金丝桃属植物叶中分泌结构的比较解剖学研究

利用整体透明法、石蜡制片法和半薄切片法,对金丝桃属9组43种l亚种1变种的植物叶分泌结构的类型、形态、结构和分布进行了比较研究。结果表明,分泌结构是金丝桃属植物叶片普遍的结构特征,根据其分泌结构的特征,可划分为分泌细胞团、分泌囊(道)和韧皮部中分泌小管道等3种分泌结构。其中,分泌细胞团按其在叶片的分布可分为叶缘型和散生型;分泌囊按其在叶横切面中的位置可分为栅栏组织型、海绵组织型、居中型(位于栅栏组织型与海绵组织型之间)和横跨叶肉组织型。根据分泌囊和分泌细胞团在该属植物叶中的分布可划分为3种类型：(1)只有分泌囊的类型;(2)只有分泌细胞团的类型;(3)具分泌囊和分泌细胞团的类型。两种主要分泌结构的类型、分布密度、分布位置及其形态等方面在组间和种间均存在—定的差异,对金丝桃属属以下等级的区分具有一定意义。在此基础上,对该属分泌结构的形态演化以及金丝桃属各组间的亲缘关系进行了探讨。     

Differential cell enlargement and its possible implication for resupination in Lemboglossum bictoniense (Orchidaceae)

Changes in the structural features of cell populations in the pedicel of Lemboglossum bictoniense (Bateman ex. Lindley) Halbinger were examined by means of light microscopy in relation to resupination, a twisting of the pedicel through 180^o prior to flower opening. Serial sections in transverse and longitudinal planes were taken from pre-resupinate and fully resupinate pedicels of flowers from a single inflorescence, and comparisons made between the tissues. The pedicel is a prismatic cylinder flattened on three sides, producing three distinct ribS. Each rib contains one central vascular bundle enclosed by cortical parenchyma. Intervening cortical parenchyma forms flanks external to a central core of three vascular bundles, each of which is split into three distinct traces at this level. Resupination is accompanied by axial and radial expansion of cortical parenchyma. Specialized raphide-bearing cells in the cortex expand axially doubling their length in the ground parenchyma. These raphide cells are localized in the rib cortex, and their expansion is reflected in greater elongation of the ribs relative to flank areas. The extra rib length is accommodated by a lateral displacement (twisting) of the ribs around the central axis of the pedicel. Tissue distortion is reduced by cell division, expansion of intercellular spaces and a radial contraction of pith parenchyma. Raphide cell elongation could be a contributing factor in pedicel twisting. The direction of resupination may be controlled by the organization of these cells into arcs on one or other side of the rib vascular bundle.     

The MADS and the Beauty: Genes Involved in the Development of Orchid Flowers

Since the time of Darwin, biologists have studied the origin and evolution of the Orchidaceae, one of the largest families of flowering plants. In the last two decades, the extreme diversity and specialization of floral morphology and the uncoupled rate of morphological and molecular evolution that have been observed in some orchid species have spurred interest in the study of the genes involved in flower development in this plant family. As part of the complex network of regulatory genes driving the formation of flower organs, the MADS-box represents the most studied gene family, both from functional and evolutionary perspectives. Despite the absence of a published genome for orchids, comparative genetic analyses are clarifying the functional role and the evolutionary pattern of the MADS-box genes in orchids. Various evolutionary forces act on the MADS-box genes in orchids, such as diffuse purifying selection and the relaxation of selective constraints, which sometimes reveals a heterogeneous selective pattern of the coding and non-coding regions. The emerging theory regarding the evolution of floral diversity in orchids proposes that the diversification of the orchid perianth was a consequence of duplication events and changes in the regulatory regions of the MADS-box genes, followed by sub- and neo-functionalization. This specific developmental-genetic code is termed the "orchid code."     

中国芸香科植物叶分泌囊比较解剖学研究

利用整体透明、石腊和薄切片方法对芸香科22属,40种和2变种植物叶分泌囊的形态结构和分布进行了比较研究。成熟分泌囊都由鞘细胞和一层上皮细胞围绕圆形腔隙构成,上皮细胞扁平,细胞壁薄、完整,故分泌囊属裂生方式发生。鞘细胞1～5层,不同种类的层数有变化,个别种缺乏。内层鞘细胞为扁平的薄壁细胞,外层的细胞壁较厚。分泌囊的形态结构、着生位置和分布密度等在不同属或不同种间存在一定差异。根据分泌囊在叶中的分布位置和形态结构特点,可将其划分为:叶缘齿缝分泌囊,叶肉分泌囊和两者混合型。叶肉分泌囊又可分海绵组织分泌囊和栅栏组织分泌囊。在此基础上对该科各类型分泌囊的形态演化关系以及各亚科或各属间的亲缘关系进行了探讨。     

龙须玉凤花——中国兰科植物一新记录种

【目的】文章报道了中国兰科玉凤花属一新记录种龙须玉凤花(Habenaria trichosantha Lindl.),提供花期照片和解剖图,并总结了其与形态近缘种之间的差异。【方法】对该物种国内野外居群植株进行了形态观察,并拍摄记录主要分类特征。【结果】龙须玉凤花过去记录分布于东喜马拉雅和中南半岛区域,现发现于滇西海拔800～1 000 m的怒江干热河谷稀树灌木草丛中;其主要识别特征为唇瓣侧裂片扇形轮廓,并分裂为具有二次分枝的长流苏,明显有别于其他同属物种。【结论】龙须玉凤花是中国新记录物种,本发现进一步丰富了中国野生兰科植物资源。     

中国野生兰科植物资源与保护利用现状*

兰科(Orchidaceae Juss.)是被子植物最大科之一,广泛分布于各种陆地生态系统中,具生态、观赏、药用、食用、文化、科研等多重价值,一直以来都是备受关注的重点保护类群。中国是野生兰科植物资源最为丰富的国家之一,具有从原始类群到高级类群的一系列进化群以及复杂多样的地理分布类型。对中国野生兰科植物资源现状和濒危、保护情况进行综合阐述、分析,并针对未来兰科植物资源的可持续利用进行展望。新版《国家重点保护野生植物名录》的发布打开了我国兰科植物保护新局面,加强对我国源远流长的兰文化和散落民间的相关传统知识的归纳整理及科学普及,重视兰科生物文化多样性的保护工作,并根据传统知识线索,探索兰花新品种和药食新资源,不仅可能成为兰科资源保护和利用的新思路和新动力,也将有助于我国生态文明建设和经济社会可持续发展。     

Anatomical development of the pericarp and seed of Oncidium flexuosum Sims (ORCHIDACEAE)

Interpretation of the anatomical structure of the ovary and fruit of the Orchidaceae family is still controversial, which makes it difficult to understand the development and dehiscence of the fruit. The genus Oncidium is polyphyletic and is currently the subject of taxonomic studies. In this study, we have investigated the anatomical development of the pericarp and seed of Oncidium flexuosum Sims to determine important diagnostic characters that, along with molecular data, can assist in defining this group. We have found a new anatomical characteristic of the family: the presence of precursor cells for fruit dehiscence, which were visible from the beginning of development and located on the outer walls of the sterile valves. In contrast with what has been observed by different authors with other species, in the mature fruit of O. flexuosum, only the endocarp of the fertile valves and a few cells near the exocarp and the vascular bundle in the sterile valves show parietal thickening, while the rest remains parenchymatous. During the development of the ovule and embryo, we have shown that the embryonic sac of this species has eight nuclei and that the embryo has a long and elaborate suspensor.     

Endogenous hormonal levels and growth of dark-incubated shoots of Catasetum fimbriatum

Apical shoots and Lateral buds of the epiphytic orchid Catasetum fimbriatum give rise to rootless etiolated stolons, when cultured in the presence of light and then transferred to the dark. The stolons are characterized by fast and continuous apical longitudinal growth. Measurements of four endogenous cytokinin, indole-3-acetic acid (IAA) and abscisic acid (ABA) levels in etiolated shoots and light-grown plants were low. However, after transfer of green plants to the dark, cytokinin Levels increased 3- and 7-fold by 10 and 30 days of incubation, respectively. IAA levels also increased significantly, but the increase was not as great as for cytokinins. A similar trend was observed in the roots. A close relationship seems to exist between both cytokinin accumulation and the formation of etiolated stolons. Variations in ABA levels were practically inconspicuous. The presence of paclobutrazol in the medium, a potent inhibitor of gibberellin synthesis, strongly inhibited etiolated and non-etiolated longitudinal shoot growth, although no apparent effect was observed on apical meristem activity.     

Leaf structure and histochemistry of Ecballium elaterium (L.) A. Rich. (squirting cucumber)

Light, scanning and transmission electron microscopy as well as histochemical reactions were employed to study the leaf structure and secretory activity of Ecballium elaterium, a hairy pharmaceutical perennial common in the Mediterranean region. The amphistomatic leaf has a peculiar structure due to special cells supporting the conductive bundles, a remarkable shortage of mechanical tissue, and the existence of pectin strands between mesophyll cells. The secreting activity is limited mostly to secretary hairs. These attributes of the Ecballium leaf fine structures do not resemble the common structure of leaves from Mediterranean plants and point to a peculiar strategy of this species coping with stress conditions of its habitat.     

Relationships between benzyladenine uptake, endogenous free IAA levels and peroxidase activities during upright shoot induction of Cymbidium ensifoilum cv. Yuh Hwa rhizomes in vitro

Studies were undertaken in order to improve the micropropagation ofCymbidiun ensifolium 'Yuh Hwa. It is easy toinduce rhizomes in vitro in this cultivar but not upright shoots, which areneeded for eventual production of a flowering plant. Exposure ofCymbidium ensifolium 'Yuh Hwa rhizomeexplants in vitro to greater than 2.5 M BA for 12weeks or longer inhibited both elongation of upright, aerial shoots and rootgrowth. Through transfer experiments, it was determined that the commitment toinduction of upright shoots occurred after 10–14 days of exposure to 2.5M BA. BA supplied at 20 M during the first 14days of culture was sufficient to induce upright shoot formation, but shootelongation did not continue under these conditions. Using radiolabelled BA,adenine was found to be a major metabolite found in the rhizome tissue at day14. BA comprised 37% of the total DPM recovered in rhizomes grown in 20M BA compared to that of 61% of the total DPM recoveredfrom rhizomes grown in 2.5 M BA. The total amount of BA takenup per gram fresh weight was similar for both green and etiolated rhizomesgrownin 2.5 M BA. Rhizomes grown in 20 M BA tookupapproximately five times as much BA as those grown in 2.5 MBA.Free IAA levels were highest in the rhizome tip (12.7 ng/g FW) anddecreased to one fourth the value at 1 cm behind the tip. Free IAAlevels increased initially in rhizornes transferred to medium with or without20M BA (although at different amounts) and then decreased. Whenactivated charcoal was added to the medium as well as BA there was no initialincrease in IAA. When 20 M BA was added to the medium, solubleperoxidase activity increased while IAA concentrations remained at about thesame level over a 7-day period. Peroxidase activity in rhizomes eitherdecreasedor remained constant when activated charcoal was added to the medium containingBA.     

Limitations on orchid recruitment: not a simple picture

Mycorrhizal fungi have substantial potential to influence plant distribution, especially in specialized orchids and mycoheterotrophic plants. However, little is known about environmental factors that influence the distribution of mycorrhizal fungi. Previous studies using seed packets have been unable to distinguish whether germination patterns resulted from the distribution of appropriate edaphic conditions or the distribution of host fungi, as these cannot be separated using seed packets alone. We used a combination of organic amendments, seed packets and molecular assessment of soil fungi required by three terrestrial orchid species to separate direct and indirect effects of fungi and environmental conditions on both seed germination and subsequent protocorm development. We found that locations with abundant mycorrhizal fungi were most likely to support seed germination and greater growth for all three orchids. Organic amendments affected germination primarily by affecting the abundance of appropriate mycorrhizal fungi. However, fungi associated with the three orchid species were affected differently by the organic amendments and by forest successional stage. The results of this study help contextualize the importance of fungal distribution and abundance to the population dynamics of plants with specific mycorrhizal requirements. Such phenomena may also be important for plants with more general mycorrhizal associations.     

Effects of wounding on the terpene content of twigs of maritime pine (Pinus pinaster Ait.)

Summary After wounding the cortical tissues of twigs of Pinus pinaster, we investigated changes in diterpene resin acid content and the ultrastructural modification of secretory structures. There was an increase in total resin acid content in the cortical and woody tissues located near the wound. Not all resin acids responded in the same way, but in wounded tissues the amounts of isopimaric acid and of the group of dehydroabietic, levopimaric and palustric acids significantly increased. The composition of cortical tissues becomes closely related to that of woody tissues. The resin acid enrichment of cortical tissues is correlated with the reactivation of the epithelial cells of the resin ducts and the de novo synthesis of resin acids demonstrated by labelling with ₁₄CO².     

齐云山自然保护区兰科植物资源分布及其区系特点

根据调查,齐云山自然保护区有兰科(Orchidaceae)植物33属62种,以地生兰占优势,有22属45种;附生兰11属16种;腐生兰1属1种。从海拔分布来看,1000 m以上的高海拔区域主要分布的是中国特有种和温带分布种;400 m以下的低海拔区域则以热带分布种为主。单种属有21属,占保护区兰科植物总属数的63.6 %。保护区兰科植物属的地理成分可划分为11个分布型和2个变型,种以东亚分布占主体。保护区特有种丰富,中国特有种15种。与邻近地区相比,保护区兰科植物与井冈山自然保护区的相似性系数最高(44.0%),与庐山自然保护区的最低(38.2%)。     

Arbuscular, ecto-related, orchid mycorrhizas—three independent structural lineages towards mycoheterotrophy: implications for classification?

The classification of mycorrhizas in seven equally ranked types glosses over differences and similarities and, in particular, does not acknowledge the structural diversity of arbuscular mycorrhizas. This article emphasizes the parallel continua of ecto-related mycorrhizas and arbuscular mycorrhizas, exemplified within Ericaceae and Gentianales, respectively, as well as the proprietary development of orchid mycorrhizas, all three of which have independently developed mycoheterotrophic plants. A hierarchical classification according to structural similarities is suggested.     

Anatomical aspects of the gynoecium of species of Anthurium sect. Urospadix Engl. (Araceae,Alismatales)

Anthurium sect. Urospadix includes approximately 70 species differently distributed in Eastern Brazil, Western South America, and Central America. The present work studied the gynoecia of species of section Urospadix to describe their anatomical features. In all the species studied, the apical portion of the gynoecium differentiates into a stigma covered with short trichomes and an adjacent region formed by isodiametric cells. The stylar canal comprises short, unicellular secretory trichomes extending up to the ovarian aperture. Carpels are apically symplicate and basally synascidiate with a septum that does not reach the apical portion of the locule. The apical portion of the septum differentiates into long, secretory trichomes while the subapical one differentiates into the placenta. Locules are filled with mucilage. Since the epidermis of the region adjacent to the stigma, the length of the stylar portion, and the number of cell layers of the ovarian septum vary among the species studied, they may be useful for further taxonomic and systematic purposes. The present work is the first detailed report of trichome location and distribution on the gynoecia of Anthurium.     

Anatomy and photosynthetic parameters of roots and leaves of two shade-adapted orchids, Dichaea cogniauxiana Shltr. and Epidendrum secundum Jacq.

This study compares photosynthetic and structural features of Dichaea cogniauxiana and Epidendrum secundum leaves and roots. The diurnal titratable acidity fluctuations indicated crassulacean acid metabolism (CAM) in E. secundum leaves, associated with anatomical features like thick cuticle, large and vacuolated cells, and reduced stomata size and frequency. Roots of both species had chloroplasts in their cortical parenchyma. However, neither the roots nor D. cogniauxiana leaves did show tissue sap acidity fluctuations. This indicates C₃ metabolism in these organs. This lack of oscillation of organic acids in Epidendrum roots was at odds with a CAM-like ¹³C ratio, suggesting that in spite of active CO₂ fixation in roots during the day, the bulk of carbon is imported from the leaves. Roots of both species showed Fv/Fm, ΔF/Fm′, ETR values similar to reports from other non-foliar photosynthetic organs. Besides reducing root carbon cost, root photosynthesis may also be important by alleviating potential hypoxia, since water-saturated velamen severely impedes the gas exchange between radicular cortex.