Anther Cap Research Articles

A new Lycaste (Orchidaceae: Maxillariinae) from Costa Rica

Lycaste bruncana from Costa Rica is described and illustrated. This species is sister to L. tricolor, its closest relative, from which is easily distinguished by the lip shape, with a narrow isthmus and spathulate midlobe, the lanate to lanulose infrastigmatic surface, the pollinarium with a longer stipe, the subrectangular pollinia and the tomentose anther cap. However, among Costa Rican species of Lycaste, the most remarkable character of L. bruncana is the twisted column, which may be indicative of a reproductive barrier. Information related to biogeography, distribution, morphology, molecular data and pollination is provided and discussed.

Pollination biology of Cymbidium goeringii (Orchidaceae) in China

The genus Cymbidium comprises three subgenera with ca. 50 species. Interactions between pollinators and plants have been studied in the two subgenera Cymbidium and Cyperorchis, but only a few studies in the subgenus Jensoa have been reported. Here we report on the reproductive characteristics of C. goeringii (in sub- genus Jensoa) in three populations in the southwest of Hunan Province, China, during the winter from December 2005 to March 2006. Floral phenological and morphological features, behavior of visitors, the breeding system, and fruit sets under natural conditions were studied. The flowers of C. goeringii were strongly fragrant, but did not present any rewards to the visitors. The flowering period of C. goeringii in the studied populations lasted about 40 days, and most flowers (about 60%) opened within 30 days. Flowers opened immediately when temperature increased obviously and reached to about 16 . The flowering ℃ time of the pollinated flowers, unpollinated flow- ers and the flowers with pollinarium removed were similar. Two bees of Apidae, Apis cerana cerana (honeybee) and Anthophora melanognatha, were observed visiting flowers of C. goeringii, but only the honeybees performed as pollinators. The honeybees mostly visited the orchid flowers at 10:00-17:00 on sunny days with temperature above 10 . A total of ℃ only thirteen visits were observed during 20 days of observation, indicating pollinators were rare. Honeybees directly landed on the upper surface of the labellum and inserted their heads into the flowers between column and labellum, while the hind legs trod on the surface of the curved downward mid-lobe of label- lum. When a honeybee landed on the labellum of a flower, the labellum moved up and down slightly. After the honeybee entered the flower further, its head might touch the foot of the column. At this time, the body of the honeybee was parallel with the upper surface of the labellum. Then the honeybee used its front legs to scratch on the callus ridges on the upper surface of the labellum, and its hind legs hooked the edges of the side lobe of label- lum, trying to exit forcibly from the flower. During exiting process, sometimes the honeybee's body was arched owing to tension. In this case, the surface of the scutellum came into close contact with the viscidium and then pollinaria, together with the anther cap, were removed. When this honeybee visited next flower, the pollinaria would be adhered to the stigma when it arched its body during the exiting process. Three plant species flowered synchronously with C. goeringii in the studied areas, but their flowers were different with C. goeringii in color or shape. Because C. goeringii is rewardless to pollinators, the flowers probably attract visitors by olfactory stimu- lus. Breeding system experiments showed no spontaneous autogamy and pollination success relying on pollinators in C. goeringii. Artificial pollination resulted in 90% fruit set by induced autogamy, 100% by pollinating within clone, and 100% by xenogamous pollination, respectively. These results indicate that C. goeringii is highly self-compatible and the fruit production is pollen limited. Because pollinators are essential for fruit set of C. goeringii in natural habitats, protection of wild honeybee populations or apiculture is likely a simple but effective strategy to maintain the orchid populations.

Anther Cap Retention Prevents Self-pollination by Elaterid Beetles in the South African Orchid Eulophia foliosa

Pollination by insects that spend long periods visiting many flowers on a plant may impose a higher risk of facilitated self-pollination. Orchids and asclepiads are particularly at risk as their pollen is packaged as pollinia and so can be deposited on self-stigmas en masse. Many orchids and asclepiads have adaptations to limit self-deposition of pollinia, including gradual reconfiguration of pollinaria following removal. Here an unusual mechanism--anther cap retention--that appears to prevent self-pollination in the South African orchid Eulophia foliosa is examined. Visits to inflorescences in the field were observed and pollinators collected. Visitation rates to transplanted inflorescences were compared between a site where putative pollinators were abundant and a site where they were rare. Anther cap retention times were determined for removed pollinaria and atmospheric vapour pressure deficit was recorded concurrently. Anther cap anatomy was examined using light microscopy. Eulophia foliosa is pollinated almost exclusively by Cardiophorus obliquemaculatus (Elateridae) beetles, which remain on the deceptive inflorescences for on average 301 s (n = 18). The anther cap that covers the pollinarium is retained for an average of 512 s (n = 24) after pollinarium removal by beetles. In all populations measured, anther cap dimensions are greater than those of the stigmatic cavity, thus precluding the deposition of self-pollinia until after the anther cap has dropped. An anatomical investigation of this mechanism suggests that differential water loss from regions of the anther cap results in opening of the anther cap flaps. This is supported by observations that as atmospheric vapour pressure deficits increased, the duration of anther cap retention was reduced. Flowers of E. foliosa are specialized for pollination by elaterid beetles. Retention of anther caps for a period exceeding average visit times by beetles to inflorescences appears to prevent facilitated self-pollination in E. foliosa effectively.

Doing the twist: a test of Darwin's cross-pollination hypothesis for pollinarium reconfiguration

Mating success in plants depends largely on the efficiency of pollen dispersal. For hermaphrodite plants, self-pollination, either within or among flowers, can reduce mating opportunities because of pollen and ovule discounting and inbreeding depression. Self-pollination may be particularly detrimental in plants such as orchids and asclepiads that package each flower's pollen into one or more pollinia which, together with accessory structures, comprise a pollinarium. Darwin proposed that physical reconfiguration of pollinaria serves as a mechanism for reducing the likelihood of self-pollination. To be effective, the time taken for pollinarium reconfiguration would need to exceed that spent by a pollinator on a plant. We investigated pollinarium reconfiguration (including pollinarium bending, pollinium shrinking and anther cap retention) in 19 species and found a strong positive relationship between reconfiguration time and the duration of pollinator visits. Reconfiguration times were also consistently longer than pollinator visit times. These results provide strong support for Darwin's idea that this mechanism promotes cross-pollination.

Morphology of floral papillae in Maxillaria Ruiz & Pav. (Orchidaceae).

The labellar papillae and trichomes of Maxillaria Ruiz & Pav. show great diversity. Although papillae also occur upon other parts of the flower (e.g. column and anther cap), these have not yet been studied. Labellar trichomes of Maxillaria are useful in taxonomy, but hitherto the taxonomic value of floral papillae has not been assessed. The aim of this paper is to describe the range of floral papillae found in Maxillaria and to determine whether papillae are useful as taxonomic characters. Light microscopy, histochemistry, low-vacuum scanning and transmission electron microscopy. A total of 75 taxa were studied. Conical papillae with rounded or pointed tips were the most common. The column and anther cap usually bear conical, obpyriform or villiform papillae, whereas those around the stigmatic surface and at the base of the anther are often larger and swollen. Labellar papillae show greater diversity, and may be conical, obpyriform, villiform, fusiform or clavate. Papillae may also occur on multiseriate trichomes that perhaps function as pseudostamens. Labellar papillae contain protein but most lack lipid. The occurrence of starch, however, is more variable. Many papillae contain pigment or act as osmophores, thereby attracting insects. Rewards such as nectar or a protein-rich, wax-like, lipoidal substance may be secreted by papillae onto the labellar surface. Some papillae may have a protective role in preventing desiccation. Species of diverse vegetative morphology may have identical floral papillae, whereas others of similar vegetative morphology may not. Generally, floral papillae in Maxillaria have little taxonomic value. Nevertheless, the absence of papillae from members of the M. cucullata alliance, the occurrence of clavate papillae with distended apices in the M. rufescens alliance and the presence of papillose trichomes in some species may yet prove to be useful.

The structure and function of orchid pollinaria

Cohesive masses of pollen known as pollinia have evolved independently in two plant families — Orchidaceae and Asclepiadaceae. Yet, the bilateral symmetry of orchids has allowed a greater degree of specialization in pollination systems and a much greater diversity in the morphology of pollinaria — units comprising the pollinia(um) together with accessory structures for attachment to the pollinator. Pollinaria differ in the degree of cohesion of pollen in the pollinium, which may be soft, sectile (comprised of sub-units known as massulae) or hard. A single hard pollinium may contain more than a million pollen grains, yet pollen:ovule ratios in orchids are several orders of magnitude lower than in plants with powdery pollen due to the lack of wastage during transport to the stigma. Attachment of pollinia to the pollinator is usually achieved by means of a viscidium that adheres most effectively to smooth surfaces, such as the eyes and mouthparts of insects and beaks of birds. The stalk connecting a pollinium to the viscidium may be comprised of a caudicle (sporogenous in origin) and/or a stipe (derived from vegetative tissue), or be lacking altogether. Caudicles and stipes may undergo a gradual bending movement 20 s to several hours after withdrawal from the flower, the main function of which appears to be to reduce the possibility of geitonogamous pollination. Other mechanisms that promote outcrossing and pollen export in orchids include pollen carryover (achieved by sectile or soft pollinia), temporary retention of the anther cap, protandry and self-incompatibility (rare among orchids). Pollinaria ensure that large pollen loads are deposited on the stigma, thus enabling the fertilization of the large numbers of ovules in the flowers of Orchidaceae. Pollinaria also ensure efficient removal of pollen from the anther, minimal pollen wastage during transit, and a high probability of deposition on conspecific stigmas.

A New Species of Angraecum (Orchidaceae) from South Central Africa

Epiphytic or lithophytic herb up to 12 cm high; roots matted, emerging from base of stem, up to 20 cm long and 1.2 to 1.8 mm in diameter; stem erect to pendent, covered with old leaf sheaths, up to 3 cm long and 0.5 cm diameter. Leaves glistening green, punctate on upper surface, spreading, subfalcate, tirangular to subterete, coriaceous, with a shallow sulcus towards the base, longest up to 11 x 0.4 cm, apices obtuse. Inflorescence 1-flowered; bract up to 5 x 2.5 mm, lanceolate, acuminate; ovary plus pedicel curved, sigmoid, up to 5 cm long and 0.4 cm in diameter; flowers resupinate, fleshy, white. Dorsal sepal narrowly lanceolate from a broad base, up to 4 x 0.5 mm, lateral sepals similar but falcate towards the base and embracing the base of the spur. Petals narrowly lanceolate, up to 3.5 x 0.4 cm, acute; petals reflexed. Lip smooth, porrect, narrowly ovate, up to 4 cm long and 1.6 cm broad at the base with drawn out acute epichile; basal attachment to column thickened laterally; spur pendent, filiform, 10 13 cm long and 1.5 mm in diameter. Column up to 2.5 x 5 mm; anther cap ? suboblong, notched on the lower border, papillose; pollinia in 2 pairs, viscidia and stipites separate, clavate, falcate. Fruit ellipsoid, ribbed, up to 3 cm long and 0.9 cm in diameter (Fig. 1).

Sarcoglottis caudata (Orchidaceae) and Vellozia kolbekii (Velloziaceae), Two New Species from Minas Gerais, Brazil

During a vegetation survey of the Sao Jose mountain range in Minas Gerais, Brazil, the species Sarcoglottis caudata (Orchidaceae) and Vellozia kolbekii (Velloziaceae) were discovered; they are here described as new to science. Sarcoglottis caudata R. J. V. Alves, sp. nov. TYPE: Brazil. Minas Gerais: Tiradentes, Serra de Sao Jose D'El Rei, summits of quartzite tabular mountains, 1,200 m, Oct. 1989, R. J. V. Alves 959 (holotype, RB). Figure 1. Planta S. rupestri Barb. Rodr. var. parviforae Cogn. aliquanto proxima sed apice labelli caudato, sepalo intermedio ad apicem inciso, petalis basi ad sepalum intermedium connatis differt. Geophyte, 6-8 cm tall, green herb with 1 to 3 flowers, leafless when flowering (September). Leaves unknown. Bracts linearly lanceolate, 1 cm long, 3 mm wide at base, only at base of flowers. Flowers erect, 2 cm long, externally sparsely hairy, green. Lateral sepals 10 mm long, connate to about /4 of basal length, basally continuous with the ovary, asymmetrically linear. Dorsal sepal 9 mm long, 3 mm wide, lanceolate, caudate with incise apex, basally adnate to petals; petals 6 mm long, 1 mm wide, linearly asymmetric, apex rounded; labellum white, base widely sagittate, apex long-caudate. Labellum basally rhombic, apically caudate, 7 mm long, 3 mm wide, with undivided venation consisting of 3 main veins, 2 pairs of thinner, lateral veins that form a loop with the lamina (apically connected, Fig. 1). Column ca. 2 mm long, sulcate. Anther cap membranous. Rostellum rhombic, 1 mm long. Habitat. Grows in white quartzitic sand deposits on slopes and summits of tabular mountains, in areas where the accumulated rainwater upwells from a shallow layer of sand lying directly on the bedrock or hardpan. The substrate is alternately wet (summer) and dry (winter). Distribution. Known only from the Sao Jose D'E1 Rei range, Tiradentes, Minas Gerais, Brazil. The unique labellum shape indicates that Sarcoglottis caudata forms a new subgroup in the genus. It is similar to S. rupestris var. parviflora in habit and habitat. Pabst & Dungs (1975, 1977) r cognized 29 species of Sarcoglottis K. B. Presl from Brazil, of which S. aphylla (Ridley) Schltr., S. cogniauxiana (Barb. Rodr.) Schltr., S. neuroptera (Reichb. f. & Warming) Schltr. and S. rupestris Barb. Rodr. are from Minas Gerais. Somewhat earlier, Hoehne (1945) stated that the above species are so closely allied that they should be joined into one. According to the present data, S. caudata is known only from the Sao Jose range, while the type of S. rupestris var. parvifora was found in the vicinity of Sao Joao D'E1 Rei. More new species of Sarcoglottis can be expected from the isolated campo rupestre ranges of Minas Gerais. Most of the described species are endemic to small ranges, and some are only known from type collections. Vellozia kolbekii R. J. V. Alves, sp. nov. TYPE: Brazil. Minas Gerais: Tiradentes, Serra de Sao Jose D'El Rei, 1,200 m, 22 Oct. 1989, R. J. V. Alves 852 (holotype, SPF; phototype, NHB). Figures 2, 3. Velloziae brachypodae Lyman B. Smith & Ayensu proxima sed caudice multo longiore, tepalis longioribus, ovario obscure trigonaliter que tereti, staminibus paucioribus, foliis capsulaque glabris differt. Heliophyllous phanerophyte. Caudex sparingly branched, usually 150 cm tall (rarely over 300 cm), erect, 5-15 cm diam. including the golden-yellow, persistent leaf sheaths. Leaves ca. 8 to 10 produced in each season, ca. 12 live and 65 dry in each rosette, 33 cm long (without the sheaths), base 14 mm wide, blades parchmentlike, narrowly triangular, attenuate, glabrous except for the finely setoseserrulate margins; venation of lamina consists of median vein with 27 congruent secondary veins on either side; scapes subterminal, 3-8 per rosette, pedicel ca. 9 cm long, 3 mm diam., cylindric, curved so that the flowers are naturally in horizontal position, reaching about /4 length of the leaves, glabrous at the base, slightly verrucose under the ovary (i.e., subapically). Ovary smooth, glabrous, in fresh flowers 7 mm diam., 12 mm long, cylindric to fusiform; NOVON 2: 299-301. 1992. This content downloaded from 157.55.39.105 on Fri, 13 Jan 2017 18:14:22 UTC All use subject to http://about.jstor.org/terms

Regulation of Anthocyanin Synthesis in Cymbidium Flowers: Effects of Emasculation and Ethylene

Summary Emasculation, by removal of the pollinia and the anther cap, and treatment with ethylene induced red coloration of Cymbidium lips. This coloration was shown to be a result of anthocyanin accumulation that was preceded by a pronounced increase in the activity of phenylalanine ammonia-lyase. Ethylene-induced coloration of isolated lips was inhibited by treatment with 2,5 norbornadiene, cycloheximide and actinomycin-D. The latter, however, was less effective. The results therefore indicate that emasculation and ethylene-induced anthocyanin synthesis is regulated both at the translational and transcriptional levels. The red color of the lip was composed of at least six anthocyanins that were based on three different aglucones, i.e. cyanidin, peonidin and malvidin. Both emasculation and ethylene led to an increase in the total amount of pigment in the lip but had no effect on the relative contribution of the different anthocyanin species. The role of red coloration in pollination biology is discussed.

Interorgan Translocation of 1-Aminocyclopropane-1-Carboxylic Acid and Ethylene Coordinates Senescence in Emasculated Cymbidium Flowers

In Cymbidium flowers, emasculation by removal of the pollinia and the anther cap leads within 24 hours to red coloration of the labellum (lip). Lip coloration, being the first sign of senescence in these flowers, has been ascribed to the action of ethylene in the lip. When a small incision in the base of the lip is made prior to emasculation, or when the lip is excised and placed in water within 10 to 15 hours after emasculation, coloration is considerably delayed. This indicates that a coloration-associated factor is moving in or out of the lip. Measurements of ethylene production of excised flower parts, isolated at different times after emasculation, showed an increase only in the central column; the other flower parts, including the lip, did not show a measurable change. In contrast, in situ measurements of the ethylene production of the central column and the remaining portion of the flower revealed a simultaneous increase in all the flower parts following emasculation. Similarly, application of radiolabeled 1-aminocyclopropane-1-carboxylic acid (ACC) to the top of the central column in situ leads to the production of radiolabeled ethylene by all the flower parts. In addition, the ethylene production of isolated lips, measured immediately after excision, was initially high but ceased within 10 to 15 minutes. Treatment of the central column in situ with ethylene or ethephon did not stimulate ACC production but did stimulate lip coloration and this was accompanied by an increased internal ethylene concentration in the lip. The data indicate that endogenously produced as well as applied ACC is rapidly translocated from the site of production or application to all the other flower parts where it is immediately converted into ethylene. By excision of a flower organ, the influx of ACC is prevented, causing a rapid decrease in ethylene production. In addition, it was found that ethylene may also be translocated in physiologically significant amounts within the flower. The roles of ACC and ethylene as mobile senescence or wilting factors in emasculation- and pollination-induced senescence is discussed.

Interrelationship between the Different Flower Parts during Emasculation-Induced Senescence inCymbidium Flowers

In Cymbidium flowers emasculation by removal of the anther cap and the pollinia, led to rapid colouration of the lip and advanced wilting of the petals and sepals. The ethylene production of whole flowers showed an emasculation-induced early peak in ethylene evolution followed some days later by a second increase concomitant with the wilting of the flower. In non-emasculated flowers the ethylene production increased later and simultaneously with colouration of the lip and wilting of the petals and sepals. At all stages of senescence, the contribution of the lip, petals, and sepals to the total amount of ethylene produced was negligible. Parallel to the increase in ethylene production of whole flowers, an increase in 1-aminocyclopropane-l-carboxylic acid (ACC) and malonyl-ACC (MACC) in the central column and, to a lesser extent, in the ovary was observed. Also an increase in internal ethylene concentration was demonstrated and this, in contrast, was apparent in all the different flower parts. The activity of the ethylene-forming enzyme in lips, petals, and sepals showed an increase after emasculation and such an effect could also be induced by treatment of isolated lips with low concentrations of ethylene. The data indicate that senescence in Cymbidium flowers is regulated by the central column and perhaps the ovary and that both ACC and ethylene may play a signalling role in inter-organ communication.

A Synopsis of Ipsea (Orchidaceae)

Hooker (1890) places Ipsea alongside Pachystoma and Spathoglottis in the tribe Epidendreae, subtribe Erieae. The latest treatment by Dressler (1981), who groups Ipsea among Calanthe, Pachystoma, Phaius and Spathoglottis etc. in the third of seven tentative alliances within the subtribe Bletiinae, would seem the most logical. Habit and column structure are similar and the number of pollinia are the same in Ipsea, Calanthe, Pachystoma and Spathoglottis. The pollinaria of Ipsea, although typical of the Bletiinae, differs markedly from those of Pachystoma and Spathoglottis and may possibly have more of an affinity with the New World Bletia Ruiz & Pav. The pollinia of Calanthe and Spathoglottis are cylindric or clavate and those of Pachystoma globular, whereas in Ipsea they are laterally flattened as they are in Bletia. The presence of two fleshy tubercles on the anther cap is a character not observed in other members of the subtribe Bletiinae.

Comparative Flower Development in the Cleistogamous Species Viola odorata. II. An Organographic Study

Comparative ontogenetic study of the shoot apices and floral primordia of Viola odorata revealed significant differences between the dimorphic flowers in this cleistogamous (CL) species. Both the shoot apices and floral primordia of plants in the chasmogamous (CH) phase are larger than those in the CL phase. Form divergence occurs at petal initiation, and by the time of meiosis in the anthers, the CH flower is considerably larger in size. Mature CL flowers exhibit morphological modifications of the anterior petal spur, repressed growth of the staminal nectaries, and a recurving of the style which remains enclosed within the cone formed by five terminal anther caps. Pollination in the CL flower occurs as a result of pollen tubes penetrating the wall of an undehisced anther sac and growing to the stigmatic cavity nearby.

A New Species of Stolzia (Orchidaceae) from Tanzania

A dwarf creeping epiphytic herb. Pseudobulbs proximal on a creeping rhizome, globose, slightly dorsiventrally flattened, up to 1-3 x 0-8 cm, tightly covered with scarious sheaths when young, 1or 2-leaved at apex. Leaves erect or suberect, subcoriaceous, oblong to oblanceolate, obtuse, up to 8 X 1-5 cm, with a slender sulcate petiole up to 1-2 cm long. Inflorescence basal, up to 1 cm long, 1-flowered; bract longer than pedicel and ovary, ovate, acuminate, 5 mm long. Flower large for the genus, fleshy, inflated, ellipsoidal, dark maroon. Sepals united for basal three-quarters, subacute to apiculate at free apices, 1-1 x 0-5 cm, bearing long white hairs on inner surface. Petals lanceolate, acute, with incurved margins, 6 x 2-5 cm, with long white hairs on inner surface and margins. Lip fleshy, conduplicate, entire, ovate-elliptic, rounded at apex, minutely papillose, 3-5 x 2 mm, basally sulcate in centre. Column short, 0-7 mm long, with an erose apex; foot 1-5 mm long, forming an obscure chin-like mentum with the lateral sepals; anther cap papillose; pollinia 8, 4 large and 4 slightly smaller. (Fig. 1.).

The effect of emasculation on the endogenous cytokinin levels of cymbidium flowers

Removal of the pollinaria and anther caps of cymbidium flowers resulted in anthocyanin accumulation in the lips and columns of the flower, followed by the senescence of petals and sepals. These changes correlated well with a decrease in the endogenous cytokinin levels in all parts of the flowers after emasculation. While it is presently not known how senescence is initiated, it is significant that at least 6 different cytokinins appear to be present in the anthers and that the total cytokinin level of these structures is much higher than in the rest of the cymbidium flower. This in itself may have an important function in preventing the onset of senescence.