Research Institute of Forestry New Technology, Chinese Academy of Forestry, Beijing 100091, China.
Mountain Tai Forest Ecosystem Research Station of National Forestry and Grassland Administration, Forestry College of Shandong Agricultural University, Taian 271018, China.
Tree Physiol. 2021 Sep 10;41(9):1601-1610. doi: 10.1093/treephys/tpab028.
Stomatal regulation serves as an important strategy for plants to adapt to drought. However, the understanding of how complexes of plant-functional traits vary along the continuum from isohydry to anisohydry remains insufficient. In this study, we investigated a proxy of the degree of iso/anisohydry-the water potential at stomatal closure-and a series of functional traits of leaves and branches in 20 temperate broadleaf species planted in an arid limestone habitat in northern China. The results showed that the water potential at stomatal closure was significantly correlated with many functional traits. At the anisohydric end of the spectrum, species had a higher leaf carbon content and vein density, a greater stomatal length, a thicker lower leaf epidermis, higher embolism resistance, higher wood density, a greater Huber value, a greater ratio of fiber wall thickness to xylem lumen diameter, a larger proportion of total fiber wall area to xylem cross-sectional area, a lower water potential at the turgor loss point (TLP), a smaller relative water content at the TLP, a lower osmotic potential at full turgor and a smaller specific leaf area. It is concluded that a continuum of coordination and trade-offs among co-evolved anatomical and physiological traits gives rise to the spectrum from isohydry to anisohydry spanned by the 20 tree species, and the anisohydric species showed stronger stress resistance, with greater investment in stems and leaves than the isohydric species to maintain stomatal opening under drought conditions.
气孔调节是植物适应干旱的重要策略。然而，对于植物功能性状复合体如何沿着等水合到非等水合的连续体变化，人们的理解仍然不足。本研究以 20 种在中国北方干旱石灰岩生境中种植的温带阔叶树种为研究对象，通过测定气孔关闭时的水分势（一种衡量等/非等水合程度的代理指标）以及叶片和枝条的一系列功能性状，探讨了这种程度的等/非等水合性。结果表明，气孔关闭时的水分势与许多功能性状显著相关。在非等水合的一端，物种具有更高的叶片碳含量和叶脉密度、更大的气孔长度、更厚的下表皮、更高的栓塞抗性、更高的木材密度、更大的 Huber 值、更大的纤维壁厚度与木质部腔直径的比值、更大的总纤维壁面积与木质部横截面积的比值、更低的膨压丧失点（TLP）水分势、更小的 TLP 相对含水量、更高的完全膨压时的渗透势以及更小的比叶面积。研究结果表明，协调和权衡共同进化的解剖和生理性状的连续体导致了这 20 个树种的等水合到非等水合的连续谱，非等水合树种比等水合树种具有更强的抗逆性，在干旱条件下，为了维持气孔开放，它们在茎和叶上的投资更大。
