School of Agriculture, Food and Ecosystem Sciences, Faculty of Science, The University of Melbourne, 500 Yarra Boulevard, Richmond, Victoria 3121, Australia.
Royal Botanic Gardens Victoria, Birdwood Avenue, Melbourne, Victoria 3004, Australia.
Tree Physiol. 2023 Sep 6;43(9):1501-1513. doi: 10.1093/treephys/tpad066.
Succulence describes the amount of water stored in cells or organs, regardless of plant life-form, including woody and herbaceous plants. In dry environments, plants with greater survival often have greater leaf succulence. However, it is unclear how leaf succulence relates to plant drought resistance strategies, including isohydry (closing stomata to maintain leaf water status) and anisohydry (adjusting cell turgor to tolerate low leaf water status), which exist on a continuum that can be quantified by hydroscape area (larger hydroscape area indicates more anisohydric). We evaluated 12 woody species with differing leaf succulence in a glasshouse dry-down experiment to determine relationships among leaf succulence (degree of leaf succulence, leaf succulent quotient and leaf thickness) and plant drought response (hydroscape area, plant water use, turgor loss point and predawn leaf water potential when transpiration ceased). Hydroscape areas ranged from 0.72 (Carpobrotus modestus S.T.Blake; crassulacean acid metabolism (CAM) plants) to 7.01 MPa2 (Rhagodia spinescens R.Br.; C3 plants), suggesting that C. modestus was more isohydric and R. spinescens was more anisohydric. More isohydric species C. modestus, Carpobrotus rossii (Haw.) Schwantes and Disphyma crassifolium (L.) L.Bolus (CAM plants) had greater leaf succulence, lower root allocation, used stored water and ceased transpiration at higher predawn leaf water potential, shortly after reaching their turgor loss point. The remaining nine species that are not CAM plants had larger hydroscape areas and ceased transpiration at lower predawn leaf water potential. Greater leaf succulence was not related to cumulative water loss until transpiration ceased in drying soils. All 12 species had high turgor loss points (-1.32 to -0.59 MPa), but turgor loss point was not related to hydroscape area or leaf succulence. Our data suggest that overall greater leaf succulence was related to isohydry, but this may have been influenced by the fact that these species were also CAM plants.
肉质描述了细胞或器官中储存的水分量，无论植物的生活型如何，包括木本和草本植物。在干燥的环境中，具有更高生存能力的植物通常具有更大的叶片肉质。然而，目前尚不清楚叶片肉质与植物抗旱策略之间的关系，包括等水合作用（关闭气孔以维持叶片水分状态）和非等水合作用（调节细胞膨压以耐受低叶片水分状态），这两种策略存在于可以通过水景面积（较大的水景面积表示更非等水合）来量化的连续体中。我们在温室干燥实验中评估了 12 种具有不同叶片肉质的木本物种，以确定叶片肉质（叶片肉质程度、肉质叶系数和叶片厚度）与植物抗旱响应（水景面积、植物耗水量、膨压损失点和蒸腾停止时的清晨叶片水势）之间的关系。水景面积范围从 0.72（Carpobrotus modestus S.T.Blake；景天酸代谢（CAM）植物）到 7.01 MPa2（Rhagodia spinescens R.Br.；C3 植物），表明 C. modestus 更等水合，R. spinescens 更非等水合。更等水合的物种 C. modestus、Carpobrotus rossii（Haw.）Schwantes 和 Disphyma crassifolium（L.）L.Bolus（CAM 植物）具有更大的叶片肉质、较低的根系分配、利用储存的水和在较高的清晨叶片水势时停止蒸腾，这是在达到膨压损失点之后不久。其余 9 种不是 CAM 植物的物种具有更大的水景面积，并在较低的清晨叶片水势时停止蒸腾。在干燥土壤中蒸腾停止之前，更大的叶片肉质与累积水分损失无关。所有 12 种植物的膨压损失点都很高（-1.32 至-0.59 MPa），但膨压损失点与水景面积或叶片肉质无关。我们的数据表明，总的来说，更大的叶片肉质与等水合作用有关，但这可能受到这些物种也是 CAM 植物的事实的影响。
