Ethylene induced cyanide resistant respiration in orchid petal cells

Respiration of isolated Aranda orchid petal cells increased markedly after cut flowers were treated with ethylene. An increase in respiration was observed 15 to 20h after treatment which was further enhanced in the presence of oxygen and ethylene. Ethylene induces the development of a cyanide resistant pathway in fully opened orchid flower tissues where the cyanide resistant capacity is negligible. However, there appears a shift back to the cyanide sensitive pathway some time after induction.     

Effects of floral display and plant abundance on fruit production of Ryncholaelia glauca (Orchidaceae)

Flowering plant density can increase number of visits and fruit set in multi-flowering plants, however this aspect has not been studied on few flower species. We studied the effects of individual floral display and plant density on the fruit production of the epiphytic, moth-pollinated orchid, Ryncholaelia glauca, in an oak forest of Chavarrillo, Veracruz, Mexico. Species is non-autogamous, and produced one flower per flowering shoot each flowering season. We hypothesized that orchids with more flowering shoots and those on trees with clumps of conspecific should develop more fruits than isolated ones. R. glauca population flowers synchronouly, and individual flowers last up to 18 days, with flowers closing rapidly after pollination. Individuals produced few flowers per year, although some plants developed flowers in both seasons and fewer of them developed fruits both years. There was no relationship between flower number per orchid, or per host tree, with the number of fruits developed per plant. Host trees with flowering and fruiting orchids were randomly dispersed and the pattern of distribution of flowering and fruiting plants was not related. Apparently, pollinators visit the flowers randomly, with no evidence of density dependence. The fruit set of R. glauca was as low as fruit set of multi-flowered orchids moth pollinated, suggesting that fruit set on moth pollinated orchids could be independent of the number of flowers displayed.     

Why flowers close at noon? A case study of an alpine species Gentianopsis paludosa (Gentianaceae)

Repeatable floral closure with diurnal rhythms, that is, flower opening in the morning and closing in the evening, was widely reported. However, the rhythm of flower opening in the morning but closing in the midday received much less attention. Gentianopsis paludosa, Gentianaceae, has an obvious petal movement rhythm opening in the morning and closing at noon at northeast of the Qinghai‐Tibetan Plateau. In this study, we examined the effects of temperature (T), relative humidity (RH), and illumination intensity (II) on G. paludosa''s flower closure. Furthermore, we monitored the environmental changes inside and outside of the flowers, aiming to test the effect of floral closure on the stability of microenvironment inside the flower. Finally, we artificially interrupted temporal petal closure and investigated its effects on reproductive fitness. The results showed that high/low temperature contributed more to the flower closure than low RH, while illumination intensity had no significant effect on it. The medium temperature, relative humidity and illumination intensity (environmental conditions at 10:00) did not delay flower closure when flowers at pre‐closing period or stimulate reopen when flowers full closed. Floral closure provided a stable temperature condition and a higher RH condition inside the flower. Meanwhile, compulsive opening and delayed closure of flowers decreased the seed‐set ratio while no effect was found when flowers were forced to close. We conclude that endogenous rhythm regulates floral closure. The rhythm of petal movement providing a stable microenvironment for G. paludosa, increasing the seed production and saving energy from flower opening maintenance, which might be an adaptive strategy to against unfavorable environmental conditions.     

The Roles of Colour and Shape in Pollinator Deception in the Orchid Mantis Hymenopus coronatus

The orchid mantis Hymenopus coronatus (Insecta: Mantodea) is a deceptive predator that attracts pollinators as prey. Their resemblance to a flower has given rise to the hypothesis that they are flower mimics. However, floral mimicry as a predatory strategy, and in particular, how predatory floral mimicry functions at a mechanistic level is poorly understood. Two main morphological characteristics are thought to make orchid mantises appear similar to flowers and thus attractive to pollinators: (1) their ‘flower‐like’ white colouration and (2) their ‘petal‐shaped’ expansions of exoskeleton on their mid‐femur and hind femur (femoral lobes). I investigated the contribution of these colour and shape characteristics to pollinator attraction using artificial orchid mantis models. Models with the ‘flower‐like’ white colouration of the orchid mantis had higher rates of pollinator inspection than brown models. Manipulating overall body shape by removing or changing the orientation of the ‘petal‐shaped’ femoral lobes did not affect the attractiveness of models. As certain flower‐like characteristics (symmetry and petals) did not affect the attractiveness of models, pollinators may not necessarily cognitively misclassify orchid mantises as flowers. Rather, mantises may be exploiting sensory biases of their pollinator prey, and their UV‐absorbing white colouration may be sufficient to lure pollinators. The effectiveness of using artificial models established here provides a basis for future research into orchid mantis morphology and the fine‐scale interactions between orchid mantises and pollinators.     

Diel changes in the CO2 exchange rates of reproductive organs of the tropical tree Durio zibethinus

The daily variations in the in situ CO₂ exchange of the reproductive organs of Durio zibethinus trees, growing in an experimental field at University Putra Malaysia (UPM), were examined at different growth stages. Reproductive organs emerged on the leafless portions of branches inside the crown. The photon flux densities (PFD) in the chambers used for the measurements were less than 100 mol m^–2 s^–1 and were 40% of the PFD outside of the crown. The daytime net respiration rate and the nighttime dark respiration rate were higher at the time of flower initiation and during the mixed stages, when flower buds, flowers, and fruit coexist, than at the flower bud stage. The net respiration rate was lower than the daytime dark respiration rate at given temperatures, especially at the flower bud and fruit stages. Conversely, the net respiration rate was similar to the daytime dark respiration rate at the mixed stage. Photosynthetic CO₂ refixation reduced the daily respiratory loss by 17, 5, 0.3, and 24% at the flower bud, flower initiation, mixed, and fruit stages, respectively.     

Circadian rhythmicity in emission of volatile compounds by flowers of Rosa hybrida L. cv. Honesty

Quantitative headspace analyses of rose flowers showed no significant differences in composition of emitted volatile compounds between flowers on the intact plant and cut flowers placed in vase water containing sucrose at 0, 15 or 30 g · l⁻¹. Volatile components emitted were geraniol, nerol, citronellol, E-citral, Z-citral, methylgeranylate, trans-caryophyllene, β-cubebene, dihydro-β-ionone, 2-phenylethanol, 2-phenylethylacetate, 3,5-dimethoxytoluene and hexylacetate. When exposed to a 12-h photoperiod these components showed maximum emission during the light period and a rhythmicity which differed for the individual compounds. The circadian nature of the rhythmicity was confirmed by the continuation of rhythmicity during continued darkness or light, and was characterized by `transient' and `free running' periods of 27 and 24 h, respectively, and a phase shift of 12 h in rhythmicity when a 24-h period of continuous darkness was followed by re-exposure to a 12-h photoperiod. Rhythmicity in emission was not observed when flowers were kept in darkness before flower bud opening, but started immediately upon exposure to a 12-h photoperiod. Received: 14 April 1998 / Accepted: 28 May 1998     

Photosynthetic utilization of radiant energy by CAM Dendrobium flowers

14CO2 fixation was observed in orchid Dendrobium flowers; its rate decreased with the flower development. Chlorophyll (Chl) fluorescence in different developmental stages of flowers was compared to other green plant parts (leaf, inflorescence stalk, and fruit capsule). The photochemical efficiency of photosystem 2 (PS2) (Fv/Fm) of a leaf was 14-21 % higher than that of a mature flower perianth (sepal, petal, and labellum) which had a much lower total Chl content and Chl a/b ratio. A higher quantum yield of PS2 (ΦPS2) than in the mature flowers was observed in all green parts. Flower sepals had higher Chl content, Chl a/b ratio, and Fv/Fm values than the petal and labellum. During flower development the Chl content, Chl a/b ratio, Fv/Fm, and qN decreased while ΦPS2 and qP remained constant. An exposure of developing flowers to irradiances above 50 µmol m-2 s-1 resulted in a very drastic drop of ΦPS2 and qP, and a coherent increase of qN as compared to other green plant organs. A low saturation irradiance (PFD of 100 µmol m-2 s-1) and the increase in qN in the flower indicate that irradiation stress may occur since there is no further protection when the flower is exposed to irradiances above 100 µmol m-2 s-1. A low Chl/carotenoid ratio in mature flower perianth as a consequence of Chl content reduction in the course of flower development suggests a relief of irradiation stress via this mean.     

Ethylene production by young Aranda orchid flowers and buds

A high rate of ethylene production was observed in buds and young flowers of Aranda orchid, which increased with bud growth, reaching a high value in half-opened flower. This was followed by a gradual decline but it increased again when the flowers showed sign of senescence. Aminooxylacetic acid (AOA) inhibited ethylene production and bud expansion of Aranda buds.     

Visual discrimination between two sexually deceptive <Emphasis Type="Italic">Ophrys</Emphasis> species by a bee pollinator

Almost all species of the orchid genus Ophrys are pollinated by sexual deception. The orchids mimic the sex pheromone of receptive female insects, mainly hymenopterans, in order to attract males seeking to copulate. Most Ophrys species have achromatic flowers, but some exhibit a coloured perianth and a bright, conspicuous labellum pattern. We recently showed that the pink perianth of Ophrys heldreichii flowers increases detectability by its pollinator, males of the long-horned bee Eucera berlandi. Here we tested the hypothesis that the bright, complex labellum pattern mimics the female of the pollinator to increase attractiveness toward males. In a dual-choice test we offered E. berlandi males an O. heldreichii flower and a flower from O. dictynnae, which also exhibits a pinkish perianth but no conspicuous labellum pattern. Both flowers were housed in UV-transmitting acrylic glass boxes to exclude olfactory signals. Males significantly preferred O. heldreichii to O. dictynnae flowers. In a second experiment, we replaced the perianth of both flowers with identical artificial perianths made from pink card, so that only the labellum differed between the two flower stimuli. Males then chose between both stimuli at random, suggesting that the presence of a labellum pattern does not affect their choice. Spectral measurements revealed higher colour contrast with the background of the perianth of O. heldreichii compared to O. dictynnae, but no difference in green receptor-specific contrast or brightness. Our results show that male choice is guided by the chromatic contrast of the perianth during the initial flower approach but is not affected by the presence of a labellum pattern. Instead, we hypothesise that the labellum pattern is involved in aversive learning during post-copulatory behaviour and used by the orchid as a strategy to increase outcrossing.     

蝴蝶兰花发育的分子生物学研究进展

蝴蝶兰花非常独特且高度进化,如萼片瓣化、瓣片特化为唇瓣、雌雄蕊合生成合蕊柱及子房发育须由授粉启动等,是单子叶植物花发育研究的理想材料。近年来蝴蝶兰花发育分子生物学取得了重要进展。该文就近年来国内外有关蝴蝶兰开花转换及花器官发育相关基因研究以及B类基因与兰花花被的进化发育关系方面的研究进展进行综述。研究表明:MADS基因在蝴蝶兰开花转换及花器官发育过程中起重要作用,推测其中的DEF(DE-FICIENS)-like基因早期经过2轮复制,形成了4类不同的DEF-like基因,进而决定兰花花被属性。蝴蝶兰花发育分子生物学的深入研究,将极大地利于通过基因工程手段提高蝴蝶兰花品质如花色改良及花期调控等,推动分子育种进程。     

Pollination and floral ecology of Arundina graminifolia (Orchidaceae) at the northern border of the species’ natural distribution

Arundina graminifolia is an early successional plant on Iriomote Island, the Ryukyus, Japan, where it is endangered. Populations flower for more than half a year, and many inflorescences bloom for one to several months. The nectarless gullet flowers, which open for up to six days, are self-compatible but cannot self-pollinate spontaneously; thus they rely on pollinating agents for capsule production. Field observations at two habitats identified at least six species of bees and wasps, primarily mate-seeking males of Megachile yaeyamaensis and Thyreus takaonis, as legitimate pollinators. Thus, this orchid is a pollinator generalist, probably owing to its long blooming period and simple flower morphology. Carpenter bees, which were previously reported to pollinate this orchid, frequently visited flowers but were too large to crawl into the labellum chamber and never pollinated the flowers. Extrafloral nectaries on inflorescences attracted approximately 40 insect taxa but were not involved with pollination. Fruit-set ratios at the population level varied spatiotemporally but were generally low (5.2–12.4 %), presumably owing to infrequent flower visits by mate-seeking pollinators and the lack of food rewards to pollinators.     

Flower colour adaptation in a mimetic orchid

Although the tremendous variability in floral colour among angiosperms is often attributed to divergent selection by pollinators, it is usually difficult to preclude the possibility that floral colour shifts were driven by non-pollinator processes. Here, we examine the adaptive significance of flower colour in Disa ferruginea, a non-rewarding orchid that is thought to attract its butterfly pollinator by mimicking the flowers of sympatric nectar-producing species. Disa ferruginea has red flowers in the western part of its range and orange flowers in the eastern part--a colour shift that we hypothesized to be the outcome of selection for resemblance to different local nectar-producing plants. Using reciprocal translocations of red and orange phenotypes as well as arrays of artificial flowers, we found that the butterfly Aeropetes tulbaghia, the only pollinator of the orchid, preferred both the red phenotype and red artificial flowers in the west where its main nectar plant also has red flowers, and both the orange phenotype and orange artificial flowers in the east, where its main nectar plant has orange flowers. This phenotype by environment interaction demonstrates that the flower colour shift in D. ferruginea is adaptive and driven by local colour preference in its pollinator.     

Pollinator limitaton in a deceptive orchid, Pogonia japonica, on a floating peat mat

Deceptive orchid species that offer no floral rewards to pollinators often experience pollinator limitation because they. The breeding system and fruit set were investigated in order to examine pollinator limitation for a population of a deceptive orchid, Pogonia japonica , on a floating peat mat in Mizorogaike Pond, western Japan. Fruit sets for outcross-pollinated, self-pollinated and pollinator-excluded flowers were 75%, 80%, and 0%, respectively. Thus, this species was self-compatible but neither autogamous nor apogamous. The fruit set for open-pollinated flowers was 22.9% and 17.4% in 1994 and 1995, suggesting that pollinator limitation did occur in the field. Larger flowers were more likely to develop into fruit than smaller ones in open pollination (36% vs 8%). Thus, flower size seems to affect fruiting of this species. No effective visits by major pollinators such as bees, which could carry pollinia, were observed during 16.5 h of observation during daytime. Instead, thrips were often found moving on gynostemium or pollinia and circumstantial evidence that suggests thrips may partly transfer pollen in pieces out of a granular pollinium of P. japonica was obtained. Pogonia japonica should come to use thrips as a pollinator to supplement low fruit set under limited flower visitation by major pollinators.     

The carbon balance of flowers of Diplacus aurantiacus (Scrophulariaceae)

Summary Measurements and modeling of photosynthesis, respiration and growth in flowers of Diplacus aurantiacus, a semidrought-deciduous shrub, indicate that they can provide 18%–25% of their total carbon requirements through photosynthesis of flower parts. Daily photosynthetic carbon fixation exceeds daily respiratory CO₂ loss during most non-fruiting stages of development. However, this carbon gain fails to meet the requirements for new biomass construction during bud growth and corolla expansion. During fruiting stages, insufficient carbon is fixed to fully supply either respiration or growth.The calyx performs most of the flower's photosynthesis throughout the life of the flower. However, during stages of fruit development, the contribution of the ovary to flower photosynthesis may equal that of the calyx.     

Thynnine wasps discriminate among heights when seeking mates: tests with a sexually deceptive orchid

The flower of a sexually deceptive orchid, Chiloglottis reflexa, mimics both the sex pheromone and the appearance of a female thynnine wasp (Neozeloboria nr. proxima). The flower is pollinated when visited by male wasps, who attempt mating with the flower. We have used these mimetic flowers to investigate mating behavior of the male wasps. In field choice experiments, males strongly prefer to visit flowers that are very low in the habitat, 15 cm, vs. flowers that are placed at 55 or 105 cm. These studies suggest that male precopulatory response is strongly dependent on the microlocation of the female (or female mimic). Other insect-mimicking orchids, which together attract several groups of Hymenoptera, may be useful in analogous experiments on mating behavior. Additionally, these experiments help elucidate features of the mimetic flowers, particularly stature, that act to efficiently attract potential pollinators.     

Pollination of the lady's slipper Cypripedium henryi Rolfe (Orchidaceae)

The pollination ecology of Cypripedium henryi Rolfe, a slipper orchid endemic to west China, was investigated, and its floral shape, size, colour, and scent were analysed. Examination of the breeding system suggests that the flowers are self-compatible, but need pollen vectors for successful reproduction. The flower is rewardless; over 15 insects belonging to Araneida, Hymenoptera, Diptera, Lepidoptera, and Coleoptera were recorded as flower visitors, but most only alighted or rested on the flower. In the total 32 h of observations over 2 years, female Lasioglossum bees were found to be the most frequent visitors and the only pollinators. They showed a high visitation frequency and, surprisingly, re-visited the same flowers frequently. Cypripedium henryi probably attracts pollinators visiting the flowers through general food deception (odour components, colour, false nectar guides), as well as special structures (slippery labellum, slippery staminode). Although three Lasioglossum species visited the flowers, only L. sauterum Fan et Ebmer was found with pollen. Lasioglossum flavohirtum Ebmer was large and climbed out from the entrance. Morphologically, L. sichuanense Fan et Ebmer could be considered as a potential pollinator, but the collected specimens were found to have no pollen of C. henryi on their bodies. It was speculated that the particular floral scent of C. henryi discouraged the entrance of L. sichuanense bees. Lasioglossum sauterum was matched morphologically to the flower, but not all of the visitations resulted in effective pollinations, as some flowers of C. henryi were frequently re-visited and the pollen mass had been taken away by bees on previous visitations. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 156 , 491–499.     

Relationship of visual and olfactory signal parameters in a food-deceptive flower mimicry system

Pollinators such as bees are attracted to flowers by their visualdisplay and their scent. Although most flowers reinforce visitsby providing pollen and/or nectar, there are species—notablyfrom the orchid family—that do not but do resemble rewardingspecies. These mimicry relationships provide ideal opportunitiesfor investigating the evolution of floral signals and theirimpact on pollinator behavior. Here, we have reanalyzed a caseof specialized food mimicry between the orchid Orchis israeliticaand its model, the lily Bellevalia flexuosa. Based on currentknowledge of insect sensory physiology, we were able to characterizeboth the visual and olfactory signals of model and mimic, aswell as of two phylogenetically related orchids. By using acolor vision model, we mapped each species' visual signals tothe perceptual space of honeybees and found an apparent shiftof the mimic's visual signals towards the model. We confirmthat visual mimicry is present. We analyzed the flower odorsby using gas chromatography/mass spectroscopy. We related thesesignals to the perceptual space of the pollinators by testingthe scent extracts physiologically, using in vivo brain imaging.We found no evidence of olfactory mimicry. The results indicatethat evolutionary pressure acts on the visual, but not olfactory,traits of O. israelitica toward a higher similarity to its model.Apparently, odor mismatch does not prevent a bee from landingon a flower that has the expected visual display. The resultstherefore argue for the dominance of visual stimuli in short-distanceflower choice. The orchid may still depend on long-distanceolfactory attraction originating from neighboring model plants.     

Hawkmoth pollination of the African epiphytic orchid Mystacidium venosum, with special reference to flower and pollen longevity

 The pollination biology of Mystacidium venosum Harv. ex Rolfe, an epiphytic orchid endemic to southern Africa, was investigated. The white flowers of this orchid have long spurs (c 4.5 cm) and contain dilute sucrose-dominated nectar which is secreted during the afternoon and early evening. Scent, dominated by Jasmine lactone and (E, E)-Farnesol, is emitted in the evening. A breeding system experiment established that self pollination results in inferior quality fruits. Field observations at three sites in Kwa-Zulu Natal, South Africa, in 1998 and 1999 showed that hawkmoths were frequent visitors to the orchid shortly after dusk, and carry pollinaria along the length of their tongues. No evidence for directional selection on spur length was found at any of the three sites. Results showed that flower longevity is strongly reduced by pollination, while pollinaria removal had only a small effect. Pollinia removed from flowers remained viable for up to 20 days under outdoor conditions. Received August 15, 2000 Accepted April 17, 2001     

The floral biology ofThelymitra epipactoides (Orchidaceae), and the implications of pollination by deceit on the survival of this rare orchid

Thelymitra epipactoides has a highly variable visual display achieved through polychromatic flowers and variable inflorescence size, bearing between 7 and 31 flowers, which attract foraging polylectic bees. Only bees of the genusNomia were observed carrying pollinia and successfully pollinating the orchid. The genusNomia contains polylectic, pollen gathering species that store pollen in both the crop and scopa on the hind legs. The absence of a reward for the bees indicates the orchid is relying on deception to attract visitors. The relationship of deception to mimicry is discussed. Once on the flower, tactile, visual and possibly olfactory stimuli direct bees to the false anther formed by the voluminous column wings, where morphological adaptations of the flower ensure that the pollinarium is deposited on the gaster of the bee to effect pollination. — The lack of seed set observed on the Victorian coast appears to be due to the absence of pollinators from the heath and grassland communities in which the orchid grows. This may well be a consequence of the reduced number of plants flowering in the community (a result of the elimination of fire at these sites), thus not maintaining a floral community attractive to potential pollinators.