The Morphology and Permeability of Isolated Cuticular Membranes of Hoya carnosa R. Br. (Asclepiadaceae)

This investigation is in part an extension of previous leafcuticle observations made on 52 other taxa among 34 families.Dewaxed, chemically isolated, adaxial and abaxial cuticularmembranes and transverse leaf sections of the wax-flower plant(Hoya carnosa R. Br.) were examined using ordinary stainingtechniques and light-microscopy methods. Evidence is presentedfor the existence of ubiquitous, discrete, naturally occurringcuticular pores, concomitant with anticlinally oriented trans-cuticularcanals, distributed randomly throughout the cuticular matrix.The surface of the adaxial cuticular membrane contains approx.6540 unclustered pores per mm², the abaxial approx. 4680 poresper mm². Pore and canal diameters range between 0.5 and 0.75µm. The canals are often arcuate and their lengths aredirectly related to cuticle thickness. No correlations werefound between cuticle thickness and either pore numbers or poreand canal diameters. Based upon experiments with various pHindicators, solutions, and stains, the dewaxed, dry cuticularmembrane of H. carnosa appears to be both distinctly hydrophilicand selectively permeable through a myriad of microscopicallyvisible pores and canals permeating its matrix. A de novo interpretationof gross cuticle morphology based solely upon light microscopyobservations is presented by semi-diagrammatic illustrations. Hoya carnosa R. Br., wax-flower (wax-plant), cuticular membranes, cuticular pores, transcuticular canals, permeability     

Characteristics of external and internal NAD(P)H dehydrogenases in Hoya carnosa mitochondria

This study aims at characterizing NAD(P)H dehydrogenases on the inside and outside of the inner membrane of mitochondria of one phosphoenolpyruvate carboxykinase??crassulacean acid metabolism plant, Hoya carnosa. In crassulacean acid metabolism plants, NADH is produced by malate decarboxylation inside and outside mitochondria. The relative importance of mitochondrial alternative NADH dehydrogenases and their association was determined in intact??and alamethicin??permeabilized mitochondria of H. carnosa to discriminate between internal and external activities. The major findings in H. carnosa mitochondria are: (i) external NADPH oxidation is totally inhibited by DPI and totally dependent on Ca²⁺, (ii) external NADH oxidation is partially inhibited by DPI and mainly dependent on Ca²⁺, (iii) total NADH oxidation measured in permeabilized mitochondria is partially inhibited by rotenone and also by DPI, (iv) total NADPH oxidation measured in permeabilized mitochondria is partially dependent on Ca²⁺ and totally inhibited by DPI. The results suggest that complex I, external NAD(P)H dehydrogenases, and internal NAD(P)H dehydrogenases are all linked to the electron transport chain. Also, the total measurable NAD(P)H dehydrogenases activity was less than the total measurable complex I activity, and both of these enzymes could donate their electrons not only to the cytochrome pathway but also to the alternative pathway. The finding indicated that the H. carnosa mitochondrial electron transport chain is operating in a classical way, partitioning to both Complex I and alternative Alt. NAD(P)H dehydrogenases.     

Circadian rhythmicity of fragrance emission in flowers of Hoya carnosa R. Br.

In flowers of Hoya carnosa R. Br. the nocturnal emission of fragrance occurs according to an endogenous circadian rhythmicity. This was demonstrated by the continuation of rhythmical emission for two to three cycles under conditions of permanent illumination. The free-running period was approx. 29 h under these conditions. The inversion of light/dark cycles caused the entrainment of the next peak of emission by approx. 12 h whether the inversion was started with a light period or a with dark period prolonged for 12 h. When only the flower used for fragrance analysis was subjected to an inverted photoperiod, the rest of the plant remaining under the original light/dark cycle, the synchronization of fragrance emission occurred according to the Zeitgeber perceived by the individual flower.     

Survival and division in protoplasts from tobacco (Nicotiana tabacum) depends on the physiological state of the individual donor plant

Variation in the survival potential of protoplasts isolated from different leaf positions and from individuals within a batch of N. tabacum L. cv. Xanthi-ne is reported. Foliar application of growth regulators and nutrients to unstressed, waterlogged and waterstressed donor plants, demonstrates the prophylactic role of such treatments. It is suggested that intrabatch variation may be related to fluctuations in water supply to the individual donor plants. Vegetative propagation via buds in vitro improved the quality of donors compared with seed raised plants. Further, tissue culture progeny were more tolerant of in vivo waterlogging. The high osmotic pressure of the tissue culture medium may induce this tolerance. The results are discussed in the context of an overall strategy to control the quality of donor plants for protoplast isolation.     

Observations on pollination inSarcostemma (Asclepiadaceae)

Field observations on pollination in New World species of the genusSarcostemma R. Br. sensuHolm are reported. Morphological and anatomical comparisons of pollinated flowers ofSarcostemma subg.Ceramanthus Kuntze (New World) andSarcostemma subg.Sarcostemma (Old World) are presented.     

A taxonomic revision of Calotropis (Asclepiadaceae)

The genus Calotropis of the tribe Asclepiadeae of Asclepiadaceae subfamily Ascle-piadoideae is revised throughout its Tange in tropical and subtropical Africa and Asia. The three species recognized are keyed out, illustrated and described with appropriate bibliography, synonymy, notes on ecology, distribution and uses. Distribution maps for the species are provided. The taxonomic position of the genus is discussed and a historical review is provided.     

Hoya somadeeae sp. nov. (Apocynaceae,Asclepiadoideae) Thailand and lectotypification of Hoya wrayi

A new species from evergreen montane forests of Thailand, Hoya somadeeae Rodda & Simonsson is here described and illustrated. The new species may be superficially confused with the Peninsular Malaysia endemic H. wrayi King & Gamble, but is clearly separated from it by the very elongated peduncles, up to 20 cm long, the revolute corollas, and outer processes of corona lobes with a membranaceous basal appendage. Morphological affinities between the new species and other Hoya species from Thailand and neighbouring Myanmar and Peninsular Malaysia are discussed.     

Cytological and morphological differentiation in Caralluma burchardii (Asclepiadaceae)

Meve, U. 1995. Cytological and morphological differentiation in Carallurna burchardii (Asclepiadaceae). — Nord. J. Bot. 15: 459–467. Copenhagen. ISSN 0107–055X.
Caralluma burchardii is revised based on detailed investigations of vegetative and floral morphology, as well as chromosome numbers. The species is now divided into two taxa, the dodecaploid ssp. burchardii , an endemic of the Canary Islands, and ssp. rnaura , a hexaploid from the west coast of Morocco. The high ploidy levels involved, the highest known in the Asclepiadaceae, are discussed in conjunction with biogeographical aspects.     

Corona and anther skirt in Hoya (Apocynaceae, Marsdenieae)

The so called revolute margins of the corona in the genus Hoya (Marsdenieae) are homologous to the anther skirt. The anther skirt is primarily formed of two latero-basal lobes of the anther. In Hoya these lobes are fused with the underside of the basal process of the staminal corona and have evolved into a dominant structure of the gynostegium. Embedded in the anther skirt is the nectar tube, formed by the basal elongation of the guide rail. In many species, however, the function of nectar secretion for pollinator reward has been transferred to the anther skirt beneath the basal process of the corona. A survey of the Marsdenieae shows that the potential for developing an anther skirt is present in several other genera as well, though nowhere has it evolved into such elaborated structures as in Hoya.     

Notes on the Ceropegiae (Asclepiadaceae) of Ethiopia

The following 4 species and 1 subspecies are described as new: Ceropegia recurvata, C. microgaster, C. erergotana, C.burgeri and Huernia macrocarpa subsp. harerghensis ; one variety of Ceropegia stenoloba is elevated to a full species: C. moyalensis and 2 species transferred from Angolluma to Pachycymbium: P. gilbertii and P. semitubißora.     

12种鹅绒藤属（萝藦科）植物花粉器形态学研究

用光学显微镜对萝藦科（Asclepiadaceae）鹅绒藤属（Cynanchum）12种植物花粉器形态进行了观察。结果表明：花粉块的形态有3种类型：球形、长球形和超长球形。着粉腺的形态有6种类型：长圆形、方形、近方形、三角形、正三角形和近三角形。花粉器形态学结果对青羊参（Cynanchum otophyllum）在鹅绒藤属中的分类具有较大意义;支持《中国植物志》第63卷中对催吐白前组（Sect. Vincetoxicum）的分组处理;结合鹅绒藤属花粉块下垂,娃儿藤属（Tylophora）花粉块平展的特点,支持将娃儿藤属作为一个独特类群的观点。     

A new species of Ceropegia (Asclepiadaceae) from India

Ceropegia schumanniana , a new species belonging to Asclepiadaceae is described from the Western Ghats of India.     

Morpho-ecological aspects on the pollination ofCalotropis procera (Asclepiadaceae) in Israel

Calotropis procera (Asclepiadaceae) grows in Israel under extremely hot climatic conditions. Flower morphology is adapted towards the concealment of nectar, in order to protect it against robbery by ants and from evaporation. Pollinia while being inserted within the stigmatic chamber, are soaked in the liquid nectar which, by its concentration controls pollen germination. Two Carpenter bees (Xylocopa) are the only pollinators and their behavior on flowers is discussed.     

The genus Sarcostemma R.Br. (Asclepiadaceae) in Madagascar

The Madagascar! representatives of the genus Sarcostemma are investigated. All Malagasy material studied can be assigned to four taxa. S. viminale ssp. viminale occurs in Madagascar as well as on other islands along the African coast and on the African mainland: the other three species are endemic to Madagascar. All four species occur in the southern, arid part of the island, to which S. decorsei is endemic. S. membranaceum and S. elachistemmoides are new. All species are described and illustrated and a key and distribution maps are presented.     

The outer epidermal wall structure of African Stapelieae (Asclepiadaceae)

The outer epidermal walls of 65 species incorporated in 14 genera of the tribe Stapelieae were investigated by light and electron microscopy (TEM, SEM). The species, all of them stem succulents preferring the semi-arid regions of the Palae-otropics, possess an outer epidermal wall, which is relatively simple in structure. The whole plant body is covered by a massive wax layer, in addition some species bear wax crystals. A cutin layer follows beneath, reticulate over its whole expanse and not divided into a cuticle proper and cutinized layers. A cellulose layer, which often exhibits enclosed cutinbodies, delimits the wall against the plasmalemma.     

青阳参花部特征及其传粉适应性

对青阳参花（Cynanchum otophyllum）部综合特征、访花昆虫种类、访花行为及传粉过程进行了研究,结果表明,青阳参花结构复杂,两个子房基部离生、花柱联合与雄蕊形成合蕊柱,柱头表面被邻近花药的侧翼紧密包围形成5个柱头腔。青阳参的花粉形成独特的花粉块,一次传粉过程可以转运大量的花粉。东方蜜蜂（Apis cerana）是青阳参的主要传粉昆虫,其传粉包括两个过程：（1）当蜜蜂的口器或足插入着粉腺的槽口后借助蜜蜂的力量将花粉块从花上拔起;（2）当蜜蜂再次访花时将携带的花粉块插入其中一个柱头腔。花粉块里面的花粉粒住柱头腔中萌发出花粉管,然后沿着花柱道向下生长最后进入子房。在整个花期仡粉保持有相对较高的生活力,而其柱头可授性则在7天后逐渐降低。     

青阳参种子的萌发

青阳参（Cynanchum otophyllum）种子在11月成熟时有休眠习性。收获后将其种子种植在自然温室内,到第二年的春天种子才会萌发,且大多数种子在3月28至4月4日间萌发,这期间的日平均最高和最低温度分别为19．0℃和9．9℃。层积能有效地打破青阳参种子的休眠,休眠种子通过大约1周的层积便能萌发。种子在有光的条件下层积1周后转移到25／15℃的黑暗条件下萌发率可达到75．4％。青阳参种子不论在有光的条件下还是在黑暗环境中层积2～3周后转入30／20和25／15℃进行变温处理,其萌发率最低能达到66．4％,而转入20／10℃变温处理其萌发率最多只能达到20．1％,但若层积6周,即便在20／10℃变温处理的情况下其萌发率也可以达到65．3％以上。