Faculty Opinions recommendation of A cucurbit androecy gene reveals how unisexual flowers develop and dioecy emerges.

2015 ◽  
Author(s):  
Alejandro Schaffer
Keyword(s):  
Unisexual Flowers

Studies in the Alismataceae. XI. Development of the inflorescence and flowers of Wiesneria triandra (Dalzell) Micheli

2000 ◽  
Vol 77 (11) ◽  
pp. 1569-1579
Author(s):  
W A Charlton
Keyword(s):  
Shoot Development ◽  
Annual Plant ◽  
Foliage Leaf ◽  
The Family ◽  
Unisexual Flowers ◽  
Male Flowers ◽  
Female Flowers

Wiesneria triandra (Dalzell) Micheli is an unusual annual plant of the Alismataceae with spike-like inflorescences bearing unisexual flowers. Shoot development follows the sympodial pattern of other Alismataceae, but the cycle is so condensed that initiation of each foliage leaf is followed by inflorescence formation. The plant develops a tufted habit by the formation of an unusual accesory bud adjacent to each inflorescence. Male flowers have three sepals, three petals, three stamens, and usually three carpellodes; female flowers have a similar perianth, three staminodes, and three or more carpels. Up to the first three carpels, floral parts are arranged in alternating trimerous whorls. Additional carpels may occur above and between those of the first whorl. The androecium is particularly unusual for the Alismataceae since it has conventional alternation of stamens with petals rather than the antipetalous pairs of stamens commonly perceived in the family, but the phylogenetic postion of Wiesneria within the family (as revealed by other studies) indicates that the apparently conventional androecium of Wiesneria represents a derived state rather than a primitive one. The unisexual flowers also represent a derived state.

Pollination ecology of Monstera obliqua (Araceae) in French Guiana

2007 ◽  
Vol 23 (5) ◽  
pp. 607-610 ◽  
Author(s):  
Mathieu Chouteau ◽  
Melanie McClure ◽  
Marc Gibernau
Keyword(s):  
French Guiana ◽  
Pollination Ecology ◽  
Lower Portion ◽  
Floral Rewards ◽  
Pollination Mechanisms ◽  
Unisexual Flowers ◽  
Male Flowers ◽  
Female Flowers

Data on pollination ecology of Araceae are still scarce and most concern species belonging to the subfamily Aroideae (García-Robledo et al. 2004, Gibernau 2003, Ivancic et al. 2004, 2005; Maia & Schlindwein 2006). In this subfamily, inflorescences consist of unisexual flowers: female flowers are located in the lower portion and the male flowers are in the upper portion of the inflorescence (Mayo et al. 1997). In the documented neotropical Aroideae, pollinators are nocturnal beetles and pollination mechanisms take place within a floral chamber during a short flowering cycle (generally 24–48 h) with floral rewards (sterile flowers rich in proteins and/or lipids) for the beetle pollinators, the secretion of resin to secure pollen on the pollinator, and the production of heat and odours (Chouteau et al. 2007, García-Robledo et al. 2004, Gibernau & Barabé 2002, Gibernau et al. 1999, 2000, 2003; Maia & Schlindwein 2006, Young 1986).

scholarly journals Anatomy and development of the reproductive units of Mapania pycnostachya and Hypolytrum schraderianum (Mapanioideae, Cyperaceae)

2016 ◽  
Vol 64 (5) ◽  
pp. 389 ◽  
Author(s):  
Mariana Maciel Monteiro ◽  
Vera Lúcia Scatena ◽  
Aline Oriani
Keyword(s):  
Vascular System ◽  
General Pattern ◽  
Developmental Study ◽  
Developmental Studies ◽  
Reproductive Unit ◽  
Unisexual Flowers ◽  
Single Flower ◽  
Male Flowers ◽  
Different Levels

The typical mapaniid reproductive unit, which comprises several bracts, stamens and a gynoecium, may be interpreted as a single flower. Although developmental studies suggest that the mapaniid reproductive units are inflorescences, the units in species such as Hypolytrum schraderianum Nees are much reduced and strongly resemble a single flower. Therefore, an anatomical and developmental study of the reproductive units of Mapania pycnostachya (Benth.) T.Koyama and H. schraderianum was conducted to better understand their structure. In both species, two lateral bracts (prophyll-like units) are the first to emerge, followed by staminal and gynoecial primordia. The reproductive units of M. pycnostachya have two inner bracts (leaf-like structures) that initiate after the stamens. In H. schraderianum, they are absent. In both species, the reproductive units have spiral phyllotaxy and staminal traces that join the vascular system of the reproductive-unit axis at different levels. The vasculature pattern of these units differs from the cyperoid flowers. On the basis of these results, it is inferred that the reproductive units of both species are inflorescences, composed of unisexual flowers. It is also inferred that this structure is the general pattern for Mapanioideae and that loss of male flowers and inner bracts has occurred during evolution of the subfamily.

Cryptic dioecy in Actinidia polygama: a test of the pollinator attraction hypothesis

2004 ◽  
Vol 82 (2) ◽  
pp. 214-218 ◽  
Author(s):  
Tetsuhiro Kawagoe ◽  
Nobuhiko Suzuki
Keyword(s):  
Fruit Production ◽  
Sexual System ◽  
Dioecious Species ◽  
Pollinator Attraction ◽  
Cryptic Dioecy ◽  
Actinidia Polygama ◽  
Unisexual Flowers ◽  
Sterile Pollen ◽  
Female Flowers

Female flowers of some dioecious species are known to develop stamens with sterile pollen, a sexual system known as cryptic dioecy. A convincing hypothesis explaining this phenomenon is that stamens in female flowers attract pollinators and so ensure seed production. However, because this hypothesis has rarely been tested experimentally, we tested it in a cryptically dioecious species, Actinidia polygama (Sieb. et Zucc.) Planch. ex Maxim. Our findings show that pollinators do not show a consistent preference based on the sex of the flowers, and that the removal of stamens from female flowers results in a significant reduction in the frequency of insect visits and fruit production. These results strongly support the pollinator attraction hypothesis in A. polygama. Given the evident role of stamens in female flowers in A. polygama reproduction, we discuss why cryptic dioecy is a rare phenomenon.Key words: Actinidia polygama, cryptic dioecy, pseudopollen, pollinator attraction, unisexual flowers.

Sporoderm morphogenesis in Euphorbia obesa and Croton gratissimus

Bothalia ◽  
1983 ◽  
Vol 14 (3/4) ◽  
pp. 849-856 ◽  
Author(s):  
M. L. Frean
Keyword(s):  
Pollen Morphology ◽  
Pollen Grains ◽  
Physiological Adaptation ◽  
Structure Characteristic ◽  
Pollen Type ◽  
Electron Microscope Level ◽  
Pollen Characters ◽  
Pollen Types ◽  
Unisexual Flowers ◽  
Taxonomic Grouping

Pollen grains of the Euphorbiaceae show a number of pollen types which can be clearly distinguished. Generally different genera are characterized by a specific pollen type.  Euphorbia obesa Hook. f. and Croton gratissimus Burch, subsp.  subgratissimus (Prain) Burtt Davy, represent two genera within the Crotonoideae with different morphology, each type characteristic for the respective genus. Taxonomically, the genus Euphorbia with apetalous flowers consisting of a naked pistil surrounded by several staminate flowers within a cyathium, is considered more advanced than the genus  Croton. In  Croton the inflorescence is a raceme with unisexual flowers. The floral whorls of the male show numerous anthers and both calyx and a showy corolla are present. Both genera are insect pollinated. In both  Euphorbia obesa and  Croton gratissimus the pollen wall in section shows columellae, a structure characteristic of angiosperms. However the present ontogenetic studies show that the formation of the columellae differs entirely in the two pollen types. The final stratification of the wall as well as the morphology of the grains differ and evaluation of the exine structure indicates that phylogenetically Croton pollen shows more advanced characters than  Euphorbia — contradicting the floral phylogeny. This study conducted at light and electron microscope level compares the two pollen types morphologically and ontogenetically, concentrating mainly on the formation of the exine which is tectate-perforate in the prolate tricolpate grain of Euphorbia obesa and semi-tectate in the anaperturate, spheroidal grain of Croton gratissimus. The aim of the study was to evaluate the significance of pollen characters in taxonomic and phylogenetic relationships within the Euphorbiaceae. The differing pollen morphology which is related to the taxonomic grouping of tribes within the subfamily (Crotonoideae) emphasizes diversity, which may result from physiological adaptation. The study shows that the same functional end may well be achieved in different ways and this may be a factor underlying the diversity in the heterogeneous family Euphorbiaceae.

Kanakomyrtus (Myrtaceae): A New Endemic Genus from New Caledonia with Linear Stigma Lobes and Baccate Fruits

2009 ◽  
Vol 34 (2) ◽  
pp. 330-344 ◽  
Author(s):  
Neil Snow
Keyword(s):  
New Species ◽  
Reproductive Biology ◽  
New Caledonia ◽  
Field Work ◽  
Windward Side ◽  
Generic Type ◽  
Distribution Maps ◽  
Close Relationship ◽  
Unisexual Flowers ◽  
Species Descriptions

Kanakomyrtus (Myrtaceae) is a newly described genus endemic to New Caledonia. Kanakomyrtus myrtopsidoides, the generic type, is transferred from Eugenia. Five new species are described: K. mcphersonii, K. revoluta, K. dawsoniana, K. prominens, and K. longipetiolata. The genus occurs in forests at elevations between 500–1,600 m on the relatively mesic windward side of the Grande Terre. It is distinct from other baccate genera of Myrtaceae by a combination of linear stylar lobes, densely glandular stamens and stigmas, and a short but densely hoary indumentum that is brownish when dry. The thinly membranous partitions that partially extend between the seeds of some species suggest a close relationship to Archirhodomyrtus and some species traditionally placed in Rhodomyrtus and Octamyrtus. Four of the six species have unisexual flowers, but much additional field work is needed to assess the reproductive biology of the genus. Following IUCN guidelines, four species are proposed as either Endangered or Critically Endangered, whereas the remaining species are considered Vulnerable and of Low Concern. Species descriptions, illustrations, distribution maps, and keys to species of the genus and related taxa of baccate Myrtaceae from New Caledonia are included.

ORGAN INITIATION AND THE DEVELOPMENT OF UNISEXUAL FLOWERS IN THE TASSEL AND EAR OF ZEA MAYS

1983 ◽  
Vol 70 (3) ◽  
pp. 450-462 ◽  
Author(s):  
P. C. Cheng ◽  
R. I. Greyson ◽  
D. B. Walden
Keyword(s):  
Zea Mays ◽  
Unisexual Flowers

The floral development and anatomy of Carica papaya (Caricaceae)

1999 ◽  
Vol 77 (4) ◽  
pp. 582-598 ◽  
Author(s):  
LP Ronse Decraene ◽  
E F Smets
Keyword(s):  
Calcium Oxalate ◽  
Carica Papaya ◽  
Floral Development ◽  
Floral Anatomy ◽  
Structural Basis ◽  
Unisexual Flowers ◽  
Stigmatic Exudate ◽  
Large Ovary ◽  
Further Development ◽  
Shed Light

Floral development and anatomy of Carica papaya L. have been investigated to shed light on (i) the morphology of the flower, (ii) the structural basis for the pollination mechanism, and (iii) the relationships of the Caricaceae. Carica is mostly dioecious with a strong dimorphism between staminate and pistillate flowers. The development of staminate flowers resembles that of pistillate flowers up to the initiation of the stamens. Further development leads to highly diverging morphologies. In staminate flowers a combination of contorted growth and the development of a common stamen-petal tube produces a long floral tube. The gynoecium grows into a central spearlike pistillode. The pistillate flowers have no traces of stamens and initiate five antesepalous carpel primordia. Common basal growth leads to the development of a large ovary with staglike stigmatic lobes and intruding placentae covered with numerous ascending ovules. Floral anatomy of staminate and pistillate flowers is described. The nature of the colleters is discussed. The morphological basis for reward production in C. papaya is clarified, and conflicting views on pollination are discussed. Nectaries of staminate flowers are located on the central rudimentary pistil and not at the base of the stamens, as previously reported. The anthers contain packages of calcium oxalate crystals. Pistillate flowers produce no nectar but have a stigmatic exudate. We compared the floral development and anatomy of Carica with that of Adenia (Passifloraceae) and Moringa (Moringaceae) in the view of a relationship with other glucosinolate-producing families. Although a derivation of the unisexual flowers from bisexual ancestors is probable, Storey's hypothetical derivation of pistillate flowers is not supported by the floral ontogeny and vasculature.Key words: Adenia, Caricaceae, Moringa anatomy, calcium oxalate packages, dioecy, floral structure, nectaries, ontogeny, pollination, systematic relationships.

Allocation of resources to sex functions in flowering plants

1991 ◽  
Vol 332 (1262) ◽  
pp. 91-102 ◽  
Keyword(s):  
Resource Allocation ◽  
Natural Selection ◽  
Population Level ◽  
Theoretical Models ◽  
Flowering Plants ◽  
Allocation Of Resources ◽  
Biological Reality ◽  
Theoretical Predictions ◽  
Allocation Patterns ◽  
Unisexual Flowers

The study of allocation of resources offers the possibility of understanding the pressures of natural selection on reproductive functions. In allocation studies, theoretical predictions are generated and the assumptions as well as the predictions can be tested in the field. Here, we review some of the theoretical models, and discuss how much biological reality can be included in them, and what factors have been left out. We also review the empirical data that have been generated as tests of this body of theory. There are many problems associated with estimating reproductive resources, and also with testing how allocation of these resources affects reproductive and other components of fitness, and we assess how important these may be in allowing empirical results to be interpreted. Finally, we discuss the relevance of resource allocation patterns to the evolution of unisexual flowers, both at the level of individual plants (monoecy, andro- and gynomonoecy) and at the population level (dioecy).

Sciaphila kozushimensis (Triuridaceae), a new mycoheterotrophic plant from Kozu Island, Izu Islands, Japan, based on morphological and molecular data

Phytotaxa ◽  
2020 ◽  
Vol 436 (2) ◽  
pp. 157-166 ◽  
Author(s):  
KENJI SUETSUGU ◽  
AKIHIKO KINOSHITA
Keyword(s):  
New Species ◽  
Molecular Analysis ◽  
Molecular Data ◽  
Flowering Stage ◽  
Unisexual Flowers ◽  
Mycoheterotrophic Plants ◽  
Male Flowers ◽  
Morphological And Molecular Data ◽  
A New Species ◽  
Izu Islands

A new species of Sciaphila (Triuridaceae), S. kozushimensis Suetsugu, is described from Kozu Island, Izu Islands, Japan. The new species is similar to S. tosaensis in having unisexual flowers (the female towards the base of the rachis), perianth-segments without any appendages and club-shaped style that is as long as or slightly exceeds ovary in the flowering stage. However, it is distinguishable by smaller male flowers, wide and acuminate male perianth segments and somewhat dissimilar perianth segments. An illustration and molecular analysis based on ITS sequences of the new species are provided. A key to the Japanese Sciaphila is also provided for identification of these rare mycoheterotrophic plants.

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