Zailaa Joseph, Trueba Santiago, Browne Marvin, Fletcher Leila R, Buckley Thomas N, Brodersen Craig R, Scoffoni Christine, Sack Lawren
School of the Environment, Yale University, New Haven, Connecticut, USA.
Department of Biological Sciences, California State University, Los Angeles, Los Angeles, California, USA.
Plant Cell Environ. 2025 Feb;48(2):1555-1573. doi: 10.1111/pce.15208. Epub 2024 Oct 27.
Identifying the physiological mechanisms by which plants are adapted to drought is critical to predict species responses to climate change. We measured the responses of leaf hydraulic and stomatal conductances (K and g, respectively) to dehydration, and their association with anatomy, in seven species of California Ceanothus grown in a common garden, including some of the most drought-tolerant species in the semi-arid flora. We tested for matching of maximum hydraulic supply and demand and quantified the role of decline of K in driving stomatal closure. Across Ceanothus species, maximum K and g were negatively correlated, and both K and g showed steep declines with decreasing leaf water potential (i.e., a high sensitivity to dehydration). The leaf water potential at 50% decline in g was linked with a low ratio of maximum hydraulic supply to demand (i.e., maximum K:g). This sensitivity of g, combined with low minimum epidermal conductance and water storage, could contribute to prolonged leaf survival under drought. The specialized anatomy of subg. Cerastes includes trichomous stomatal crypts and pronounced hypodermis, and was associated with higher water use efficiency and water storage. Combining our data with comparative literature of other California species, species of subg. Cerastes show traits associated with greater drought tolerance and reliance on leaf water storage relative to other California species. In addition to drought resistance mechanisms such as mechanical protection and resistance to embolism, drought avoidance mechanisms such as sensitive stomatal closure could contribute importantly to drought tolerance in dry-climate adapted species.
识别植物适应干旱的生理机制对于预测物种对气候变化的响应至关重要。我们测量了在一个共同花园中种植的七种加利福尼亚鼠李属植物叶片水力传导率和气孔导度（分别为K和g）对脱水的响应，以及它们与解剖结构的关联，其中包括半干旱植物区系中一些最耐旱的物种。我们测试了最大水力供应与需求的匹配情况，并量化了K下降在驱动气孔关闭中的作用。在鼠李属物种中，最大K和g呈负相关，并且随着叶片水势降低（即对脱水高度敏感），K和g均急剧下降。g下降50%时的叶片水势与最大水力供应与需求的低比率（即最大K:g）相关。g的这种敏感性，再加上低最小表皮导度和水分储存，可能有助于在干旱条件下叶片的长期存活。Cerastes亚属的特殊解剖结构包括具毛的气孔窝和明显的皮下组织，并且与更高的水分利用效率和水分储存相关。将我们的数据与其他加利福尼亚物种的比较文献相结合，Cerastes亚属的物种相对于其他加利福尼亚物种表现出与更高耐旱性和对叶片水分储存的依赖相关的特征。除了机械保护和抗栓塞等抗旱机制外，敏感气孔关闭等避旱机制可能对适应干旱气候的物种的耐旱性有重要贡献。
