Title: Eco-physiological responses of alpine plant species to low air pressure

Abstract

Alpine ecosystems are experiencing high rates of warming due to climate change which, is resulting in a significant upward shift of plant species in elevation as an attempt to track their thermal niches. The shift in the distribution of some species upwards sites of higher altitudes could imply broad changes ranging from the physiological response of individuals to alterations in the ecosystem functioning. In fact, plant species will be exposed to new environmental and geographical constraints together with the establishment of new biotic interactions. The objective of the present work is to elucidate the direct effects of low air pressure on the ecophysiology and performance of several plant species. For this purpose, three plant species (Trifolium pratensis, Hieracium pilosella and Arabidopsis thaliana) were grown in a controlled chambers with different air pressure conditions (100, 85, 75 and 60kPa). Diurnal variation of temperature, relative humidity, and light intensity were kept similar between chamber.The duration of the exp riment was one month after which, some ecophysiological parameters were determined and compared (growth, leaf gas exchange, chlorophyll fluorescence, C/N ratio and stable carbon isotope composition (δ13C)). Preliminary results showed that low air pressure decreases gas exchange rate, transpiration, stomatal conductance and growth parameters of the three species studied. Furthermore, low air pressure increases specific leaf area at 75kPa, whereas it decreases total carbon, C/N ratio and above plant biomass at 60kPa. We conclude that the upshift in the distribution of plant species in alpine environment could result in the appearance and development of new traits that will be of decisive importance in their adaptation process, distribution ranges and survival which, might have high evolutionary and ecological consequences.