Investigador Principal: Patricia Sáez
Universidad de Concepción
Warming is one of the most important characteristics of climate change, increase temperatures are already evident in the Antarctic, being this especially important given that ambient temperature is the main factor governing ecosystem processes and biodiversity in this region. Within of these processes, photosynthesis is one of the most affected by environmental changes and is considered as one of the most heat-sensitive processes. Increased temperature may affect the photosynthesis; warming leaves by above their thermal optimum, potentially to a point where electron transport or enzyme associated are labile. Thus is likely that the factors that limit the photosynthesis and the energy proportion drawn towards photosynthesis will be affected. Deschampsia antarctica and Colobanthus quitensis are the only two vascular plants that have colonized the Antarctic. In general, these plants are frequently exposed to low temperature and events of high light intensity, which may induce photo-inhibition. In this way the study of the mechanisms associated with light management is of major importance to understand the possible effects of warming on antarctic plants physiology. Regarding warming, has been proposed that its trend in Antarctic is higher in some areas, thus plants growing in most southern regions exposed to lower temperatures, are also exposed to greater warming trend, this differences within the Antarctic gradient could elicit different responses to warming. The increase in temperature due to warming, could favors the oxidative capacity of Rubisco, it means that reduces their carboxylation specificity factor. However, as the antarctic plants grow usually under sub-optimal temperatures for photosynthesis, being this limited by the low temperatures in field, it is likely that increase in temperature product of climate change resulting in an increase in specificity factor of Rubisco for carboxylation and a reduction in photosynthetic limitations. Given the greater warming trend in the south, this tendency could be higher plants coming from more southern conditions. On this basis it is hypothesized that: Plants from boreal populations of Maritime Antarctic have higher photosynthetic capacity and lower photoprotection than southern populations; these differences are explained by an acclimation response to temperature and not due to genotypic variations. In specific it is hypothesized that: 1. Warming will increase the energy partitioning toward photosynthesis, therefore populations that experience a higher photosynthetic enhancement will also exhibit a higher decrease in their capacity to dissipate the excess of absorbed light energy and a higher reduction in the antioxidant protection against low-temperature-induced photoinhibition; 2. The increase in the specificity factor of Rubisco as a consequence of warming will be higher in plants coming from southern populations than boreal ones; and 3. Warming will decrease diffusive and biochemical limitations on photosynthesis more strongly in southern populations compare with boreal ones. To prove it, it is raises study the effect of warming on photosynthetic performance of D. antarctica and C. quitensis coming from different climatic conditions within antarctic latitudinal gradient through photosynthetic limitations, photoprotection and enzymatic properties. For this, field and laboratory experiments will be conducted. Two sites have been selected to perform the study: one on King George Island and the other near the southern most distribution of vascular plants, in Lagotellerie Island. In order to distinguish if possible differences in photosynthetic performance and photoprotection parameters correspond to acclimation or genetic variations, plants from both sites will be culture under common garden in laboratory. Additionally, since it is not possible to establish whether the effects observed in laboratory will be equivalent to that observed in field, reciprocal transplants will be carried out. Photosynthetic performance and photoprotection will be analyzed using gas exchange and fluorescence analyses. Leaf samples will be taken for detect possible differences in gene sequences associated to photosynthetic process (Rubisco, Rubisco activase, VDE). Additionally, experiments for determined photosynthetic response temperature and optimal photosynthetic temperature will be carried out and attributes associated to photosynthetic performance will be analyzed. The study of this attributes is essential to understand photosynthetic responses to rising warming and for contribute to predicting the fate of their populations in the climate change scenario.