Captación y asimilación de nitrato bajo condiciones de déficit hídrico en dos genotipos de Chenopodium quinoa Willd (Amaranthaceae)
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2017
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es
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Universidad Andrés Bello
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La sequía afecta la disponibilidad de los nutrientes en el suelo y su captación y asimilación realizada por las plantas. Los mecanismos para hacer frente a la interacción de los estreses de nitrógeno y déficit hídrico en las distintas especies dependen de su adaptación a ambientes particulares. Chenopodium quinoa Willd (Amaranthaceae) es una especie que ha ganado gran atención por su resistencia a diversos estreses. En esta tesis se trabajó con dos genotipos contrastantes en origen: Socaire (de San Pedro de Atacama) y Faro (VI Región). El objetivo general de este trabajo consistió en estudiar el efecto la disponibilidad de nitrato y del déficit hídrico sobre los mecanismos de captación y asimilación de nitrato en los genotipos mencionados. Para esto, se definieron las concentraciones de N óptima (NO) y limitante (NL), y se estudió el efecto del déficit hídrico; por lo cual se obtuvieron 4 tratamientos (NO control y tratadas (NOC y NOT) y NL control y tratadas (NLC y NLT). Las condiciones de NLC redujeron la biomasa, la longitud de la raíz, el número de raíces secundarias, el área foliar y área foliar especifica. Estas respuestas fueron similares entre los genotipos, sin embargo, debido a una mayor reducción de las proteínas, clorofilas, y qL (apagamiento fotoquímico) podemos sugerir una mayor sensibilidad a las condiciones de NL en el genotipo Faro. La actividad nitrato reductasa y glutamina sintetasa en raíz incrementó bajo condiciones de NLC sugiriendo una pronta capacidad de ajuste fisiológico en ambos genotipos de C. quinoa. La expresión de los transportadores de NO3- tuvieron una gran diferencia basal entre los genotipos, siendo en general mayor en Socaire que en Faro, sin embargo, la expresión CqNRT2 (un transportador de NO3- de alta afinidad) incrementó en ambos genotipos en respuesta a NLC, exaltando el rol de estos tipos de transportadores bajo estas condiciones.
Por otro lado, el déficit hídrico no indujo cambios fisiológicos más allá de los producidos por la nutrición diferencial en muchos de los parámetros estudiados. Aunque redujo el contenido de proteínas y clorofilas en Socaire, pero no en Faro, el cual mostró un incremento en la disipación térmica (NPQ) bajo NLT, lo cual es visto como un mecanismo de fotoprotección. En general, el déficit hídrico tuvo un efecto diferencial dependiendo del transportador de NO3- y genotipo.
Con estos datos podemos sugerir que los genotipos presentan mecanismos comunes en la captación de nitrógeno bajo condiciones de déficit de nitrógeno, sin embargo, en la interacción N y déficit hídrico Faro presenta mecanismos asociados a disipación térmica, no observados en Socaire. La hipótesis se acepta parcialmente.
The drought events affect the availability of nutrients in the soil and the uptake and assimilation by plants. The mechanisms to cope with the interaction of nitrogen stress and water deficit in different species depend on their genetic adaptation to particular environments. Chenopodium quinoa Willd (Amaranthaceae) is an specie that has gained great attention because of resistance to various stresses. In this thesis, we worked with two genotypes contrasting in origin: Socaire (from San Pedro de Atacama) and Faro (O’Higgins Region). The general objective of this work was to study the effect of nitrate availability and water deficit on nitrate uptake and assimilation mechanisms in the above genotypes. We defined optimal and limiting concentrations of N in the growth of both genotypes and we studied the effect of water stress by stop of irrigation which resulted in 4 treatments: NO control and treated (NOC and NOT) and NL control and treated (NLC and NLT). NLC conditions reduced biomass, root length and number of secondary roots, while at the aerial level reductions were observed in leaf area and specific leaf area. These responses were similar in both genotypes; however, due to a greater reduction of the proteins, chlorophylls, and qL (photochemical quenching) we can suggest a greater sensitivity to NL conditions in the Faro genotype. Nitrate reductase and Glutamine synthetase activity in roots increased under NLC conditions suggesting an early physiological adjustment capacity in both C. quinoa genotypes. Regard NO3 - transports large basal differences were found between genotypes, which was higher in Socaire than Faro. However, the expression CqNRT2 (a high affinity transporter) increased in both genotypes in response to NL, exalting the role of these types of transporters under such conditions. On the other hand, water deficit did not induce physiological changes beyond those produced by differential nutrition. Although proteins and chlorophylls content was reduced in Socaire, but not in Faro, which could be related with the fact that Faro showed an increase in thermal dissipation (NPQ) under NLT which is considered a photoprotective mechanism. In general, water deficit had a differential effect depending on the NO3 - transporter and genotype. With these data, we can suggest that genotypes present common mechanisms in the nitrogen uptake under nitrogen deficit conditions, however, in the interaction N and water deficit, Faro presents mechanisms associated with thermal dissipation, not observed in Socaire. The hypothesis is partially accepted.
The drought events affect the availability of nutrients in the soil and the uptake and assimilation by plants. The mechanisms to cope with the interaction of nitrogen stress and water deficit in different species depend on their genetic adaptation to particular environments. Chenopodium quinoa Willd (Amaranthaceae) is an specie that has gained great attention because of resistance to various stresses. In this thesis, we worked with two genotypes contrasting in origin: Socaire (from San Pedro de Atacama) and Faro (O’Higgins Region). The general objective of this work was to study the effect of nitrate availability and water deficit on nitrate uptake and assimilation mechanisms in the above genotypes. We defined optimal and limiting concentrations of N in the growth of both genotypes and we studied the effect of water stress by stop of irrigation which resulted in 4 treatments: NO control and treated (NOC and NOT) and NL control and treated (NLC and NLT). NLC conditions reduced biomass, root length and number of secondary roots, while at the aerial level reductions were observed in leaf area and specific leaf area. These responses were similar in both genotypes; however, due to a greater reduction of the proteins, chlorophylls, and qL (photochemical quenching) we can suggest a greater sensitivity to NL conditions in the Faro genotype. Nitrate reductase and Glutamine synthetase activity in roots increased under NLC conditions suggesting an early physiological adjustment capacity in both C. quinoa genotypes. Regard NO3 - transports large basal differences were found between genotypes, which was higher in Socaire than Faro. However, the expression CqNRT2 (a high affinity transporter) increased in both genotypes in response to NL, exalting the role of these types of transporters under such conditions. On the other hand, water deficit did not induce physiological changes beyond those produced by differential nutrition. Although proteins and chlorophylls content was reduced in Socaire, but not in Faro, which could be related with the fact that Faro showed an increase in thermal dissipation (NPQ) under NLT which is considered a photoprotective mechanism. In general, water deficit had a differential effect depending on the NO3 - transporter and genotype. With these data, we can suggest that genotypes present common mechanisms in the nitrogen uptake under nitrogen deficit conditions, however, in the interaction N and water deficit, Faro presents mechanisms associated with thermal dissipation, not observed in Socaire. The hypothesis is partially accepted.
Notas
Tesis (Magíster en Biotecnología)
Palabras clave
Fisiología Vegetal, Plantas (Necesidad de Agua), Efectos de los Micronutrientes, Aspectos Ambientales, Chile