NORMAL FLORAL ONTOGENY AND COOL TEMPERATURE-INDUCED ABERRANT FLORAL DEVELOPMENT IN GLYCINE MAX (FABACEAE)

Floral onset in soybean (Glycine max cv. Ransom) is characterized by precocious initiation of axillary meristems in the axils of the most recently initiated leaf primordium. During floral transition, leaf morphology changes from trifoliolate leaf with stipules, to a three-lobed bract, to an unlobed bract. Soybean flowers initiated at 26/22 C day/night temperatures are normal, papilionaceous, and pentamerous. Sepal, petal, and stamen whorls are initiated unidirectionally from the abaxial to adaxial side of the floral apex. The median sepal is located abaxially and the median petal adaxially on the meristem. The organogeny of ‘Ransom’ flowers was found to be: sepals, petals, outer stamens plus carpel, inner stamens; or, sepals, petals, carpel, outer stamens, inner stamens. The outer stamen whorl and the carpel show possible overlap in time of initiation. Equalization of organ size occurs only within the stamen whorls. The sepals retain distinction in size, and the petals exhibit an inverse size to age relationship. The keel petals postgenitally fuse along part of their abaxial margins; their bases, however, remain free. Soybean flowers initiated at cool day/night temperatures of 18/14 C exhibited abnormalities and intermediate organs in all whorls. The gynoecium consisted of one to ten carpels (usually three or four), and carpel connation varied. Fusion of keel petals was often lacking, and stamen filaments fused erratically. Multiple carpellate flowers developed into multiple pods that were separate or variously connate. Intermediate type organs had characteristics only of organs in adjacent whorls. These aberrant flowers demonstrate that the floral meristem of soybean is not fixed or limited in its developmental capabilities and that it has the potential to produce alternate morphological patterns.     

Flower development in Abrus precatorius (Leguminosae: Papilionoideae: Abreae) and a review of androecial characters in Papilionoideae

The jequirity bean (Abrus precatorius) is well known because of its shiny black and red coloured seeds and because of the poison (abrin) it contains. The genus Abrus is placed in a monogeneric tribe Abreae which is placed in a relatively isolated systematic position at the base of Millettieae. To contribute to a better understanding of this taxon, a detailed ontogenetic and morphologic analysis of its flowers is presented. Floral primordia are subtended by an abaxial bract and preceded by two lateral bracteoles which are formed in short succession. Sepal formation is unidirectional starting abaxially. All petals are formed simultaneously. The carpel is formed concomitantly with the outer (antesepalous) stamen whorl, which arises unidirectionally, starting in an abaxial position. In the inner, antepetalous stamen whorl two abaxial stamens are formed first, followed by two lateral stamen primordia. The adaxial, antepetalous position remains organ free (i.e. this stamen is lost). Later in development the nine stamen filaments fuse to form an adaxially open sheath. The filament bases of the two adaxial outer-whorl stamens grow inwards, possibly to provide stability and to compensate for the lost stamen. In the mature flower a basal outgrowth can be found in the position of the lost stamen. However this is more likely to be an outgrowth of the filament sheath rather than a remnant of the lost stamen. These ontogenetic patterns match in parts those found in other Millettieae (unidirectional formation of sepals and stamens, simultaneous petal formation). In contrast, the complete loss of a stamen is rather unusual and supports the isolated position of Abreae and probably justifies (among other characters) its tribal status. A review of androecial characters shows that androecial merosity is on the one hand extremely variable among Leguminosae, varying from a single stamen per flower to more than 500. On the other hand it is noteworthy that the number of stamens becomes stabilised in more derived Papilionoideae such as the large non-protein-amino-acid-accumulating clade (NPAAA clade). This indicates that the androecium has played an important role in the success of a major part of Leguminosae.     

Comparative floral development in the tribe Mentheae (Nepetoideae: Lamiaceae) and its bearing on the evolution of floral patterns in asterids

A comparative developmental study of flowers was carried out using epi-illumination light microscopy on four genera of Lamiaceae (Nepeta, Rosmarinus, Salvia, andZiziphora), representing all three subtribes of Mentheae. All species examined share unidirectional (adaxial to abaxial) sepal initiation, except Rosmarinus, which has the reverse unidirectional sequence, starting abaxially. Initiated but suppressed bracteoles were detected only in Rosmarinus. In Rosmarinus, Salvia, and Ziziphora, initiation of petals and stamens proceeds unidirectionally from the abaxial side. Floral initiation of Nepeta has bidirectional inception of petals and unidirectional stamen initiation from the adaxial side. Temporal overlap in organ initiation between petal and stamen whorls occurs in all taxa, though this feature is more prominent in Rosmarinus. Significant structural and developmental features that distinguish the four genera include: (1) polysymmetric calyx tube, highly tomentose corolla and deeply four-partitioned ovary in Nepeta; (2) monosymmetric two-lipped calyx and shallowly four-partitioned ovary in Ziziphora; and (3) suppression of adaxial stamens in Salvia and Rosmarinus. Adaxial stamens are absent from Rosmarinus, but reduced stamens remain as staminodia in Salvia. In a phylogenetic context, the late monosymmetry of Nepeta and very early monosymmetry of Rosmarinus could both be regarded as derived conditions compared with the early monosymmetry ofSalvia and Ziziphora.     

FLORAL DEVELOPMENT IN GYMNOTHECA CHINENSIS (SAURURACEAE)

The development of the inflorescence and flowers are described for Gymnotheca chinensis Decaisne (Saururaceae), which is native only to southeast China. The inflorescence is a short terminal spike of about 50–70 flowers, each subtended by a small bract. There are no showy involucral bracts. The bracts are initiated before the flowers, in acropetal order. Flowers tend to be initiated in whorls of three which alternate with the previous whorl members. No perianth is present. The flower contains six stamens, and four carpels fused in an inferior ovary containing 40–60 ovules on four parietal placentae. Floral symmetry is dorsiventral from inception and throughout organ initiation. Floral organs are initiated in the following order: 1) median adaxial stamen, 2) a pair of lateral common primordia which bifurcate radially to produce two stamen primordia each, 3) median abaxial stamen, 4) a pair of lateral carpel primordia, 5) median adaxial carpel, 6) median abaxial carpel. This order of initiation differs from that of any other Saururaceae previously investigated. The inferior ovary results from intercalary growth below the level of stamen attachment; the style elongates by intercalary growth, and the four stigmas remain free. The floral structure of Gymnotheca is relatively advanced compared to Saururus, but its assemblage of specializations differs from that of either Anemopsis or Houttuynia, the other derived genera in the Saururaceae.     

Floral development and phyllotactic variation in Ceratophyllum demersum (Ceratophyllaceae)

The floral development of staminate and pistillate flowers of Ceratophyllum demersum was observed, with particular focus on the phyllotactic variation in staminate flowers, using scanning electronic microscopy (SEM). We discerned patterns of development of some important new morphological features, e.g., the difference and discontinuity between the organ initiation in stamens and that in bracts (or tepals) and the initial presence of a mucilaginous appendage on each pistil. Female flowers are considered to be very specialized through reduction. In male flowers stamen initiation changes between early and late floral development. The four or five stamens in the outermost whorl initiate first on the abaxial and lateral sides of the floral apex and only later on the adaxial side (unidirectional). Later the inner stamens initiate spirally, and this is the main pattern in the stamen initiation. Members of each whorl differ among themselves in time of initiation and in ultimate size. The phyllotactic variation in staminate flowers of Ceratophyllum, suggested by previous studies, is derived from the variation in stamen number and the difference of stamen initiation between the early and later stages. The development in Ceratophyllum has some similarities to those of ANITA plants except for Nymphaeales.     

FLORAL DEVELOPMENT IN CAESALPINIA (LEGUMINOSAE)

Utilizing scanning electron microscopy, we studied the early floral ontogeny of three species of Caesalpinia (Leguminosae: Caesalpinioideae): C. cassioides, C. pulcherrima, and C. vesicaria. Interspecific differences among the three are minor at early and middle stages of floral development. Members of the calyx, corolla, first stamen whorl, and second stamen whorl appear in acropetal order, except that the carpel is present before appearance of the last three inner stamens. Sepals are formed in generally unidirectional succession, beginning with one on the abaxial side next to the subtending bracts, followed by the two lateral sepals and adaxial sepal, then lastly the other adaxial sepal. In one flower of C. vesicaria, sepals were helically initiated. In the calyx, the first-initiated sepal maintains a size advantage over the other four sepals and eventually becomes cucullate, enveloping the remaining parts of the flower. The cucullate abaxial sepal is found in the majority of species of the genus Caesalpinia. Petals, outer stamens, and inner stamens are formed unidirectionally in each whorl from the abaxial to the adaxial sides of the flower. Abaxial stamens are present before the last petals are visible as mounds on the adaxial side, so that the floral apex is engaged in initiation of different categories of floral organs at the same time.     

Flower or spikelet? Understanding the morphology and development of reproductive structures in Exocarya (Cyperaceae, Mapanioideae, Chrysitricheae)

Fundamental questions of floral morphology remain unresolved in the grasslike monocots in order Poales, including what constitutes a flower and what constitutes a spikelet. The mapaniid sedges have particularly complex spikeletlike structures, variously interpreted as clusters of flowers or spikelets. Recent phylogenetic studies of Cyperaceae have identified the mapaniid clade as sister to the rest of the family, but the homology of mapaniid reproductive units (RUs) and spikeletlike units (SLUs) to other sedge flowers and spikelets is unclear. We examined reproductive development in the mapaniid Exocarya sclerioides. Inflorescence branches terminated in a SLU with bracts and 1-4 RUs. RUs had four small leaflike structures (LLSs): two lateral LLSs, each associated with a stamen, an abaxial LLS associated with a stamen, and an adaxial LLS. The gynoecium terminated the RU. All RUs were axillary to bracts, and unexpanded bracts and RUs were produced beyond expanded RUs, so SLUs were racemose. RUs developed from a single primordium that initiated two lateral LLSs, then two lateral stamens, then the gynoecium. Initiation of the abaxial LLS and stamen and the adaxial LLS followed. We hypothesize that the RU is a sympodial branch that terminates in a hermaphroditic flower with two stamens and a gynoecium; the two lateral LLSs are halves of a deeply divided prophyll.     

大戟科麻疯树属三种植物花器官发生

利用扫描电子显微镜观察了大戟科Euphorbiaceae麻疯树属Jatropha麻疯树J. curcas L.、佛肚树J. podagrica Hook.和棉叶麻疯树J. gossypifolia L.花器官发生。结果表明: 麻疯树、佛肚树和棉叶麻疯树花萼原基均为2/5型螺旋发生。在同一个种不同的花蕾中, 花萼的发生有两种顺序: 逆时针方向和顺时针方向。远轴面非正中位的1枚先发生。5枚花瓣原基几乎同时发生。雄花中雄蕊两轮, 外轮对瓣, 内轮对萼。研究的3种麻疯树属植物雄蕊发生方式有两种类型: 麻疯树亚属麻疯树的5枚外轮雄蕊先同时发生, 5枚内轮雄蕊后同时发生, 佛肚树亚属佛肚树和棉叶麻疯树雄蕊8-9枚, 排成两轮, 内外轮雄蕊同时发生。雌花的3枚心皮原基为同时发生。麻疯树属单性花, 雌花的子房膨大而雄蕊退化, 雄花的雄蕊正常发育, 子房缺失。根据雄蕊发生方式, 支持将麻疯树属分为麻疯树亚属subgen. Jatropha和佛肚树亚属subgen. Curcas。     

Floral ontogeny in<Emphasis Type="Italic"> Lespedeza thunbergii</Emphasis> (Leguminosae: Papilionoideae: Desmodieae): variations from the unidirectional mode of organ formation

Floral ontogeny of Lespedeza thunbergii was studied with the use of scanning electron microscopy (SEM). The ontogeny varies in all whorls from the undirectional mode, which has been long held to be the rule in Leguminosae. In the sepal whorl, the lateral and the adaxial sepals are formed simultaneously, which is interpreted as a tendency towards whorled organ formation. Whorled organ formation is shown in the petal whorl. The antesepalous stamen whorl varies least from the unidirectional mode. Here, the adaxial stamens are formed successively. This is seen as a remnant of an original helical organ formation in Papilionoideae. Within the antepetalous stamen whorl, the two abaxial stamens and the adaxial stamen are formed first, followed by the two lateral stamens. This is a rarely found phenomenon, which is hard to interpret at the present state of knowledge. Concerning the mature flower, it is shown that nectar stomata are found in a distinct area on the adaxial side of the flower. The presented new characteristics should be an initial step toward further work on taxa of the tribe Desmodieae. These studies will broaden the data set and enable a detailed phylogenetic analysis.     

Floral ontogeny of <Emphasis Type="Italic">Schisandra chinensis</Emphasis> (Schisandraceae): implications for androecial evolution within <Emphasis Type="Italic">Schisandra</Emphasis> and <Emphasis Type="Italic">Kadsura</Emphasis>

The organogenesis of staminate and carpellate flowers of Schisandra chinensis (Schisandraceae) was investigated with scanning electron microscopy, with observations on the development of tepals reported for the first time. The results showed that there is no interval between the initiation of the last tepal and that of the first stamen or carpel, and that the shapes of tepal, stamen, and carpel primordia are similar. The tepals and stamens of staminate flowers are initiated acropetally in a continuous spiral Fibonacci phyllotaxis, with no carpel structures observed; the filaments are not connate. The organogenesis of the carpellate flowers is similar to that of the staminate flowers, but with no evidence of stamen development. The carpels are ascidiate without postgenital fusion. Three androecial characters of Schisandra and Kadsura are discussed in a phylogenetic context. The subglobose or obovoid androecium of Schisandra propinqua and Schisandra plena may be homologous with that in sections Kadsura and Sarcocarpon. The plesiomorphic form of the androecium within the two genera is likely to be elongate with more than ten free stamens.     

Elucidating the unusual floral features of Swartzia dipetala (Fabaceae)

In this study, we evaluated the floral ontogeny of Swartzia dipetala, which has peculiar floral features compared with other legumes, such as an entire calyx in the floral bud, a corolla with one or two petals, a dimorphic and polyandrous androecium and a bicarpellate gynoecium. We provide new information on the function of pollen in both stamen morphs and whether both carpels of a flower are able to form fruit. Floral buds, flowers and fruits were processed for observation under light, scanning and transmission electron microscopy and for quantitative analyses. The entire calyx results from the initiation, elongation and fusion of three sepal primordia. A unique petal primordium (or rarely two) is produced on the adaxial side of a ring meristem, which is formed after the initiation of the calyx. The polyandrous and dimorphic androecium also originates from the activity of the ring meristem. It produces three larger stamen primordia on the abaxial side and numerous smaller stamen primordia on the adaxial side. These two types of stamens bear morphologically similar ripening pollen grains. However, prior to the dehiscence of thecae and presentation of pollen in the anther, only the pollen grains of the larger stamens contain amyloplasts. Two carpel primordia are initiated as distinct protuberances, alternating with the larger stamens, in a slightly inner position in the floral meristem, constituting the bicarpellate gynoecium. Both carpels are able to form fruit, although only one fruit is generally produced in a flower. The increase in gynoecium merism probably results in an increase in the surface deposition of pollen grains and consequently in the chance of pollination. This is the first study to thoroughly investigate organogenesis and the ability of the carpel to form fruit in a bicarpellate flower from a member of Fabaceae, in addition to the pollen ultrastructure in the heteromorphic stamens associated with the ‘division of labour’ sensu Darwin. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 173 , 303–320.     

THE DEVELOPMENTAL BASIS FOR SEXUAL EXPRESSION IN CERATONIA SILIQUA (LEGUMINOSAE: CAESALPINIOIDEAE: CASSIEAE)

The flowers of Ceratonia siliqua, an anomalous caesalpinioid legume in the tribe Cassieae, are unusual in being unisexual and in lacking petals. Inflorescence development, organogeny, and flower development are described for this species. All flowers are originally bisexual, but one sex is suppressed during late development of functionally male and female flowers. Ceratonia siliqua is highly plastic in sexuality of individuals, inflorescence branching pattern, racemose or cymose inflorescences, bracteole presence, terminal flower presence, organ number per whorl, missing floral organs, pollen grain form, and carpel cleft orientation. Order of initiation is: five sepals in helical order, then five stamens in helical order together with the carpel. Each stamen is initiated as two alternisepalous primordia that fuse to become a continuous antesepalous ridge; in some flowers, the last one or two stamens of the five may form as individual antesepalous mounds. Petal rudiments are occasional in mature flowers. Position of organs is atypical: the median sepal is on the adaxial side in Ceratonia, rather than abaxial as in most other caesalpinioids. This feature in Ceratonia may be viewed as a link to subfamily Mimosoideae, in which this character state is constant.     

Intriguing thigmonastic (sensitive) stamens in the Plains Prickly Pear Opuntia polyacantha (Cactaceae)

The movement of sensitive stamens in flowers of the Plains Prickly Pear (Opuntia polyacantha) is described in detail along with the external and internal filament anatomy. The goals of this investigation were: (1) to provide a synthesis of floral phenology and determine whether this rather unique stamen movement is nastic or a tropism and (2) to conduct macro- and micro-morphological analyses of filaments to determine if there are anatomical traits associated with this movement. To better understand the internal and external structure in sensitive filaments of O. polyacantha, we performed comparative anatomical analyses in two additional species from the Opuntioideae with stamens lacking such sensitivity. The consistent unidirectional movement of stamens, independent of the area stimulated, indicates a thigmonastic response. This movement serves multiple purposes, from enhancing pollen presentation to facilitating cross-pollination, protecting pollen and preventing insects from robbing pollen. Anatomically, the sensitive and non-sensitive filaments exhibit different tissue organization. Cuticle thickness, presence of capsular structures, two layers of curved cells, and more and larger intercellular spaces are characteristic of sensitive filaments. A thin unicellular epidermal layer is characteristic in sensitive filaments versus 2–3 epidermal layers in non-sensitive filaments. Another striking feature in sensitive filaments is the presence of papillae and capsular structures. We believe that these elements are related to water mobility with subsequent contraction during the thigmonastic response. Capsular structures might have a role in fluid mobility according to the stimulus of the filaments. We hypothesize that the thigmonastic response is controlled by cells with elastic properties, as evidenced by the plasmolyzed curved and contracted cells in the filaments and the fact that the movement is activated by changes in cell turgor followed by contraction as a result of plasmolysis.     

Inflorescence and floral ontogeny in Crocus sativus L. (Iridaceae)

Inflorescence and floral ontogeny of the perennial, herbaceous crop Crocus sativus L. were studied using epi-illumination light microscopy. After production of leaves with helical arrangement a determinate inflorescence forms which becomes completely transformed into a single terminal flower. In some cases, bifurcation of the inflorescence meristem yields two or three floral meristems. The order of floral organs initiation is outer tepals – stamens – inner tepals – carpels. Stamens and outer tepals are produced from the lateral bifurcation of three common stamen-tepal primordia. Within each whorl, organs start developing unidirectionally from the adaxial side, except for the stamens which begin to grow from the abaxial side. Specialized features during organ development include interprimordial growth between tepals forming a perianth tube, fusion at the base of stamen filaments, and formation of an inferior ovary with unfused styles.     

COMPARATIVE STUDY OF THE FLORAL VASCULATURE IN SAURURACEAE

The floral vascular systems are compared among all six taxa of Saururaceae, including the two species of Gymnotheca which have not been studied previously. All are zygomorphic (dorsiventrally symmetrical), not radial as sometimes reported, in conformity with dorsiventral symmetry during organogenesis. Apocarpy in the two species of Saururus (with four carpels and six free stamens) is accompanied by a vascular system of four sympodia, each of which supplies a dorsal carpellary bundle, two ventral carpellary bundles, and one or two stamen traces. The level at which the ventral bundles diverge is the major difference in vasculature between the two species. The other four taxa are all syncarpous, and share some degree of stamen adnation and/or connation. The vascular systems also show varying degrees of fusion. The two species of Gymnotheca (with four carpels and six stamens) are very similar to each other; in both, the ventral traces of adjacent carpels fuse to form a placental bundle, which supplies the ovules and then splits into a pair of ventral strands. The flowers of Houttuynia cordata (with only three carpels and three adnate stamens) are sessile. Each flower is vascularized by three sympodia; the median adaxial sympodium is longer than the other two sympodia before it diverges to supply the adaxial organs. Three placental bundles also are formed in Houttuynia, but the three bundles differ in their origin. The median abaxial placental bundle diverges at the same level as the three sympodial bundles of the flower, while the other two lateral placental bundles diverge at a higher level from the median adaxial sympodium. Anemopsis californica, with an inferior ovary of three carpels, sunken in the inflorescence axis, and six stamens adnate to the carpels, has a vascular system very similar to that of Houttuynia cordata. The modular theory of floral evolution is criticized, on the bases of the known behavior of apical meristems and properties of vascular systems. The hypothesis is supported that saururaceous plants may represent a line of angiosperms which diverged very early.     

The discovery of polyandry in Curculigo (Hypoxidaceae): implications for androecium evolution of asparagoid monocotyledons

BACKGROUND AND AIMS: Individual flowers of the monocot Curculigo racemosa (Hypoxidaceae, Asparagales) are regularly polyandrous. To evaluate the significance of this almost unique character among Asparagales for flower evolution of asparagoid monocots, flowers of C. racemosa were studied comparatively. METHODS: Anthetic flowers as well as early floral developmental stages were studied by light and scanning electron microscopy. KEY RESULTS: Despite the polyandry, floral development is similar to that of other Asparagales with a developmental gradient from adaxial to abaxial. Stamens initiate simultaneously and the diameter of staminal primordia is about half of that in species with six anthers. The number of stamens is not fixed (12-26) and varies within the same inflorescence. Surprisingly, the gynoecium can be four- or six-locular, besides the normal trimerous state. CONCLUSIONS: The discovery of a polyandrous Curculigo reveals plasticity of stamen number at the base of Asparagales. Orchidaceae - sister to all other Asparagales - has a reduced stamen number (three, two or one), whereas in Hypoxidaceae - part of the next diverging clade - either the normal monocot stamen number (six), polyandry (this study) or the loss of three anthers (Pauridia) occurs. However, at present it is impossible to decide whether the flexibility in stamen number is autapomorphic for each group or whether it is a synapomorphy. The small size of stamen primordia of Curculigo is conspicuous. It allows more space for additional androecial primordia. Stamens are initiated as independent organs, and filaments are not in bundles, hence C. racemosa is not secondarily polyandrous as may be the case in the distantly related Gethyllis of asparagoid Amaryllidaceae. The increase in carpel number is a rare phenomenon in angiosperms. A possible explanation for the polyandry of C. racemosa is that it is a natural SUPERMAN-deficient mutant, which shows an increase of stamens, or ULTRAPETALA or CARPEL FACTORY mutants, which are polyandrous and changed in carpel number.     

太原黄耆(豆科)花器官及胚珠发育研究

太原黄耆是新近发表的物种,分布于中国陕西和山西。该实验利用扫描电子显微镜对太原黄耆的花器官发生和发育过程进行观察研究。结果显示:(1)太原黄耆的各轮花器官都是从远轴端向近轴端单向连续发生,在不同轮之间存在花器官重叠发生的现象。(2)在花的发育过程中,出现2种共同原基,即初级共同原基和次级共同原基,由初级共同原基发育成对萼雄蕊原基和次级共同原基,再由次级共同原基发育成花瓣原基和对瓣雄蕊原基。(3)雄蕊管近轴端基部开口是在进化过程中产生的特殊结构,是一种对传粉者的适应机制,从而有利于传粉活动的进行。(4)胚珠为倒生胚珠,具有2层珠被,认为倒生胚珠是内外2层珠被共同作用的结果。     

Changes in growth kinetics of stamen filaments cause inefficient pollination in massugu2, an auxin insensitive, dominant mutant of Arabidopsis thaliana

We investigated the physiological and molecular basis of lower fecundity of massugu2 ( msg2 ), which is a dominant mutant of an auxin primary response gene, IAA19 , in Arabidopsis thaliana . By measuring the length of all stamens and pistils in inflorescences and the reference growth rate of pistils, we constructed growth curves of pistils and stamens between stages 12 and 15 of flower development. Pistil growth was found to consist of a single exponential growth, while stamen growth consisted of three exponential phases. During the second exponential phase, the growth rate of stamen filaments was ∼10 times greater than the growth rates in the other two phases. Consequently, stamens whose growth was initially retarded grew longer than the pistil, putting pollen grains on the stigma. msg2-1 stamens, on the other hand, exhibited a less obvious growth increase, resulting in less frequent contact between anthers and stigma. MSG2 was expressed in the stamen filaments and its expression almost coincided with the second growth phase. Stamen filaments appeared to elongate by cell elongation rather than cell division in the epidermal cell file. Considering that MSG2 is likely to be a direct target of the auxin F-box receptors, MSG2 may be one of the master genes that control the transient growth increase of stamen filaments.     

Relationships between floral organization, architecture, and pollination mode inDillenia (Dilleniaceae)

The flowers ofDillenia are highly elaborate pollen-flowers adapted to buzzpollination byXylocopa bees. Two major forms of floral architecture (revolver flowers and roundabout flowers) are associated with two different pollination modes. In the first (e.g.,D. suffruticosa), the pollination organs are connivent to a cone; the pollinator grasps the entire cone with its legs and buzzes it; it revolves around its axis and repeats the buzzing in different positions. In the second (e.g.,D. alata, D. philippinensis), the stylar branches are spreading and the stamens are arranged in two sets of two different forms and colourations. The inner set has fewer and longer stamens that are cryptic pollination stamens; those of the outer set are shorter but optically conspicuous feeding stamens. The pollinator squeezes itself under the stylar branches and handles only the outer set by grasping part of the set at a time; it moves tangentially around the flower with several buzzing-stops; when buzzing pollen is sprayed onto its side and back from the inner stamen set. Centrifugal polyandrous androecia are a constitutive feature of flowers inDilleniaceae. InDillenia the centrifugal initiation of stamens proceeds for an unusually long time and is still not finished when the gynoecium is completely closed (in contrast toTetracera). The differentiation of heteranthery seems to be functionally correlated with the extended centrifugal inception. The latest formed stamens are small and sterile in many species. Generic features ofDillenia flowers can be understood from the roundabout architecture: big size, increased number of carpels, syncarpy forming a firm pedestal and spreading firm stylar branches with small, concave stigmas at the end, stamens with short, stout filaments and much elongated poricidal anthers, heteranthery, recurved stamens of the inner set.Dedicated to emer. Univ.-Prof. DrFriedrich Ehrendorfer on the occasion of his 70th birthday     

月季花瓣数量遗传分析

以‘窄叶藤本月季花’( Rosa chinensis ‘Zhaiye Tengben Yuejihua’)ב月月粉’( R. chinensis ‘Old Blush’)杂交群体为材料, 分析其花瓣数量的分离特点, 对单瓣花与重瓣花的花芽分化过程进行观察, 并对花瓣、雄蕊及瓣化雄蕊进行表皮细胞超微结构的观察.结果显示...