Additional Stamens Research Articles

Variations in the morphology of Hibiscus rosa-sinensis crested peach flowers in nature

Hibiscus rosa-sinensis has a wide variety of flowers. The variations even can be observed in one hybrid only. The hybrid is known as crested flower (double type I), one of four categories of H. rosa-sinensis flower shapes in nature. This study purpose was to categorize the variation in crested flowers based on morphological observation using 200 samples. The observations showed the form of crested peach could be divided into three groups: crested peach that resembles a single flower (crested single-like), which resembles a double flower (crested double-like), and a transitional between single-like and double-like flower (crested intermediate-like). Groupings are based on the length of the staminal column which measured at the closest distance between the corolla position and the additional stamen or petal. The length of the staminal column on a crested single-like is more than 4 cm (a > 4 cm), whereas the crested double-like is less than 1 cm (a < 1 cm), and the crested intermediate-like is 1–4 cm (1 ≤ a ≤ 4). Groupings are also reinforced by comparing the average number of staminodium petaloid, stamen-petal intermediate, and stamen. The crested single-like has a 1:2:2 ratio, the crested intermediate-like has a 2:1:1 ratio, while the crested double-liked has a 5:1:1 ratio. Of the total 200 crested samples used in the study, 89.5 % of them had intermediate-like forms, while 6.5 % were double-like, and 4 % single-like. It can be concluded that the real crested of H. rosa-sinensis is an intermediate-like form.

Floral Development of the Endangered Genus Medusagyne (Medusagynaceae-Malpighiales): Spatial Constraints of Stamen and Carpel Increase

Premise of research. The floral development of the monotypic genus Medusagyne is investigated to understand the mechanisms of stamen and carpel increases in light of its proposed affinity with Ochnaceae.Methodology. Flowers at different stages of development were investigated with SEM.Pivotal results. Flowering shrubs are andromonoecious. Flowers arise in cymes at the end of shoots. Initiation of staminate and bisexual flowers is similar for sepals and petals, which arise in a spiral sequence. Stamen initiation is centrifugal on a broad circular primordium but becomes more or less irregular by the insertion of additional stamens between the older stamens. In staminate flowers the globular floral apex is completely covered with stamens, with no trace of carpels. Bisexual flowers emerge on the lower branches and develop a broad stamen ring surrounding a whorl of 13–16 carpels. Carpels initiate in a ring around the massive floral apex and develop mainly in a vertical direction. Carpels are progressively swamped in the stamen mass by a simultaneous expansion of filaments, and styles become irregularly compressed in older buds. The adaxial expansion of carpel tissue eventually overtops the floral apex as a roof. Measurements of buds show that carpel and stamen numbers are linked with the proportional size of the floral apex relative to the whole size of the flower bud.Conclusions. The unusual floral development of Medusagyne supports the separation of the genus in its own family, although several characters link it with the Ochnaceae clade. Stamen initiation and expansion shows much similarity with Eucryphia in Cunoniaceae. It is suggested that the larger number of carpels is intimately linked with the higher stamen numbers. Constraints of space and a vertical growth pattern of the floral apex cause the peculiar morphology of the gynoecium and the variably delayed stamen initiation.

SUPERMAN prevents class B gene expression and promotes stem cell termination in the fourth whorl of Arabidopsis thaliana flowers

The molecular and genetic networks underlying the determination of floral organ identity are well studied, but much less is known about how the flower is partitioned into four developmentally distinct whorls. The SUPERMAN gene is required for proper specification of the boundary between stamens in whorl 3 and carpels in whorl 4, as superman mutants exhibit supernumerary stamens but usually lack carpels. However, it has remained unclear whether extra stamens in superman mutants originate from an organ identity change in whorl 4 or the overproliferation of whorl 3. Using live confocal imaging, we show that the extra stamens in superman mutants arise from cells in whorl 4, which change their fate from female to male, while floral stem cells proliferate longer, allowing for the production of additional stamens.

Establishment of a natural floral variant of Shepherd’s purse in the wild: analysis of life-history traits in ‘Capsella apetala’ (Brassicaceae)

Background and aims – Molecular studies in model systems have pushed forward our understanding of floral developmental genetics, but the evolutionary significance of such modifications in natural populations is rather unexplored. To improve our knowledge in this field, the sympatric occurrence of two floral variants of Capsella bursa-pastoris (L.) Medik. in the wild appears to be an ideal model system. In our study, wild- type plants showing small white petals and the homeotic variant ' Stamenoid petals ' ( Spe also known as Capsella apetala Opiz), in which petals are replaced by additional stamens, will be compared to evaluate potential ecological differentiation.Material and methods – Progenies from field collections were used in common garden experiments to detect possible differences in several life-history traits involved in the reproductive fitness of both variants. A second experiment was intended to shed light on the relative hybridization rate among floral variants, using the enzyme aspartate aminotransferase (AAT) as a molecular marker.Results – Comparing fitness revealed that the two variants invested differently into their progeny. Wild-type plants showed more fruits per plant, whereas Spe showed higher investment in seeds per fruit. However, the overall reproductive output (seeds/plant) is almost equal. Wild-type donates more pollen for cross- fertilization, because floral visits are more common in this variant. Furthermore, both variants are separated in the onset of flowering, with Spe having a significant later onset of flowering.Conclusion – We conclude that the maintenance of the floral variant within a broad wild-type population is driven by complementary mechanisms including high rates of self-fertilization and ecological differentiation. Taking into account that fitness is not reduced in Spe, the floral variant might in fact have the potential to be a promising model to study speciation at an early stage.

Mapping a floral trait in Shepherds purse – ‘Stamenoid petals’ in natural populations of Capsella bursa-pastoris (L.) Medik

Striking feature of angiosperm diversity is the huge number of variations in corolla morphology including complex innovations like variations in symmetry or the identity and number of floral organs. Throughout the Brassicaceae, the disymmetric flower structure is highly conserved. Still, quite a few floral alterations occur like a variant of Common Shepherds purse (Capsella bursa-pastoris), in which all petals have been transformed into additional stamens. This “decandric” phenotype has been reported for the first time about 200 years ago. In some of the original locations the variant has been recovered recently. The long term persistence indicates the establishment of an evolutionary novelty in wild populations in sympatric occurrence with wild-type plants. Due to this fact the floral variant has become an interesting model for evolutionary studies. The phenotype is heritable and just a single locus, termed “Stamenoid petals” (Spe), is assumed to be involved in the molecular origin. To unravel the chromosomal localization of this locus, a linkage map analysis was carried out using molecular markers (AFLPs, RAPDs). The final map includes 15 linkage groups and the floral trait was integrated on linkage group 12 (CBP12) including six AFLP markers. Out of these, five markers were successfully sequenced and revealed sequence identities with chromosome IV of the A. thaliana genome. Interestingly, AGAMOUS is located on this chromosome, the only class C floral organ identity gene in the A. thaliana genome, which is compatible with the assumption that Spe is an allele of AGAMOUS rather than a regulator of that gene.

Characterization of the Ra1 maize gene involved in inflorescence architecture

The genetic and molecular control of inflorescence and flower development has been extensively studied in model dicotyledonous plants such as Arabidopsis but even now little is known about monocotyledonous species. In maize several mutants have been isolated that perturbed normal inflorescence development. In particular, the Ramosa1 (Ra1) gene, coding for a zinc finger transcription factor, plays a role in inflorescence structure by determining the number of branches. Although the mechanism by which Ra1 acts is unclear, inflorescence meristems in these regions assume a branch meristem identity rather than becoming spikelet pairs. In this work we characterize a new mutation of Ra1 gene that originated spontaneously from a B73 inbred line. This loss-of-function mutation is caused by the deletion of the lysine residue at position 53 in the RA1 putative zinc-finger domain. This is the first evidence for a single amino acid deletion in the zinc finger domain that knocks out the function of the RA1 protein. This result strongly suggests that the RA1 protein functions by acting as a DNA-binding protein, probably involved in transcriptional regulation. Furthermore, Ra1 overexpression in the Arabidopsis ortholog superman (sup) mutant, whose flowers are characterized by the presence of additional stamens, was not able to restore the correct stamen number, indicating that SUP and Ra1 genes do not share an identical function.

Patterns of anomalous floral development in the Asian Passiflora (subgenus Decaloba: supersection Disemma)

Approximately 22 species of Passiflora are native to the Old World. All of these species are placed in subgenus Decaloba, supersection Disemma. Within Disemma, three species vary in stamen and carpel number (≤ eight stamens and five carpels). The mode of development was determined for two of the anomalous species, P. moluccana var. glaberrima and P. siamica. Ontogenetic patterns were compared to normal development in P. perakensis and P. holosericea. Passiflora siamica develops additional stamens through dédoublement of a single widened stamen primordium, while P. moluccana var. glaberrima exhibits congenital dédoublement where stamens emerge already doubled. Phylogenetic analysis using ITS and the trnL-F intron and spacer resolve the anomalous species as monophyletic and sister to P. perakensis. This signifies a single loss of genetic regulation in stamen and carpel number within Disemma. Floral whorls were examined across the Passifloraceae, Malesherbiaceae, Turneraceae, and Flacourtiaceae s.l.. Similar doubling in these families suggests that this Eurosid lineage may have a genetic propensity for variability in floral whorl number.

Floral ontogeny, pattern formation, and evolution in Hibbertia and Adrastaea (Dilleniaceae)

Floral development was compared with scanning electron microscopy in 12 Australian species of Hibbertia representing most of its morphological variation, and in the related Adrastaea (Dilleniaceae). Calyx and corolla arise in quincuncial helices in radially symmetrical species, while the petals initiate unidirectionally from one side in zygomorphic species. Stamen number (3-200+) proliferates by centrifugal addition of individual primordia or by innovations of common primordia and ring meristems. Common primordia arise in single-stamen positions alternately with petals, and each produces one to several stamens centrifugally that remain attached to a shared base and form a stamen fascicle. A ring meristem in Adrastaea initiates a whorl of five stamens, alternate with the first stamens but outside their whorl. In radially symmetrical species of Hibbertia, a first ring of stamens is supplemented centrifugally by additional stamens on a meristem ring. The first stamens in zygomorphic species of Hibbertia initiate as a terminal ridge on the floral apex, with subsequent stamens added centrifugally on one side and two carpels initiated on the opposite side. The carpels arise as a simultaneous ring in radially symmetrical flowers, or as a simultaneous pair in zygomorphic species. Staminodial presence is viewed as of minor significance. Four pollinator syndromes are proposed for Hibbertia, related to differing floral architecture.

The additional stamens of flo10-1 mutants of Arabidopsis thaliana are compromised in production and viability of pollen

flo10-1 (superman-2) is a floral mutant in Arabidopsis thaliana that normally produces female sterile flowers. This phenotypic aberration results from a combination of increased stamen number and reduced or abnormal carpels that are nonfunctional. The flowers of flo10-1 contain two lateral and four median stamens, as seen in wild-type plants; however, they also contain several additional stamens. All stamen types have been examined with respect to frequency and location within the flower. The amount of pollen produced from each of the three types of stamens of flo10-1 and the viability of this pollen were also examined and compared with wild-type (cv. Columbia) to determine the consequences of this mutation on male fertility. Both the lateral and median stamens of flo10-1 and wild-type plants produced similar amounts of pollen per stamen and demonstrated no significant difference in viability. Per stamen, the additionals of flo10-1 produced significantly less pollen than those of the laterals and medians. Furthermore, the pollen produced from these additional stamens was significantly less viable. Although less abundant and viable, pollen produced by additional stamens can effectively fertilize ovules, producing normal, healthy plants.Key words: pollen (viability, production), stamen, male fertility, flower development, Arabidopsis thaliana, flo10-1.

The additional stamens of &lt;i&gt;flo10-1&lt;/i&gt; mutants of &lt;i&gt;Arabidopsis thaliana&lt;/i&gt; are compromised in production and viability of pollen

The additional stamens of &lt;i&gt;flo10-1&lt;/i&gt; mutants of &lt;i&gt;Arabidopsis thaliana&lt;/i&gt; are compromised in production and viability of pollen

FON1, an Arabidopsis gene that terminates floral meristem activity and controls flower organ number.

A novel gene that regulates floral meristem activity and controls floral organ number was identified in Arabidopsis and is designated FON1 (for FLORAL ORGAN NUMBER1). The fon1 mutants exhibit normal vegetative development and produce normal inflorescence meristems and immature flowers before stage 6. fon1 flowers become visibly different from wild-type flowers at stage 6, when the third-whorl stamen primordia have formed. The fon1 floral meristem functions longer than does that of the wild type: after the outer three-whorl organ primordia have initiated, the remaining central floral meristem continues to produce additional stamen primordia interior to the third whorl. Prolonged fon1 floral meristem activity also results in an increased number of carpels. The clavata (clv) mutations are known to affect floral meristem activity. We have analyzed the clv1 fon1, clv2 fon1, and clv3 fon1 double mutants. These double mutants all have similar phenotypes, with more stamens and carpels than either fon1 or clv single mutants. This indicates that FON1 and CLV genes function in different pathways to control the number of third- and fourth-whorl floral organs. In addition, to test for possible interactions between FON1 and other floral regulatory genes, we have constructed and analyzed the relevant double mutants. Our results suggest that FON1 does not interact with TERMINAL FLOWER1, APETALA1, APETALA2, or UNUSUAL FLORAL ORGAN. In contrast, normal LEAFY function is required for the expression of fon1 phenotypes. In addition, FON1 and AGAMOUS both seem to affect the domain of APETALA3 function, which also affects the formation of stamen-carpel chimera due to fon1 mutations. Finally, genetic analysis suggests that FON1 interacts with SUPERMAN, which also regulates floral meristem activity.

ORGAN INITIATION AND DEVELOPMENT OF INFLORESCENCES AND FLOWERS OF ACACIA BAILEYANA

Inflorescence and floral ontogeny are described in the mimosoid Acacia baileyana F. Muell., using scanning electron microscopy and light microscopy. The panicle includes first‐order and second‐order inflorescences. The first‐order inflorescence meristem produces first‐order bracts in acropetal order; these bracts each subtend a second‐order inflorescence meristem, commonly called a head. Each second‐order inflorescence meristem initiates an acropetally sequential series of second‐order bracts. After all bracts are formed, their subtended floral meristems are initiated synchronously. The sepals and petals of the radially symmetrical flowers are arranged in alternating pentamerous whorls. There are 30–40 stamens and a unicarpellate gynoecium. In most flowers, the sepals are initiated helically, with the first‐formed sepal varying in position. Petal primordia are initiated simultaneously, alternate to the sepals. Three to five individual stamen primordia are initiated in each of five altemipetalous sectorial clusters. Additional stamen primordia are initiated between adjacent clusters, followed by other stamens initiated basipetally as well as centripetally. The apical configuration shifts from a tunica‐corpus cellular arrangement before organogenesis to a mantle‐core arrangement at sepal initiation. All floral organs are initiated by periclinal divisions of the subsurface mantle cells. The receptacle expands radially by numerous anticlinal divisions in the mantle at the summit, concurrently with proliferation of stamen primordia. The carpel primordium develops in terminal position by conversion of the floral apex.

INITIATION OF STAMENS, CARPELS, AND RECEPTACLE IN THE CACTACEAE

Five taxa representing the three tribes of the Cactaceae have similar patterns of stamen and carpel initiation but display differences in early receptacle development. The first ring of stamens and the carpels arise simultaneously from subsurface layers. The bases of carpels are congenitally connate. Additional stamens are initiated centrifugally. The shape of the floral meristem within the ring created by the first stamens varies. In Pereskia corrugata it remains broadly convex; in Opuntia engelmannii it forms a depression with a small convex central region; in Epiphyllum strictum it forms a broad shallow depression; in Echinocereus reichenbachii var. albispinus it develops a deep depression; and in Mammillaria compressa it develops a depression prior to stamen and carpel initiation. Changes in receptacle shape result from cessation of apical growth and activation of an intercalary ring meristem. These two processes occur earlier in ontogeny in the more advanced of these five taxa.

Floral organogenesis of Limnocharis flava

Besides a trimerous calyx and corolla, the mature flower exhibits a polyandric androecium and an apocarpous gynoecium consisting of a whorl of carpels. Yet the primary pattern of the flower is completely trimerous and tetracyclic. After the inception of three sepals and three petals, three antesepalous primary androecial primordia are initiated each of which forms three stamens (i.e. secondary androecial primordia). Opposite these three groups of three stamen primordia, three groups of three carpels are initiated, possibly on three extremely inconspicuous primary gynoecial primordia. Additional carpel primordia are formed in varying numbers between the original three groups. Even before carpel inception, the three primary androecial primordia merge laterally thus forming an androecial ring. Additional stamen primordia arise on this ring first between the three groups of three stamen primordia and then in centrifugal direction as the androecial ring broadens basally. Eventually four whorls of stamens and two to three whorls of staminodia are formed secondarily on the androecial ring which arose from the primary primordia. Morphogenesis and construction of the flowers of Limnocharis flava differs in two major respects from those of all other taxa of the Alismatales studied thus far: (1) there are no stamen pairs primarily associated with the petals, and (2) the first-formed carpel primordia do not alternate with the stamen primordia of the preceding whorl, thus violating Hofmeister's rule of alternation.

Development of Dionaea Muscipula. I. Flower and Seed

1. The terminal bud of the short perennial rhizone of Dionaea forms a scape which bears a cymose inflorescence of from two to fourteen actinomorphic, pentacyclic flowers. 2. The arrangement of the vascular bundles of the stamens in the receptacle of young flowers is considered as further proof of Payer's statement that the stamens develop respectively in alternipetalous and epipetalous whorls. Moreover, when more than ten stamens (five in each cycle) develop, the vascular bundle of one or more of the five epipetalous stamens is divided and supplies the additional stamen or stamens. This is not in accord with the view held by Payer that dedoublement may occur in either whorl. 3. The four microsporangia of each stamen develop in the usual manner. 4. In the early prophase of the microsporocytes, of which forty-eight to sixty develop in each sporangium, prochromosomes are discernible. 5. Each of the four nuclei resulting from the second meiotic division of the microsporocyte has fifteen haploid chromosomes....