought stress developed. The possible implication of reactive O2 intermediates in drought stress-induced senescence of alfalfa leaves is discussed in the light of the pattern of enzymatic scavenging systems.

138 citations


Cited by
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Journal ArticleDOI
TL;DR: An overview of ROS homeostasis and signalling in response to drought and salt stresses is provided and the current understanding of ROS involvement in stress sensing, stress signalling and regulation of acclimation responses is discussed.
Abstract: Water deficit and salinity, especially under high light intensity or in combination with other stresses, disrupt photosynthesis and increase photorespiration, altering the normal homeostasis of cells and cause an increased production of reactive oxygen species (ROS). ROS play a dual role in the response of plants to abiotic stresses functioning as toxic by-products of stress metabolism, as well as important signal transduction molecules. In this review, we provide an overview of ROS homeostasis and signalling in response to drought and salt stresses and discuss the current understanding of ROS involvement in stress sensing, stress signalling and regulation of acclimation responses.

2,872 citations

Journal ArticleDOI
TL;DR: Vesicular-arbuscular mycorrhizal fungi can affect the water balance of both amply watered and droughted host plants and the influence of soil drying on the fungi is discussed.
Abstract: Vesicular-arbuscular mycorrhizal fungi can affect the water balance of both amply watered and droughted host plants. This review summarizes these effects and possible causal mechanisms. Also discussed are host drought resistance and the influence of soil drying on the fungi.

1,964 citations

Journal ArticleDOI
TL;DR: The Rhizobium-legume (herb or tree) symbiosis is suggested to be the ideal solution to the improvement of soil fertility and the rehabilitation of arid lands and is an important direction for future research.
Abstract: Biological N2 fixation represents the major source of N input in agricultural soils including those in arid regions. The major N2-fixing systems are the symbiotic systems, which can play a significant role in improving the fertility and productivity of low-N soils. The Rhizobium-legume symbioses have received most attention and have been examined extensively. The behavior of some N2-fixing systems under severe environmental conditions such as salt stress, drought stress, acidity, alkalinity, nutrient deficiency, fertilizers, heavy metals, and pesticides is reviewed. These major stress factors suppress the growth and symbiotic characteristics of most rhizobia; however, several strains, distributed among various species of rhizobia, are tolerant to stress effects. Some strains of rhizobia form effective (N2-fixing) symbioses with their host legumes under salt, heat, and acid stresses, and can sometimes do so under the effect of heavy metals. Reclamation and improvement of the fertility of arid lands by application of organic (manure and sewage sludge) and inorganic (synthetic) fertilizers are expensive and can be a source of pollution. The Rhizobium-legume (herb or tree) symbiosis is suggested to be the ideal solution to the improvement of soil fertility and the rehabilitation of arid lands and is an important direction for future research.

1,542 citations

Journal ArticleDOI
TL;DR: The analysis suggests that stomatal closure is the earliest response to drought and the dominant limitation to photosynthesis at mild to moderate drought, however, in parallel, progressive down-regulation or inhibition of metabolic processes leads to decreased RuBP content, which becomes the dominant limit at severe drought, and thereby inhibits photosynthetic CO2 assimilation.

1,350 citations

Journal ArticleDOI
TL;DR: Thiol/disulphide exchange reactions, particularly involving the glutathione pool and the generation of the oxidant H2O2, are central components of signal transduction in both environmental and biotic stresses.
Abstract: Plants adapt to environmental stresses through specific genetic responses. The molecular mechanisms associated with signal transduction, leading to changes in gene expression early in the stress response, are largely unknown. It is clear, however, that gene expression associated with acclimatory responses is sensitive to the redox state of the cell. Of the many components which contribute to the redox balance of the cell, two factors have been shown to be crucial in mediating stress responses. Thiol/disulphide exchange reactions, particularly involving the glutathione pool and the generation of the oxidant H2O2, are central components of signal transduction in both environmental and biotic stresses. These molecules are multifunctional triggers, modulating metabolism and gene expression. Both are able to cross biological membranes and diffuse or be transported long distances from their sites of origin. Glutathione and H2O2 may act alone or in unison, in intracellular and systemic signalling systems, to achieve acclimation and tolerance to biotic and abiotic stresses.

1,312 citations