酸枣叶片结构可塑性对自然梯度干旱生境的适应特征

叶片是植物体暴露于环境中面积最大的器官,其最易感知环境变化而发生形态和结构上的改变。为探究植株叶片结构对不同生境的适应机理,研究以生长在烟台-石家庄-宁夏-新疆不同地域气候条件形成的自然梯度干旱环境中的酸枣为试验材料,应用植物显微技术研究酸枣叶片的结构的可塑性对不同自然梯度干旱环境的适应特征。结果表明:酸枣叶表皮着生有表皮毛,表皮细胞外覆有角质层与蜡质。叶肉为全栅型,栅栏组织发达,海绵组织退化,叶肉中有晶体及大量的分泌细胞。从烟台至新疆随生境梯度干旱加剧,酸枣叶片叶面积逐渐变小,叶片厚度依次增加,叶表皮角质层加厚,且上角质层厚度大于下角质层厚度;叶片上下表皮细胞长径及短径先增后降,栅栏组织总厚度和密度依次增大、层数减少,各层栅栏组织细胞的长径逐渐增加。叶脉薄壁细胞相对厚度逐渐减小,导管管径增大,晶体(草酸钙晶体)数增多。在梯度干旱环境中酸枣植株通过减小叶面积、提高栅栏组织密度、增加叶片及角质层厚度降低蒸腾作用,减少水分散失;通过增大导管管径提高水分利用率;通过增加晶体数量提高叶片机械性能,改变细胞的渗透势、提高吸水和保水能力。上述叶片结构的变化是酸枣植株长期对不同自然梯度干旱生境的适应特征。由此可知,叶片形态结构中叶面积、叶片厚度、角质层及叶肉组织(栅栏组织)随环境变化的可塑性较大。     

淮北相山恢复演替群落优势树种的水分生理生态研究

对淮北相山不同恢复演替阶段植被中4个优势树种叶片的水分生理指标进行研究,结果表明：在同一生境(混交林)下,广布优势种（酸枣和牡荆）比局部优势种（柘树和构树）具有更强的耐旱性,但后者的资源获取能力更强,生长速度更快;酸枣和牡荆的耐旱机理不同,酸枣为低水势耐旱植物;牡荆为高水势耐旱植物。酸枣和牡荆的叶片水分生理指标均随群落环境的不同而表现出一定表型可塑性,它们在不同群落中的耐旱性依次为：混交林林内>混交林林缘>灌丛>灌草丛>人工侧柏林。生理可塑性导致酸枣和牡荆具有更宽的生态幅和更强的耐旱性,这是它们在相山成为广布优势种的重要原因。     

扁担木叶片和次生木质部解剖和水分生理特征的可塑性

基于叶片和次生木质部解剖特征及水分生理指标观测,研究了淮北相山不同群落中扁担木的表型可塑性.结果表明,扁担木叶片结构表现出中生特点：叶为异面叶,较薄,角质层不甚发达,气孔密度较小.次生木质部表现出旱生特点：导管频率和复孔率较高,导管分子短而窄,纤维很短,射线很低.扁担木叶片、次生木质部的解剖和水分生理特征均表现出一定的可塑性,其可塑性指数高低顺序为次生木质部解剖特征（0.24）＞水分生理特征（0.19）＞叶片解剖特征（0.18）.与侧柏林和混交林相比,灌丛中扁担木个体对干旱生境有一定的适应能力,表现在次生木质部导管分子短,导管频率高,单孔率低,木纤维短,射线矮小,具有较大的相对输导率和较小的脆性指数;叶片水势、组织含水量、自由水含量较低,叶面积、比叶面积较小,而束缚水含量、束缚水自由水比值较高.扁担木的解剖和生理可塑性,使之能忍受群落演替早期的干旱生境,更好地适应演替后期的中生环境,从而成为广布种和混交林中的优势种.     

藏东南色季拉山薄毛海绵杜鹃叶解剖结构特征与环境适应性

以藏东南色季拉山9个不同海拔梯度的薄毛海绵杜鹃(Rhododendron aganniphum var.schizopeplum)叶片为试验材料,采用石蜡切片技术,测定10项叶片解剖结构指标,应用叶片解剖结构指标的可塑性指数和相关性分析方法探索薄毛海绵杜鹃对藏东南色季拉山强紫外辐射和高寒环境的适应性。结果表明:(1)薄毛海绵杜鹃叶片为异面叶,上表皮有明显的角质层,下表皮有表皮毛,栅栏组织细胞2～3层。(2)随着海拔的升高,叶片角质层厚度、上下表皮厚度、栅栏组织厚度、海绵组织厚度、叶片厚度呈现明显增大趋势,而组织结构紧密度和疏松度变化不显著,主脉突起度呈现下降趋势。(3)各项叶片解剖结构指标的可塑性指数显示,薄毛海绵杜鹃在解剖结构上表现出较小的可塑性,对外界环境的适应能力较弱。(4)依据薄毛海绵杜鹃各项叶片解剖结构指标的相关性分析结果,除海绵组织厚度与栅栏组织厚度、下表皮厚度与上角质层厚度之间相关性不显著外,其余各指标之间均呈显著相关关系,且叶片的解剖结构指标方面也存在明显的协同进化现象。研究发现,藏东南色季拉山薄毛海绵杜鹃通过增加叶片角质层厚度、表皮厚度和叶肉厚度等解剖结构指标的方式增强对外界极端环境的适应能力,从而有利于其在恶劣的高山生境下生存繁衍,使该物种成为生态位理论中的广幅种。     

不同区域长柄扁桃叶片解剖结构及其抗旱性分析

采用常规石蜡切片技术、光学显微镜观察,选取叶片厚度、角质层厚度、主脉厚度、上表皮栅栏组织厚度等10项旱生指标对来自河北丰宁、内蒙古乌审旗和固阳、陕西神木和榆阳共5个地区的长柄扁桃分别在正常生长和干旱胁迫后进行叶片解剖结构分析,探讨其抗旱的解剖结构特征,为长柄扁桃地区间引种和品种选育提供理论依据。结果表明:(1)河北地区长柄扁桃旱害指数最高,旱害最严重,自身耐旱性能最差;神木和固阳地区的旱害指数均低于河北丰宁与乌审旗地区;榆阳区的旱害指数最小,其抵抗干旱能力最强。(2)5个地区的长柄扁桃叶片结构具有相似性,表皮均具有角质层,主脉为双韧维管束,栅栏组织排列紧密整齐,大部分具有上下两层栅栏组织;抗旱性最弱的河北丰宁地区长柄扁桃叶片最大且最薄,上表皮、角质层及叶片紧密度等均最小,栅栏组织细胞只有一层且排列比较疏松,海绵组织细胞排列散乱、不规则且细胞间隙较大,叶脉维管组织口径小,疏导功能微弱;抗旱性最强的榆阳区长柄扁桃的叶片最小且最厚,对应的角质层、上表皮厚度、叶片紧密度等也最大,双层栅栏组织,第一层细胞细长排列紧密,第二层较短,维管组织发达,含较多的贮水细胞(粘液细胞和含晶细胞)。(3)根据5个地区长柄扁桃的旱害指数和叶片解剖结构的各指标参数比较,并通过隶属函数法分析结果表明,各地区长柄扁桃抗旱性顺序为:陕西榆阳区>陕西神木>内蒙古固阳>内蒙古乌审旗>河北丰宁。     

青藏高原2种柳属植物叶片解剖结构和光合特征的比较

对青藏高原不同海拔生境条件下2种柳属植物墨竹柳(Salix maizhokunggarensis)和左旋柳(Salix paraplesia var.subintegra)叶片结构和光合特征进行了比较研究,以探讨植物对高原环境变化的适应性.结果表明:随着海拔的升高,2种柳的叶片解剖结构和光合特征呈规律性变化,主要表现为除气孔面积趋于变小外,叶片的厚度、栅栏细胞的层数、上下表皮的角质层厚度、第一层栅栏组织细胞密度、气孔密度及叶片主脉厚度等指标均呈增加趋势;但海拔的变化对2种柳树叶片结构中的叶片类型、表皮细胞的形状和排列、栅栏细胞的形状、栅栏组织的发达程度、胞间隙以及主脉维管组织的发达程度的影响不明显;随海拔升高,2种柳树的Pn、Gs和Ci值均显著降低,而Ls值显著升高.通过叶片结构和光合数据分析,研究认为2种柳树叶片适应高原环境变化的策略相似,且均以结构变化和牺牲碳同化能力为代价来适应高原环境.     

我国荒漠不同生态类型植物的旱生结构

 本文研究了我国荒漠15种不同类型植物的解剖结构。结果表明,超旱生和旱生植物具有典型的旱生结构,尤以超旱生植物明显,例如沙冬青、梭梭。 旱生结构的基本特征是：叶片及角质层厚,具表皮毛、腺毛、瘤状或乳状突起,气孔下陷,栅栏组织及贮水组织发达,构成等面叶及肉质叶,具含晶细胞和粘液细胞;维管束鞘、维管束帽及纤维细胞的存在,增强了植株的坚固性。中生植物叶片及角质层较薄：气孔平置或拱起,栅栏组织及海绵组织同等发育,胞间隙大,为背腹叶,这是典型的中生结构。     

七种阔叶常绿植物叶片的生态解剖学研究

对 7种常绿阔叶植物叶片的解剖学特征的观察结果表明 ,它们的叶片在结构上均表现出典型的旱生特点 :异面叶 ,上表皮细胞较厚且排列紧密 ,具发达的角质膜 ,无气孔器分布 ,下表皮细胞较小 ,气孔器密度较大 ;栅栏组织细胞层数较多 ,排列紧密 ,海绵组织细胞排列极其疏松 ,并形成通气组织 ;中脉及其输导组织和机械组织发达。越冬叶和越夏叶在解剖结构上存在一定的差异 :前者在角质膜 ,叶片厚度和栅栏组织厚度等方面比后者厚 ,而在气孔密度和输导组织方面则比后者略有减少或不发达。这些差异 (发育可塑性 )是常绿阔叶植物适应冬、夏季截然不同的两种生境 (生境的时间异质性 )的表现形式     

延安城区10种阔叶园林植物叶片结构及其抗旱性评价

利用石蜡切片法和指甲油印迹法,对延安城区10种阔叶园林植物叶片解剖结构——叶片厚度、上下表皮角质层厚度、上下表皮厚度、栅栏组织厚度、海绵组织厚度、中脉厚度、维管束厚度、下表皮气孔密度、气孔长度、气孔宽度等进行测定,对栅栏组织与海绵组织厚度比、叶片结构紧实度、维管束厚度与叶脉厚度比等15个植物抗旱性指标进行分析,并运用方差分析和主成分分析,结合抗旱隶属函数法对物种间的抗旱性进行综合评价。结果表明:(1)15个旱性指标在10种阔叶园林植物间差异显著,变异系数为19.34%～73.73%,均具有较高灵敏度。(2)10种植物叶片均具备抵抗干旱环境的解剖结构,表皮、角质层、栅栏组织、叶脉、维管束等较为发达,气孔主要分布在下表皮,国槐为等面叶,其余为异面叶。(3)叶片上下表皮厚度、栅栏组织厚度、维管束厚度、气孔密度可作为园林植物抗旱性综合评价的主要指标,10种阔叶园林植物的抗旱性大小顺序为:樱花>月季>红叶李>国槐>紫丁香>紫藤>爬山虎>丝绵木>连翘>紫叶小檗。     

马蔺叶片解剖结构特征与其抗旱性关系研究

通过温室模拟干旱胁迫试验,从中国北方不同生境生长的15份野生马蔺种质材料鉴定出3个不同抗旱性群体(强抗旱、中度抗旱和弱抗旱),从中选择具代表性的不同抗旱级别的4份马蔺种质,进行其叶片组织解剖结构特征的观察和比较,以进一步证实马蔺叶片解剖结构特征及其与抗旱性的关系。结果表明,各种质材料间叶片厚度、上下表皮细胞厚度、角质层厚度、气孔密度、栅栏组织厚度、海绵组织厚度、栅栏组织/海绵组织厚度、CTR值和SR值等结构参数指标均与马蔺种质材料抗旱性存在密切的关系。其中,强抗旱种质材料的叶片厚度、上下表皮细胞厚度和角质层厚度大,气孔密度大,栅栏组织和海绵组织较发达,叶片组织紧密度大、疏松度小,栅栏组织/海绵组织厚度比较高;弱抗旱种质材料的叶片厚度、上下表皮细胞厚度和角质层厚度小,气孔密度小,栅栏组织和海绵组织较薄,叶片组织紧密度小、疏松度大,栅栏组织/海绵组织厚度比较低。     

成都地区10种园林灌木叶片结构与抗旱性关系研究

利用石蜡切片法和指甲油印迹法,对成都地区10种常见园林灌木叶片解剖结构的13个指标:主脉厚度、叶片厚度、上下表皮角质层厚度、上下表皮厚度、栅栏组织厚度、海绵组织厚度、下表皮气孔密度、气孔长度、气孔宽度、叶片结构紧密度、栅栏组织与海绵组织厚度比(栅海比)进行测定和分析,再用方差分析和主成分分析法选取有代表性的指标,结合隶属函数法对物种间的抗旱性进行综合评价。结果显示,13个指标的变异系数为17.40%～68.20%,在10种园林灌木间差异极显著。10种植物都属于异面叶,组织结构易于辨识(三角梅的下表皮角质层太薄,无法测出数据)。叶片结构紧密度、栅海比、气孔密度、气孔长、气孔宽、栅栏组织厚度可作为评价这10种园林灌木抗旱性的重要指标。抗旱性由强到弱依次为:红花继木、鸭脚木、红叶石楠、栀子、西洋杜鹃、海桐、山茶、雀舌黄杨、三角梅和金边大叶黄杨。其中红花继木、鸭脚木、红叶石楠和栀子属于强抗旱品种,可用于屋顶、边坡等区域种植。     

EVOLUTION OF LEAF ARCHITECTURE IN THE CHAPARRAL SPECIES FREMONTODENDRON CALIFORNICUM SSP. CALIFORNICUM (STERCULIACEAE)

The chaparral species Fremontodendron californicum ssp. californicum and the cloud forest species Cheirostemon platanoides arose from a common mesophytic stock. The leaf of C. platanoides is proposed as a model for the ancestral leaf and provides an architectural baseline allowing identification of the types and relative magnitudes of morphological and anatomical modifications which have occurred in the leaf of F. californicum. The leaf of F. californicum reflects intense selection for reduced surface area; however, both deletion and addition of lobes has occurred. Vein density has increased due to a greater number of more highly branched terminal veinlets. Mechanical structures, i.e., sclerenchyma, cuticle, show a quantitative reduction; whereas, water storage tissue, i.e., mucilage cells, has been augmented at the expense of spongy mesophyll. The leaf has become weakly isolateral and the number of palisade strata has increased. No increase in the volume of palisade tissue per unit volume of mesophyll is apparent due to a reduction in palisade cell length and palisade packing density. Total leaf thickness has not increased. The indumentum shows selection for non-living, pedestalled stellate trichomes which form a transpiration-limiting canopy above the stomata. Stomatal density has decreased while guard cell dimensions have become larger. Some structural modifications in F. californicum appear to have evolved directly in response to long-term water stress, others seem more directly related to leaf diminution. Xeroplastic changes in foliar structure are in some cases unreliable indicators of ultimate xeromorphic modifications arising in an evolutionary context.     

Responses of leaf structure and photosynthetic properties to intra-canopy light gradients: a common garden test with four broadleaf deciduous angiosperm and seven evergreen conifer tree species

Spectra of leaf traits in northern temperate forest canopies reflect major differences in leaf longevity between evergreen conifers and deciduous broadleaf angiosperms, as well as plastic modifications caused by within-crown shading. We investigated (1) whether long-lived conifer leaves exhibit similar intra-canopy plasticity as short-lived broadleaves, and (2) whether global interspecific relationships between photosynthesis, nitrogen, and leaf structure identified for sun leaves adequately describe leaves differentiated in response to light gradients. We studied structural and photosynthetic properties of intra-tree sun and shade foliage in adult trees of seven conifer and four broadleaf angiosperm species in a common garden in Poland. Shade leaves exhibited lower leaf mass-per-area (LMA) than sun leaves; however, the relative difference was smaller in conifers than in broadleaves. In broadleaves, LMA was correlated with lamina thickness and tissue density, while in conifers, it was correlated with thickness but not density. In broadleaves, but not in conifers, reduction of lamina thickness was correlated with a thinner palisade layer. The more conservative adjustment of conifer leaves could result from a combination of phylogenetic constraints, contrasting leaf anatomies and shoot geometries, but also from functional requirements of long-lived foliage. Mass-based nitrogen concentration (N(mass)) was similar between sun and shade leaves, and was lower in conifers than in deciduous broadleaved species. Given this, the smaller LMA in shade corresponded with a lower area-based N concentration (N(area)). In evergreen conifers, LMA and N(area) were less powerful predictors of area-based photosynthetic rate (A (max(area))) in comparison with deciduous broadleaved angiosperms. Multiple regression for sun and shade leaves showed that, in each group, A (max(mass)) was related to N(mass) but not to LMA, whereas LMA became a significant codeterminant of A (max(mass)) in analysis combining both groups. Thus, a fundamental mass-based relationship between photosynthesis, nitrogen, and leaf structure reported previously also exists in a dataset combining within-crown and across-functional type variation.     

元江干热河谷植物叶片解剖和养分含量特征

研究了元江干热河谷旱田植物（旱季可浇灌,水分较好）和山坡半萨王纳植被中（自然状况,水分较差）共20种的叶片形态解剖特征,以及7种山坡植物叶片养分含量特征.结果表明,山坡植物叶片比叶重大,气孔密度大,气孔长度小,海绵组织/栅栏组织的值小等.元江干热河谷山坡植物叶片养分含量低,1.3%＞Ca＞N＞K＞1%＞Mg＞P＞S.除氮元素外,其它元素种间差别1～3倍.与热带植物群落叶片养元素含量相比,热带雨林＞元江山坡植物＞东南亚沙地旱生林和巴西矮卡廷加群落,表明元江干热河谷植物叶片具有明显的旱生性形态解剖特征,且叶片养分含量也较低.     

Changes of Leaf Morphological, Anatomical Structure and Carbon Isotope Ratio with the Height of the Wangtian Tree （Parashorea chinensis） in Xishuangbanna, China

Leaf morphological and anatomical structure and carbon isotope ratio （δ^13C） change with increasing tree height. To determine how tree height affects leaf characteristics, we measured the leaf area, specific leaf mass （ratio of leaf mass to leaf area [LMA]）, thickness of the total leaf, cuticle, epidermis, palisade and sponge mesophyll, stomata traits and δ^13C at different heights of Parashorea chinensis with methods of light and scanning electron microscopy （SEM） and isotope-ratio mass spectrometry. The correlation and stepwise regression between tree height and leaf structure traits were carried out with SPSS software. The results showed that leaf structures and δ^13C differed significantly along the tree height gradient. The leaf area, thickness of sponge mesophyll and size of stomata decreased with increasing height, whereas the thickness of lamina, palisade mesophyll, epidermis, and cuticle, ratios of palisade to spongy thickness, density of stomata and vascular bundles, LMA and δ^13C increased with tree height. Tree height showed a significant relationship with all leaf indices and the most significant relationship was with epidermis thickness, leaf area, cuticle thickness, δ^13C. The δ^13C value showed a significantly positive relationship with LMA （R = 0.934）. Our results supported the hypothesis that the leaf structures exhibited more xeromorphic characteristics with the increasing gradient of tree height.     

Leaf biomechanics, morphology, and anatomy of the deciduous mesophyte Prunus serrulata (Rosaceae) and the evergreen sclerophyllous shrub Heteromeles arbutifolia (Rosaceae)

Leaf tensile properties were compared between the mesic deciduous tree Prunus serrulata (var. "Kwanzan") and the xeric and sclerophyllous chaparral evergreen shrub Heteromeles arbutifolia (M. Roem). All values for biomechanical parameters for H. arbutifolia were significantly greater than those of P. serrulata. The fracture planes also differed between the two species with P. serrulata fracturing along the secondary veins, while H. arbutifolia most often fractured across the leaf irrespective of the vein or mesophyll position, thus yielding qualitative differences in the stress-strain curves of the two species. Anatomically, P. serrulata exhibits features typical for a deciduous mesophytic leaf such as a thin cuticle, a single layer of palisade mesophyll, isodiametric spongy mesophyll, and extensive reticulation of the laminar veins. Heteromeles arbutifolia leaves, however, are typically two- to three-fold thicker with a 35% higher dry mass/fresh mass ratio. The vascular tissue is restricted to the interface of the palisade and spongy mesophyll near the center of the leaf. Both epidermal layers have a thick cuticle. The palisade mesophyll is tightly packed and two to three layers thick. The spongy mesophyll cells are ameboid in shape and tightly interlinked both to other spongy cells as well as to the overlying palisade layer. We conclude that the qualitative and quantitative biomechanical differences between the leaves of these two species are likely due to a complex interaction of internal architectural arrangement and the physical/chemical differences in the properties of their respective cell walls. These studies illustrate the importance that morphological and anatomical correlates play with mechanical behavior in plant material and ultimately reflect adaptations present in the leaves of chaparral shrubs that are conducive to surviving in arid environments.