润楠属广布种和狭域种幼苗生理生态特征

Eco-Physiological Traits of Leaves from Basal Angiosperm Machilus Species with Localized and Widespread Distribution

润楠属植物属于基部被子植物类群,大部分物种局限分布于热带亚热带森林的潮湿生境,但也有些物种分布范围较广。本研究以润楠属11个物种的幼苗为材料,测定了一系列植物叶片水力学性状和解剖结构,包括:比叶重、叶片密度、气孔密度、叶脉密度、膨压丧失点水势、栅栏组织和海绵组织厚度等。结果表明:与其它分布在热带亚热带地区的被子植物相比,润楠属植物的叶脉密度较低,推测叶脉密度受强烈的进化限制;该属植物叶脉密度与气孔密度、栅栏和海绵组织的比值呈显著的正相关,表明该属植物能够维持叶片水平的水分供需平衡;广布种比狭域种具有更低的叶片膨压丧失点和更高的叶片密度,耐旱能力更强,但是比叶重差异不显著;叶片的膨压丧失点与物种的最大树高呈反比,即更高的物种叶片耐失水能力更强,说明植物叶片耐旱性与植物本身的遗传特性有关。本研究结果显示,叶片水力学性状可以较好地用于解释润楠属植物的地理分布。

Machilus species are basal angiosperms, which are mostly distributed in humid tropical and subtropical forest habitats,though a few species are widely distributed. In this study,we measured hydraulic-related traits of sapling leaves from 11 Machilus species,which included leaf mass per area,leaf density,stomatal density,vein density,leaf turgor loss point,and palisade and spongy tissue thickness. We found that, on average, Machilus species had lower vein density compared with that of other tropical and subtropical angiosperms,indicating this trait was strongly influenced by evolution. Leaf vein density was positively and significantly correlated with stomatal density and the ratio of palisade to spongy tissue thickness,indicating the balance between leaf water transpirational demand and supply.Compared with localized species, widespread species were more drought-tolerant and exhibited lower turgor loss point and higher leaf density. Turgor loss point was negatively and significantly correlated with maximum tree height across species,indicating that leaf drought resistance was controlled by genetics. Our study suggests that leaf hydraulic traits can be used to explain the geographical distribution of Machilus species.