不同水分处理下几种柽柳属植物幼株木质部栓塞及其解剖结构特征

本研究借助木质部导水率及栓塞测量系统，分别对多枝柽柳、刚毛柽柳和紫杆柽柳扦插幼株的木质部水力特性对不同土壤水分处理的响应进行分析。以光学、扫描电子显微镜技术，对各柽柳幼株茎和根(2.5 mmd < 4 mm)木质部导管、纹孔解剖特征进行测量观察；对木质部导水效率与其解剖特征之间的关系进行讨论。结果表明:1)各柽柳植物幼株茎木质部自然栓塞度(PLC值，%)与土壤质量含水率之间有显著负相关关系(r=-0.796, P=0.01)，即随着土壤含水率的下降，其木质部PLC值增大，导水率均有降低；水分条件充足的情况下，各柽柳植物茎木质部PLC值仍然较高(33%~52%)，其中刚毛柽柳的PLC值(33%)显著低于其他2种柽柳(P < 0.05)，但随着干旱胁迫程度的加剧其PLC值显著提高(P < 0.05)；严重干旱胁迫处理下，紫杆柽柳茎的PLC值达到84%，明显高于多枝柽柳和刚毛柽柳(P < 0.05)；3种柽柳植物幼株茎木质部栓塞对土壤干旱处理的敏感程度依次为紫杆柽柳、刚毛柽柳、多枝柽柳。2)各柽柳植物幼株茎、根木质部导管及纹孔数量特征之间有不同程度的体内和种间差异性(P < 0.05)，而其纹孔膜结构上没有明显的差异，纹孔膜上未见微孔。3)各柽柳植物幼株木质部K_s(max)值与导管水力直径(D_h)，导管表面积(V_a)之间具有显著正相关关系(r=0.848, P=0.033; r=0.814, P=0.049)，而与单导管指数(V_s)之间有极显著负相关关系(r=-0.925, P=0.008)。4)紫杆柽柳茎具有导管直径大、导管连接度高、导水率和自然栓塞度高等抗栓塞能力较低植物的木质部特征，但它同时具窄纹孔口等抗栓塞能力强植物的某些解剖特征。研究结果为柽柳属植物抗旱性能或生态适应机理的研究提供新的基础数据。 

Xylem anatomical features and native xylem embolism of several Tamarix spp. species seedlings under different water treatments

Three different Tamarix spp. species (T. ramosissima, T. hispida, T. androssowii) cuttage seedlings were treated with different soil water levels (control, slight drought stress and severe drought stress) for investigating the effects of soil water treatment on the xylem hydraulic features. Xylem hydraulic specific conductivity (K_s(max))and native embolism rates were measured using a XYLEM xylem embolism meter. Xylem vessel and inter-vessel pit features were observed by LM and SEM technique. The relations between xylem hydraulic features with its anatomical characteristics were analyzed. Results showed that:1) the xylem native embolism rates of seedling stem of Tamarix L. species (PLC value, %)had close relations with soil moisture level(r=-0.796, P=0.01), the xylem PLC value increased with the decrease of soil water content; under the optimal water conditions, all Tamarix L. species had higher native PLC values (33%-52%), among them, T. hispida had lower level of PLC value(33%, P < 0.05) than other two species. However, PLC value increased significantly after different drought stress(P < 0.05); stem PLC values of T. androssowii increased to 84% under severe drought stress treatment, and it was significantly higher than other two species(P < 0.05). According to the response of xylem native embolism to different drought stress treatment, the order of stem xylem sensitivity to drought was showed as T. androssowii> T. hispida> T. ramosissima. 2) There were significant inter-plant and inter-specific differences in stem and root xylem vessel and inter-vessel pit quantitative features among 3 Tamarix species(P < 0.05); SEM images indicated that there were no obvious qualitative differences in the inter-vessel pit membrane structures of different Tamarix species. In all species, root and stem xylem intact pit membrane were observed as an uniform deposition of microfibrils across the surface, with no visible pores. 3) Correlation analysis revealed that there was positive significant correlations between xylem K_s(max) value and vessel hydraulic diameter(D_h), vessel surface area(V_a) (r=0.848, P=0.033; r=0.814, P=0.049), and negative relations with solitary vessel index(V_s) (r=-0.925, P=0.008). 4) T. androssowii stem xylem not only had larger vessles, higher vessel grouping index, higher efficiency of hydraulic conductivity and native embolism, which were the xylem characteristics of lower embolism resistant plants, but also had the anatomical features of higher embolism resistant plants such as narrow elliptical pit aperture. Results would deepen the understanding of drought resistant ability of Tamarix species from xylem function and anatomy aspects.