| Summary: | Atmospheric CO2 concentration has increased from preindustrial level of 280 μmol CO2 mol-1 air (ppm) to currently more than 400 ppm. Intergovernmental Panel on Climate Change foresees that atmospheric CO2 concentration will continue increasing to reach at the end of this century 700 ppm. Due to its greenhouse effect, elevated atmospheric CO2 concentration is leading to higher atmospheric temperatures, a phenomenon that is being accompanied by episodes of less water availability or drought periods. Grapevine (Vitis vinifera L.) is a plant species very sensitive to those environmental factors. Fruit-bearing cuttings of red and white Tempranillo were grown under elevated CO2 (around 700 ppm, versus 400), high temperature (ambient temperature + 4ºC, versus ambient) and water deficit (cyclic drought, versus well irrigated) in temperature gradient greenhouses located at the University of Navarra (Pamplona, Spain) for three consecutive growing seasons (years 2013, 2014 and 2015). Vegetative growth (total vegetative mass and leaf area) was significantly reduced by drought (consistent the three years) and was more associated to a worse substrate water status than to decreases in leaf water content. In spite of decreasing leaf water content in both cultivars, elevated CO2 stimulated more vegetative than reproductive growth. The largest increases of elevated CO2 were observed in leaf and root growth in white and red Tempranillo, respectively. There was a clear interaction between temperature and water availability. Yield was significantly reduced by drought and was year-dependent, being especially low in 2015 due to eventual heat shocks episodes. The high temperatures of the heat shocks (above 35ºC) induced berry burn and browning and finally loss of 50% of the berries. The response of berry quality to climate change-related factors was highly variable and depended on the year. However, some general conclusions can be reached from the three years of experimentation. Thus, the simulated climate change scenarios affected to a greater extent the technological maturity parameters (primary metabolism) than the phenolic maturity (secondary metabolism). In particular, high temperature and drought significantly and consistently increased must pH, due to the decrease in malic acid. On the contrary, elevated CO2 decreased pH associated with significant increases in tartaric acid. These changes of the must affect its quality and potentially that of the resulting wine. Under elevated CO2 concentration, grapevine photosynthesis increases, modulated by temperature and water availability. However, under prolonged exposure to elevated CO2, grapevine down-regulates photosynthesis, decreasing photosynthetic capacity. Grapevine plants underwent photosynthetic acclimation after a long exposure to elevated CO2, regardless of temperature and water availability. Evidence comes from photosynthetic capacity decreases, leaf starch accumulation, and increases in leaf carbon/nitrogen ratio. Photosynthetic acclimation was well correlated to leaf starch, but not to soluble sugars. The white Tempranillo has altered its response to prolonged exposure to elevated CO2. For any given sink size or any given leaf starch accumulation, white Tempranillo always had higher levels of photosynthetic acclimation than the red one. Data suggest that mutation in white Tempranillo has affected loci other than grape color.
|
|---|