This is a combination of a review and original data on floral structure, development, and biology of representatives of all families of the ANITA grade and, in addition, Chloranthaceae and Ceratophyllaceae. Since the ANITA grade has been identified as the basalmost grade of extant angiosperms based on molecular studies by a number of authors, it has become possible to search for potential plesiomorphies among flowers of extant basal angiosperms. They may include the following traits: flowers small, pollination by small insects (dipters, thrips, moths); flowers with moderate or low number of floral organs, in spiral (or whorled) arrangement, with a tendency to form organ series in Fibonacci numbers (3, 5, 8); flowers bisexual (but easily becoming unisexual because of low level of synorganization between organs), protogynous; tepals (in spiral flowers) with gradual transitions between bractlike, sepal‐like, and petal‐like forms; stamens with short filaments, anthers with a connective tip, with more or less ...

The flowers in extant basal angiosperms and inferences on ancestral flowers

A comparative study on gynoecium structure in basal angiosperms revealed new features relevant to systematics. In addition, based on the new phylogenetic framework on basal angiosperms gained by molecular systematics, an evolutionary evaluation of gynoecial character states has become possible. Angiospermy patterns are diverse and are here tentatively grouped into four types according to the mode of carpel closure: (1) by secretion, without postgenital fusion; (2) with a continuous secretory canal but partial postgenital fusion at the periphery; (3) with an incomplete secretory canal and complete postgenital fusion at the periphery; (4) by complete postgenital fusion. In most basal angiosperms the carpels are free, and the inner space of each carpel is occluded from the outside by secretion and not by postgenital fusion (angiospermy type 1). Correlated with this feature is a pronounced ascidiate shape of the carpels. The carpels tend to be shortly stipitate. In relatively many basal clades with pluricarpe...

https://www.jstor.org/stable/10.1086/317572

Gynoecium Structure and Evolution in Basal Angiosperms

Gynoecium diversity and systematics of the paleoherbs

The Pollination of Trimenia moorei (Trimeniaceae): Floral Volatiles, Insect/Wind Pollen Vectors and Stigmatic Self‐incompatibility in a Basal Angiosperm

A remarkable number of the defining features of flowering plants are expressed during the life history stage between pollination and fertilization. Hand pollinations of Amborella trichopoda (Amborellaceae) in New Caledonia show that when the stigma is first receptive, the female gametophyte is near maturity. Pollen germinates within 2 h, and pollen tubes with callose walls and plugs grow entirely within secretions from stigma to stylar canal and ovarian cavity. Pollen tubes enter the micropyle within 14 h, and double fertilization occurs within 24 h. Hundreds of pollen tubes grow to the base of the stigma, but few enter the open stylar canal. New data from Amborella, combined with a review of fertilization biology of other early-divergent angiosperms, show that an evolutionary transition from slow reproduction to rapid reproduction occurred early in angiosperm history. I identify increased pollen tube growth rates within novel secretory carpel tissues as the primary mechanism for such a shift. The opportunity for prezygotic selection through interactions with the stigma is also an important innovation. Pollen tube wall construction and substantial modifications of the ovule and its associated structures greatly facilitated a new kind of reproductive biology.

https://bsapubs.onlinelibrary.wiley.com/doi/pdf/10.3732/ajb.0800070

Isabelle Orban

Papers

Reproductive-biology of Nymphaea-capensis Thunb Var Zanzibariensis (casp) Verdc (nymphaeaceae)

Regular articleReproductive biology ofNymphaea capensisThunb. var.zanzibariensis(Casp.) Verdc. (Nymphaeaceae)