Abstract
The impact of climate change on viticulture is of major importance. Several international and indigenous grapevine cultivars have been examined for their adaptive performance to drought and heat stresses. However, the underlying physiological mechanisms are not well known. In the present study we examined the short-term effects of light and moderate drought stress (DS) as well as heat stress (HS) on physiological and biochemical attributes in two grapevine cultivars: Chardonnay (international) and Xynisteri, an indigenous adapted to the specific Cypriot microclimate. Xynisteri plants exhibited decreasing leaf stomatal conductance and photosynthetic rate as well as increasing total phenols and antioxidant capacity under DS conditions. These reactions were concomitant to a rapid accumulation of hydrogen peroxide and lipid peroxidation in leaves, associated to an increase of the antioxidant superoxide dismutase activity. However, Chardonnay plants did not exhibit the same responses as Xynisteri against DS (i.e., stomatal closure, total phenolics and antioxidants) over the first four days. Additionally, Chardonnay showed leaf damage with increased lipid peroxidation levels and activation of catalase and peroxidase. Interestingly, HS increased leaf stomatal conductance and decreased total phenolic content, flavonoids and antioxidant capacity in Chardonnay after 20 d of stress. In both cultivars, HS had milder effects compared to DS, and again Xynisteri showed better performance than Chardonnay in terms of damage index and antioxidative activities. Overall, Xynisteri adaptation to DS and HS was higher than that of Chardonnay, and both cultivars reacted more to the short-term DS than to HS. Although the Xynisteri performances under stress conditions provide an important resource for adaptation to stressful conditions, the impacts on earliness, yield and grape quality remain to be explored.
Highlights
Plants will be increasingly challenged by climate change characterized by frequent and severe events of heat and drought
Grapevines plants were exposed to drought stress (DS) and heat stress (HS) conditions up to 20 d, and during that period, daytime temperature averaged 30.85 ± 0.37 ◦ C and 39.31 ± 0.49 ◦ C for outdoors and indoors, respectively (Figure S1)
The increased temperatures during the daytime reflected relative humidity decreases, while the opposite occurred during night time
Summary
Plants will be increasingly challenged by climate change characterized by frequent and severe events of heat and drought. Long-living trees have evolved a diversity of adaptive mechanisms to minimize their fitness costs under stressful conditions [1]. These adaptations operate at the physiological and molecular levels and involve regulation of stomatal opening, change of photosynthetic rate, Rubisco activity and chlorophyll binding proteins at the chloroplast, imbalance in redox homeostasis, production of reactive oxygen species (ROS) and synthesis of protective compounds and enzymes [2,3,4,5,6]. Physiological responses mainly depend on morphological traits (leaf size, leaf length, width) and anatomical traits (leaf thickness, palisade and spongy parenchyma). A greater extent of palisade parenchyma is reflected with more frequent sap movement (due to higher vessel density in stem anatomy) [11] and transmission of water and minerals to the main leaves, vegetative shoots and fruits [12]
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