Pollen tube reallocation in two preanthesis cleistogamous species, Ranalisma rostratum and Sagittaria guyanensis ssp. lappula (Alismataceae)

Pollen deposition on stigmas and pollen tube growth in two apocarpous species, Ranalisma rostratum and Sagittaria guyanensis ssp. lappula (Alismataceae), were examined with fluorescence microscopy. The reallocation of pollen tubes among pistils was observed in both species. The percentage of pollinated stigmas per flower was only 22.0% in R. rostratum and 51.0% in S. guyanensis, though the seed/ovule ratios are higher than 65% in both species. The number of pollen grains on each single stigma ranged from 0 to 96 in R. rostratum, and from 0 to 125 in S. guyanensis. When more than one pollen grain deposited on a stigma, all pollen tubes grew to the ovary, but only one of them turned towards the ovule and finally entered the nucleus. The other tubes grew through the receptacle tissue into ovules of adjacent carpels whose stigmas were unpollinated or pollinated later. The intercarpellary growth of pollen tubes could be a mechanism to increase the efficiency of sexual reproduction in an apocarpous gynoecium with low pollination on the pistils.     

Developmental study on the inflorescence and flower of Caldesia grandis Samuel (Alismataceae)

The inflorescence and floral development of Caldesia grandis Samuel is reported for the first time in this paper. The basic units of the large cymo‐thyrsus inflorescence are short panicles that are arranged in a pseudowhorl. Each panicle gives rise spirally to three bract primordia also arranged in a pseudowhorl. The branch primordia arise at the axils of the bracts. Each panicle produces spirally three bract primordia with triradiate symmetry (or in a pseudowhorl) and three floral primordia in the axils of the bract primordia. The apex of the panicle becomes a terminal floral primordium after the initiations of lateral bract primordia and floral primordia. Three sepal primordia are initiated approximately in a single whorl from the floral primordium. Three petal primordia are initiated alternate to the sepal primordia, but their subsequent development is much delayed. The first six stamen primordia are initiated as three pairs in a single whorl and each pair appears to be antipetalous as in other genera of the Alismataceae. The stamen primordia of the second whorl are initiated trimerously and opposite to the petals. Usually, 9–12 stamens are initiated in a flower. There is successive transition between the initiation of stamen and carpel primordia. The six first‐initiated carpel primordia rise simultaneously in a whorl and alternate with the trimerous stamens, but the succeeding ones are initiated in irregular spirals, and there are 15–21 carpels developed in a flower. Petals begin to enlarge and expand when anthers of stamens have differentiated microsporangia. Such features do not occur in C. parnassifolia. In the latter, six stamen primordia are initiated in two whorls of three, carpel primordia are initiated in 1–3 whorls, and there is no delay in the development of petals. C. grandis is thus considered more primitive and C. parnassifolia more derived. C. grandis shares more similarities in features of floral development with Alsma, Echinodorus, Luronium and Sagittaria. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society, 2002, 140 , 39–47.     

Acylated anthocyanins in inflorescence of spider flower (Cleome hassleriana)

Five anthocyanins, cyanidin 3-(2′′-(6′′′-caffeoyl-β-glucopyranosyl)-6′′-(E-p-coumaroyl)-β-glucopyranoside)-5-β-glucopyranoside, cyanidin 3-(2′′-(6′′′-E-sinapoyl-β-glucopyranosyl)-6′′-(E-p-coumaroyl)-β-glucopyranoside)-5-β-glucopyranoside, cyanidin 3-(2′′-(6′′′-feroyl-β-glucopyranosyl)-6′′-(E-p-coumaroyl)-β-glucopyranoside)-5-β-glucopyranoside, pelargonidin 3-(2′′-(6′′′-E-sinapoyl-β-glucopyranosyl)-6′′-(E-p-coumaroyl)-β-glucopyranoside)-5-β-glucopyranoside, and pelargonidin 3-(2′′-(6′′′-E-p-coumaroyl-β-glucopyranosyl)-6′′-(E-p-coumaroyl)-β-glucopyranoside)-5-β-glucopyranoside, together with five known anthocyanins have been identified in flowers of Cleome hassleriana Queen line. One monoacylated and four diacylated cyanidin 3-sophoroside-5-glucosides were identified as the main anthocyanins in flowers with mauve colouration, while a homologous glycosidic pattern based on pelargonidin was found in the five main anthocyanins from flowers with pink colouration. The anthocyanins identified in C. hassleriana share the same glycosidic pattern as anthocyanins isolated from the genera Raphanus, Brassica and Iberis in the sister family Brassicaceae.     

Morphology and anatomy of inflorescence and inflorescence axis in Paepalanthus sect. Diphyomene Ruhland (Eriocaulaceae,Poales) and its taxonomic implications

Paepalanthus sect. Diphyomene has inflorescences arranged in umbels. The underlying bauplan seems however to be more complex and composed of several distinct subunits. Despite appearing superficially very similar, the morphology and anatomy of the inflorescences can supply useful information for the understanding of the phylogeny and taxonomy of the group. Inflorescences of Paepalanthus erectifolius, Paepalanthus flaccidus, Paepalanthus giganteus, and Paepalanthus polycladus were analyzed in regard to branching pattern and anatomy. In P. erectifolius, P. giganteus and P. polycladus the structure is a tribotryum, with terminal dibotryum, and with pherophylls bearing lateral dibotrya. In P. flaccidus, the inflorescence is a pleiobotryum, with terminal subunit, and without pherophylls. Secondary inflorescences may occur in all species without regular pattern. Especially when grown in sites without a pronounced seasonality, the distinction between enrichment zone (part of the same inflorescence) and new inflorescences may be obscured. The main anatomical features supplying diagnostic and phylogenetic information are as follows: (a) in the elongated axis, the thickness of the epidermal cell walls and the cortex size; (b) in the bracts, the quantity of parenchyma cells (c) in the scapes, the shape and the presence of a pith tissue. Therefore, P. sect. Diphyomene can be divided in two groups; group A is represented by P. erectifolius, P. giganteus and P. polycladus, and group B is represented by P. flaccidus. The differentiation is based in both, inflorescence structure and anatomy. Group A presents a life cycle and anatomical features similar to species of Actinocephalus. Molecular trees also point that these two groups are closely related. However, inflorescence morphology and blooming sequence are different. Species of group B present an inflorescence structure and anatomical features shared with many genera and species in Eriocaulaceae. The available molecular and morphology based phylogenies still do not allow a precise allocation of the group in the bulk of basal species of Paepalanthus collocated in P. sect. Variabiles. The characters described and used here supply however important information towards this goal.     

Chloroplast DNA variation and phylogeographic patterns in the Chinese endemic marsh herb Sagittaria potamogetifolia

We examined chloroplast DNA (cpDNA) atpB–rbcL intergenic spacer sequences variation within Sagittaria potamogetifolia, an endangered and endemic marsh herb in China. Sequence data were obtained from 54 individuals in six extant populations of the species. Sequences appeared to evolve neutral (Tajima's criterion D = −1.59826, 0.1 > P > 0.05 and Fu and Li's tests D* = −1.44484, P > 0.1; F* = −1.83446, P > 0.1). Eleven haplotypes were identified in S. potamogetifolia. A relatively high level of haplotype diversity (h = 0.0.699) and low level of nucleotide diversity (pi = 0.0035 ± 0.0020) were detected in S. potamogetifolia. Pairwise comparisons of F_st and Nm deduced from cpDNA variation suggested no significant genetic differentiation between populations of S. potamogetifolia excepted for the WY-1 population. Low genetic differentiation among populations and also among regions was consistently indicated by both hierarchical analyses of molecular variance (AMOVA) and the structure of a neighbor-joining tree. Lack of population differentiation between populations or between regions in cpDNA sequences may be due to effects of lower substitution rates or lineage sorting. In the minimum spanning network, all tip haplotypes except for the haplotype J were unique to a particular population, while the interior nodes except for the haplotype E were widespread (haplotype A). From nested clade analysis (NCA), the evolutionary events such as restricted gene flow with isolation by distance and allopatric fragmentation were inferred to responsible for the current distribution of S. potamogetifolia populations, as well as their genetic diversity.     

Structure of the inflorescence and flower ofPetalonyx linearis (Loasaceae)

Fossil chloranthoid androecia,Chloranthistemon endressii gen. et spec. nov. are described from the Upper Cretaceous (Upper Santonian or Lower Campanian) of Scania, southern Sweden. They are three-lobed and dorsiventrally flattened with all pollen sacs borne laterally and inclined toward the presumed adaxial surface. The central lobe bears two pairs of pollen sacs, the lateral lobes a single pair each. The morphology, anatomy and valvate dehiscence of the fossil androecia is very similar to that seen in extant species ofChloranthus andSarcandra, but the in situ pollen differs from that of all extantChloranthaceae in being spiraperturate. A single chloranthoid androecium from the Lower Cretaceous (Upper Albian) of Maryland, North America has a more generalized structure thanChloranthistemon endressii. It consists of three stamens that are fused at the base, and each stamen bears two pairs of oppositely positioned pollen sacs. Combined with anatomical information from recentChloranthus the Lower Cretaceous specimen suggests that the androecium in the living genus has arisen by fusion and other modifications of three separate stamens each with a normal complement of four pollen sacs. The structure of both the Upper and Lower Cretaceous androecia suggest that these fossilChloranthaceae were insectpollinated. Macrofossil evidence combined with information from dispersed pollen indicates that theChloranthaceae diversified early in angiosperm fossil history and were an important component of Mid-Cretaceous plant communities.     

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.     

Observations on the reproductive ecology of Thalassia testudinum (Hydrocharitaceae) II. Leaf width as a secondary sex character

Short-shoots of Thalassia testudinum Banks ex König were collected from 5 sites in Florida. A total of 284, 625-cm² quadrat samples, containing 6182 shhort-shoots was analyzed for leaf width, inflorescence number and sex (the latter if determinable). Although leaf widths and reproductive densities differed at the 5 sites, leaf width was consistently greater when reproductive structures were present, and when the number of inflorescences increased. The mean number of inflorescences per short-shoot was significantly higher for shoots bearing male inflorescences compared to female shoots. Female inflorescences were normally solitary; male short-shoots usually had 2 or 3 inflorescences. Sex ratios were male-biased for 4 of the 5 sites. Comparisons of leaf widths between the sexes indicated that leaf width constituted a secondary sex character for this species. Female short-shoots tend to have narrower leaves than male short-shoots. This relationship should also be considered when evaluating the significance of morphogeographic and stress-related variation in leaf width for this species.     

Early inflorescence and floral development in Cocos nucifera L. (Arecaceae: Arecoideae)

Palms are generally characterized by a large structure with a massive crown that creates difficulties in anatomical studies. The flowering behaviour of palm species may be a useful indicator of phylogenetic relationships and therefore evolutionary events. This paper presents a detailed histological study of reproductive development in coconut (Cocos nucifera L.), from initiation up to maturation of staminate and pistillate flowers. Reproductive development in coconut consists of a sequence of individual events that span more than two years. Floral morphogenesis is the longest event, taking about one year, while sex determination is a rapid process that occurs within one month. The inflorescence consists of different ultimate floral structural components. Pistillate flowers are borne in floral triads that are flanked by two functional staminate flowers. The staminate flowers are born in floral diads towards the base of the rachilla followed by solitary flowers in the middle to top of the rachilla. Three primary phases were identified in reproductive development, namely, transition of axillary bud into inflorescence bud, formation of floral buds, and sexualisation of individual flower buds. All developmental events with respect to stage or time of occurrence were determined.     

Homologies of the flower and inflorescence in the early-divergent grass Anomochloa (Poaceae)

? Premise of the study: The grass subfamily Anomochlooideae is phylogenetically significant as the sister group to all other grasses. Thus, comparison of their structure with that of other grasses could provide clues to the evolutionary origin of these characters. ? Methods: We describe the structure, embryology, and development of the flower and partial inflorescence of the monotypic Brazilian grass Anomochloa marantoidea. We compare these features with those of other early-divergent grasses such as Pharus and Streptochaeta and closely related Poales such as Ecdeiocolea. ? Key results: Anomochloa possesses several features that are characteristic of Poaceae, notably a scutellum, a solid style, reduced stamen number, and an ovary with a single ovule that develops into a single indehiscent fruit. Interpretation of floral patterning in Anomochloa is problematic because the ramification pattern of the florets places the bracts and axes in unusual positions relative to the primary inflorescence axis. Our study indicates that there is a single abaxial carpel in Anomochloa, probably due to a cryptic type of pseudomonomery in Anomochloa that resembles the pseudomonomery of other grasses. On the other hand, the Anomochloa flower differs from the "typical" grass flower in lacking lodicules and possessing four stamens, in contrast with the tristaminate condition that characterizes many other grasses. ? Conclusions: Using the median part of the innermost bract as a locator, we tentatively homologize the inner bract of the Anomochloa partial inflorescence with the palea of other grasses. In this interpretation, the pattern of monosymmetry due to stamen suppression differs from that of Ecdeiocolea.     

Flowering and seasonal changes in flower sex ratio and frequency of flower visitors in a population of Saxifraga hirculus

The open, dish-shaped flowers of Saxifraga hirculus reflected ultraviolet and yellow light, contained very small amounts of nectar, and contained an average of about 75300 pollen grains per flower. Almost 11% of the pollen was inviable. Stigmatic pollen loads and seed set decreased during the course of the season. The plant appeared to be fully between-ramet compatible and partially within-ramet compatible. Seed set for the population was 30.3%. The protandrous flower opened during the day and had male and female phases of nine and three days, respectively. The protandrous system reduced the number of pollination days by a third.
At least 26 species of insects, 16 of which were syrphids, visited the flowers. Based on the number of flower visits, four species were the dominant visitors of S. hirculus: Eurimyia lineata and Neoascia tenur (Diptera: Syrphidae); Asindulum nigrum (Diptera: Mycetophilidae), and Zygaena trlfolii (Lepidoptera: Zygaenidae). Eurimyia lineata was the most frequent visitor (51% of all visits). As the season advanced, the visits by E. lineata decreased, whereas the visits by A. nigrum increased. Z. trifolli disappeared completely towards the end of the season. Only two thirds of the pollination days were "good" foraging days for these visitor species. The four major visitor species spent an average of 11.7, 27.4, 30.7 and 22.6 s per flower, respectively. Estimates suggest that about 6.5 visits (which is equal to 2.6 min of flower-visiting) and 2100 grains of pollen were required to produce one seed.     

Pollinator responses to variation in floral display and flower size in dioecious Sagittaria latifolia (Alismataceae)

In animal-pollinated plants with unisexual flowers, sexual dimorphism in floral traits may be the consequence of pollinator-mediated selection. Experimental investigations of the effects of variation in flower size and floral display on pollinator visitation can provide insights into the evolution of floral dimorphism in dioecious plants. Here, we investigated pollinator responses to experimental arrays of dioecious Sagittaria latifolia in which we manipulated floral display and flower size. We also examined whether there were changes in pollinator visitation with increasing dimorphism in flower size. In S. latifolia, males have larger flowers and smaller floral displays than females. Visitation by pollinators, mainly flies and bees, was more frequent for male than for female inflorescences and increased with increasing flower size, regardless of sex. The number of insect visits per flower decreased with increasing floral display in males but remained constant in females. Greater sexual dimorphism in flower size increased visits to male inflorescences but had no influence on the number of visits to female inflorescences. These results suggest that larger flower sizes would be advantageous to both females and males, and no evidence was found that females suffer from increased flower-size dimorphism. Small daily floral displays may benefit males by allowing extended flowering periods and greater opportunities for effective pollen dispersal.     

Branch length mediates flower production and inflorescence architecture of Fouquieria splendens (ocotillo)

The capacity of individual branches to store water and fix carbon can have profound effects on inflorescence size and architecture, thus on floral display, pollination, and fecundity. Mixed regression was used to investigate the relation between branch length, a proxy for plant resources, and floral display of Fouquieria splendens (ocotillo), a woody, candelabraform shrub of wide distribution in arid North America. Long branches produced three times as many flowers as short branches, regardless of overall plant size. Long branches also had more complex panicles with more cymes and cyme types than short branches; thus, branch length also influenced inflorescence architecture. Within panicles, increasing the number of cymes by one unit added about two flowers, whereas increasing the number of cyme types by one unit added about 21 flowers. Because flower production is mediated by branch length, and because most plants have branches of various lengths, the floral display of individual plants necessarily encompasses a wide range of inflorescence size and structure.     

Unisexual flower, spikelet, and inflorescence development in monoecious/dioecious Bouteloua dimorpha (Poaceae, Chloridoideae)

Unisexual flowers have evolved repeatedly in the angiosperms. In Poaceae, multiple transitions from bisexual to unisexual flowers are hypothesized. There appear to be at least three distinct developmental mechanisms for unisexual flower formation as found in members of three subfamilies (Ehrhartoideae, Panicoideae, Pharoideae). In this study, unisexual flower development is described for the first time in subfamily Chloridoideae, as exemplified by Bouteloua dimorpha. Scanning electron microscopy (SEM) and anatomy were used to characterize the development of male (staminate) and female (pistillate) flowers, spikelets, and inflorescences. We found the developmental pathway for staminate flowers in B. dimorpha to be distinct from that described in the other three subfamilies, showing gynoecial arrest occurs at a different stage with possible loss of some cellular contents. However, pistillate flowers of B. dimorpha had some similarity to those described in other unisexual-flowered grasses, with filament and anther differentiation in abortive stamens. Comparing our findings with previous reports, unisexual flowers seem to have evolved independently in the four examined grass subfamilies. This analysis suggests the action of different genetic mechanisms, which are consistent with previous observations that floral unisexuality is a homoplasious condition in angiosperms.     

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.     

Habitat differentiation in the threatened aquatic plant genus Baldellia (L.) Parl. (Alismataceae): Implications for conservation

A comparative analysis of the habitats of Baldellia ranunculoides (subsp. ranunculoides and subsp. repens) and Baldellia alpestris (Alismataceae) was carried out across central and western Europe. Soil samples from 43 populations were analyzed and the composition of accompanying vegetation was analyzed by canonical correspondence and indicator species analysis. Significant differences in the habitat conditions and the accompanying vegetation were found between the three taxa. B. ranunculoides subsp. repens is growing in lowland water bodies on acidic substrates (pH 5–6.3) which are markedly richer in organic matter and poorer in cations, especially in Ca²⁺. B. ranunculoides s. str. is also a lowland taxon, but grows on more mineral and basic substrates (pH 7–9), usually rich in Ca²⁺. The endemic B. alpestris grows in the most distinct habitats, on substrates with low pH and with very low Ca²⁺ concentrations, at much higher altitudes than the other taxa and in very specific plant communities that have almost no affinities with those of the two lowland Baldellia-taxa. The Baldellia-taxa are threatened by eutrophication of their habitats. Moreover, many of the extant populations, in particular those of B. ranunculoides s. str., are very small and will be threatened by environmental stochasticity. Reintroduction and the creation of new populations might reduce the risk of extinction. Information given on the detailed habitat preferences of the Baldellia-taxa could help conservation efforts for these endangered taxa and identify suitable sites for (re-) introductions.     

Genetics and evolution of inflorescence and flower development in grasses

Inflorescences and flowers in the grass species have characteristic structures that are distinct from those in eudicots. Owing to the availability of genetic tools and their genome sequences, rice and maize have become model plants for the grasses and for the monocots in general. Recent studies have provided much insight into the genetic control of inflorescence and flower development in grasses, especially in rice and maize. Progress in elucidating the developmental mechanisms in each of these plants may contribute greatly to our understanding of the evolution of development in higher plants.     

水鳖科植物花和花序的形态学及发育的基本式样

通过野外调查 ,结合实体解剖和扫描电镜观察 ,对国产水鳖科植物花和花序的分化式样及花部结构多样性进行了研究 ,并探讨了水鳖科植物的花部发育的基本式样 ,结果表明 ,在花部是三基数的植物中 ,如水筛属 (Blyxa)、水车前属 (Ottelia)等 ,花器官原基以轮状 ,向心发育 ,辐射对称的方式发生 ,后一轮倾向于与前一轮相交替 ;在花部非三基数的植物中 ,如虾子草属 (Nechamandra) ,苦草属 (Vallisneria)等 ,由于部分花器官缺失 ,花器官原基呈不规则发生。