Importancia de la conductancia del mesófilo sobre la fotosíntesis de plantas alto-andinas en Chile central: evaluando el rol de la temperatura ambiental.
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Date
2025
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Universidad de Concepción
Abstract
Esta tesis doctoral explora el papel de la conductancia mesofílica (gm) en los procesos fotosintéticos de plantas alpinas en diferentes elevaciones del centro de Chile. La importancia de la gm radica en su impacto directo sobre la difusión de CO2 dentro del mesófilo de la hoja, lo que es un determinante crucial de las tasas fotosintéticas. Al centrarse en plantas zonales y azonales, este estudio investiga las adaptaciones fisiológicas y morfológicas asociadas a la asimilación de carbono, que facilitan la supervivencia y productividad bajo las condiciones ambientales únicas de diferentes plantas de gran altitud. También, se examina específicamente cómo la gm responde a la temperatura de crecimiento y contribuye a las capacidades adaptativas de las plantas alpinas. Se evalúan las diferencias en la respuesta de la gm entre plantas zonales y azonales y sus estrategias ecológicas únicas de acuerdo con su entorno particular. Las hipótesis de este trabajo son: (1) la fotosíntesis no muestra diferencias altitudinales debido a mecanismos compensatorios, como una mayor densidad estomática (SD) en plantas tanto zonales como azonales. En las plantas zonales, la masa foliar por área (LMA) y la limitación del mesófilo no cambian con la altitud, ya que tanto los hábitats de gran altitud como los de baja altitud presentan condiciones ambientales adversas, como bajas temperaturas y baja humedad del suelo, respectivamente. En contraste, para las plantas azonales, existe un mayor LMA y una mayor limitación del mesófilo a gran altitud. (2) Los cambios de gm ante distintas condiciones ambientales se deben a cambios anatómicos como el grosor de la pared celular y la disposición de los cloroplastos. (3) La temperatura es el factor que impulsa las tasas fotosintéticas más bajas en las plantas de gran altitud y el mecanismo subyacente a las variaciones en la fotosíntesis neta (AN) asociadas a la temperatura involucra cambios en el LMA y, en consecuencia, en la gm. Los resultados sugieren que la gm no solo es el principal factor limitante en la difusión de CO2 en las plantas alpinas, sino también un rasgo dinámico que varía significativamente con la elevación, el tipo de planta y la temperatura. Además, se observó cómo las variaciones en el grosor de la pared celular y la disposición de los cloroplastos se correlacionan con los cambios en gm. A través de este análisis exhaustivo, el estudio no solo contribuye a nuestra comprensión de la fisiología vegetal, sino que también mejora nuestro conocimiento sobre cómo los ecosistemas alpinos pueden funcionar en respuesta a sus condiciones ambientales. En conclusión, esta investigación ofrece valiosos conocimientos sobre los procesos fundamentales de adaptación de las plantas a grandes altitudes, destacando el papel crítico de la conductancia mesofílica. Establece las bases para futuros estudios ecológicos y fisiológicos, con el objetivo de dilucidar las complejas interacciones entre la morfología vegetal, los rasgos fisiológicos y los factores ambientales en las regiones montañosas. Las implicaciones de estos hallazgos son significativas para contribuir a predecir las respuestas de la vegetación alpina a los cambios ambientales y para la conservación y gestión de estos ecosistemas sensibles.
This doctoral thesis explores the role of mesophyll conductance (gm) in the photosynthetic processes of alpine plants at different elevations in central Chile. The importance of gm lies in its direct impact on CO2 diffusion within the leaf mesophyll, which is a crucial determinant of the photosynthetic rates of alpine vegetation. By focusing on both zonal and azonal plants, this study investigates the physiological and morphological adaptations that facilitate survival and productivity under the unique environmental conditions of different high-altitude ecosystems. It also specifically examines how gm responds to growth temperature and contributes to the adaptive capacities of alpine plants. Differences in gm responses between zonal and azonal plants are highlighted, revealing how these groups exhibit unique ecological strategies according to their specific environments. The hypotheses of this study are: (1) Photosynthesis does not show altitudinal differences due to compensatory mechanisms such as higher stomatal density (SD) in both zonal and azonal plants. In zonal plants, LMA and mesophyll limitation do not change with altitude, as both high- and low-altitude habitats present adverse environmental conditions, such as low temperatures and low soil moisture, respectively. In contrast, azonal plants exhibit higher LMA and greater mesophyll limitation at high altitudes. (2) Changes in gm under different environmental conditions are due to anatomical modifications such as cell wall thickness and chloroplast arrangement. (3) Temperature is the driving factor behind lower photosynthetic rates in high-altitude plants, and the mechanism underlying temperature-associated variations in AN involves changes in LMA and, consequently, in gm. The results suggest that gm is not only the main limiting factor in CO2 diffusion in alpine plants but also a dynamic trait that varies significantly with elevation, plant type, and temperature. Additionally, this thesis delves into the anatomical traits that support these responses. Variations in cell wall thickness and chloroplast arrangement were found to correlate with changes in gm. Through this comprehensive analysis, the study not only contributes to our understanding of plant physiology but also enhances our knowledge of how alpine ecosystems function in response to their environmental conditions. In conclusion, this research provides valuable insights into the fundamental adaptation processes of plants at high altitudes, highlighting the critical role of mesophyll conductance. It lays the foundation for future ecological and physiological studies aimed at elucidating the complex interactions between plant morphology, physiological traits, and environmental factors in mountainous regions. The implications of these findings are significant for predicting the responses of alpine vegetation to environmental changes and for the conservation and management of these sensitive ecosystems.
This doctoral thesis explores the role of mesophyll conductance (gm) in the photosynthetic processes of alpine plants at different elevations in central Chile. The importance of gm lies in its direct impact on CO2 diffusion within the leaf mesophyll, which is a crucial determinant of the photosynthetic rates of alpine vegetation. By focusing on both zonal and azonal plants, this study investigates the physiological and morphological adaptations that facilitate survival and productivity under the unique environmental conditions of different high-altitude ecosystems. It also specifically examines how gm responds to growth temperature and contributes to the adaptive capacities of alpine plants. Differences in gm responses between zonal and azonal plants are highlighted, revealing how these groups exhibit unique ecological strategies according to their specific environments. The hypotheses of this study are: (1) Photosynthesis does not show altitudinal differences due to compensatory mechanisms such as higher stomatal density (SD) in both zonal and azonal plants. In zonal plants, LMA and mesophyll limitation do not change with altitude, as both high- and low-altitude habitats present adverse environmental conditions, such as low temperatures and low soil moisture, respectively. In contrast, azonal plants exhibit higher LMA and greater mesophyll limitation at high altitudes. (2) Changes in gm under different environmental conditions are due to anatomical modifications such as cell wall thickness and chloroplast arrangement. (3) Temperature is the driving factor behind lower photosynthetic rates in high-altitude plants, and the mechanism underlying temperature-associated variations in AN involves changes in LMA and, consequently, in gm. The results suggest that gm is not only the main limiting factor in CO2 diffusion in alpine plants but also a dynamic trait that varies significantly with elevation, plant type, and temperature. Additionally, this thesis delves into the anatomical traits that support these responses. Variations in cell wall thickness and chloroplast arrangement were found to correlate with changes in gm. Through this comprehensive analysis, the study not only contributes to our understanding of plant physiology but also enhances our knowledge of how alpine ecosystems function in response to their environmental conditions. In conclusion, this research provides valuable insights into the fundamental adaptation processes of plants at high altitudes, highlighting the critical role of mesophyll conductance. It lays the foundation for future ecological and physiological studies aimed at elucidating the complex interactions between plant morphology, physiological traits, and environmental factors in mountainous regions. The implications of these findings are significant for predicting the responses of alpine vegetation to environmental changes and for the conservation and management of these sensitive ecosystems.
Description
Tesis presentada para optar al grado de Doctor en Sistemática y Biodiversidad
Keywords
Flora andina, Fotosíntesis, Temperatura atmosférica