摘要
【目的】栓塞脆弱性是木本植物水力学研究的热点,一般通过建立栓塞脆弱性曲线(VC)来评定。离心机法是建立VC的主要方法之一,前人研究普遍认为Cavitron离心机法建立长导管树种VC时,离心枝条内的导管被切开,大量开口导管的存在造成栓塞假象,致使曲线呈现极为脆弱的“r型”,显著高估了植物的栓塞脆弱性。本研究拟在种间水平检验脆弱曲线类型是否受开口导管比例的影响,为离心机法评估植物栓塞脆弱性的可靠性提供参考,从而更准确地评估植物抗栓塞能力,为抗旱树种选择提供可靠依据。【方法】选取具不同导管长度的9个树种,根据Cavitron离心机转子直径的大小(27.4 cm),将9个树种分为3类:长导管树种(平均导管长度>15 cm:刺槐、桑、紫薇)、中导管树种(平均导管长度10~15 cm:女贞、桃、沙棘)和短导管树种(平均导管长度<10 cm:元宝槭、榛、秦白杨)。使用Cavitron离心机法建立VC,采用注气法测定最大和平均导管长度,分析开口导管比例与VC曲线特征的关系。【结果】长导管树种及短导管树种的元宝槭和榛的VC能用单威布尔函数良好拟合,中导管树种和短导管树种秦白杨的VC能用双威布尔函数良好拟合。长导管树种刺槐和桑的VC相似,呈“r型”,而紫薇呈“s型”;中导管树种女贞、沙棘及短导管树种秦白杨的VC呈2条“s型”曲线组成的双威布尔形,而中导管树种桃的VC更接近于“s型”;短导管树种元宝槭和榛的VC均呈“s型”。长导管树种的平均导管长度(Lv)接近20 cm,两端开口的导管比例(F27.4)达20%左右,一端开口到离心机转子中心的导管比例(F13.7)达60%左右;中导管树种的Lv接近离心机转子半径(13.7 cm),F27.4达10%左右,F13.7达40%左右;短导管树种的Lv在5 cm以下,F27.4均小于0.1%,F13.7最大为2.68%。9个树种的栓塞脆弱性指标P12、P50(分别对应导水率损失12%、50%时的木质部水势)均与开口导管比例(F27.4、F13.7)呈显著正相关(P<0.05),但P88(导水率损失88%时对应的木质部水势)与开口导管比例不具有显著相关。【结论】在种间水平验证开口导管比例能使Cavitron离心机建立的VC发生类型变化,当开口导管比例极少时,脆弱曲线呈“s型”,随着开口导管比例增多可能会造成“r型”曲线及介于“s型”与“r型”之间的“中间型”曲线。此结论能进一步支持开口导管栓塞假象的假说,为Cavitron离心机法测定栓塞脆弱性时的树种选择提供理论依据。
【Objective】Plant embolism vulnerability is a hot issue in hydraulics studies of woody plants,and is generally assessed by establishing vulnerability curve(VC).Centrifuge method is one of the main method being applied to establish the VC.Previous studies have generally believed that when the Cavitron centrifuge method was used to establish the VC of a long-vesselled tree species,the vessels inside the centrifuged branch was cut open,and the presence of a large number of open vessels causing the embolism artifact,resulting in extremely vulnerable“r-shaped”curve,so significantly overestimated the cavitation vulnerability of plants.This study was intended to test whether the type of VC is affected by the proportion of open vessels at the inter-specific level,and to lay a foundation for the reliability of centrifuge method in assessing the plant embolism vulnerability,therefore,the plant’s cavitation resistance can be more accurately evaluated,which provides a reliable basis for the selection of drought-resistant tree species in ecological construction.【Method】Nine tree species with different vessel lengths were selected.According to the Cavitron centrifuge rotor diameter(27.4 cm),nine tree species were divided into three categories:long-vesselled species(average vessel length>15 cm,Robinia pseudoacacia,Morus alba and Lagerstroemia indica),medium-vesselled species(average vessel length 10-15 cm,Ligustrum lucidum,Amygdalus persica,Hippophae rhamnoides)and short-vesselled species(average vessel length<10 cm,Acer truncatum,Corylus heterophylla,Populus alba‘I-101’×(P.alba×P.glandulosa‘84K’).The VCs were established by Cavitron centrifuge.Maximum and mean lengths of vessels were measured by air injection technique.Relationships between open vessels fractions and characteristics of the VCs were analyzed.【Result】The VCs of long-vesselled species and short-vesselled species of A.truncatum and C.heterophylla could be well fitted by single Weibull function,while the VCs of medium-vesselled species and short-vesselled species of I-101×84K could be well fitted by double Weibull function.The VCs of long-vesselled R.pseudoacacia and M.alba were similar,showing“r-shaped”,while that of L.indica was“s-shaped”;the VCs of medium-vesselled H.rhamnoides and L.lucidum,and short-vesselled I-101×84K were double Weibull shape consist of two“s-shaped”curves,while the VC of medium-vesselled A.persica was closer to“s-shaped”;the VCs of short-vesselled A.truncatum and C.heterophylla were both“s-shaped”.The mean vessel lengths(Lv)of long-vesselled species were close to 20 cm,the proportion of vessels with both ends opened(F27.4)was about 20%,the proportion of vessels opened from one end to the center of centrifuge rotor(F13.7)was about 60%;the Lv of medium-vesselled species was close to the radius of centrifuge rotor(13.7 cm),F27.4was about 10%,and F13.7was about 40%;the Lv of short-vesselled species was below 5 cm,F27.4 was less than 0.1%,and the maximum value of F13.7was 2.68%.The embolism vulnerability indices P12 and P50(xylem water potentials correspond to hydraulic loss of 12%and 50%,respectively)of nine species were positively correlated with the proportion of open vessels(F27.4and F13.7),but P88(xylem water potential corresponds to hydraulic loss of 88%)was not significantly correlated with the proportion of open vessels.【Conclusion】At the inter-specific level,this study verified that the proportion of open vessels significantly affected the types of embolism vulnerability curves established by Cavitron centrifuge.When the proportion of open vessels was very few,the VCs were“s-shaped”,but with the increase of the proportion of open vessels,the“r-shaped”and“intermediate-shaped”curve may be formed.This conclusion further supports the hypothesis of open vessel artifacts,and provides a theoretical basis for the selection of tree species when measuring the embolism vulnerability by Cavitron centrifuge.
作者
赵涵
黄瑾
张友静
鲁彦君
姜在民
蔡靖
Zhao Han;Huang Jin;Zhang Youjing;Lu Yanjun;Jiang Zaimin;Cai Jing(College of Forestry, Northwest A & F University, Yangling 712100;College of Life Sciences, Northwest A & F University ,Yangling 712100;Qinling National Forest Ecosystem Research Station, Yangling 712100)
出处
《林业科学》
EI
CAS
CSCD
北大核心
2020年第5期50-59,共10页
Scientia Silvae Sinicae
基金
国家自然科学基金项目(31570588)。
