Gender expression and inflorescence structure of Pappea capensis Eckl. and Zeyh. (Sapindaceae)

Gender and the structure of the inflorescence and flowers of Pappea capensis (Sapindaceae) are investigated in a locality around Pretoria (22-27°S and 25-32°E). The trees flower over a long period (December to April) and are basically monoecious, starting with male flowers followed by female flowers towards the end of the flowering period, although some trees may be predominantly male and some predominantly female. The inflorescence is a reduced thyrse with small flowers. Male flowers have five ephemeral petals, eight stamens and a rudimental pistil. Female flowers comprise a 3-lobed ovary, a single style and stigma and eight staminodes.     

Pollen and resource limitations to lifetime seed production in a wild population of the endangered plant Disanthus cercidifolius var. longipes H. T. Chang (Hamamelidaceae)

Disanthus cercidifolius Maxim. var. longipes H. T. Chang, a plant species that only occurs in a few counties in Hunan, Jiangxi and Zhejiang Provinces and with a relatively small number of individuals, is ranked as a second Class endangered species for conservation in China. We have studied the effect of pollen and resources available to female reproduction, and the reproductive mechanism of “excess flowers with low fruit set” in Disanthus cercidifolius Maxim. var. longipes H. T. Chang was discussed. Results are as follows Pollen from different sources has significant effects on fruit set and seed set of Disanthus cercidifolius Maxim. var. longipes H. T. Chang. The pollen source rather than pollen numbers significantly affected reproduction of this species. In wild populations, producing one fruit needs about 54.8 flowers, and one satiation seed needs about 6.60 flowers or 83.19 ovules. After fertilizing, which was propitious to flower development, the abortion rate of flower buds was decreasing, but the flowering rate was increasing. The fruit set and seed set was also significantly increasing, while abortion rate of fruit was significantly decreasing. With the increasing percentages of cutting leaves, the fruit set decreased, but the abortion rate of fruit shows no significant differentiation among treatments. After cutting branches that were puny, broken and insectin-fested branches, the flower number seemed to be decreasing, but the fruit set and seed set all increased significantly. After removing some flowers, the fruit set was calculated with respect to the number of flowers remaining after the treatment increased with increasing of percentages of flower removal, whereas fruit set calculated with respect to the initial number of flowers remained constant, and the mean weights of per fruit and per seed all decreased significantly. Sufficient spatial or temporal heterogeneities in nutrient levels might allow limitation of seed set by resources and pollen in a natural population, while supplying resources may indirectly affect pollination by increasing attraction of the flowers to pollinators. There were very low fruit and seed sets in natural populations of Disanthus cercidifolius Maxim. var. longipes H. T. Chang. Different factors may have interacted to effect a low fruit set. A joint adoption of the “selection abortion hypothesis”, “ovary reserve hypothesis” and “male function hypothesis” seems to be the most likely explanation for the reproductive strategy of “excess flowers with few fruit sets” in Disanthus cercidifolius Maxim. var. longipes H. T. Chang.     

Flavonoids from the flowers of Adenium obesum (Forssk.) Roem. & Schult., Mandevilla sanderi (Hemsl.) Woodson,and Nerium oleander L. (Apocynaceae)

Twenty-two ornamental flowers from different Adenium obesum, Mandevilla sanderi, and Nerium oleander cultivars/seedlings were analyzed for the presence of anthocyanins, flavonols, and chlorogenic acid using nuclear magnetic resonance (NMR) and mass spectrometry (MS). Cyanidin 3-O-[6-O-(rhamnosyl)-galactoside] and cyanidin 3-O-(galactoside) were identified as the major and minor anthocyanins, respectively, in three A. obesum seedlings that had red and red-purple flowers.Cyanidin 3-O-[2-O-(xylosyl)-galactoside] was identified as the major anthocyanin, whereas cyanidin 3-O-[6-O-(rhamnosyl)-galactoside] and cyanidin 3-O-(galactoside) were identified as the minor anthocyanins in 8 M. sanderi cultivars that had red and red-purple flowers. Cyanidin 3-O-[6-O-(rhamnosyl)-galactoside] and cyanidin 3-O-(galactoside) were identified as the major anthocyanins, whereas cyanidin 3-O-[2-O-(xylosyl)-galactoside] was identified as the minor anthocyanin in 8 N. oleander cultivars with red and red-purple flowers. Low levels of anthocyanins were detected in the N. oleander and M. sanderi cultivars that had white flowers, and there were no anthocyanins detected in the N. oleander cultivars with yellow flowers. Chlorogenic acid and four flavonols, quercetin 3-O-[6-O-(rhamnosyl)-galactoside], quercetin 3-O-[6-O-(rhamnosyl)-glucoside], kaempferol 3-O-(galactoside), and kaempferol 3-O-[6-O-(rhamnosyl)-galactoside], were identified in the flowers from all 22 cultivars/seedlings investigated.     

The floral biology ofTricyrtis latifolia Maxim. (Liliaceae)

The floral biology ofTricyrtis latifolia was investigated at four sites: Nigorigo, Kurumijima and Hikagedaira-san, Gifu Prefecture, and Jöge, Miyagi Prefecture. The flowers open fully by 3 a.m., and anthesis begins at about 8 a.m. Most pollen is taken away by bumblebees by 10 a.m. The distal parts of the trifid style-branches (each branch is further bifid) and the immature stigmata are above the anthers in the first day flowers. The distal parts of the style-branches with their extension curve downward and are positioned under the anthers on the morning of the second day and the stigmata are fully matured. The flowers wilt by the third day. The primary pollinators ofT. latifolia wereBombus diversus andB. honshuensis in three sites; only the former was a primary pollinator at the Jōge site. Bees forage the first and second day flowers, and their backs contact the anthers and stigmata of the second day flowers while the bees are sucking nectar. Breeding experiments showed thatT. latifolia was fairly self-compatible. The avoidance of autogamy and the possibility of geitonogamy are discussed.     

Dimalonated anthocyanins from the flowers of Salvia splendens and S. coccinea

The pigments of Salvia splendens flowers (scarlet cvs) have been identified as pelargonidin 3-caffeoylglucoside-5-dimalonylglucoside and pelargonidin 3-p-coumaroylglucoside-5-dimalonylglucoside. The flowers of S. coccinea contain the same pigments in the corolla but the calyx contains, in addition, the cyanidin analogues.     

Honey bee handling behaviour on the papilionate flower of Robinia pseudoacacia L.

Papilionate flowers, such as those of Robinia pseudoacacia L., show tripping mechanisms that prevent pollen release: only those bees which apply the right force on petals induce pollen to be deposited on their bodies. Apis mellifera is considered a poor visitor of such flowers, since individuals are usually too weak to trip the mechanism. Despite this, the honey bee pays frequent visits to flowers of R. pseudoacacia and produces a much appreciated unifloral honey. We investigated how bees manipulate R. pseudoacacia flowers, whether they contact the plant’s reproductive core and if there is any appreciable difference related to the manipulation of individual flowers. Honey bees showed two strategies for resource collection, namely legitimate visits and robberies. Legitimate visits were more frequent and about 63 % entailed contact with the flower’s reproductive core. We distinguished two behaviours, one to achieve successful positioning on the flower and the other for nectar intake. These behaviours were clearly perceptible and described by different curves of time frequency distribution. From the beginning to the end of anthesis, flowers were classified into four types on the basis of their morphological and phenological traits. Positioning time differed significantly depending on the flower type, with less time needed for more ageing flowers. Time spent in nectar intake was instead highly variable and independent of flower ageing. Selecting the right flower type would appear to lead to obtaining the R. pseudoacacia reward, overcoming species-specific physical inability. Moreover, the role of honey bees as pollinators of R. pseudoacacia is considered. Finally, the relations between petal characteristics and strength needed to trip the mechanism in papilionate flowers is also discussed in the light of nectar foragers.     

Pollination of Cyphomandra endopogon var. endopogon (Solanaceae) by Eufriesea spp. (Euglossini) in French Guiana

The pollination systems of two closely related genera.Cyphomandra andSolanum, differ in rewards offered and pollinator activity. I suggest that the anther differences which define these two genera have evolved in response to the different pollination systems. Male euglossine bees of the genusEufriesea were observed to pollinate the flowers ofCyphomandra endopogon var.endopogon while gathering aromatic compounds from the anther connectives. Samples of the compound collected from the flowers and the bees were tentatively identified as ocimene, a terpene.     

Different ontogenetic processes promote dicliny in Ficus L. (Moraceae)

The absence of reproductive organs in flowers may ontogenetically arise from inception or by abortion during development. Ficus L., a species-rich genus of angiosperms, is an interesting model for floral developmental studies because of the diversity of sexual systems it contains. This study compares the floral morphology of Ficus citrifolia (monoecious), Ficus religiosa (monoecious), Ficus racemosa (secondarily monoecious), and Ficus hispida (gynodioecious) across development to establish the ontogenetic pathways that result in diclinous flowers. Figs were collected at various developmental stages and were prepared for surface (scanning electron microscopy) and histological (light microscopy) analyses. Dicliny in Ficus is defined by stamen absence from inception in pistillate flowers and either pistil absence from inception (F. citrifolia, F. racemosa and F. religiosa) or by abortion (F. hispida) in staminate flowers. The perianth is formed by a single whorl of sepals, as found in other families related to Moraceae. The gynoecium is tubular during development, a condition that may be related with pseudomonomery. The staminate and neutral flowers in F. hispida develop by similar mechanisms. The diversity in the sexual systems in Ficus results from combinations of different floral morphs (dicliny), which originate from both previously established ontogenetic mechanisms (loss of reproductive organ function by abortion or from inception). These mechanisms act independently of phylogenetic proximity or mechanisms of sex system evolution in Ficus. Other aspects of floral development observed in Ficus are discussed in relation to their systematic position and reproductive biology.     

Preformation and distribution of staminate and pistillate flowers in growth units of Nothofagus alpina and N. obliqua (Nothofagaceae)

Background and Aims

The distribution and differentiation times of flowers in monoecious wind-pollinated plants are fundamental for the understanding of their mating patterns and evolution. Two closely related South American Nothofagus species were compared with regard to the differentiation times and positions of staminate and pistillate flowers along their parent growth units (GUs) by quantitative means.

Methods

Two samples of GUs that had extended in the 2004–2005 growing season were taken in 2005 and 2006 from trees in the Lanín National Park, Patagonia, Argentina. For the first sample, axillary buds of the parent GUs were dissected and the leaf, bud and flower primordia of these buds were identified. The second sample included all branches derived from the parent GUs in the 2005–2006 growing season.

Key Results

Both species developed flowering GUs with staminate and/or pistillate flowers; GUs with both flower types were the most common. The position of staminate flowers along GUs was similar between species and close to the proximal end of the GUs. Pistillate flowers were developed more distally along the GUs in N. alpina than in N. obliqua. In N. alpina, the nodes bearing staminate and pistillate flowers were separated by one to several nodes with axillary buds, something not observed in N. obliqua. Markovian models supported this between-species difference. Flowering GUs, including all of their leaves and flowers were entirely preformed in the winter buds.

Conclusions

Staminate and pistillate flowers of N. alpina and N. obliqua are differentiated at precise locations on GUs in the growing season preceding that of their antheses. The differences between N. alpina and N. obliqua (and other South American Nothofagus species) regarding flower distribution might relate to the time of anthesis of each flower type and, in turn, to the probabilities of self-pollination at the GU level.Key words: Branch, bud, growth unit, Markovian models, Nothofagus alpina, N. obliqua, Patagonian forests, pistillate flower, preformation, staminate flower     

Mechanism of 2-acetyl-1-pyrroline biosynthesis in Bassia latifolia Roxb. flowers

The flowers of Bassia latifolia are known to contain 2-acetyl-1-pyrroline (2AP), the compound responsible for pleasant aroma in basmati and other scented rice. Four growth stages of Bassia flowers were identified and 2AP contents were analysed in each stage. It was found that 2AP (3.30 ppm) gets synthesized only in fleshy corolla of mature flowers (fourth stage). The activity of γ-aminobutyraldehyde dehydrogenase (AADH); an enzyme responsible for synthesis of γ-aminobutyricacid (GABA) from γ-aminobutyraldehyde (GABald) was assessed in these four stages. The AADH activity was absent in the fourth stage. It was concluded that ceased activity of AADH in fourth stage flowers leads to the accumulation of γ-aminobutyraldehyde which is cyclised spontaneously to Δ¹-pyrroline, the key precursor of 2AP. Δ¹-pyrroline further reacts unenzymatically with methylglyoxal to form 2AP.     

Morphology and anatomy of male cones of Pseudotaxus chienii (W.C. Cheng) W.C. Cheng (Taxaceae)

Results of the present study indicate that male cones of Pseudotaxus chienii are representing inflorescences with strongly reduced flowers. The results fit quite well with investigations showing that sporangiophores of Taxus and also of Pseudotaxus comply with reduced flowers. The only difference between male cones in Taxus and Pseudotaxus is the absence of pherophylls in Taxus. Furthermore our results complete a transition series beginning with Cephalotaxus going on to Pseudotaxus and ending with Taxus and Torreya. In this progression Pseudotaxus can be regarded as an intermediate link between the inflorescences of Cephalotaxus and the simple, unbranched cones of Taxus. The entire transition series shows that sporophyll-like sporangiophores can be derived by reduction of lateral cones. There is however no sign that a similar process has occurred in other conifer groups.     

Reproductive biology of Echinodorus longipetalus (Alismataceae): Sexual morphs,breeding system and pollinators

The floral biology, pollinators and breeding system of Echinodorus longipetalus Micheli were studied in a marshy area of the district of Taquaritinga (State of São Paulo), southeastern Brazil. E. longipetalus is gynodioecious and as far as is known, this is the first record of unisexual flowers, besides perfect flowers, in Echinodorus. Proportion of female individuals in the studied population is 50% and produces 31% more flowers than hermaphrodites. Perfect and pistillate flowers of E. longipetalus are similar in appearance and are pollinated by several species of Hymenoptera (mainly by Xylocopa (Neoxylocopa) suspecta Moure & Camargo). Perfect flowers offer pollen as a reward. Pistillate flowers attract floral visitors by deceit with their staminodes that resemble the stamens of the perfect flowers. Visits to pistillate flowers are quick (1–2 s), while visits to perfect flowers last up to 120 s. The perfect flowers are self-compatible and produce fruits through spontaneous self-pollination (control flowers), whereas the pistillate ones only set fruits through cross-pollinations. Perfect and pistillate flowers set more fruits under natural conditions than in manual treatments, respectively. Although the pistillate and perfect flowers bear a strong similarity, the selective pollinator behavior seems to be responsible for the increase of fruit set in perfect flowers.     

Reproductive biology of Echinodorus longipetalus (Alismataceae): Sexual morphs,breeding system and pollinators

The floral biology, pollinators and breeding system of Echinodorus longipetalus Micheli were studied in a marshy area of the district of Taquaritinga (State of São Paulo), southeastern Brazil. E. longipetalus is gynodioecious and as far as is known, this is the first record of unisexual flowers, besides perfect flowers, in Echinodorus. Proportion of female individuals in the studied population is 50% and produces 31% more flowers than hermaphrodites. Perfect and pistillate flowers of E. longipetalus are similar in appearance and are pollinated by several species of Hymenoptera (mainly by Xylocopa (Neoxylocopa) suspecta Moure & Camargo). Perfect flowers offer pollen as a reward. Pistillate flowers attract floral visitors by deceit with their staminodes that resemble the stamens of the perfect flowers. Visits to pistillate flowers are quick (1–2 s), while visits to perfect flowers last up to 120 s. The perfect flowers are self-compatible and produce fruits through spontaneous self-pollination (control flowers), whereas the pistillate ones only set fruits through cross-pollinations. Perfect and pistillate flowers set more fruits under natural conditions than in manual treatments, respectively. Although the pistillate and perfect flowers bear a strong similarity, the selective pollinator behavior seems to be responsible for the increase of fruit set in perfect flowers.     

Ultraviolet reflectance and absorption patterns in flowers of Nymphaea alba L., Nymphaea candida presl and Nuphar lutea (L.) Sm. (Nymphaeaceae)

Ultraviolet (u.v.) patterns of flowers of Nymphaeaceae as an important colour component for flower-visiting insects have been totally neglected in studies of their floral biology. The three day-flowering species studied show distinct u.v. patterns. Both Nymphaea species show hogh absorption in the centre of the flowers and u.v.-reflective thecae. In Nymphaea alba L. a radial u.v. stripe reflection pattern is visible on the stigmatic disc in u.v. photographs, which is weakly developed in Nymphaea candida Presl flowers. The flowers of Nuphar show the most distinct u.v. reflection pattern in the form of a circle formed by the u.v.-reflective tips and filaments of the stamens, in contrast to the shiny petals and u.v.-absorptive stigmatic disc, thecae and sepals.     

Spiranthes ovalis var. Erostellata (Orchidaceae), a new autogamous variety from the Eastern United States

Examination of flowers from herbarium specimens ofSpiranthes ovalis revealed two kinds of column structure. Some plants, including the type, have flowers with a normally developed rostellum and viscidium; other plants that have flowers in which these structures are entirely lacking are here described asSpiranthes ovalis var.erostellata. Self-pollination in the new variety was proven by pollinia removal and observation of plants in insect-proof cages. The var.erostellata has a somewhat smaller perianth with sepals 3.5–5 instead of 4–6.1 mm long and is more common and more widespread than the typical variety.     

Floral isolation between Aquilegia formosa and Aquilegia pubescens

The acquisition of floral nectar spurs is correlated with increased species diversity across multiple clades. We tested whether variation in nectar spurs influences reproductive isolation and, thus, can potentially promote species diversity using two species of Aquilegia, Aquilegia formosa and Aquilegia pubescens, which form narrow hybrid zones. Floral visitors strongly discriminated between the two species both in natural populations and at mixed-species arrays of individual flowers. Bees and hummingbirds visited flowers of A. formosa at a much greater rate than flowers of A. pubescens. Hawkmoths, however, nearly exclusively visited flowers of A. pubescens. We found that altering the orientation of A. pubescens flowers from upright to pendent, like the flowers of A. formosa, reduced hawkmoth visitation by an order of magnitude. In contrast, shortening the length of the nectar spurs of A. pubescens flowers to a length similar to A. formosa flowers did not affect hawkmoth visitation. However, pollen removal was significantly reduced in flowers with shortened nectar spurs. These data indicate that floral traits promote floral isolation between these species and that specific floral traits affect floral isolation via ethological isolation while others affect floral isolation via mechanical isolation.     

Evolutionary,genetic, environmental and hormonal-induced plasticity in the fate of organs arising from axillary meristems in Passiflora spp.

Tendrils can be found in different plant species. In legumes such as pea, tendrils are modified leaves produced by the vegetative meristem but in the grape vine, a same meristem is used to either form a tendril or an inflorescence. Passiflora species originated in ecosystems in which there is dense vegetation and competition for light. Thus climbing on other plants in order to reach regions with higher light using tendrils is an adaptive advantage. In Passiflora species, after a juvenile phase, every leaf has a subtending vegetative meristem, and a separate meristem that forms both flowers and a tendril. Thus, flowers are formed once a tendril is formed yet whether or not this flower will reach bloom depends on the environment. For example, in Passiflora edulis flowers do not develop under shaded conditions, so that tendrils are needed to bring the plant to positions were flowers can develop. This separate meristem generally forms a single tendril in different Passiflora species yet the number and position of flowers formed from the same meristem diverges among species. Here we display the variation among species as well as variation within a single species, P. edulis. We also show that the number of flowers within a specific genotype can be modulated by applying Cytokinins. Finally, this separate meristem is capable of transforming into a leaf-producing meristem under specific environmental conditions. Thus, behind what appears to be a species-specific rigid program regarding the fate of this meristem, our study helps to reveal a plasticity normally restrained by genetic, hormonal and environmental constraints.     

Mutations perturbing petal cell shape and anthocyanin synthesis influence bumblebee perception of Antirrhinum majus flower colour

We wished to understand the effects on pollinator behaviour of single mutations in plant genes controlling flower appearance. To this end, we analysed snapdragon flowers (Antirrhinum majus), including the mixta and nivea mutants, in controlled laboratory conditions using psychophysical tests with bumblebees. The MIXTA locus controls petal epidermal cell shape, and thus the path that incident light takes within the pigment-containing cells. The effect is that mixta mutant flowers are pink in comparison to the wild type purple flowers, and mutants lack the sparkling sheen of wild type flowers that is clearly visible to human observers. Despite their fundamentally different appearance to humans, and even though bees could discriminate the flowers, inexperienced bees exhibited no preference for either type, and the flowers did not differ in their detectability in a Y-maze—either when the flowers appeared in front of a homogeneous or a dappled background. Equally counterintuitive effects were found for the non-pigmented, UV reflecting nivea mutant: even though the overall reflectance intensity and UV signal of nivea flowers is several times that of wild type flowers, their detectability was significantly reduced relative to wild type flowers. In addition, naïve foragers preferred wild type flowers over nivea mutants, even though these generated a stronger signal in all receptor types. Our results show that single mutations affecting flower signal can have profound effects on pollinator behaviour—but not in ways predictable by crude assessments via human perception, nor simple quantification of UV signals. However, current models of bee visual perception predict the observed effects very well.     

乙烯利诱导网纹甜瓜主蔓两性花花芽分化的形态和解剖学研究

以网纹甜瓜(Cucumis melo L.var. reticulatus Naud.)品种’西域1号’为试验材料,于幼苗3叶1心期喷施浓度为150 mg·L^-1的乙烯利溶液进行处理,诱导主蔓形成两性花,以清水为对照,分别对处理和对照植株不同时期的主蔓和侧蔓花芽分化过程进行形态和解剖学观察。结果表明：经乙烯利处理后,幼苗植株主蔓花原基持续向两性花分化,最终发育形成两性花。未经处理植株的主蔓花原基在分化早期与两性花发育过程相同,但在雌蕊出现后,不再继续发育,最终发育形成雄花。处理植株主蔓两性花发育过程与侧蔓两性花发育过程相同。