Evaluación de la tolerancia de Brassica oleracea L. var. italica al estrés por microplásticos y factores abióticos mediante parámetros fisiológicos y perfiles de metabolitos.
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Date
2025
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Universidad de Concepción
Abstract
Esta Tesis Doctoral abordó de manera integrada los efectos de los microplásticos (MPs) sobre la fisiología vegetal y la seguridad de los sistemas agroalimentarios, considerando su interacción con estreses abióticos asociados al cambio climático, tales como el aumento de CO₂ y las altas temperaturas. A partir de una revisión crítica y actualizada de la literatura científica y de un ensayo experimental controlado con brotes de Brassica oleracea L. var. italica (brócoli), se analizaron tanto los riesgos que los MPs representaban para la productividad y calidad de los cultivos, como los mecanismos fisiológicos, enzimáticos y metabolómicos que explicaban sus impactos en las plantas. En el capítulo II se realizó una revisión bibliográfica que evidenció que los microplásticos eran capaces de modificar parámetros esenciales de la fisiología vegetal, afectando la germinación, el desarrollo radicular, la fotosíntesis, la acumulación de metabolitos secundarios y la interacción con microorganismos del suelo. Además, actúaron como vectores de contaminantes inorgánicos y orgánicos persistentes, alterando la expresión génica y generando estrés oxidativo. Los MPs de origen biodegradable (como PLA o PBAT) provocaron respuestas más rápidas e intensas, mientras que los no degradables, como el poliestireno (PS) y el polietileno (PE), tendieron a modificar la estructura del suelo, reducir su porosidad, alterar la retención hídrica y afectar la dinámica microbiana y nutricional a largo plazo. En cultivos del género Brassica, la literatura mostraba una disminución del peso fresco, una reducción de pigmentos fotosintéticos y una acumulación compensatoria de antocianinas y glucosinolatos, lo que reflejaba una reconfiguración del metabolismo secundario hacia rutas defensivas. A su vez, se observó que la presencia de MPs en el suelo incrementó las emisiones de CO₂ debido a la degradación de plásticos biodegradables y a la estimulación de la actividad microbiana heterótrofa, contribuyendo a la retroalimentación del cambio climático. Por lo tanto, los microplásticos no solo son contaminantes emergentes, sino moduladores ambientales que, dependiendo del tipo de polímero y las condiciones edafoclimáticas, pueden amplificar o mitigar las respuestas de estrés en las plantas. Ante este escenario, se propone avanzar en metodologías estandarizadas para la cuantificación de MPs en matrices agrícolas y en la aplicación de tecnologías ómicas y de aprendizaje automático que permitan identificar biomarcadores de exposición y desarrollar modelos predictivos de impacto fisiológico y ecológico. El capítulo III de esta tesis se basó en un diseño factorial (2×2×3) que combinó
dos niveles de CO₂ (≈500 y 1000 ppm), dos temperaturas (20 y 28 °C) y tres tipos de polímero (sin plástico, poliestireno y polietileno) en brotes de Brassica oleracea var. italica cultivados bajo condiciones controladas. Se evaluaron parámetros morfológicos, hormonales, enzimáticos y metabolómicos mediante técnicas cromatográficas y análisis multivariados, con el fin de identificar patrones de respuesta y compensaciones entre crecimiento y defensa. Los resultados mostraron que la temperatura fue el factor dominante, regulando las hormonas de crecimiento, la actividad antioxidante y el metabolismo secundario. A 20 °C se observó una mayor acumulación de glucosinolatos, especialmente glucorafanina e indol-3-ilmetilglucosinolato, indicando una activación de rutas defensivas de tipo basal. En contraste, a 28°C no se registró incremento de estos compuestos, pero sí un aumento significativo de antocianinas y derivados sinápicos, junto con una mayor actividad de catalasa y menor biomasa, lo que refleja una reorientación metabólica hacia mecanismos antioxidantes y un claro trade-off entre crecimiento y defensa. El CO₂ elevado actuó como modulador secundario, favoreciendo la biomasa radicular y la síntesis de auxinas, aunque atenuó la acumulación de glucosinolatos. En tanto, el tipo de polímero mostró efectos específicos. El poliestireno promovió una mayor producción de compuestos fenólicos, mientras que el polietileno redujo la expansión radicular y foliar, con respuestas más marcadas en escenarios cálidos. Los análisis multivariados confirmaron la existencia de dos ejes principales de respuesta fisiológica. El primero, que explicó un 46 % de la varianza total, contrapuso metabolitos defensivos (glucosinolatos, antocianinas y sinapatos) frente a hormonas de crecimiento y biomasa, reforzando la hipótesis del equilibrio crecimiento–defensa. El segundo eje, responsable del 23 % de la varianza, separó los compuestos indólicos de los alifáticos, indicando una reorganización del metabolismo secundario en función de la temperatura y la interacción con los MNPs. Las correlaciones entre parámetros revelaron asociaciones positivas significativas entre la actividad catalasa y el contenido de sinapatos (r = 0.78) y antocianinas (r = 0.74), así como una correlación negativa con la biomasa aérea (r = −0.69), lo que confirma el acoplamiento entre defensa antioxidante y producción de metabolitos fenólicos. Complementariamente, los modelos predictivos desarrollados mediante redes neuronales artificiales (ANN) permitieron estimar con alta precisión (R² > 0.9; RMSE < 0.05) las concentraciones de glucosinolatos y hormonas de crecimiento a partir de las condiciones ambientales y del tipo de polímero, demostrando la aplicabilidad del aprendizaje automático en la predicción de respuestas bioquímicas bajo escenarios multiestrés. Lo que observamos en este estudio fue que los micro/nanoplásticos actuaron como moduladores, capaces de amplificar o reconfigurar las respuestas fisiológicas inducidas por la temperatura y el CO₂, más que como agentes tóxicos directos. Estos resultados resaltan la importancia de adoptar enfoques multiestrés y de integrar herramientas de metabolómica y modelamiento predictivo para comprender cómo los contaminantes emergentes afectan la resiliencia y la calidad de los cultivos en un contexto de cambio climático. Desde una perspectiva aplicada, esta tesis aporta un marco experimental y conceptual para el estudio de contaminantes emergentes en agroecosistemas, incorporando herramientas de metabolómica avanzada y modelamiento predictivo como apoyo a la toma de decisiones en agricultura sostenible.
This doctoral thesis addressed, in an integrated manner, the effects of microplastics (MPs) on plant physiology and the safety of agri-food systems, considering their interaction with abiotic stresses associated with climate change, such as increased CO₂ and high temperatures. Based on a critical and updated review of the scientific literature and a controlled experimental trial using Brassica oleracea L. var. italica (broccoli) sprouts, both the risks that MPs pose to crop productivity and quality and the physiological, enzymatic, and metabolomic mechanisms underlying their impacts on plants were analyzed. Chapter II presents a literature review showing that microplastics can alter key parameters of plant physiology, affecting germination, root development, photosynthesis, the accumulation of secondary metabolites, and interactions with soil microorganisms. Furthermore, they act as vectors of persistent inorganic and organic contaminants, modifying gene expression and inducing oxidative stress. Biodegradable MPs (such as PLA or PBAT) triggered faster and more intense responses, whereas non-degradable MPs, such as polystyrene (PS) and polyethylene (PE), tended to modify soil structure, reduce porosity, alter water retention, and affect microbial and nutrient dynamics in the long term. In Brassica crops, the literature reports reductions in fresh weight, decreases in photosynthetic pigments, and compensatory accumulations of anthocyanins and glucosinolates, reflecting a reconfiguration of secondary metabolism toward defensive pathways. Moreover, the presence of MPs in soil was found to increase CO₂ emissions due to the degradation of biodegradable plastics and the stimulation of heterotrophic microbial activity, contributing to climate change feedback. Therefore, microplastics should be viewed not only as emerging pollutants but also as environmental modulators that, depending on polymer type and edaphoclimatic conditions, can amplify or mitigate plant stress responses. In light of this, the thesis emphasizes the need to advance standardized methodologies for MP quantification in agricultural matrices and to apply omics and machine learning technologies to identify exposure biomarkers and develop predictive models of physiological and ecological impact. Chapter III was based on a factorial design (2×2×3) that combined two levels of CO₂ (≈500 and 1000 ppm), two temperatures (20 and 28 °C), and three polymer conditions (no plastic, PS, and PE) applied to Brassica oleracea var. italica sprouts grown under controlled conditions. Morphological, hormonal, enzymatic, and metabolomic parameters were evaluated through chromatographic techniques and multivariate analyses to identify response patterns and trade-offs between growth and defense. The results showed that temperature was the dominant factor, regulating growth hormones, antioxidant activity, and secondary metabolism. At 20 °C, there was a greater accumulation of glucosinolates, particularly glucoraphanin and indol-3-ylmethyl glucosinolate, indicating activation of basal defensive pathways. In contrast, at 28 °C, glucosinolate levels did not increase; instead, there was a significant rise in anthocyanins and sinapate derivatives, together with higher catalase activity and lower biomass, revealing a metabolic shift toward antioxidant mechanisms and a clear growth–defense trade-off. Elevated CO₂ acted as a secondary modulator, enhancing root biomass and auxin synthesis but attenuating glucosinolate accumulation. The type of polymer produced specific effects: PS stimulated the synthesis of phenolic compounds, while PE reduced root and leaf expansion, with more pronounced effects under heat stress. Multivariate analyses confirmed the existence of two main physiological axes: the first (46 % of total variance) opposed defensive metabolites (glucosinolates, anthocyanins, sinapates) to growth hormones and biomass, reinforcing the growth–defence balance hypothesis; the second (23 %) separated indolic from aliphatic glucosinolates, indicating a reorganization of secondary metabolism as a function of temperature and MP interaction. Correlation analyses revealed strong positive associations between catalase activity and sinapate (r = 0.78) and anthocyanin content (r = 0.74), and a negative correlation with aerial biomass (r = −0.69), confirming the link between antioxidant defense and phenolic metabolism. Additionally, predictive models developed using artificial neural networks (ANNs) accurately estimated glucosinolate and hormone concentrations (R² > 0.9; RMSE < 0.05) based on environmental conditions and polymer type, demonstrating the potential of machine learning to predict biochemical responses under multi-stress scenarios. In general, the study showed that micro/nanoplastics act as context-dependent modulators, capable of amplifying or reconfiguring physiological responses induced by temperature and CO₂ rather than behaving as direct toxic agents. These findings highlight the importance of adopting multi-stress approaches and integrating metabolomic and predictive modeling tools to better understand how emerging contaminants affect crop resilience and quality in the context of climate change. From an applied perspective, this thesis provides an experimental and conceptual framework for studying emerging pollutants in agroecosystems, integrating advanced metabolomic analyses and predictive modeling as valuable tools for decision-making in sustainable agriculture.
This doctoral thesis addressed, in an integrated manner, the effects of microplastics (MPs) on plant physiology and the safety of agri-food systems, considering their interaction with abiotic stresses associated with climate change, such as increased CO₂ and high temperatures. Based on a critical and updated review of the scientific literature and a controlled experimental trial using Brassica oleracea L. var. italica (broccoli) sprouts, both the risks that MPs pose to crop productivity and quality and the physiological, enzymatic, and metabolomic mechanisms underlying their impacts on plants were analyzed. Chapter II presents a literature review showing that microplastics can alter key parameters of plant physiology, affecting germination, root development, photosynthesis, the accumulation of secondary metabolites, and interactions with soil microorganisms. Furthermore, they act as vectors of persistent inorganic and organic contaminants, modifying gene expression and inducing oxidative stress. Biodegradable MPs (such as PLA or PBAT) triggered faster and more intense responses, whereas non-degradable MPs, such as polystyrene (PS) and polyethylene (PE), tended to modify soil structure, reduce porosity, alter water retention, and affect microbial and nutrient dynamics in the long term. In Brassica crops, the literature reports reductions in fresh weight, decreases in photosynthetic pigments, and compensatory accumulations of anthocyanins and glucosinolates, reflecting a reconfiguration of secondary metabolism toward defensive pathways. Moreover, the presence of MPs in soil was found to increase CO₂ emissions due to the degradation of biodegradable plastics and the stimulation of heterotrophic microbial activity, contributing to climate change feedback. Therefore, microplastics should be viewed not only as emerging pollutants but also as environmental modulators that, depending on polymer type and edaphoclimatic conditions, can amplify or mitigate plant stress responses. In light of this, the thesis emphasizes the need to advance standardized methodologies for MP quantification in agricultural matrices and to apply omics and machine learning technologies to identify exposure biomarkers and develop predictive models of physiological and ecological impact. Chapter III was based on a factorial design (2×2×3) that combined two levels of CO₂ (≈500 and 1000 ppm), two temperatures (20 and 28 °C), and three polymer conditions (no plastic, PS, and PE) applied to Brassica oleracea var. italica sprouts grown under controlled conditions. Morphological, hormonal, enzymatic, and metabolomic parameters were evaluated through chromatographic techniques and multivariate analyses to identify response patterns and trade-offs between growth and defense. The results showed that temperature was the dominant factor, regulating growth hormones, antioxidant activity, and secondary metabolism. At 20 °C, there was a greater accumulation of glucosinolates, particularly glucoraphanin and indol-3-ylmethyl glucosinolate, indicating activation of basal defensive pathways. In contrast, at 28 °C, glucosinolate levels did not increase; instead, there was a significant rise in anthocyanins and sinapate derivatives, together with higher catalase activity and lower biomass, revealing a metabolic shift toward antioxidant mechanisms and a clear growth–defense trade-off. Elevated CO₂ acted as a secondary modulator, enhancing root biomass and auxin synthesis but attenuating glucosinolate accumulation. The type of polymer produced specific effects: PS stimulated the synthesis of phenolic compounds, while PE reduced root and leaf expansion, with more pronounced effects under heat stress. Multivariate analyses confirmed the existence of two main physiological axes: the first (46 % of total variance) opposed defensive metabolites (glucosinolates, anthocyanins, sinapates) to growth hormones and biomass, reinforcing the growth–defence balance hypothesis; the second (23 %) separated indolic from aliphatic glucosinolates, indicating a reorganization of secondary metabolism as a function of temperature and MP interaction. Correlation analyses revealed strong positive associations between catalase activity and sinapate (r = 0.78) and anthocyanin content (r = 0.74), and a negative correlation with aerial biomass (r = −0.69), confirming the link between antioxidant defense and phenolic metabolism. Additionally, predictive models developed using artificial neural networks (ANNs) accurately estimated glucosinolate and hormone concentrations (R² > 0.9; RMSE < 0.05) based on environmental conditions and polymer type, demonstrating the potential of machine learning to predict biochemical responses under multi-stress scenarios. In general, the study showed that micro/nanoplastics act as context-dependent modulators, capable of amplifying or reconfiguring physiological responses induced by temperature and CO₂ rather than behaving as direct toxic agents. These findings highlight the importance of adopting multi-stress approaches and integrating metabolomic and predictive modeling tools to better understand how emerging contaminants affect crop resilience and quality in the context of climate change. From an applied perspective, this thesis provides an experimental and conceptual framework for studying emerging pollutants in agroecosystems, integrating advanced metabolomic analyses and predictive modeling as valuable tools for decision-making in sustainable agriculture.
Description
Tesis presentada para optar al grado de Doctor en Ciencias de la Agronomía
Keywords
Brassica oleracea L., Microplásticos, Fisiología vegetal - Chile