摘要:植物茎干导水系统起着植株水分长距离输导功能，深入了解植物导水解剖结构和功能对于认识植物水分、养分输导和分配策略具有重要意义，然而相关研究还是主要集中在木本乔、灌木物种上，而对于多年生草本物种的相关研究还未引起人们的重视。以黄土高原多年生草本物种为研究对象，在黄土高原沿降雨梯度（250-530 mm）布设12个采样点，采集了30种多年生草本物种的主根解剖材料，并分析了该地区草本物种根部导管解剖结构及空间分异特征。研究结果表明1）多年生草本物种根部导管特征参量具有较大的变异性，在固定测量范围内导管数量、导管直径、导管分数、总水分传导效率的变化范围分别为25-295个、24.46-54.58 μm、2.42%-33.16%、0.034-25.357 kg m^-1 MPa^-1 s^-1。2）多年生草本根部导管直径、导管分数和导水效率均沿降雨量的增加呈不断下降趋势，其中以导水效率下降趋势最为明显（R=-0.3—-0.362，P<0.05），这表明水分条件是限制黄土高原草本物种根部导水特征空间变异的主要因素。3）多年生草本根部导管直径和导水效率以半荒漠分布为主的蒺藜科草本物种中数值最高，其次是人工种植为主的豆科草本物种，而以自然分布为主的菊科草本物种的导管参量数值最低，这表明黄土高原不同类群草本物种的导水特征和输水策略存在较大差异性。



Abstract:Plant stem xylem system of woody species has an important role in long-distance water transport, and the scientific description of anatomical xylem structure and functions are essential for understanding the transportation mechanism and allocation strategies of water and nutrient of woody species. However, the related research on perennial herbaceous species has received scant attention. In this study, the main root samples of 30 perennial herbaceous along the precipitation gradient (from 250 mm to 530 mm) in the Loess Plateau were collected. We measured eight hydraulic conductivity traits and analyzed their spatial variability. The results indicated that 1) the value of xylem traits had comparatively large magnitude of variability. The number of vessel, vessel fraction, mean vessel diameter and total water transfer efficiency ranged from 25 to 295, 24.46 μm to 54.58 μm, 2.42% to 33.16%, and 0.034 kg m^-1 MPa^-1 s^-1 to 25.357 kg m^-1 MPa^-1 s^-1, respectively. 2) The vessel diameter, vessel fraction and water transfer efficiency of xylem conduits roughly kept steady decreasing trend with the increasing precipitation. In particular, the negative relationship between water transfer efficiency and precipitation approached the significant levels (r=-0.3—-0.362, P<0.05). This emphasized the fact that moisture availability exerted significant influence on spatial variability of hydraulic conduct traits of the perennial herbaceous species in the Loess Plateau. 3) The value of vessel diameter and water transfer efficiency were the highest of the herbaceous species in the family of Zygophyllaceae that mainly distributed in sub-desert regions, followed by the herbaceous species (planted species) of Leguminosae family, and the lowest value were found in the herbaceous species (native species) of Compositae family, indicating the heterogeneous hydraulic traits and diverse water transfer strategies of different phyto-groups of perennial herbaceous species on the Loess Plateau.





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