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Universidad Complutense de Madrid (2019)

Physiological strategies in orophytes from Sierra de Guadarrama in response to harsh environments

Magaña Ugarte, Rosina

Titre : Physiological strategies in orophytes from Sierra de Guadarrama in response to harsh environments

Estrategias fisiológicas de respuesta a ambientes adversos en orófitos de la Sierra de Guadarrama

Auteur : Magaña Ugarte, Rosina

Université de soutenance : Universidad Complutense de Madrid

Grade : Doctoral Tesis 2019

Résumé
The impending changes in climatic conditions (i.e. decrease in rainfall regimes and increasing temperatures) as an outcome of climate change, coupled to a greater incidence of human disturbance, underlines the challenges and vulnerability faced by Mediterranean high-mountain plant communities. Albeit increased research efforts have demonstrated the effects of environmental factors over plant physiology, along with the responses and adaptation capacity on high-mountain plant species ; these primarily concern the vegetation from temperate mountains (i.e. alpine), while studies on Mediterranean high-mountain flora, including their Spanish elements, remain scarce. The latter exposes the urgent need to identify the specific responses and strategies to counteract the seasonal aggravation of summer stress in the remaining species comprising these Mediterranean high-mountain communities. This in view of the expected lengthening and increased intensity of the summer season in these mountains. In turn, these studies will enable discerning potential alterations in community structure and dynamics, fostering their conservation. OBJECTIVES : The main objective of the present PhD Thesis is to study the physiological mechanisms driving the response to adverse conditions in high-mountain specialists and narrowly-distributed species inhabiting the Sistema Central mountainous range, for instance Armeria caespitosa and Erysimum penyalarense. Specifically, we aimed to unveil the strategies in response to the main abiotic stressor driving plant life in Mediterranean high-mountains, i.e. summer stress. In turn, we assessed the involvement of well-known responses in lowland species. For instance, osmolyte accumulation (proline and non-structural carbohydrates, NSC) in response to drought and occasional freezing stress befalling the brief growing season. In addition, we evaluated the protective role of photosynthetic and “accessory” pigments in response to the seasonal aggravation of summer stress and diurnal climatic variations, respectively. Lastly, we assessed the adaptive capacity of a high-mountain hemicryptophyte using herbarium specimens from the past 71 years to the long-term climate exacerbation in these high-mountain areas, via morphological and micro-morphological leaf traits related to transpiration-mediated cooling and photosynthetic gain... Présentation

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