In situ warming in the Antarctic: effects on growth and photosynthesis in Antarctic vascular plants.

The Antarctic Peninsula has experienced a rapid warming in the last decades. Although recent climatic evidence supports a new tendency towards stabilization of temperatures, the impacts on the biosphere, and specifically on Antarctic plant species, remain unclear. We evaluated the in situ warming effects on photosynthesis, including the underlying diffusive, biochemical and anatomical determinants, and the relative growth of two Antarctic vascular species, Colobanthus quitensis and Deschampsia antarctica, using open top chambers (OTCs) and gas exchange measurements in the field. In C. quitensis, the photosynthetic response to warming relied on specific adjustments in the anatomical determinants of the leaf CO2 transfer, which enhanced mesophyll conductance and photosynthetic assimilation, thereby promoting higher leaf carbon gain and plant growth. These changes were accompanied by alterations in the leaf chemical composition. By contrast, D. antarctica showed no response to warming, with a lack of significant differences between plants grown inside OTCs and plants grown in the open field. Overall, the present results are the first reporting a contrasting effect of in situ warming on photosynthesis and its underlying determinants, of the two unique Antarctic vascular plant species, which could have direct consequences on their ecological success under future climate conditions.

Los autores agradecen a CONICYT-FONDECYT 11130332, CONICYT-PIA ART11-02, CONICYT, Atracción de Capital Humano Avanzado del Extranjero (MEC-80130020), CONICYT PFB-023 y al Instituto Antártico Chileno (INACH AN-02-12 y FI_02-13). Un agradecimiento especial a la tripulación de la Estación Arctowski y a la Academia Polaca de Ciencias por su apoyo y ayuda durante nuestro trabajo de campo. Los autores agradecen al Dr. Charles L. Guy (Universidad de Florida) su corrección en inglés y su ayuda con la gramática. Los permisos de entrada y recolección de plantas en la ASPA 128 fueron facilitados por el INACH.

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