5个蔷薇科树种栓塞疲劳及其与导管解剖结构的关系

Cavitation Fatigue in Five Rosaceae Species and Its Relationships with Vessel Anatomy

栓塞疲劳是植物已发生过一次栓塞,经过栓塞恢复后再次遇到干旱胁迫时其抗栓塞能力减弱的现象。栓塞疲劳会削弱木质部的水分运输,威胁干旱事件下植物的生长和生存。作为北温带代表性之一的物种,蔷薇科植物常遭受干旱胁迫。为明确蔷薇科常见树种是否发生栓塞疲劳现象,并揭示造成疲劳现象种间差异的木质部解剖学机理,以梨(Pyrus bretschneideri)、苹果(Malus pumila)、桃(Prunus persica)、李(Prunus salicina)和樱桃(Prunus pseudocerasus)为材料,通过Cavitron离心机技术评估栓塞疲劳的发生及程度,分析栓塞疲劳程度(degree of cavitation fatigue,DCF)与木质部导管解剖结构特征(导管直径、密度、连接度、内径跨度、导管间壁厚、导管抗垮塌能力)的关系。结果表明,5个树种都发生栓塞疲劳现象,均为“脆弱树种”。各树种的栓塞疲劳程度均>70%,桃的疲劳程度最大(88.01±0.85)%,苹果的疲劳程度最小(74.21±2.16)%。DCF与导管密度呈显著负相关(P<0.05),与导管间壁厚呈极显著正相关(P<0.01),表明导管密度越小、导管间壁厚度越厚的树种发生的栓塞疲劳程度越大。考虑到导管间纹孔结构对树种栓塞抗性发挥重要作用,未来研究应结合木质部导管水平和纹孔水平进行全面分析以提高在气候变化下频繁干旱事件对树木抗栓塞能力影响的认知。

Cavitation fatigue is a phenomenon in which a plant has already experienced cavitation once,and after embolism refilling,its embolism resistance is reduced when it is exposed to drought stress again.Embolism fatigue can weaken water transport in xylem of plants and threaten plant's growth and survival during drought.As one of the representative species in the northern temperate zone,Rosaceae tree species are often subjected to drought stress.In the study,to determine whether cavitation fatigue occurs in common Rosaceae tree species and to reveal the xylem anatomical mechanism causing interspecific differences in cavitation fatigue,Pyrus bretschneideri,Malus pumila,Prunus persica,P.salicina,P.pseudocerasus were used as research materials,assessing the occurrence and degree of cavitation fatigue by Cavitron centrifuge technique and analyzing the correlation between the degree of cavitation fatigue and the anatomical traits of xylem vessels(vessel diameter,vessel density,intervessel contact fraction,conduit wall span,double vessel wall thickness,theoretical vessel implosion resistance).All species suffered from cavitation fatigue and were"weakened species".The degree of cavitation fatigue(DCF)of all species was above 70%,with the largest DCF for P.persica(88.01±0.85)%and the least DCF 7 for M.pumila(74.21±2.16)%.DCF was negatively correlated with vessel density(P<0.05)and positively correlated with inter-catheter wall thickness(P<0.01),suggesting that the species with less vessel density and thick double vessel wall exhibits a high degree of cavitation fatigue.Considering that the important role of intervessel pit structure in cavitation resistance of tree species,future studies should perform a comprehensive analysis combining xylem vessel and pit level to improve our knowledge of the impact of frequent drought events on tree embolism resistance under climate change.