The floral organogenesis of <Emphasis Type="Italic">Koelreuteria bipinnata</Emphasis> and its variety <Emphasis Type="Italic">K. bipinnata</Emphasis> var. <Emphasis Type="Italic">integrifolia</Emphasis> (Sapindaceae): evidence of floral constraints on the evolution of monosymmetry

The floral organogenesis and anatomy of Koelreuteria bipinnata and its variety K. bipinnata var. integrifolia (Sapindaceae) has been investigated to clarify the identity of the two taxa in relation to other species of Koelreuteria, and to understand the shift to monosymmetry in the genus. Although the floral development is highly similar, we found a number of striking differences. Flowers arise in thyrses, with lateral branches forming cincinni of 5–9 flowers. Sepals initiate in a spiral sequence. Five petals arise unidirectionally alternating to the sepals. The last formed petal and one stamen between sepals 3 and 5 are strongly delayed, appearing as a common primordium, while this petal is completely suppressed in var. integrifoliola. Eight stamens initiate sequentially, differ in size and partly precede the development of petals. The gynoecium develops as a triangular primordium on which three carpellary lobes become demarcated simultaneously. Placentation is axile. Septal slits occurring within the style are interpreted as a deep-reaching non-nectariferous extension of the stigma. The massive, oblique disk with crenate apex develops in an extrastaminal position, but is interrupted on the radius of the lost petal. Floral developmental evidence supports variety K. bipinnata var. integrifolia rather than being synonym of K. bipinnata. Floral development is compared with K. paniculata and is discussed in the context of floral evolution of Sapindaceae. Our study demonstrates the importance of developmental shifts on floral evolution. The triangular gynoecium has a strong spatial impact in obliquely reorganizing the symmetry of the flower. It is demonstrated that spatial constraints of calyx and ovary are responsible for the reduction in one of the petals, two stamens and a shift in symmetry of the flower.     

Isolation and characterization of the C-class MADS-box gene from the distylous pseudo-cereal <Emphasis Type="Italic">Fagopyrum esculentum</Emphasis>

In the model species Arabidopsis thaliana, the floral homeotic C-class gene AGAMOUS (AG) specifies reproductive organ (stamen and carpels) identity and floral meristem determinacy. Gene function analyses in other core eudicots species reveal functional conservation, subfunctionalization and function switch of the C-lineage in this clade. To identify the possible roles of AG-like genes in regulating floral development in distylous species with dimorphic flowers (pin and thrum) and the C function evolution, we isolated and identified an AG ortholog from Fagopyrum esculentum (buckwheat, Family Polygonaceae), an early diverging species of core eudicots preceding the rosids-asterids split. Protein sequence alignment and phylogenetic analysis grouped FaesAG into the euAG lineage. Expression analysis suggested that FaesAG expressed exclusively in developing stamens and gynoecium of pin and thrum flowers. Moreover, FaesAG expression reached a high level in both pin and thrum flowers at the time when the stamens were undergoing rapidly increased in size and microspore mother cells were in meiosis. FaesAG was able to substitute for the endogenous AG gene in specifying stamen and carpel identity and in an Arabidopsis ag-1 mutant. Ectopic expression of FaesAG led to very early flowering, and produced a misshapen inflorescence and abnormal flowers in which sepals had converted into carpels and petals were converted to stamens. Our results confirmed establishment of the complete C-function of the AG orthologous gene preceding the rosids-asterids split, despite the distinct floral traits present in early- and late-diverging lineages of core eudicot angiosperms.     

A comparison of early floral ontogeny in wild-type and floral homeotic mutant phenotypes of <Emphasis Type="Italic">Primula</Emphasis>

Primula flowers are heteromorphic with individual plants producing either pin-form or thrum-form flowers. We have used scanning electron microscopy to observe early development of wild-type flowers of primrose (Primula vulgaris), cowslip (P. veris), and the polyanthus hybrid (P. x tommasinii x P. vulgaris). Floral ontogeny in Primula is different from that observed in the well-studied models Antirrhinum majus and Arabidopsis thaliana and our studies reveal morphological landmark events that define the sequence of early floral development in Primula into specific stages. Pin-form and thrum-form flowers are indistinguishable during early development with differentiation of the two floral morphs occurring beyond the differentiation of floral organs. Early ontogeny of flowers with homeotic mutant phenotypes was also studied to determine the timing of developmental reprogramming in these mutants. Phenotypes studied included Hose in Hose and Jack in the Green that develop petaloid sepals and leafy sepals, respectively, and Jackanapes plants that carry both these dominant mutations. Recessive double and semi- double flowers that produce additional whorls of petals and/or stamens in place of carpels were also studied. We describe a previously undocumented recessive Primula mutant phenotype, sepaloid, that produces sepals in place of petals and stamens, and a new non-homeotic, dominant mutant phenotype Split Perianth, in which sepals and petals fail to fuse to form the typical calyx and corolla structures. The molecular basis of these mutant phenotypes in relation to the ABC model is discussed.     

Inflated trichornes in flowers of Bauhinia (Leguminosae: Caesalpinioideae)

TUCKER, S. C., RUGENSTEIN, S. R. & DERSTINE, K. S., 1984. Inflated trichomes in flowers of Bauhinia (Leguminosae: Caesalpinioideae). An unusual kind of bifid multicellular inflated trichome is reported to occur on floral organs of II species of Bauhinia (Leguminosae-Caesalpinioideae), They occur on sepals, petals, stamens, carpels, receptacle, leaves, and stems, but not on all organs in each species. Their development in B. malabarica is described.     

The floral development and floral anatomy ofChrysosplenium alternifolium, an unusal member of the Saxifragaceae

The floral development and anatomy ofChrysosplenium alternifolium were studied with the scanning electron microscope and light microscope to understand the initiation sequence of the floral organs and the morphology of the flower, and to find suitable floral characters to interpret the systematic position of the genus within the Saxifragaceae. The tetramerous flower shows a highly variable initiation sequence. The median sepals and first stamens arise in a paired sequence resembling a dimerous arrangement, but the first sepal and stamen arise on the side opposite to the bract. Transversal sepals and stamens emerge sequentially, as one side often precedes the other; sepals and stamens occasionally arise on common primordia. Initiation of the gynoecium is more constant with two median carpel primordia arising on a sunken floral apex. Several flowers were found to be pentamerous with a 2/5 initiation sequence. Flowers were invariably found to be apetalous without traces of petals in primordial stages; this condition is interpreted as an apomorphy. It is postulated that the development of a broad gynoecial nectary is responsible for the occurrence of an obdiplostemonous androecium. The gynoecium shows a number of anatomical particularities not observed in other Saxifragaceae. The presence and distribution of colleters is discussed.     

蓝堇草属(毛茛科)花形态发生的扫描电子显微镜观察

花的发生和发育过程研究可以发现早期进化的轨迹,为系统发育的研究提供重要线索。蓝堇草属(Leptopyrum)为毛茛科唐松草亚科一单种属,仅包含蓝堇草一种,其花的发生和发育过程仍为空白。为了深入理解唐松草亚科乃至毛茛科花发育多样性和演化规律,该文运用扫描电子显微镜(SEM)观察了蓝堇草各轮花器官的形态发生和发育过程。结果表明:该属植物所有的萼片、花瓣、雄蕊和雌蕊均为螺旋状发生,花器官排列式样也为螺旋状; 5枚萼片原基宽阔,5枚花瓣原基圆球形、位于萼片原基的间隔,且在后期表现为延迟发育现象,雄蕊原基较小、为圆球形; 花瓣原基和雄蕊原基连续发生,无明显的时空间隔,但与萼片原基有时空间隔; 心皮原基为马蹄形对折,柱头组织由单细胞乳突组成; 胚珠倒生、具单珠被。该属花器官螺旋状排列、胚珠具单珠被在唐松草亚科中是独有的性状,花发育形态学证据支持了该属的特殊性。     

Floral development of petaloid Alismatales as an insight into the origin of the trimerous Bauplan in monocot flowers

Monocots are remarkably homogeneous in sharing a common trimerous pentacyclic floral Bauplan. A major factor affecting monocot evolution is the unique origin of the clade from basal angiosperms. The origin of the floral Bauplan of monocots remains controversial, as no immediate sister groups with similar structure can be identified among basal angiosperms, and there are several possibilities for an ancestral floral structure, including more complex flowers with higher stamen and carpel numbers, or strongly reduced flowers. Additionally, a stable Bauplan is only established beyond the divergence of Alismatales. Here, we observed the floral development of five members of the three ‘petaloid’ Alismatales families Butomaceae, Hydrocharitaceae, and Alismataceae. Outer stamen pairs can be recognized in mature flowers of Alismataceae and Butomaceae. Paired stamens always arise independently, and are either shifted opposite the sepals or close to the petals. The position of stamen pairs is related to the early development of the petals. In Butomaceae, the perianth is not differentiated and the development of the inner tepals is not delayed; the larger inner tepals (petals) only permit the initiation of stamens in antesepalous pairs. Alismataceae has delayed petals and the stamens are shifted close to the petals, leading to an association of stamen pairs with petals in so-called stamen–petal complexes. In the studied Hydrocharitaceae species, which have the monocot floral Bauplan, paired stamens are replaced by larger single stamens and the petals are not delayed. These results indicate that the origin of the floral Bauplan, at least in petaloid Alismatales, is closely linked to the position of stamen pairs and the rate of petal development. Although the petaloid Alismatales are not immediately at the base of monocot divergence, the floral evolution inferred from the results should be a key to elucidate the origin of the floral Bauplan of monocots.     

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.     

FLORAL DEVELOPMENT IN MANGROVE RHIZOPHORACEAE

The flowers of mangrove Rhizophoraceae (tribe Rhizophoreae) are adapted to three different pollination mechanisms. Floral development of representative species of all four genera suggests that the ancestral flower of the tribe was unspecialized, with successively initiated whorls of separate sepals, petals, antisepalous stamens, and antipetalous stamens; at its inception, the gynoecium had a united, half-inferior ovary and separate stigmatic lobes. This developmental pattern is found in Rhizophora mangle (wind-pollinated) and Ceriops decandra (insect-pollinated). In Kandelia, all floral organs distal to the sepals are initiated simultaneously, and there has apparently been an evolutionary amplification in the number of stamens to about six times the number of petals. Explosive pollen release evolved independently in C. tagal and in Bruguiera. In the former, all stamens belong to one whorl and arise simultaneously upon a very weakly differentiated androecial ring primordium. In Bruguiera, the androecial ring is pronounced, and two whorls of stamens arise upon it; the primordia of the antisepalous whorl arise first but are closer to the center of the apex than the antipetalous stamen primordia. The antisepalous stamens bend toward and are enclosed by the petals early in development. In all genera, the inferior ovary develops by zonal growth of receptacular tissue; additional intercalary growth above the placenta occurs in Bruguiera. In general, floral specialization is accompanied by an increase in the width of the floral apex compared to the size of the primordia, increasing fusion of the stylar primordia, and decreasing prominence of the superior portion of the ovary. Apparent specializations of petal appendages for water storage, including the presence of sub-terminal hydathodes (previously unreported in any angiosperm), were found in two species in which flowers remain open during the day but were absent from two species normally pollinated at night or at dawn. Distinctive tribal characteristics that may aid in phylogenetic analysis include the mode of development of the inferior ovary; the aristate, bifid, usually fringed petals that individually enclose one or more stamens; the intrastaminal floral disc; and the initially subepidermal laticiferous cell layer in the sepals and ovary.     

Floral anatomy of the Styracaceae, including observations on intra-ovarian trichomes

DICKISON, W. C., 1993. Floral anatomy of the Styracaceae, including observations on intra-ovarian trichomes All eleven genera of the Styracaceae were examined with respect to floral morphology and anatomy. Floral structure and vascularization are described in detail. Flowers of the family exhibit different degrees and patterns of specialization. All Styracaceae show some degree of basal non-divergence of perianth members, forming a hypanthium that is adnate to the ovary wall to a lesser or greater extent. The extent of reduction and amplification in the number of sepals, petals, stamens, and carpels varies widely among genera, and generally the non-divergence, decrease, or increase in parts is not equally pronounced in the different whorls of the same flower. Genera cannot be readily aligned in an intergrading sequence of morphological advancement. Stamen form and anatomy is variable. A fibrous endothecium ranges from well-developed to weakly formed or absent. A nearly uniform feature of the styracaceous gynoecium is the presence of incompletely septate ovaries. The major points of variation in the floral vascular system relate to the number, mode of origin, and degree of independence of sepallary traces; degree of independence of the androecial vasculature; the level at which the common petal and petalad-stamen or sepal and sepalad-stamen bundles separate to their component parts; organization of the ventral ovarian supply; and the occurrence of ventral bundles in the style. Floral vascularization provides evidence that the family was derived from an obdiplostemonous ancestor. A unitegmic ovule is predominant in the family and starch is present in the megagametophyte of some taxa. An unusual feature of the flowers of the Styracaceae is the occurrence of stellate and lignified intra-ovarian trichomes. Numerous similarities in floral morphology and anatomy between Styracaceae and Ericales are pointed out.     

FLORAL MORPHOLOGY,ORGANOGENESIS AND INTERPRETATION OF THE INFERIOR OVARY IN DOWNINGIA BACIGALUPII

The inflorescence of Downingia bacigalupii (Campanulaceae; Lobelioideae) is an indeterminate spike. Axillary flowers have a long, linear, inferior ovary with parietal placentation, a pentamerous synsepalous calyx, zygomorphic sympetalous corolla, syngenesious stamens, and a bicarpellate, syncarpous gynoecium. On the basis of floral vascular anatomy the inferior ovary is interpreted as appendicular, representing adnation of outer floral whorls to the gynoecium. Floral ontogeny shows that sepals are initiated in an adaxial to abaxial sequence rather than the 2/5 phyllotaxis reported for other members of Lobelioideae. Growth of the common bases of sepal lobes forms a floral cup and initiation of the following floral whorls occurs along the inner margins of the cup. Continued basal growth of the cup-shaped bud results in the formation of the elongated inferior ovary. Earlier evidence for the interpretation of a cup-shaped receptacle during development of epigynous flowers is reexamined and it is concluded that the concave floral bud of D. bacigalupii can also be interpreted as common growth of connate floral whorls, supporting interpretations based on vascular anatomy. Comparison of floral development between Downingia bacigalupii and Pereskia aculeata (Cactaceae) reveals ontogenetic differences between flowers with appendicular and receptacular cups.     

Floral Development and Anatomy ofMoringa oleifera(Moringaceae): What is the Evidence for a Capparalean or Sapindalean Affinity?

Floral development and anatomy ofMoringahave been investigatedin the context of the disputed view of a capparalean affinity.Flowers arise in terminal or axillary panicles. Sepals arisesequentially and petals simultaneously. Antepetalous stamensarise simultaneously and precede the antesepalous staminodes,which emerge sequentially. Within their respective whorls, thepetals and stamens become twisted along different orientations.The gynoecium develops as a ring primordium on which three carpellarylobes become demarcated simultaneously. A saccate ovary bearsnumerous ovules on a parietal placentation and is topped bya hollow style. The interpretation of laminal placentation isdenied. Monothecal anthers are formed by the failure of onehalf to initiate. The flowers present a peculiar form of zygomorphyrunning transversally from the petal between sepals 3 and 5to sepal 4. The shape and position of petals and stamens isrelated to a pollen presentation mechanism with bowl-shapedanthers on different levels. The floral anatomy also reflectsthe zygomorphy of the flower. AlthoughMoringashares importantmorphological features with certain members of the Sapindalesand Capparales, differences in ontogeny make a close relationshipwith either Capparales or certain Sapindales appear uncertain.Copyright1998 Annals of Botany Company Moringa,Moringaceae, Capparales, Sapindales, floral ontogeny, floral anatomy.     

MORPHOLOGICAL STUDIES IN ZYGOPHYLLACEAE. I. THE FLORAL DEVELOPMENT AND VASCULAR ANATOMY OF NITRARIA RETUSA

The floral development and vascular anatomy of Nitraria retusa were investigated in order to understand its characteristic androecium of 15 stamens and to clarify the systematic position of the genus relative to Zygophyllaceae. Sepals arise in a helical sequence and are relatively small at maturity. Petals are initiated almost simultaneously or in a rapid helical sequence. Five stamen primordia arise opposite the sepals. Next, two other antesepalous primordia are incepted centrifugally to the first primordia on the remaining receptacular surface. The outer stamens tend to be squeezed between the petals and upper stamens and appear to make up an antepetalous whorl of stamens. Three carpels arise from a low ringwall and grow into a hairy trilocular pistil. In each locule a single pendulous ovule is present. Disclike nectarial tissue is initiated in pits between the stamens and petals. Long trichomes develop on its surface. It is concluded that the androecium is linked with a haplostemonous condition because the stamens of each triplet develop on strictly localized sectors. The distinction between stamens arising on complex primordia and the inception of three independent units is explained by the “principle of variable proportions.” The vasculature also tends to confirm that the outer stamen pairs belong to antesepalous triplets.     

Comparative floral development in Lardizabalaceae (Ranunculales)

Lardizabalaceae, one of seven families of Ranunculales, represent a monophyletic group. The family has functionally unisexual flowers with the organs in trimerous whorls, petaloid sepals and sometimes nectariferous petals. Among Ranunculales, Lardizabalaceae share several floral characters and climbing habit with Menispermaceae, but molecular analyses indicate that Circaeasteraceae and Lardizabalaceae form a strongly supported clade. Morphological and ontogenetic studies of flowers have proved to be a good complement to molecular data in clarifying relationships. Floral organogenesis has been studied in very few species of the family. This study investigates the comparative floral development of three species from three genera (Decaisnea, Akebia and Holboellia) of Lardizabalaceae using scanning electron microscopy. Flowers have a whorled phyllotaxis. Within each whorl, the organs are initiated either simultaneously or in a rapid spiral sequence. In Akebia, six sepals are initiated, but one to three sepals of the second whorl do not further develop. The presence of three sepals in Akebia is thus a developmentally secondary simplification. The petals (if present) are retarded in early developmental stages; stamens and petals are different in shape from the beginning of development. The retarded petals may not be derived from staminodes in Lardizabalaceae. © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 166 , 171–184.     

Functional Conservation of an <Emphasis Type="Italic">AGAMOUS</Emphasis> Orthologous Gene Controlling Reproductive Organ Development in the Gymnosperm Species <Emphasis Type="Italic">Taxus chinensis</Emphasis> var. <Emphasis Type="Italic">mairei</Emphasis>

Arabidopsis AGAMOUS (AG) has roles in specifying reproductive organ (stamens and carpels) identity, floral meristem determinacy, and repression of A-function. To investigate possible roles of AG orthologous genes in gymnosperm species and evolution of C function, we isolated and identified AG orthologous gene TcAG from Taxus chinensis var. mairei (family Taxaceae, order Coniferales), a member of the last divergant lineage from higher Conifer that sisters to Gnetales. Sequence alignment and phylogenetic analysis grouped TcAG into the gymnosperm AG lineage. TcAG was expressed in both developing male and female cones, but there was no expression in juvenile leaves. Ectopic expression of TcAG in an Arabidopsis ag mutant produced flowers with the third whorl petaloid stamen and fourth whorl normal carpel, but failed to convert first whorl sepals into carpeloid organs and second whorl petals into stamenoid organs. A 35S::TcAG transgenic Arabidopsis ag mutant had very early flowering, and produced a misshapen inflorescence with a shortened floral axis. Our results suggest that establishment of the complete C-function occurred gradually during AG lineage evolution even in gymnosperms.     

FLORAL ANATOMY OF KRAMERIA LANCEOLATA

The anatomy of each of the series of floral organs of Krameria lanceolata was examined. The sepals are characterized by three main veins each, an undifferentiated mesophyll, and stomata on the upper epidermis. The fleshy petals are distinguished by their numerous veins as well as by palisade-like epidermal cells on the outer surface. The three partially united petals have each a single vein and long, narrow epidermal cells similar to those on other floral organs. The stamens are united at their bases and bear tetra-sporangiate, conical anthers. The gynoecium includes a sterile and a fertile carpel. In the receptacle the veins to the sepals and petals are separated by a wide gap; those to the petals and stamens, by a narrow gap. Anatomical characteristics of the flower dissociate Krameriaceae from the legumes with which they have frequently been thought to be allied.     

Floral ontogeny in legume genera Petalostylis, Labichea, and Dialium (Caesalpinioideae: Cassieae), a series in floral reduction

Floral ontogeny of taxa of two subtribes (Labicheinae, Dialiinae) of caesalpinioid tribe Cassieae, characterized by reduced number of floral organs, was compared. All three taxa studied are distichous; Petalostylis labicheoides flowers are solitary in leaf axils, Labichea lanceolata has few-flowered racemes, and Dialium guineense has numerous-flowered cymes. The first sepal primordium in each is initiated abaxially and nonmedianly. Order of organogenesis in Petalostylis is: five sepals bidirectionally, five petals and carpel simultaneously, then five stamens bidirectionally, starting abaxially. The order in Labichea is: five sepals helically (one lagging in time), five petals unidirectionally starting abaxially, the carpel and petals concurrently, then two stamens successively, starting laterally. Order in Dialium is: five sepals bidirectionally, the single petal adaxially, and lastly the carpel and two stamens concurrently. Specializations include (1) reduction of the five sepals to four by fusion in Petalostylis and Labichea; (2) reduction of petal number to one in Dialium; (3) reduction of stamen number to two in Labichea and Dialium, and reduction of functional stamens to three in Petalostylis; and (4) an elaborate, late-developing style in Petalostylis. Floral asymmetry, another specialization, characterizes Labichea, expressed by dissimilar stamens, while the other genera have zygomorphic flowers. Floral ontogenies are compared with other taxa of Cassieae.     

Homeotic, Meristic and Cytological Floral Mutants of Thryptomene calycina (family Myrtaceae)

Twenty plants with various phenotypic abnormalities to the flowerswere selected from very large populations of Thryptomene calycinain the Grampian and Black Ranges. Most of these had impairedreproductive function. Normal flowers were epigynous with fivesepals, five petals, five anthers, a single style and two anatropousovules. The mutants were two partially male sterile, tetraploidplants with large flowers, one of which occasionally producedadditional flowers from the leaf axils with peduncles as wellas pedicels; one plant which produced a proportion of hexapetaloidflowers with six stamens; three gross mutants with fleshy, bracteoidpointed petals and sepals, no stamens, vestigial styles andstigmas, exposed ovules and no inferior ovary; one plant withfleshly, bracteoid pointed sepals, vestigial style and stigmabut with exposed ovular structures replaced by four to fivesterile ovules generally inside an abnormal ovary; two plantswith reduced ovary diameter and sterile ovules, shortened style,five reduced sepals and petals and five to eight anthers; threeanthocyanin-free plants; three plants with pink sepals; twoplants with half-sized flowers which produced a proportion offasciated stems; one plant which occasionally produced flowerswithout pedicels which virtually resulted in organs which wereleaf-flower composites; two plants which produced sepals andpetals which contained chlorophyll and prematurely senesced,and had partial substitution of petals by anthers.Copyright1993, 1999 Academic Press Thryptomene calycina, Myrtaceae, Victorian lace flower, floral mutations, mutants, homeotic, meristic, tetraploid, fasciation, male sterility, cut flowers     

DIOECY IN BAUHINIA RESULTING FROM ORGAN SUPPRESSION

Bauhinia malabarica and B. divaricata have both been reported to have dimorphic flowers; floral development of these species has been investigated and compared using SEM. B. malabarica is subdioecious, with three types of flowers: perfect, staminate, and carpellate. Individual trees usually have only one type of flower. Perfect and carpellate flowers have similar initiation of floral organs; each has five sepals, five petals, two whorls of five stamen primordia and a carpel primordium. The carpels of carpellate flowers do not differ from those of perfect flowers throughout development. Both have a gynophore or stipe and a cuplike hypanthium. Stamen development diverges markedly after mid-development: the perfect flowers have ten stamens in two whorls, the outer with longer filaments than the inner. All stamens have anthers, which are covered abaxially with abundant inflated trichomes. Carpellate flowers have a circle of short cylindrical staminodia, each bearing a few hairs, about the base of the carpel on the rim of the hypanthium. Heteromorphy in B. malabarica is effected by suppression of stamen development, even though the usual number of stamen primordia is initiated. Suppression of stamens occurs at midstage in development in carpellate flowers of B. malabarica, and is complete. In B. divaricata nine stamen primordia are released from suppression in late stage, undergo intercalary growth and form a staminodial tube around the carpel stipe. The dimorphy in B. divaricata is expressed late in bud enlargement as divergent rates of growth in the carpel in the two morphs.     

Floral ontogeny of Sinojackia xylocarpa (Styracaceae), with special reference to the development of the androecium

Using scanning electron microscopy, we studied the floral ontogeny of Sinojackia xylocarpa. There are 6–7 (–8) sepals. Sepal initiation is staggered; adaxial sepals arise later than abaxial and lateral ones. There are (5–) 6–7 (–8) petals, initiated simultaneously. Petals alternate with the sepals, and occasionally there are two petals instead of one between two sepals. The (10–) 12–14 (–16) stamens are initiated centripetally in two sets (whorls). These floral organ numbers deviate from those of the otherwise mostly pentamerous family Styracaceae. The ovary consists of three (rarely four) locules. In each of the locules, two rows of ovules are differentiated basipetally. Placentation is axile with (5–) 6 (–7) ovules in each locule. Ovules are unitegmic and are ascending with the micropyle directed downwards. Intra‐ovarian trichomes are present as in other representatives of Styracaceae and seem to be an apomorphic character of the family as they are absent in the closely related Symplocaceae and Diapensiaceae. Various levels of organ union occur in anthetic S. xylocarpa. The calyx is synsepalous and the ovary syncarpous. Possibly, the basal connation of petals and stamens is postgenital (and not congenital), but this needs further study. The outward curvature of the young anthers of the inner stamen whorl superficially simulates an obdiplostemonous androecium. However, the sequence of stamen initiation shows a diplostemonous pattern.