Homeosis, morphogenetic gradient and the determination of floral identity in the inflorescences ofPhilodendron solimoesense (Araceae)

A comparative developmental study of the inflorescence ofPhilodendron solimoesense was conducted using scanning electron microscopy. The spadix ofP. solimoesense is characterized by unisexual flowers. Staminate flowers are initiated on the upper portion of the spadix while pistillate flowers develop on the lower portion of the spadix. An intermediate zone located between the upper male and lower female portion of the inflorescence consists of sterile male flowers. Within this intermediate zone a row of flowers exhibit polarity with respect to the identity of sexual organs. Stamens are initiated on the flank of the floral meristem facing the upper male zone and carpels are initiated on the portion of the floral meristem facing the lower female zone. The resulting flowers therefore assume a bisexual identity. At the level of the inflorescence, all floral buds are initiated along a series of contact parastichies and the continuity of these parastichies is not disrupted at any level in the male, intermediate, and female zones on the spadix. Results from this study support the presence of a morphogenetic gradient acting at the level of the inflorescence and appears to be independent of the boundaries of floral primordia.     

BEETLE POLLINATION OF DIEFFENBACHIA LONGISPATHA (ARACEAE)

Dieffenbachia is an monoecious understory herb of tropical rain forests that exhibits a complex and specialized relationship with its beetle pollinators. The erect protogynous inflorescence has the spadix divided, with the female flowers in the basal half and male flowers in the upper half. Dieffenbachia longispatha Engler & Krause is pollinated by scarab beetles in the genera Cyclocephala and Erioscelis. The enveloping spathe of the inflorescence opens in the evening, but no flowers are sexually functional until the stigmas become receptive about 24 hr later. Beetles fly to the inflorescence in darkness, suggesting that floral odors play a role as an attractant. Beetles remain in the inflorescence for 24 hr, eating protein-rich staminodia that surround the stigmas. On the evening of the third day the anthers dehisce and beetles become covered with pollen as they crawl up the spadix in the process of leaving. Beetles fly an average of 80 m between inflorescences, usually to the nearest female inflorescence, although distances of 400–1,000 m have been observed. Minimal estimate of genetic neighborhood sizes are large for D. longispatha (750 to 8,900 plants) and neighborhood areas encompass 41,000 to 67,000 m². Experiments demonstrate that the species is self-compatible and that fruit production is pollinator limited.     

Elatostema planinerve and E. longicuspe spp. nov. (Urticaceae) from Guizhou Province,China

Two new species, Elatostema planinerve W. T. Wang & Y. G. Wei sp. nov. and E. longicuspe W. T. Wang & Y. G. Wei sp. nov. are described and illustrated from the Guizhou province, China. The former resembles E. bracteosum but differs in leaves, pistillate bracts and pistillate bracteoles; the latter is similar to E. tenuicornutum, but differs in stem surface, leaf shape, venation, cystoliths, staminate inflorescence bracts, bracteolate and staminate flowers.     

THE MORPHOLOGY AND RELATIONSHIPS OF DALECHAMPIA SCANDENS (EUPHORBIACEAE)

The circumtropical but preponderantly American genus Dalechampia, comprising nearly 100 species of twining vines (or rarely subshrubs), is strikingly isolated within the Euphorbiaceae because of its distinctive bibracteate inflorescences. There has been considerable taxonomic controversy with regard to the relationships of the genus, and it has been suggested that Dalechampia is allied to the tribe Euphorbieae because of a supposed analogy between its inflorescence and the cyathium in the Euphorbieae. Field and laboratory investigations of the common American species D. scandens, together with a comparative survey of related species, have thrown some light on these problems. The Dalechampia inflorescence seems best interpreted as consisting of a terminal staminate pleiochasium (with part of the lateral branches transformed for nectar production), juxtaposed to a 3-flowered pistillate cyme. The lips of the conspicuous bilabiate involucre are formed by the hypertrophied bracts which subtend the staminate and pistillate cymes. The bisexual inflorescences appear to be distinctly proterogynous, rather than proterandrous, as has been previously suggested. The configuration of the inflorescence—a bilaterally symmetrical pseudanthium—suggests adaptation for crosspollination, but the closing movement of the bracts makes self-pollination probable in the absence of visits by pollinators. The similarity of the Dalechampia inflorescence to the cyathium of the Euphorbieae appears to be entirely superficial, and both reproductive and vegetative data suggest that Dalechampia is related to taxa of tribe Plukenetieae.     

The development of pistillate and perfect florets in Xeranthemum squarrosum (Asteraceae)

The formation of capitulum inflorescence with two different types of floret is an interesting issue in floral biology and evolution. Here we studied the inflorescence, floral ontogeny and development of the everlasting herb, Xeranthemum squarrosum, using epi‐illumination microscopy. The small vegetative apex enlarged and produced involucral bracts with helical phyllotaxy, which subtended floret primordia in the innermost whorl. Initiation of floret primordia was followed by an acropetal sequence, except for pistillate peripheral florets. The origin of receptacular bracts was unusual, as they derived from the floral primordia rather than the receptacular surface. The order of whorl initiation in both disc and pistillate flowers included corolla, androecium and finally calyx, together with the gynoecium. The inception of sepals and stamens occurred in unidirectional order starting from the abaxial side, whereas petals incepted unidirectionally from the adaxial or abaxial side. Substantial differences were observed in flower structure and the development between pistillate and perfect florets. Pistillate florets presented a zygomorphic floral primordium, tetramerous corolla and androecium and two sepal lobes. In these florets, two sepal lobes and four stamen primordia stopped growing, and the ovary developed neither an ovule nor a typical stigma. The results suggest that peripheral pistillate florets in X. squarrosum, which has a bilabiate corolla, could be considered as an intermediate state between ancestral bilabiate florets and the derived ray florets.     

Structure of the flower and inflorescence ofHouttuynia cordata thunb

In the spike ofHouttuynia cordata with many large bracts all flowers in a spike are regularly arranged in a secondary pseudo-opposite order. Arrangment of flowers in the normal spike also follows the same order. A pistillate organ is usually borne at the terminal of the spike. Vascular anatomy of the flower, inflorescence and the arrangement of flowers suggest that this terminal organ should be interpreted as a compound structure composed of four units, each of which represents one flower with a single carpel and a single dorsal stamen. The terminal pistillate organ of a lateral spike is considered to have a structure intermediate between that of the normal hermaphoriditic flower and that of the terminal pistillate organ of the main spike.     

DEVELOPMENTAL STUDIES IN PTYCHOSPERMA (PALMAE). I. THE INFLORESCENCE AND THE FLOWER CLUSTER

This paper describes inflorescence structure, including organogenesis of the panicle and flower clusters and vasculature of flowering branches, for two species of Ptychosperma, a genus of arecoid palms. The inflorescence is an infrafoliar panicle with up to four orders of branches in a spirodistichous arrangement conforming to an irregular one-half phyllotaxy. The primordium of the inflorescence is crescentic and the apex has two tunica layers, a group of central cells, and a rib meristem. The distal flower-bearing parts or rachillae of all branches develop acropetally early in ontogeny and are vertically oriented in the bud. Although these rachillae terminate branches of different sizes and orders, they are similar in size and in number of flower clusters produced. Internodes and lower parts of branches develop later. Bracts of four types are produced: a prophyll and empty peduncular bract, bracts which subtend lateral branches, bracts subtending triads, and floral bracteoles. The prophyll and peduncular bracts are tubular and completely closed around all branches until about three months before the flowers reach anthesis. Bracts subtending lateral branches and those that subtend triads enlarge by small amounts of apical, adaxial, and marginal growth to cover subtended apices during early ontogeny, but are small to absent at maturity. Flower clusters are triads of two lateral staminate and a central pistillate flower. Organogenesis indicates that the triad is a sympodial unit. Flowers develop successively, each floral apex bearing a bracteole that subtends the next flower. The vasculature of the inflorescence may be divided into two systems. Bundles of the main axis extend acropetally into the vertically oriented branches as they are initiated and form a central cylinder of larger bundles in each branch. Flower clusters are supplied by a peripheral system of smaller bundles that develop later in relation to the developing floral organs. Bundles of the peripheral system branch frequently, but branching levels are irregular. The irregular branching of peripheral bundles appears related to the phyllotaxy of the flower clusters and the random right or left position of the first flower of the triad. The level of branching of a bundle may depend on the position of a floral primordium with respect to an existing procambial strand. Three (-4) bundles supply each staminate flower and six (-10) the pistillate flower. The histologically specialized inflorescence has stomata and contains abundant starch. Tannins and raphides, spherical silica bodies, and various forms of sclerenchyma appear in sequence and apparently provide support and protection during the long exposure of the branches.     

Manihot allemii sp. nov. (Euphorbiaceae s.s.) with entire and unlobed leaves from northern Brazil,with notes about foliar anatomy

Manihot allemii M. J. Silva is described and illustrated as a new species, and its morphological affinities and conservation status is discussed. It is most similar to M. salicifolia Pohl in having a subshrubby and erect habit and in the general aspect of its unlobed leaves, but differs from it in having leaves that are conspicuously petiolate, an inflorescence that is a congested spike‐like thyrse, entire and diminute bracts and bracteoles subtending flowers of both sexes, pistillate calyx that is deeply lobed with oblong lobes, and staminate flowers with 8 or 10 stamens. Both species belong to a group of 14 species recognized by their possession of entire and unlobed leaves, which are the subject of taxonomic studies by the second author. Some notes on the leaf anatomy of species of Manihot that have entire and unlobed leaves are also presented.     

Amorphophallus titanum Becc.: a Historical Review and Some Recent Observations

Amorphophallus titanum Becc., discovered in 1878 by OdoardoBeccari in Sumatra has flowered only a few times in botanicalgardens. Its corms may weigh as much as 50 kg, have a diameterof 50–55 cm, a circumference of nearly 2 m and be 40cmhigh. The inflorescences, which produce a fetid smell, may last3–4 days and can reach a height of 2 m. The spadix isyellow-red in colour and the spathe greenish purple. Amorphophallus titanum, Araceae, inflorescence, spadix, spathe, corm, pistillate flowers, staminate flowers     

小叶桦花序生长物候及其生态适应意义

小叶桦(Betula microphylla)是一种典型的荒漠和山地乔木植物,在中国仅分布于新疆。为了明确小叶桦花序生长物候规律及发育特征,该研究对小叶桦进行了花序物候观测,分析其生长规律及果实结籽情况。结果显示:小叶桦雄花序为越年生殖器官,物候周期为345d,其中营养生长期154d、休眠期158d、开花生长期33d;雌花序与果序为当年生殖器官,物候期为105d,其中雌花序生长期24d、果序生长期90d。虽然雄花序比雌花序的生长周期明显较长,但开花授粉均在4月中下旬,雄花序散粉期和雌花序可授粉期之间具有较高的同步性和协调性,表现出集中开花授粉模式,同时这种开花模式在自然条件下,果序的结籽数和结籽率分别为220和76.7%,种子库中具有活力的种子约每平米4万粒,表明小叶桦在荒漠极端环境中能顺利完成有性生殖过程。     

Genus Colocasiomyia (Drosophilidae: Diptera) in Sabah,Bornean Malaysia: High species diversity and use of host aroid inflorescences

A total of 21 Colocasiomyia species, including 17 undescribed species, are reported from Sabah (Mt. Kinabalu and neighboring areas), Malaysia, based on samples collected from inflorescences of 14 or 15 Araceae species. This number of species is the largest as a local fauna of this genus in the world. The high species diversity is attributed to 12 undescribed species belonging to the Colocasiomyia baechlii species group. A particular breeding habit of Colocasiomyia is sharing of the same inflorescence by a pair of species, with partial niche separation between them: one species uses exclusively the pistillate (lower female‐flower) section of the spadix for oviposition and larval development, whereas the other mostly uses the staminate (upper male‐flower) section. However, the baechlii group species show quite different patterns of host plant use: many (up to eight) species cohabit on the same inflorescence. It is unlikely that they separate their breeding niches micro‐allopatrically within an inflorescence. Instead, species composition and their proportions of individual numbers vary among different localities, seasons and host plants, with partial overlap among them. Such partial separations in local distribution, phenology and host selection would in combination contribute to their coexistence and promote the species diversity of this group.     

THE ANATOMY OF THE PISTILLATE INFLORESCENCE AND FLOWER OF CASUARINA VERTICILLATA LAMARCK (CASUARINACEAE)

The pistillate inflorescence of Casuarina verticillata is described as consisting of a primary axis bearing whorls of bracts with a cymule in the axil of each bract of the more central whorls. Each cymule consists of an atepallate, two-carpellate, syncarpous floret and two, lateral, once-lobed bracteoles. A “peripheral intercalary” meristem, in which divisions are primarily periclinal, forms a meshwork beneath the bracts from early development and moves the connate bracts centrifugally around the cymules and extends and binds the bracts, and to some extent the bracteoles, of the fertile part of the inflorescence together. Each bract receives a single trace; each cymule receives two traces. Each bundle extension of a cymule trace supplies: 1) a branch which joins its counterpart to become the anterior common carpellary bundle; 2) a second branch which joins its counterpart to become the posterior common carpellary bundle; and 3) a central branch which supplies a lateral bracteole. Within each floret, each common carpellary bundle provides a dorsal carpellary bundle, two ventral carpellary bundles (fertile anterior carpel) or one common ventral bundle (sterile posterior carpel). The ventral bundle-supplies join and form a single placental bundle which lies in the gynoecial septum, and which, in turn, supplies the two ovules in the anterior carpel. Whether the inflorescence is a simple racemose or a condensed cymose type cannot be determined from this species alone. The function of the sclerenchymatous, enclosing bracteoles and connate bracts is discussed.     

FLORAL DEVELOPMENT IN MYRISTICA (MYRISTICACEAE)

Myristica fragrans and M. malabarica are dioecious. Both staminate and pistillate plants produce axillary flowering structures. Each pistillate flower is solitary, borne terminally on a short, second-order shoot that bears a pair of ephemeral bracts. Each staminate inflorescence similarly produces a terminal flower and, usually, a third-order, racemose axis in the axil of each pair of bracts. Each flower on these indeterminate axes is in the axil of a bract. On the abaxial side immediately below the perianth, each flower has a bracteole, which is produced by the floral apex. Three tepal primordia are initiated on the margins of the floral apex in an acyclic pattern. Subsequent intercalary growth produces a perianth tube. Alternate with the tepals, three anther primordia arise on the margins of a broadened floral apex in an acyclic or helical pattern. Usually two more anther primordia arise adjacent to each of the first three primordia, producing a total of nine primordia. At this stage the floral apex begins to lose its meristematic appearance, but the residuum persists. Intercalary growth below the floral apex produces a columnar receptacle. The anther primordia remain adnate to the receptacle and grow longitudinally as the receptacle elongates. Each primordium develops into an anther with two pairs of septate, elongate microsporangia. In pistillate flowers, a carpel primordium encircles the floral apex eventually producing an ascidiate carpel with a cleft on the oblique apex and upper adaxial wall. The floral ontogeny supports the morphological interpretation of myristicaceous flowers as trimerous with either four-sporangiate anthers or monocarpellate pistils.     

Manihot gratiosa and M. lourdesii spp. nov. (Manihoteae,Euphorbiaceae) from the Brazilian Cerrado

During a botanic expedition in 2013 to study the taxonomy of the genus Manihot in the Cerrado biome, numerous specimens were collected in the Chapada dos Veadeiros region, in central Brazil. After careful analyses, two new species of this genus were discovered. Manihot gratiosa and M. lourdesii are herein described and illustrated. Both species can be distinguished from morphologically similar species by a combination of characters such as shape and overlapping of leaf lobes, indumentum, type and aspect of inflorescence, integrity of pistillate sepals, as well as shape, integrity, and size of bracts of both male and female flowers.     

THE POLLINATION BIOLOGY OF TUCKAHOE,PELTANDRA VIRGINICA (ARACEAE)

This study describes the specialized brood-site-based pollination system of Peltandra virginica Kunth (Araceae) with the chloropid fly Elachiptera formosa Loew and provides experimental evidence that gender-related changes in floral odor composition synchronize pollinator behavior with the blooming sequence. P. virginica is protogynous and does not self-pollinate because of a strong temporal separation in sexual function, and it is dependent upon insects for pollination because the spathe completely surrounds the spadix during the pistillate stage. Field observations conducted in central New Jersey and southeastern Pennsylvania showed that E. formosa is closely associated with P. virginica inflorescences. Within the floral chamber, E. formosa adults feed on pollen, mate, and find oviposition sites while the larvae complete their development. Although drosophilid and syrphid flies were collected and reared from inflorescences of both sexual stages, only E. formosa emerged from pistillate-stage inflorescences and adult E. formosa rapidly transferred fluorescent dye particles between inflorescences of both sexual stages in laboratory enclosures. These findings indicate that this fly species is the primary pollinator at our study locations. Field censuses demonstrated that although E. formosa visited P. virginica inflorescences of both sexual stages with equal frequency, the female flies preferentially oviposited within pistillate-stage inflorescences. Analysis of floral volatiles with gas chromatography-mass spectrometry showed that only the spathes emit the floral fragrance and that the composition of the floral volatiles changed during the transition from pistillate to staminate stage. A particularly noticeable change occurred in the emission ratio of the two primary floral odor components, 4,5,7-trimethyl-6,8-dioxabicyclo[3.2.1.]octane and an unidentified chemical analog with molecular weight of 142. The relationship between floral volatile composition and fly oviposition behavior was evaluated using sham inflorescences placed in the P. virginica study population. The sham inflorescences were constructed by covering spadices dissected from mature inflorescence buds with spathes excised from different-age inflorescences. After a 2-hr-long exposure period, sham inflorescences fitted with pistillate-stage spathes contained more E. formosa eggs than the sham inflorescences with staminate-stage spathes. However, the highest number of ovipositions occurred in sham inflorescences fitted with spathes excised from mature inflorescence buds. The fragrance emitted by these spathes was composed almost entirely of the two principal odor components. The decline in ovipositions observed in both real and sham inflorescences corresponded to an increase in the emission ratio of 4,5,7-trimethyl-6,8-dioxabicyclo[3.2.1.]octane to the molecular weight 142 analog. This suggests that gravid flies searching for oviposition sites used the ratio of the two primary floral volatile components as an inflorescence gender or age recognition cue.     

Heat Production in the Voodoo Lily (Sauromatum guttatum) as Monitored by Infrared Thermography

The pattern of surface temperatures of the inflorescence of Sauromatum guttatum was investigated by using an infrared camera. The male flowers are weakly thermogenic on the first day of inflorescence opening (D-day) as well as on the next day (D + 1), reaching 0.5 to 1°C above ambient temperature. The appendix (the upper sterile part of the inflorescence) is highly thermogenic on D-day, reaching 32°C, and is faintly thermogenic on D + 1, reaching 1°C above ambient temperature. The lower part of the spadix, close to the female flowers, is also thermogenic on D-day and D + 1, reaching a temperature similar to that of the appendix only on D + 1. Salicylic acid does not induce heat production in the lower part of the spadix, as it does in the appendix. Respiration of tissue slices obtained from the appendix shows that the capacity for cyanide-insensitive respiration is present in young and mature appendices. This alternative respiratory pathway is not, however, utilized in young appendix tissue, but is engaged during the maturation of that tissue.     

Pollination in Geonoma macrostachys and Three Congeners,G. acaulis,G. gracilis,and G. interrupta

A continuous 15 month study of the floral ecology of four syntopic understorey palm species of Genoma was conducted in Amazonian Peru lowland rainforest. The spicate inflorescences of G. macrostachys, G. acaulis and G. gracilis are strictly protandrous and the plants are functionally dioecious. Data suggest that in G. macrostachys and G. acaulis pollination is based on a mimicry system, the pistillate flowers mimicking the staminate ones in colour, shape and scent. Pollen-collecting meliponine bees (Hymenoptera, Apidae, Meliponinae) and pollen-feeding syrphid flies (Diptera, Syrphidae) which visit inflorescences during both sexual stages are the pollinators of G. macrostachys. Geonoma acaulis is pollinated by small pollen-feeding weevils (Coleoptera, Curculionidae, Derelomini) that visit male and female spikes. Additionally, in G. macrostachys another pollinator type, viz. euglossine bees (Hymenoptera, Apidae, Euglossinae), which are attracted and rewarded by both types of flowers may account for long-distance pollination. The palm G. gracilis shows a very distinct pollination system. Although opportunistic insect visitors are attracted to the inflorescences of this species it seems to be mainly anemophilous because pollen becomes powdery during an thesis. The branched inflorescences of G. interrupta are also protandrous, but unlike the other species of Geonoma observed, staminate and pistillate anthesis of individual flowers are, for the most, overlapping. A broad spectrum of visitors is attracted (bees, wasps, flies, and beetles), which all may act as pollinators. Outcrossing is especially encouraged during the purely female phase at the end of the flowering cycle when there are no more staminate flowers in the inflorescence. Effects on the reproductive biology and population structure of different pollination systems and breeding system are discussed.     

A NewBRACTEA(BRA) Gene Controlling the Formation of an Indeterminate Bractless Inflorescence in Arabidopsis thaliana

The morphological and genetic studies of the bramutant of Arabidopsis thaliana(L.) Heynh. from the collection of the Department of Genetics and Breeding, Moscow State University, showed that the BRAgene controls the major stages of inflorescence development: it suppresses the development of leaves subtending flowers (bracts) and inhibits the formation of the terminal flower. Inactivation of the BRAgene leads to the transition from the indeterminate bractless inflorescence characteristic of the family Cruciferaceae to the determinate bracteose inflorescence. It is suggested that the BRAgene is a regulator gene probably involved in the conversion of the bracteose determinate inflorescence to the indeterminate ebracteate inflorescence during the origin of ancestral crucifers.     

The developmental floral morphology of Montrichardia arborescens (Araceae) revisited

The spadix of Montrichardia arborescens contains unisexual flowers without a perianth. The pistillate flowers are located in the basal portion of the inflorescence, and the staminate flowers are located in the apical portion. There is a narrow :zone between male flowers and female flowers consisting of atypical flowers. The portion of the atypical flowers facing the staminate zone exhibits staminate characters (stamens), and the portion facing the pistillate zone has an aborted gynoecium. The floral development of Montrichurdia is compared with that of Philodendron and a new interpretation of the morphology of atypical flowers of Montrichardia is proposed. Ontogenetic evidence supports relationships with Philodendron rather than Cercestis. 2001 The Linnean Society of London     

A new species of <Emphasis Type="Italic">Symplocos</Emphasis> (Symplocaceae) from the Itatiaia Plateau of Brazil

Symplocos minima, a new species of Symplocos section Hopea from the Itatiaia Plateau in the Atlantic Rain Forest biome of southeastern Brazil, is described and illustrated. This species is distinguished by its densely compact shrubby habit, ascending leaves, fasciculate inflorescences with several persistent bracts, corolla with five to six erect lobes, pistillate flowers with the disc not thickened along the margin, fruiting calyx lobes obscuring the disc, and seeds sub-orbicular in cross section. The new species is morphologically related to S. itatiaiae and S. pentandra, but can be differenciated from them mainly due to the tree habit and fruiting calyx lobes not obscuring the disc in S. itatiaiae and the pistillate flowers with a disc that is thickened along the margin in S. pentandra.