Department of Plant Physiology, Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, Tartu, 51014, Estonia.
Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan, 666303, China.
Physiol Plant. 2019 Dec;167(4):661-675. doi: 10.1111/ppl.12923. Epub 2019 Feb 19.
Xylem vulnerability to cavitation and hydraulic efficiency are directly linked to fine-scale bordered pit features in water-conducting cells of vascular plants. However, it is unclear how pit characteristics influence water transport and carbon economy in tropical species. The primary aim of this study was to evaluate functional implications of changes in pit characteristics for water relations and photosynthetic traits in tropical Ficus species with different growth forms (i.e. hemiepiphytic and non-hemiepiphytic) grown under common conditions. Intervessel pit characteristics were measured using scanning electron microscopy in five hemiepiphytic and five non-hemiepiphytic Ficus species to determine whether these traits were related to hydraulics, leaf photosynthesis, stomatal conductance and wood density. Ficus species varied greatly in intervessel pit structure, hydraulic conductivity and leaf physiology, and clear differences were observed between the two growth forms. The area and diameter of pit aperture were negatively correlated with sapwood-specific hydraulic conductivity, mass-based net assimilation rate, stomatal conductance (g ), intercellular CO concentration (C ) and the petiole vessel lumen diameters (D ), but positively correlated with wood density. Pit morphology was only negatively correlated with sapwood- and leaf-specific hydraulic conductivity and D . Pit density was positively correlated with g , C and D , but negatively with intrinsic leaf water-use efficiency. Pit and pit aperture shape were not significantly correlated with any of the physiological traits. These findings indicate a significant role of pit characteristics in xylem water transport, carbon assimilation and ecophysiological adaptation of Ficus species in tropical rain forests.
木质部对空化的脆弱性和水力效率与维管植物导水细胞中边界纹孔的精细特征直接相关。然而，目前尚不清楚纹孔特征如何影响热带物种的水分运输和碳经济。本研究的主要目的是评估在不同生长形式（即半附生和非半附生）的热带榕属植物中，纹孔特征变化对水分关系和光合作用特性的功能意义，这些植物在相同条件下生长。使用扫描电子显微镜测量了 5 种半附生榕属植物和 5 种非半附生榕属植物的导管间纹孔特征，以确定这些特征与水力、叶片光合作用、气孔导度和木材密度之间是否存在关联。榕属植物在导管间纹孔结构、水力传导率和叶片生理特性方面差异很大，并且在两种生长形式之间观察到明显的差异。纹孔孔径的面积和直径与边材比水力传导率、质量基础净同化率、气孔导度（g）、胞间 CO 浓度（C）和叶柄导管腔直径（D）呈负相关，而与木材密度呈正相关。纹孔形态仅与边材和叶片比水力传导率和 D 呈负相关。纹孔密度与 g、C 和 D 呈正相关，与内在叶片水分利用效率呈负相关。纹孔和纹孔孔径形状与任何生理特征均无显著相关性。这些发现表明纹孔特征在榕属植物木质部水分运输、碳同化和热带雨林生态生理适应中具有重要作用。
