Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Cambios en la fotoquímica, intercambio de gases y crecimiento por estrés hídrico y recuperación de una planta tipo C3 y una MAC.

Auteur : Campos García, Huitziméngari

Etablissement de soutenance : Colegio de Postgraduados. Consejo Nacional de Ciencia y Tecnología (CONACYT)

Grade : Doctorado en Ciencias, especialista en Fisiología Vegetal 2012

Résumé
Low water availability is the main environmental factor limiting plant growth and yield worldwide. In addition to global climate change will probably make water scarcity an even greater limitation to plant productivity across agriculture systems. The limitation of plant growth imposed by low water availability is mainly due to reductions of plant carbon balance, which is largely dependent on photosynthesis. Current knowledge about physiological limitations to photosynthesis during developing of water deficit and recovery after re-watering is scarce, but crucial to improve the understanding of plant responses to drought and for the development of water-saving irrigation schedules in agriculture. This thesis contributes to our understanding of how plants respond to water stress and recovery, taking particularly a physiological point of view, examining the underlying relationships among carbon uptake, growth and water loss. In addition to a general review, a revision of stress concept, photosynthesis, and the use of chlorophyll fluorescence to assess photosynthetic performance are submitted (Chapter II) ; the effect of low water potential on seed germination, seedling root growth and root membrane stability of Agave lechuguilla and Agave salmiana to establish thresholds of water requirements for these arid and semi-arid succulents are treated (Chapter III) ; it’s address a study to examine the mechanism which photosynthesis is regulated during water stress and recovery in the C3 bell pepper (Capsicum annuum L.) plant (Chapter IV). The results showed that the movement of photosinthetic electron carriers leading to the reduction of end electron acceptors was reduced by water stress and together with stomatal regulation and photosynthetic metabolism imposed an important limitation on carbon assimilation. Photosynthesis recovery after re-watering was mostly limited by both stomatal closure and slow restoration of the photosynthetic electron transport chain. In Chapter V a study was performed with A. salmiana plants (a Crassulacean acid metabolism plant) with water-witholding to induce water stress, followed by re-watering to induce recovery. Analysis of OJIP transients revealed the appearance of an L and K-band suggesting a lost on the energetic connectivity between PSII units and a limitation of the oxygen evolving complex. Down-regulation of photochemical activity occurred predominantly through both inactivation of PSII reaction centre’s (transformation to heat sinks) and to an increase in the functional antenna size. The results suggest that thermal dissipation of excess energy may be an important adaptive mechanism to protect the photosynthetic apparatus from photodamage which enabled A. salmiana seedlings not only to survive during aggravating water stress but also help to preserve the integrity of the photosynthetic apparatus and recovery after re-watering. In Chapter VI a study was performed with C. annuum plants that were water stressed by reducing irrigation amounts. Several measurements were made at various intervals during the drought cycle to obtain a gradient of water stress situations. The results showed that as water stress increases, there was a progressive decline of both soil and leaf water potential, CO2 assimilation rates (A), stomatal conductance (gs) and transpiration. A direct correlation between a JIP-test parameter PItotal and important gas exchange parameters (A and gs) were shown, providing that early detection of water stress would be a useful guide to irrigation requirements. Tesis (Doctorado en Ciencias, especialista en Fisiología Vegetal).- Colegio de Postgraduados, 2012.Consejo Nacional de Ciencia y Tecnología (CONACYT)..

Mots clés : Intercambio de gases , Gas exchange, Cambio climátic, Climate change, Estrés abiótico, Abiotic stress, Tolerancia al estrés, Stress tolerance, Photosynthesis

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