枫香变红过程中叶片组织结构、光合特性及色素含量变化研究

枫香(Liquidambar formosana)因其叶片入秋后逐渐变红而极具观赏价值,是优良的景观生态树种。为了解枫香叶片结构变化与叶色的关系,该文通过连续监测枫香叶片变红过程中组织结构、光合特性及色素含量的变化,分析叶片结构与其光合特性和色素的关系。结果表明：(1)叶片变色过程中,表皮细胞均为椭圆形,紧密排列,未观察到明显的细胞变异,表面未附着绒毛和蜡质,且上表皮细胞与栅栏组织细胞间排列紧密,未出现较大的气室。(2)随着叶片逐渐变红,叶片结构变化显著,其中叶片、上表皮、栅栏组织和海绵组织厚度及气孔开度均逐渐减小,而气孔器长和宽、单个气孔器面积则逐渐增大。(3)随着叶片结构的变化,其叶绿素含量逐渐减少,致使净光合速率逐渐减小,在出现光破坏时,叶片通过在栅栏组织细胞液泡内合成花色苷来自我保护,而大量的花色苷致使叶片表面呈现红色。综上认为,叶绿素含量降低,花色素苷大量积累是导致枫香叶片变红的直接原因,而枫香叶色变红则是其一系列生理结构特征综合作用的结果。     

喀斯特地区莎叶兰的解剖构造及其环境适应性

以广西西北部雅长兰科植物保护区的莎叶兰( Cymbidium cyperifolium)为对象,采用石蜡切片法对莎叶兰叶片和根的解剖构造及其对喀斯特环境的适应性进行了研究。结果表明：(1)莎叶兰叶片的上表皮覆盖有较厚的角质层,气孔均分布于下表皮,且凸出表皮细胞之上;各表皮性状在叶片不同部位存在显著差异,叶片下部的气孔密度、气孔指数和气孔长度最大,表皮细胞密度以叶片上部的最大;叶片属于等面叶,叶肉无栅栏组织和海绵组织的分化;叶脉为明显的平行脉,且粗细交互分布;(2)莎叶兰根的横切面包括根被、皮层、中柱3部分,其中根被细胞排列紧密,为生活细胞;皮层由薄壁细胞组成;根部维管束属于辐射维管束,14原型。菌根粗壮,稀根毛,共生真菌主要分布于根被及皮层中,菌丝体通过根被薄壁细胞间隙及内、外皮层的通道细胞进行侵染。(3)莎叶兰叶片和根的结构不仅有湿生植物特征,如叶片相对较薄、气孔少且凸出表皮细胞、冠/根比值大等;还有旱生植物的特征,如叶片角质层较厚、机械组织发达、细胞结构紧密、具含晶细胞,肉质根具根被,内、外皮层细胞壁明显增厚等。这些结构是莎叶兰对当地缺水、干湿季明显、分布于林下多石砾土壤的生长环境的一种高度适应性表现。     

古林箐秋海棠叶斑结构对叶色的影响

该研究以古林箐秋海棠(Begonia gulinqingensis)为材料,通过分析叶片形态特征、上表皮光学特性、组织结构、叶绿素含量及叶绿素荧光参数(F_v/F_m),探讨了叶片色斑的形成原因。结果表明:(1)古林箐秋海棠叶斑发生频率和数量无明显规律,但发生部位相对稳定,叶斑主要发生在正对叶柄的两条主脉之间。(2)斑区有两种光反射模式,点状反射和多角形反射,栅栏组织细胞呈近等轴的圆形,排列疏松,与上表皮细胞间存在空隙;非斑区只有点状反射模式,栅栏组织细胞为漏斗型,排列紧密,与上表皮细胞间不存在空隙。(3)斑区和非斑区叶绿体均有密集的堆积基粒和丰富的类囊体膜,斑区叶绿素a、b及总叶绿素含量仅比非斑区分别低24.9%、25.2%、25.1%。(4)叶绿素荧光参数(F_v/F_m)值斑区为0.793,非斑区为0.790。虽然斑区叶绿素含量比非斑区略低,但叶绿体结构完整,且叶绿素荧光参数与非斑区无显著差异。斑区上表皮与栅栏组织细胞间的空隙可使光线到达绿色组织时发生二次反射,在叶片表皮细胞边缘形成白色多边形光反射使该区域相对周围正常叶片区域偏白,基于上述结果可推测古林箐秋海棠的淡绿色块斑形成与特殊的叶片结构有关。     

不同色彩珙桐叶片和苞片解剖结构及色素含量比较研究

以生长于同一生境下的粉红珙桐(粉红色叶片、苞片)与普通珙桐(绿色叶片、白色苞片)为试材,对比两种色彩珙桐叶片/苞片解剖结构和色素含量的差异,以揭示珙桐色彩转变的规律。结果显示：(1)两种珙桐叶片均属于异面叶类型,栅栏组织由一层长柱形细胞整齐排列而成,海绵组织排列疏松,部分粉红叶片的上表皮细胞向外凸起,绿叶无此现象;粉红叶片的总厚度及其表皮角质层、栅栏组织和海绵组织厚度都高于绿叶,而表皮较薄。(2)两种珙桐苞片均无栅栏组织和海绵组织的分化,粉红苞片上表皮细胞明显隆起,上表皮角质层增厚,而下表皮变薄。(3)粉红叶片的类黄酮、花色苷含量分别是绿色叶片的1.52倍、3.67倍,两者的光合色素含量无显著差异,但粉红叶片的叶绿素a/b值比绿色叶低很多;粉红苞片花色苷含量显著高于白色苞片,而两者类黄酮含量差异不大。研究表明,花色苷是珙桐叶片和苞片色彩转红的直接因素,类黄酮有助于叶片呈红色;粉红珙桐叶片/苞片的解剖结构发生了一定变化,对光能的利用效率更高,对阴湿环境的适应性增强。     

Spatial distribution of growth rates and of epidermal cell lengths in the elongation zone during leaf development in Lolium perenne L.

Relative elemental growth rates (REGR) and lengths of epidermal cells along the elongation zone of Lolium perenne L. leaves were determined at four developmental stages ranging from shortly after emergence of the leaf tip to shortly before cessation of leaf growth. Plants were grown at constant light and temperature. At all developmental stages the length of epidermal cells in the elongation zone of both the blade and sheath increased from 12 m at the leaf base to about 550 m at the distal end of the elongation zone, whereas the length of epidermal cells within the joint region only increased from 12 to 40 m. Throughout the developmental stages elongation was confined to the basal 20 to 30 mm of the leaf with maximum REGR occurring near the center of the elongation zone. Leaf elongation rate (LER) and the spatial distributions of REGR and epidermal cell lengths were steady to a first approximation between emergence of the leaf tip and transition from blade to sheath growth. Elongation of epidermal cells in the sheath started immediately after the onset of elongation of the most proximal blade epidermal cells. During transition from blade to sheath growth the length of the blade and sheath portion of the elongation zone decreased and increased, respectively, with the total length of the elongation zone and the spatial distribution of REGR staying near constant, with exception of the joint region which elongated little during displacement through the elongation zone. Leaf elongation rate decreased rapidly during the phase when only the sheath was growing. This was associated with decreasing REGR and only a small decrease in the length of the elongation zone. Data on the spatial distributions of growth rates and of epidermal cell lengths during blade elongation were used to derive the temporal pattern of epidermal cell elongation. These data demonstrate that the elongation rate of an epidermal cell increased for days and that cessation of epidermal cell elongation was an abrupt event with cell elongation rate declining from maximum to zero within less than 10 h.Abbreviations LER leaf elongation rate - REGR relative elemental growth rates     

梭梭叶苞状虫瘿结构特征和生长发育研究

该研究采用形态和显微结构观察方法,并结合基于转录组测序和差异表达基因富集分析,研究梭梭叶苞状虫瘿的生长发育特点以及梭梭叶苞状虫瘿与梭梭之间的相互关系,为昆虫与植物协同进化和梭梭虫害防治提供理论依据。结果表明:(1)叶苞状虫瘿的生长发育阶段可以分为3个时期,生长期、形成期和衰亡期。(2)在生长期和形成期的叶苞状虫瘿与梭梭同化枝、鳞叶部位的解剖结构有明显的差别:生长期叶苞状虫瘿的表皮细胞外的角质层损伤,但表皮细胞完整、形态差异不大、排列紧密,没有栅栏细胞组织和花环结构,只有含水量较高的海绵组织,且细胞比同化枝和鳞片小而密,细胞数量是鳞片中的2倍左右,维管柱直径比同化枝和鳞片小;形成期叶苞状虫瘿的表皮细胞外的角质层受到严重损伤,表皮细胞不完整、形态差异大、排列疏松,海绵组织含水量严重减少,维管组织不明显。(3)梭梭叶苞状虫瘿中与植物细胞正常发育相关、光合作用相关的基因富集下调表达,与胁迫相关基因富集上调表达。研究认为,梭梭的叶苞状虫瘿只为促进木虱的生长发育,在提高梭梭光合作用方面没有作用。     

Observation of Apparently Unchanging Mesophyll Cell Diameters Throughout Leaf Ontogeny in Woody Species

The expansion of plant leaves usually lasts 3–6 weeks and it is widely believed that most cell types (epidermal and mesophyll) continue to expand in unison over a similar time period. The evidence supporting this account was derived from studies of herb leaves. We observed in woody species, however, that the diameter of mesophyll cells (spongy and palisade) changed little during leaf expansion from about 5 to 100 % maximum size. To keep pace with epidermal cell enlargement and leaf area expansion, mesophyll cells divided but palisade cell length expanded as leaves grew thicker. The prolonged division of mesophyll and apparently unchanging mesophyll cell diameters constitute a novel pattern of leaf cell development, different from that previously described for herbs. Possible mechanisms that attribute the varied expansion direction and speed to the different cellulose distributions in woody and herbaceous species are suggested. This finding could contribute to an enhanced understanding of the overall mechanism of leaf development.     

How have the alpine dwarf plants in Yakushima been miniaturized? A comparative study of two alpine dwarf species in Yakushima, Blechnum niponicum (Blechnaceae) and Lysimachia japonica (Primulaceae)

Many plant species are miniaturized in the alpine region in Yakushima, Japan. To examine how these alpine dwarf plants are different from their related lowland ones of the same species, we analyzed two phylogenetically distinct species cytologically, genetically and morphologically: one is a fern species, Blechnum niponicum, and the other is an angiosperm species, Lysimachia japonica. The analysis shows that the alpine dwarf and the lowland plants in each of these species do not differ in chromosome number or genetic constitution. The organ-level comparison between the alpine dwarf and lowland plants of B. niponicum shows that the fertile leaf size correlates closely with the sterile one. By contrast, the flower size does not correlate with the leaf size in L. japonica. At the cell level, the leaf size of the alpine dwarf plants of B. niponicum consists of a smaller number of epidermal cells than that of the lowland plants of this species. On the other hand, the smaller leaf size of the alpine dwarf plants of L. japonica depends on both the smaller number and the smaller size of the epidermal cells. We conclude that plant dwarfism in Yakushima shows variation at both the organ and cell levels.     

柠条锦鸡儿小叶解剖结构的环境分异性研究

以巴丹吉林、腾格里、乌兰布和及库布齐沙漠的柠条锦鸡儿成熟叶片为研究对象,采用石蜡切片法,观察叶的横切结构,使用Motic Images Plus 2测定叶片厚度、栅栏组织细胞长和上、下表皮厚度等指标,分析比较4个沙漠的柠条锦鸡儿小叶解剖结构差异。结果表明:(1)生长环境不同,柠条锦鸡儿小叶在表皮、叶肉和叶脉结构上都存在差异,以巴丹吉林沙漠与库布齐沙漠的差异性最为显著。(2)干旱环境下,叶片变小、变厚,栅栏组织和维管束组织更为发达,巴丹吉林沙漠最为干旱,叶片最厚,栅栏组织细胞层数最多、细胞最长,导管列数最多;库布齐沙漠水分条件最好,叶片最薄,栅栏组织细胞最短且层数最少,导管列数最少。(3)对柠条锦鸡儿小叶解剖结构的各项指标与环境参数进行相关分析发现,温度和降水是影响柠条锦鸡儿小叶解剖结构变化的主要因素。     

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。     

濒危植物海南风吹楠营养器官解剖结构特征

该研究采用石蜡切片和光学显微技术,对海南风吹楠营养器官的解剖结构及其对环境的适应性进行了探讨。结果表明:海南风吹楠为典型异面叶,叶片中脉发达,中部分化出髓,上表皮外侧具角质层,内侧具1层内皮层,下表皮外侧无角质层,有气孔器分布,气孔器为双环型,略下陷;栅栏组织3~4层细胞,海绵组织4~6层细胞。茎的初生结构中表皮轻微角质化,维管束为外韧型,8~10个初生维管束围绕髓排列为1轮;茎的次生结构中,表皮外部角质层加厚,维管柱紧密排列连成环状,次生韧皮部和次生木质部发达,形成层细胞3~5层。根的初生结构中表皮细胞外壁加厚,外皮层细胞体积大,形状不规则,内侧具1层形成层,内皮层具凯氏带,初生木质部为多原型,呈辐射状排列。根的次生结构中木栓层细胞5~6层,木栓层内侧具1层木栓形成层,栓内层细胞3层。海南风吹楠营养器官具有一定耐阴和耐旱结构特征,同时与其生活的热带雨林沟谷中高温荫湿的环境相适应。     

羊柴叶形态结构的地域分异特征及其与生态因子间的关系

为探讨沙旱生植物的形态及组织结构对地域分异的响应,揭示植物形态、结构的地域分异规律。该研究以呼伦贝尔沙地、科尔沁沙地、浑善达克沙地及毛乌素沙地的羊柴(Hedysarum laeve)为对象,采用野外测量、石蜡切片技术及叶片解离技术,观察、分析了羊柴叶片形态及组织结构的地域分异特征,并就其形态、结构与生态因子间进行了相关性研究。结果表明:(1)随着干旱程度的加剧,羊柴叶片在形态上表现为变小、变厚,侧生小叶变长、变宽;在结构上表现为单位面积气孔数量减少,上、下表皮细胞变厚,栅栏组织越发达,栅栏细胞排列紧密,主脉维管束直径变大,疏导能力加强。(2)羊柴叶肉中存在大量的异细胞,具有抵御干旱及贮藏等功能,是对干旱环境长期适应的体现。(3)生长季降水量、年均降水量及年均蒸发量是形成羊柴小叶形态、结构地域分异的主要环境因子。以上结果表明植物对地域分异的响应不仅体现在外部形态上,在组织结构上同样产生相应的分异特征,而水热条件则是产生分异的主要因素。     

The fine structure and photosynthetic cost of structural leaf variegation

The leaves of some plants display an optical patchiness on their upper side, displaying light- and dark-green areas with high and low reflectance, respectively. In this investigation, we studied the fine structure of the corresponding sectors and we asked whether the lost reflected light entails a photosynthetic cost to these leaves. Four species, i.e. Arum italicum, Ranunculus ficaria, Cyclamen hederifolium and Cyclamen persicum were investigated. Scanning electron microscope examination revealed that epidermal cells of light-green sectors of all species are more bulgy than corresponding cells of neighboring dark-green leaf sectors. The comparative anatomical study revealed that (i) epidermis thickness of the light-green areas and the number of mesophyll cell layers does not differ from those of the adjacent dark-green leaf sectors and (ii) palisade cells of light-green sectors are slightly larger and more loosely arranged, allowing a much higher percentage of intercellular air spaces. The latter histological feature seems to provide the structural basis for the different optical properties between the two leaf sectors. Contrary to expectations, net photosynthetic rates (expressed on a leaf area basis) were similar in the light-green and the dark-green areas of the two cyclamen species. Yet, in C. persicum net photosynthesis was higher in the light-green areas, if expressed on a dry mass basis. The small size of the light-green spots in the rest of the test plants precluded CO₂ assimilation measurements, yet maximum linear photosynthetic electron transport rates displayed no differences between the two sectors in all plants. Thus, the assumption of a photosynthetic cost in the light-green areas was not confirmed. On the contrary, a higher construction cost was evident in the dark-green areas of three species, displaying a significantly higher specific leaf mass, without any photosynthetic benefit. The results on net photosynthesis were compatible with leaf optical properties and pigment levels. Thus, in spite of the considerably higher reflectance of the light-green areas and their lower (yet normal for a green leaf) chlorophyll levels, corresponding differences in absorptance were slight. In addition, dry mass-based pigment contents in dark-green areas were higher, while chlorophyll a/b (in two species) and carotenoid/chlorophyll ratios (in three species) were lower, pointing to a shade adaptation in these sectors. We conclude that in variegated leaves of this kind, dark-green areas are more costly to build and probably less photosynthetically active. We argue that the high pigment contents of dark-green areas establish steep light gradients in the corresponding mesophyll, rendering deeper chloroplast layers more shade adapted.     

Cytological changes in palisade cells of developing sunflower leaves

Summary Changes in the relative volume of palisade cells (V_v) allocated to various organelle compartments during postemergent leaf development was measured using stereological techniques. The surface to volume ratios (S_v) of the chloroplast and mitochondrial membranes were also measured at each stage. Three leaf stages were sampled, each was defined based on lamina length (10, 45, and 150 mm). The last stage represented a fully expanded leaf. Chloroplast and nuclear compartment V_v values changed significantly in the early stages when cells were actively dividing. Mitochondrial and vacuolar compartment V_v values showed significant changes in the latter stages during cell expansion. The oil vesicle and microbody compartments showed no significant change in V_v value during the developmental process. The surface to volume ratios of the chloroplast membranes increased significantly throughout all stages of the leaf development while mitochondrial cristae S_v values did not change. Organelle replication rates appeared to be independent of changes in cell volume with each organelle exhibiting a specific replication activity pattern. The results of this study suggest two possible mechanisms for the control of cell structural development involving both intrinsic and extrinsic factors.     

Anatomy, palynology and nutlet micromorphology of Turkish endemic Teucrium sandrasicum (Lamiaceae)

In this study, the anatomical features of the leaf and stem, besides the pollen and nutlet characteristics of Teucrium sandrasicum are investigated. T. sandrasicum, belonging to sect. Teucrium, is an endemic perennial herb growing on serpentine around Muğla province. The anatomical studies on T. sandrasicum revealed that the stem shares the general characteristics of the Labiatae family. The leaves clearly exhibit xeromorphy due to features such as the distribution of stomata on the lower surface (hipostomatic), the occurrence of guard cells below the epidermis (xeromorphic type), inrolled margins, thick cuticle layer, thick outer epidermal cell wall, a high density of trichomes and thick palisade layer of the mesophyll. The anatomical studies showed that the upper epidermal cells of the leaf include many spherocrystals. The pollen grains are prolate, medium in size, 3-colpate with verrucate ornamentation. The nutlets are ellipsoid with a reticulate-verrucate surface. The results have proven that T. sandrasicum is different from the other species of the sect. Teucrium because of the branched trichomes on the stem and the lack of eglandular trichomes on the nutlets.     

山东银莲花叶片形态结构对异质生境和海拔变化的响应

山东银莲花为一分布极其狭域的稀有物种,对海拔600 m以上的针阔混交林和山顶灌丛两种异质的生境都具有较高的适应性。为探索其适应策略,选择两种异质生境中的5个海拔梯度样带,采用常规石蜡切片法和显微观察技术,对叶片进行观察、分析和测量,通过比较叶片外部形态特征参数和内部解剖结构的差异,推测其叶片适应海拔和异质生境的响应策略。结果表明:为适应阴暗、潮湿的针阔混交林和干旱、强光照的山顶灌丛两种不同环境,山东银莲花分别表现出不同的适应策略。针阔混交林下,叶片的背腹表皮毛密度、比叶面积和气孔相对开度较山顶灌丛的大,而气孔密度、叶片厚度、栅栏组织和海绵组织的厚度较山顶灌丛的小;山顶灌丛植株叶片栅栏组织细胞排列较林下更加整齐紧密。两种生境中叶片腹面表皮毛的长度、气孔相对开度都随海拔的升高而减小,且差异明显;而叶片厚度、比叶面积、气孔指数等对600 m以上海拔变化未表现出明显的规律性。本研究将为山东银莲花的保护和利用提供理论基础及依据,为其他植物的相关研究提供参考。     

新疆12种黄芩属植物叶表皮微形态结构的研究

应用光学显微镜和扫描电镜技术对新疆12种黄芩属植物叶片上的微形态特征进行观察。结果表明:该属植物叶的上表皮细胞形状及垂周壁式样有多种形式;而下表皮细胞形状均为不规则形,垂周壁式样均为深波形,不具分类学意义,但叶片两面分布的气孔器,在不同种间气孔大小、气孔密度、气孔指数、气孔外拱盖内缘等方面都存在着显著差异;其表皮角质层纹饰和表皮毛的微形态也各有不同;大多数植物叶片表面具腺点,其大小、分布及疏密程度也有不同。植物叶表皮上的这些微形态特征,可为探讨本属种间的分类学及亲缘关系提供一定的佐证。     

Changes in distribution of nucleoids in developing and dividing chloroplasts and etioplasts ofArena sativa

Summary Nucleoid distribution in chloroplasts and etioplasts at the different developmental stages was examined with the first leaves ofAvena sativa by using a DNA-specific fluorescent probe, 46-diamidino-2-phenylindole (DAPI). In light-grown first leaves, three types of plastid nucleoid distribution were recognized. 1. Peripheral distribution in undeveloped chloroplasts which contain only a few thylakoids in the middle region of the leaf sheath. 2. Ring-like arrangement along the rim of developing and dividing young chloroplasts, of which grana were composed of four to eight layers of thylakoids, at the base of the leaf blade. The plane of the nucleoids' ring is in parallel with the face of the thylakoids. 3. Scattered distribution of 10 to 20 discrete spherular nucleoids in the stroma of fully developed chloroplasts, of which grana were composed of up to 20 thylakoids, in the regions of the middle and the tip of the leaf blade. In dark-grown first leaves two types were recognized. 1. Peripheral distribution in developing and dividing young etioplasts in the leaf sheath and the base of the leaf blade. 2. Scattered distribution of 10 or more discrete spherular nucleoids in fully developed etioplasts, containing extended prothylakoids, in the regions of the middle and the tip of the leaf blade. Ring-like arrangement of nucleoids was not observed in any etioplasts. The results indicates that spatial arrangement of plastid nucleoids dynamically changes in close relationship with the development of the inner membrane systems of plastids.     

Phylloclade anatomy in Phyllanthus section Choretropsis (Phyllanthaceae)

The phylloclade anatomy of nine Brazilian species of the genus Phyllanthus section Choretropsis was studied, and its systematic significance was analysed. The arrangement of epidermal cells varied according to the species, with the guard cells of the stomatal apparatus distributed randomly or with the longitudinal axis parallel to the branch. In both branch types, the stomata were distributed on the phylloclade surface, except in P. gladiatus which showed hypostomatic branches. In most of the species, phylloclades developed a vascular system surrounded by clusters of fibres and cortical parenchyma, which could differentiate into palisade‐like tissue and ground tissue like a true leaf blade. The distribution of the vascular system followed the cylindrical or flattened diameter shape of the branch. In subsection Choretropsis, the cylindrical branches of P. choretroides, contrary to other species, developed a second ring formed by clusters of fibres surrounded by large parenchymal cells. In subsection Applanata, the palisade‐like cells of P. flagelliformis phylloclades acquired an isodiametric shape. The highest level of specialization was observed in P. gladiatus, which developed phylloclades with a dorsiventral structure, a main vein, and small sets of lateral vascular bundles like a typical leaf blade. The tissue arrangement of different species showed a gradual pattern, which was correlated with the different branch morphology and plant architecture. Despite the transitional pattern, it was suggested that some of the phylloclades had an independent origin and convergent evolution in the Choretropsis section. The anatomy of different branch types was shown to be useful, either in isolation or in association with other morphological characters, to delimit the species and to further understand their relationships and phylogeny. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 157 , 91–102.     

六种沉香属植物叶片解剖结构研究

为比较沉香属不同种植物间的叶片形态解剖特征,将不同来源的六种沉香属植物在海南省兴隆南药园种植,运用石蜡切片法和撕片法对其成熟叶片的解剖特征进行观察,并对叶片的上下表皮,叶脉和叶横切面等12项数量性状进行统计分析。结果表明:六种沉香属植物叶片解剖结构基本一致,均为典型的异面叶,由表皮、叶肉和叶脉组成,表现出典型的旱生形态特点。表皮细胞单层,气孔微下陷,仅分布在下表皮,上下表皮上零星分布着表皮毛。叶肉组织发达,栅栏组织由1~2层排列紧密地圆柱状细胞组成,其间分布着大量的长方晶体,海绵组织内有一层排列较整齐,染色较深的异细胞组成的下皮层。主脉维管束双韧型,呈圆环状,内含大量异细胞。方差分析表明,除栅海比外,叶片厚度、叶脉条数、主脉厚度等其余11项数量指标在六种植物间差异均达到显著水平。聚类分析将这六种植物聚成3类,Aquilaria sinensis(白木香),A.crassna和A.banaensis聚为一类,A.baillonii和A.malaccensis聚为一类;A.yunnanensis(云南沉香)单独为一类。该研究结果为沉香属植物的物种鉴定提供了解剖学依据,同时对沉香属植物合理开发利用具有重要意义。