Department of Viticulture & Enology, University of California, Davis, Davis, CA 95616, USA.
USDA-ARS, Plant Genetic Resources Unit (PGRU), Geneva, NY 14456, USA.
Ann Bot. 2024 Jul 9;134(2):205-218. doi: 10.1093/aob/mcae032.
Many agricultural areas are expected to face hotter, drier conditions from climate change. Understanding the mechanisms that crops use to mitigate these stresses can guide breeding for more tolerant plant material. We tested relationships between traits, physiological function in hot conditions and historical climate associations to evaluate these mechanisms for winegrapes. We expected a more negative leaf osmotic potential at full hydration (πo), which reduces leaf turgor loss during drought, and either a metabolically cheaper or more osmoprotectant leaf chemical composition, to allow cultivars associated with hot, dry regions to maintain greater gas exchange in hot growing conditions.
We measured πo, gas exchange and leaf chemistry for seven commercially important winegrape cultivars that vary widely in historical climate associations. Vines were grown in common-garden field conditions in a hot wine-growing region (Davis, CA, USA) and measured over the hottest period of the growing season (July-September).
The value of πo varied significantly between cultivars, and all cultivars significantly reduced πo (osmotically adjusted) over the study period, although osmotic adjustment did not vary across cultivars. The value of πo was correlated with gas exchange and climate associations, but in the direction opposite to expected. Photosynthesis and πo were higher in the cultivars associated with hotter, less humid regions. Leaf chemical composition varied between cultivars but was not related to climate associations.
These findings suggest that maintenance of leaf turgor is not a primary limitation on grapevine adaptation to hot or atmospherically dry growing conditions. Thus, selecting for a more negative πo or greater osmotic adjustment is not a promising strategy to develop more climate-resilient grape varieties, contrary to findings for other crops. Future work is needed to identify the mechanisms increasing photosynthesis in the cultivars associated with hot, dry regions.
许多农业区预计将面临因气候变化导致的更热、更干燥的条件。了解作物用于缓解这些压力的机制可以指导更耐受的植物材料的培育。我们测试了性状、热条件下的生理功能与历史气候关联之间的关系，以评估这些机制在酿酒葡萄中的作用。我们期望在充分水合时具有更负的叶渗透势（πo），这可以减少干旱期间叶片膨压的损失，或者具有代谢成本更低或更具渗透调节作用的叶片化学成分，以使与炎热、干燥地区相关的品种在炎热的生长条件下保持更大的气体交换。
我们测量了七个在历史气候关联上差异很大的商业上重要的酿酒葡萄品种的 πo、气体交换和叶片化学成分。在炎热的酿酒区（美国加利福尼亚州戴维斯）的共同花园田间条件下种植葡萄藤，并在生长季节最热的时期（7 月至 9 月）进行测量。
品种间的 πo 值差异显著，所有品种在研究期间都显著降低了 πo（渗透压调整），尽管渗透压调整在品种间没有差异。πo 值与气体交换和气候关联相关，但与预期的方向相反。与较热、较干燥地区相关的品种的光合作用和 πo 值更高。叶片化学成分在品种间有所差异，但与气候关联无关。
这些发现表明，维持叶片膨压不是葡萄适应炎热或大气干燥生长条件的主要限制因素。因此，选择更负的 πo 或更大的渗透调节不是开发更具气候适应能力的葡萄品种的有前途的策略，这与其他作物的研究结果相反。需要进一步研究以确定增加与炎热、干燥地区相关的品种的光合作用的机制。
