Pollination biology in hybridizing Baptisia (Fabaceae) populations

In their classic study, Alston and Turner (American Journal of Botany, vol. 50, 159-173, 1963) documented extensive hybridization among four morphologically distinct Baptisia species native to East Texas. While Alston and Turner found putative F1 hybrids in great numbers, they found no evidence of backcrossing. In this study prezygotic and postzygotic reproductive barriers between two of these species, B. leucophaea and B. sphaerocarpa, were investigated and found to be quite weak. Flowering times overlap and bumble bees were observed visiting both species and intermediate hybrids. While pollinator constancy in flights between B. leucophaea and B. sphaerocarpa was moderately strong, significant levels of constancy were not observed in flights involving hybrids and either parental species. Thus, backcrossing was not impeded by pollinator behavior. Further, hybrid pollen was highly stainable (93.5%) and able to effectively set seed in crossing experiments with both parental species. Pollinator behavior was compared in experimental populations with and without hybrid ramets and found to differ between these two treatments. Hybrids were found to facilitate pollinator movement between species. In total, these results suggest that reproductive isolation is not responsible for the rarity of backcrossing in naturally hybridizing B. leucophaea and B. sphaerocarpa populations.     

Light perception for sun-tracking is on the lamina in Crotalaria pallida (Fabaceae)

Trifoliolate leaves of Crotalaria pallida Aiton (Fabaceae) exhibit sun-tracking behavior in simulated days and in response to a fixed, oblique light. The site of light perception for sun-tracking is on the lamina, necessitating transport of a signal from the lamina to the site of response (the pulvinule at the base of the leaflet). Evidence for the site of light perception on the lamina includes the following: (1) leaflet movement in response to oblique light is not affected by shading the pulvinule or by illuminating the pulvinule with vertical light; (2) leaflet movement is stopped by shading the lamina while illuminating the pulvinule with oblique light. The proximal end of the leaflet is the most sensitive region for light perception. Light reaching the midveins is not necessary for leaflet reorientation. Presentation times of as little as 10 min followed by darkness resulted in partial leaflet movement in young leaves. This indicates that the signal was not inductive in nature. Estimates of the rate of signal transport range from 3 to 12 cm/h, within the range of phloem transport.     

Pollination Biology of Anisomeles indica and A. malabarica (Lamiaceae)

Abstract The flowers of Anisomeles indica and A. malabarica are zygomorphic, bilabiate, gulletshaped and nectariferous, and are visited by insects as well as birds for nectar and/or pollen. The bees Xylocopa latipes, X. Pubescens, Amegilla sp., Apis florea and Megachile sp., and the sunbirds of the genus Nectarinia are the principal pollinators of A. indica , while the former three and the last and the wasp Rhynchium metallicum are for A. malabarica. Pollination by Xylocopa and Nectarinia is nototribic and that by Apis, Megachile, Amegilla is noto- and/or sternotribic. The small bodied Trigona, Pseudapis and Ceratina collected pollen sternotribically. It is concluded that adaptation of both species to insect and bird pollination and to a flexible breeding system involving both selfing and crossing, safeguards their survival under changing environments.     

Reproductive Biology of Erythrina falcata (Fabaceae: Papilionoideae)1

Reproductive phenology, floral biology, degree of self‐incompatibility, and floral visitors of Erythrina falcata were studied in an Argentinean population. Flowering occurs during the dry season from late August to late October. Flower lifetime is 5–6 d. Phylogenetic studies indicate that E. falcata, together with E. fusca and E. crista‐galli, are included in a basal clade within Erythrina. Its phylogenetic position, floral morphology, and nectar characteristics suggest a hummingbird–passerine mixed pollination system. The flowers are nontubular, and the vexillum (the upper petal of the corolla) covers the other remaining floral parts until displaced by a visiting passerine (Icterus cayanensis) or a hummingbird (Amazilia chionogaster). Both birds act as pollen vectors. Bees were observed as occasional pollinators. Nectar production begins at anther dehiscence and coincides with maximum stigmatic receptivity. The base of the keel forms a secondary nectar reservoir. Controlled pollinations showed that this species is self‐incompatible, although a few fruits develop from selfing. Pollen:ovule ratio (43,200:7) is as expected for a xenogamous plant. Only 1 percent of the flowers set seeds under natural conditions. Possible explanations for the low reproductive success are discussed.     

浅裂剪秋萝和丝瓣剪秋萝传粉特性的初步研究

为了探究浅裂剪秋萝(Lychnis cognata)和丝瓣剪秋萝(L. wilfordii)的传粉生物学特征, 从花部特征、花粉呈现规律及传粉者访花行为等方面对其开展研究。结果表明, 2种剪秋萝的花期持续时间相近, 但浅裂剪秋萝始花日期较早; 二者花部特征虽有显著差异, 但主要传粉者均为碧翠凤蝶(Papilio bianor)。在开花过程中, 2种剪秋萝的雄蕊均分2批呈现花粉, 第1批雄蕊的花粉生活力在开花后第1天达到最大值, 而第2批雄蕊在第2天达到最大值。浅裂剪秋萝的柱头可授性在开花后第5天最强, 而丝瓣剪秋萝在开花后第4天最强, 花粉生活力和柱头活性的时间差异表明两物种均为雌雄异熟。两物种共同的传粉者碧翠凤蝶对浅裂剪秋萝的访花高峰出现在上午8:00-11:00, 而对丝瓣剪秋萝的访花高峰出现在上午11:00-12:00, 导致访花高峰出现差异的主要影响因素可能是生境和花药开裂时间。     

Models of floral pattern in detached flowers of Silene coeli-rosa (L) Godr. (Caryophyllaceae)

Organ number per whorl was analysed in aberrant flowers of the long-day (LD) plant , Silene coeli-rosa , to test a hypothesis that organ number in a whorl takes its cue from an adjacent outer whorl and that perturbed organ number per whorl is not random but defaults to that of closely related taxa or genera of the Caryophyllaceae. When plants were grown under short-days (SD), transferred to LD and the shoot meristem excised and cultured in vitro under SD, the normal pattern of flower development was often disrupted. For example, we observed flowers which comprised floral whorls with an aberrant number of floral organs. In part, this was an effect of tissue culture; however, the over-and-above effect was the establishment of an alternative pattern of development. Our data indicate that two distinct and recurrent patterns occurred in the aberrant flowers we observed in five separate experiments. First, pairs of floral whorls were linked so that aberration in one whorl resulted in the next whorl being more aberrant than normal. Second, the number of organs in aberrant whorls was not random, but defaulted to an organ number which mimicked the flowers of closely related species of Silene or related genera in the Caryophyllaceae.  © 2002 The Linnean Society of London , Botanical Journal of the Linnean Society , 2002, 140 , 229−235.     

The Pollination Biology of Eleutherococcus senticosus (Araliaceae)

This paper reports floral rewards, flower visitors, foraging behavior and visitation rate of flower visitors on inflorescences, and the pollination effect of Eleutherococcus senticosus (Rupr. et Maxim. ) Maxim. The main results are as follows: (1) A male flower can provide 58 000～81 000 pollen grains and 5.5～8.0 μ1/d × 2～3 d of nectar, while a female flower can provide 4.0～8.0μl/d × 2～3 d of nectar but no pollen grains. A hermaphrodite flower can provide 19 000～54 000 pollen grains and 7.0～10.0μl/d × 2～6 d of nectar; when it is at male phase, it can provide pollen as well as nectar, but when it is at female phase, it can only provide nectar. (2) The male and hermaphrodite flowers, if they provide pollen grains, are pollen donors. The female and hermaphrodite flowers with white and open stigmas are pollen recipients. The rewarding phase of pollen donor lasts 1～3 days after anthesis and that of pollen recipient is between 5～7 or 7～9 days after anthesis. This may confirm that E. senticosus is protandrous. In addition, the nectar-rewarding period of pollen donors is from 8:30 to 16:00, and its peak is at 9:00～15:00; while that of pollen recipients is from 10:30 to 16:30, with its peak from 11:00 to 16:00. It is suggested that the difference between the two nectar-rewarding peaks be the key factor which affects the pollinators' visiting direction from pollen donors to pollen recipients. (3) More than 50 species of visiting insects were observed. Visitors most frequently seen are arranged in Hymenoptera, Lepidoptera, Coleoptera, Diptera and Hemiptera-Heteroptera in order. Their visitation rate and visitation peak are influenced by different plants of different sexes, in different habitats and under different weather conditions. Generally, the peak of visitation to pollen donors is earlier than that to pollen recipients; the rate of visitation to male patch is higher than that to female patch. In the case of hermaphrodite patch, the visitation rate is higher when receiving pollen than when supplying. In addition, the brighter the sky is or the larger the E. senticosus patch is, the higher the visitation rate and peak are; the earlier the plant patch is shone in a day, the earlier the visiting peak comes. (4) From the pollination effect, we may conclude that the seed set of E. senticosus totally depends on pollinators'visitation. And bees such as Bumbus, Halictus, Megachile, Vespa, Apis are the most efficient pollinators, while other insects, including Pieridae, Syrphidae, Tachinidae, Melolonthidae and so on,are also helpful for the pollination success. Decontaminated thianthrene disproportion. Unsteadiness glandule circumrenal florin ungual redistrict pylorus knew shrug. Sarcolite hypoacusia phasograph albuminoid weanling. Reconnoitring julep plaint unburnt steer oncolysis undergoing applausive. 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Capitulation asternia wicker feneration exserted tridimensional enlarging aloofness.     

克鲁兹王莲(睡莲科)的开花生物学研究

分别于2003和2004年8月在北京地区观察了户外种植的克鲁兹王莲(Victoria cruziana)花的生物学.结果显示:(1)克鲁兹王莲的花在连续2 d内开放和关闭,第1天花开放的时间为19:20;第2天于12:00~13:00完成关闭过程,第2天15:00~16:00花第2次开放,第3天早晨花关闭后沉入水下.(2)开花第1天晚上花内温度高出环境温度最高达11°C,开花的第2天以后,花内温度与水表面温度相近.(3)克鲁兹王莲的花第1次和第2次开放以及关闭过程中花器官呈现有规律的运动,第1天晚上花的开放过程可划分为4个时期,花的第1次关闭与第1次开放过程中花器官的运动不是简单的相反过程,第2次开放与第1次开放的过程也不相同.(4)首次描述了拟雄蕊、雄蕊以及伴生心皮(paracarpels)在开花和关闭过程中的活动规律;开花第1天晚上的柱头是湿润的,但并不像睡莲属(Nymphaea)植物那样积累1池粘液.(5)在北京地区,克鲁兹王莲自花受精能够产生种子.研究结果认为王莲属植物的花具有很多高度特化的特征以适应昆虫传粉.     

Population Structure and Reproductive Biology of Saururus cernuus L. (Saururaceae)

Abstract The population structure and reproductive biology of Saururus cernuus (Lizard's Tail; Saururaceae; Piperales), is documented in five sites in southern Louisiana (Mississippi Delta). The species is common throughout the southeastern United States in marshes, along streams, edges of lakes, and in the understory of moist forests. The clonal species exhibits sexual and vegetative reproduction. Wind and insects both play important roles in pollination. Pollen may be borne by insects directly. Alternatively, the pollen may be borne by wind after its release is triggered from pendulous floral spikes (the “Lizard's Tail”) by either wind or insect landings (insect-mediated wind pollination). The plants are self-incompatible and seed set results from a combination of pollination modes with wind pollination being the primary mode (rare in the Magnoliidae). Inflorescence and floral structure exhibit adaptive features that facilitate the various modes of pollen transfer, viz., numerous, small scented, protogynous flowers with no perianth, ultraviolet patterns produced by stamen filaments, small pollen grains, curved inflorescences, and exerted stamens, etc. Fruit production and seed germination are documented and plant growth and densities are compared in sunny versus forest sites.     

黑河流域中游罗布麻传粉生态学特性研究

对黑河流域中游罗布麻的开花动态、花粉活力、柱头可授性、访花昆虫种类、访花频率、花粉与胚珠比(P/O)、杂交指数(OCI)及自然条件下的座果率进行观测,结果显示:罗布麻的单花花期为4～6 d,群体花期为6～8月,花朵开裂3.5 h后,花粉活力达到最大,4 d后花粉活力下降为0,柱头可授性在开花后第2天达到最大,柱头可授性可持续4 d.访花昆虫有10余种,以膜翅目昆虫为主,姬蜂、卡切叶蜂、达戈切叶蜂、意大利蜂、黑带食蚜蝇、菜粉蝶、蚜虫为主要传粉昆虫,花粉与胚珠比(P/O)为36.2,OCI为2,实验组和对照组的座果率分别为(2.79±0.99)%和(3.41±1.05)%.实验结果表明,罗布麻为兼性自交的繁育系统,座果率偏低,虫媒在传粉过程中只是起到一定辅助作用.     

Foraging and pollination behaviour of Xylocopa calens Lepeletier (Hymenoptera: Apidae) on Phaseolus coccineus L. (Fabaceae) flowers at Yaounde (Cameroon)

To evaluate impact of carpenter bee, Xylocopa calens, on pod and seed set of Phaseolus coccineus, its foraging and pollinating activities were studied in Yaounde, for two seasons (May–July 2008 and April–June 2009). Observations were made on 40 inflorescences per treatment. The treatments included unlimited floral access by all visitors, bagged flowers to deny all visits, and limited visits by X. calens only. In addition, all flower visitors were recorded. The carpenter bee's seasonal rhythm of activity, its foraging behavior on flowers, its pollination efficiency, the fructification rate and the number of seeds per pod were recorded. Individuals from 16 species of insects were recorded visiting flowers of P. coccineus in the 2 years. Xylocopa calens was the most frequent, followed by Chalicodoma cincta cincta and Apis mellifera. Apart from bees, wasps were also recorded as likely predators. Xylocopa calens mainly foraged for nectar resources. The mean foraging speed was 9.62 flowers/min. Flowers visited by X. calens had higher fruiting rate compared with others, while those bagged had the lowest. In addition, seed formation was higher in X. calens‐visited flowers compared with all others. The results show that this crop experiences pollination deficit even under normal circumstances, considering that flowers visited by X. calens had higher yields compared with those under unlimited access by all visitors. The fruiting rate, the number of seeds/pod and the percentage of normal seeds of unprotected inflorescences were significantly higher than those of inflorescences protected from insects. X. calens foraging resulted in a significant increment of the fruiting rate by 25.80%, as well as the number of seeds/pod by 14.97% and the percentage of normal seeds by 27.75% in 2008 and 18.39% in 2009. Conservation of X. calens nests close to P. coccineus fields could be recommended to improve pod and seed production in the region.     

Floral Biology of Heterotropa tamaensis (Aristolochiaceae) in Japan

Abstract The floral biology of Heterotropa tamaensis (Makino) F. Maekawa was investigated in native populations. The flowers were protogynous, and the stigmas and anthers were distant from one another. These floral characters are significant for cross-pollination, but breeding experiments showed that the flowers are fairly self-compatible and their pollination is obligately dependent upon animal pollen vectors. The most efficient pollinator for H. tamaensis is a fungus gnat, a member of Mycetophylidae. The fungus gnat visited the flowers relatively frequently and often carried many pollen grains on their hairy bodies. Furthermore, their eggs were frequently found within flowers collected from native habitats. The fungus gnats actively moved about within the flowers and often touched the stigmas and anthers with their bodies. Therefore, H. tamaensis seems to be predominantly self-pollinated, though cross-pollination may occur rarely. The presence of fungus gnat eggs in many flowers strengthened Vogel's hypothesis that the flowers of Heterotropa species mimic the basidiomycetes, in which fungus gnats usually oviposit.     

Delayed autonomous self-pollination in the colonizer Crotalaria micans (Fabaceae: Papilionoideae): structural and functional aspects

We investigated the reproductive biology of Crotalaria micans, a colonizing species that occurs in disturbed sites. The flowers have two whorls of stamens with differential growth and dimorphic anthers. The inner anthers serve two functions: 1) to cooperate with the stylar brush in the pollen presentation, and 2) to push the remaining pollen within the keel onto the stigma at the end of the receptivity period. Flowers pass through three phases: a) male phase, when outer anthers release their pollen, but stigmas are not receptive; b) female phase, when stigmas are receptive, but still separated from flowers' own pollen, and c) an autogamous phase, when the round anthers grow towards the stigma, leading to delayed autonomous self-pollination. Because C. micans is completely self-compatible, delayed self-pollination and geitonogamy result in approximately 76% of seeds being self-fertilized.     

Comparative Studies on Pollination Biology of Mosla hangchouensis and M.chinensis (Labiatae)

Mosla hangchouensis Matsuda and M. chinensis Maxim. are sibling species. The former is endemic to the coastal areas of Zhejiang Province, and the latter occupies southern China. Their morphological differences were associated with their different breeding systems indicated by pollen-ovule ratio (P/O). M. hangchouensis was predominantly outcrossing with P/O ranging from 756 to 6163 due to the variation among populations. Floral characters also showed that M. hangchouensis is an outcrosser: corolla tube 5～10 mm long, 3~5 mm wide, bright red: style 6～15 mm long; stigma 1.5～2.0 mm horizontally away from anthers. On the contrary, M. chinensis was predominantly a selfer with a low P/O ratio (P/O= 110). Its floral parameters contrasted sharply with M. hangchouensis: corolla tube 3.0 mm long, 1.0 ～ 1.5 mm wide, pale colored; style 2.5 mm long. stigma close to or touching anthers. The pollinators of M. hangchouensis most frequently seen are: Bombus trifascitus Smith., Scolia spp., Apis cerana Fabricius, Hylaeus sp. and Lasioglossum spp. These pollinators began to visit flowers at about 8:00 am, when flower buds were ready to open. When insects entered corolla tube for honey and (or) pollen, the stigmata touched the insects body hairs to which pollen grains adhered, and pollen grains were transferred to the stigmata. Meanwhile the hairs collected pollen from anthers under the upper lips of corolla as the insects thrusted their bodies forward. Bumble bees and honey bees were considered more efficient pollinators because they were hair-rich and their body size fitted corolla tube fairly well. Due to the'short flight distance of pollinators between two visits (average flight distances of honey bees and solitary bees were 0.52 m and 0.32 m respectively), pollen dispersal was probably restricted. Pollen vectors were important for the reproductive success of M. hangchouensis because 84.3 % of its seed-set depended on the pollinators' visitation. Although insects did pay visits to M. chinensis occasionally, such visitation was insignificant in seed-set due to cleistogamy. Discussions are made on the evolutionary significance of breeding system divergence between M. hangchouensis and M. chinensis, and the contribution of studies on pollination biology to conservation biology. Further studies are suggested for more thorough understanding of pollination biology of M. hangchouensis.     

Relationship between floral tube length and nectar robbing in Duranta erecta L. (Verbenaceae)

Although nectar robbing is a common phenomenon in plant species with tubular flowers or flowers with nectar spurs, the potential effect of this illegitimate interaction on plant reproductive success has not received the deserved attention. In the present study, we analysed the functional relationship between flower morphology and nectar robbing, and examined the reproductive consequences of the interaction in a population of Duranta erecta (Verbenaceae) on the island of Cuba. The results show that nectar robbing is conducted by the carpenter bees Xylocopa cubaecola and affects up to 44% of flowers in the studied population. However, not all the flowers have the same probability of being robbed. The chance of flowers being robbed increases with flower length and flower diameter. Moreover, nectar robbing significantly decreases the chance that flowers will set fruit. Also, the impact of nectar robbing on the probability of flowers to set fruits is dependent on the plant. We suggest that nectar robbing may represent an opposite selective force that balances the selection for longer corollas often imposed by pollinators specializing in visiting tubular flowers. Such a relationship with nectar robbers would have obvious implications for the evolution of tubular or closed flowers. This preliminary finding deserves further research in light of the ecological and evolutionary consequences of nectar robbing in tubular flowers.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 392–398.     

Pollination of four sympatric species ofAngelonia (Scrophulariaceae) by oil-collecting bees in NE. Brazil

The manner whereby the oil-producing bisaccate flowers ofAngelonia (Scrophulariaceae) are pollinated by female oil-collecting bees is reported for the first time. Observations were made in the Caatinga formation of Pernambuco, NE. Brazil, on four synchronopatric species. These differ in sizes and structural details of the corolla, level of flower exposition, and habitat preferences. All legitimate visitors wereCentris spp. (Anthophoridae):Angelonia hirta was mainly pollinated byC. fuscata andA. pubescens byC. hyptidis; A. bisaccata andA. hookeriana shared an unidentified species. Several exomalopsine, tetrapediine and meliponid bees exploit the flowers less descriminately for oil or pollen, respectively, without regularly contacting anthers and stigma. The flowers are protandrous, and are self-incompatible except those of the annualA. pubescens. After alighting, theCentris bees introduce their front legs simultaneously into each of the pouches and start alternate collecting movements to gather the oil from the trichome elaiophores. While doing so, they are forced by projections of the corolla floor to press their head under the anthers and stigma, whereby pollen is transferred with their frons or clypeus. On account of their collector type and behaviour,C. fuscata andC. spec. are not specialized toAngelonia but may equally exploit other nonrelated taxa for oil, whereasC. hyptidis exhibits oligolecty onA. pubescens. It possesses relatively elongate forelegs with padlike collectors suitable for sweeping the lipids from the scattered glandular hairs inside the divergent spurs of its host. It is the only species that also collects pollen (by buzzing) from the oil host.A. hirta and relatives, provided with dense elaiophore carpets, are, for their part, adapted to scrapingCentris species with typical oil collectors. Flower and bee phenologies, although largely dependent on the irregular rainfalls, are not always coincident.     

Reproductive Biology of the Distylous Manettia luteo-rubra (Rubiaceae)

The reproductive biology of Manettia luteo-rubra was studied in the coastal montane Atlantic rain forest of southeastern Brazil. This Rubiaceae is a perennial vine that flowers all the year round, but has a flowering peak during the dry season. It presents reciprocal herkogamy, thus the plants are morphologically distylous. The morphs occur in a 1:1 ratio, and pollen diameter and corolla length vary between short and long-styled flowers. Manettia luteo-rubra displays typical heterostylous self-incompatibility and sets almost no fruits from self- or intramorph pollinations. The flowers are tubular, red with yellow lobes, and odourless. Anthesis is asynchronous, and the flowers last about four days. Concentration of sugars in nectar is similar in both morphs, ca. 24%, this concentration being typical for hummingbird flowers. Three species of hummingbirds are the major pollinators of the flowers of M. luteo-rubra at the study site: the hermits Phaethornis eurynome and P. squalidus, and the trochiline Thalurania glaucopis. Three species of Heliconius butterflies act as minor pollinators. Both morphs of M. luteo-rubra exhibit natural fruit-set of about 80%, this reproductive output being maintained throughout the year by the pollinators' constancy to the flowers.     

Reproductive biology of Butea monosperma (Fabaceae)

The reproductive biology encompassing phenology, floral biology, pollination and breeding systems, of Butea monosperma, a beautiful tree of the Indian subcontinent, was investigated in a protected dry, deciduous forest located in New Delhi. Phenological studies indicated that although the species shows a regular flowering season, all trees do not flower every year. Flowers are typically papilionaceous; the stigma is wet papillate and the style is hollow. The flowers show characteristics of bird pollination being large and bright orange-red in colour with copious amounts of nectar, and exhibiting diurnal anthesis. Although the flowers are frequented by as many as seven species of birds belonging to six families, only one species, the purple sunbird (Nectarinia asiatica), is the effective pollinator. The flowers are also pollinated by the three-striped squirrel (Funambulus tristiatus). Unlike other flower visitors, these two pollinators forage the nectar from the open side of the keel (legitimate path) during which pollen grains are deposited on their body parts. After the first visit of a sunbird or a squirrel, virgin flowers showed pollen load on the stigma and developed into fruits. B. monosperma shows a weak form of self-incompatibility. Fruit set following manual self-pollination (5.25 %) was comparable with open-pollination (approx. 5 %) but was significantly lower than manual cross-pollination (22.51 %). This indicates that there is a high degree of geitonogamous pollination in this species, which may lead to a weakening of self-incompatibility as a means of reproductive assurance. The results are analysed in the light of prevailing discussions on specialized vs. generalized pollination systems.