A Morphological Study of Certain Asclepiadaceae

Frye, T. C.

doi:10.1086/328303

Cited by 38 publications

(25 citation statements)

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“…Isolated tracheids not connected to the vascular supply in the funiculus are reported for Castanea (Benson, 1894), Carpinus (Benson, Sandy, and Berridge, 1906), and for Asclepias (Frye, 1902). The widespread occurrence among unrelated taxa of vascular elements centrally located in these axes once again supports derivation of the nucellus from a fertile telome.…”

Section: Origin Of the Ovule: A New Conceptmentioning

confidence: 87%

The origin of the ovule

Herr

1995

American J of Botany

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Of several theories for the origin of the ovule advanced in this century and based largely on fossil evidence, the telomic concept is widely considered the most plausible. Its principal tenet is the evolution of the integument through fusion of sterile branches or telomes around a terminal megasporangium. The only point of agreement in these theories is that the entire nucellus is a megasporangium that retains a single megaspore and the endosporic female gametophyte. Their differences center on the origin of the integument. A new concept offered here on evidence from ovules of both Paleozoic and extant seed plants significantly alters the telomic theory. It proposes that the nucellus is a sporangiophore of stem origin that bears a terminal megasporangium; that at least some of the fused integumentary telomes were fertile; and that among all features cited to characterize ovules, the unique nature of the retained megaspore alone defines the seed habit. Changes in the seed plant megaspore that extended the period of nutrient absorption over the whole course of female gametophyte development, along with complex physiological changes in the nucellus, were probably achieved along a single phylogenetic line beginning in a Late Devonian population of progymnosperms. For such a combination of events to have occurred more than once is highly unlikely, and, therefore, a monophyletic origin for seed plants is proposed. Several primitive features in ovule structure, some not evidenced since the Lower Carboniferous Period, occur in a mutant form of Arabidopsis thaliana isolated from genetically transformed plants. Their recurrence provides additional support for the proposed concept of ovule origin and also suggests that the genetic mechanisms for expression of primitive features in advanced taxa could be initiated in each case by mutation of a single homeotic gene.

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Section: Origin Of the Ovule: A New Conceptmentioning

confidence: 87%

The origin of the ovule

Herr

1995

American J of Botany

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“…Frye (1902) observed that in the mature flower there are from one to six in each group, the number and size varying even in the same flower. Usually, colleters are side by side on the organ to which they are attached, but sometimes they are placed radially.…”

Section: Taxonomic Considerationsmentioning

confidence: 93%

Structural, Functional and Phylogenetic Aspects of the Colleter

1991

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This article surveys the structural, functional and phylogenetic significance of colleters in different dicotyledonous families. Colleters are multicellular secretory structures attached to the stipule, petiole, lamina, bract, bracteole, calyx and corolla. Colleters are grouped into standard (S), dendroid (D) and brush-like (B) types on the basis of their morphology and structure. D and B-type colleters occur in certain members of Rubiaceae that also have bacterial leaf nodules. Besides the normal structure, epithelial hairs, thin-walled subepidermal cells, laticifers and vasculature are present in many colleters of Apocynaceae. It is probable that the colleter functions to protect the developing meristem by secreting a viscous fluid. Exudate of D-type colleters are mucilaginous, providing the substrate necessary for the nutrition of endophytic bacteria.

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“…Rev effected when a pollinium lodges in a stigmatic chamber (79). Pollen tubes subsequently grow down the stylar canal and finally enter the ovary (17,25). Pollen tubes subsequently grow down the stylar canal and finally enter the ovary (17,25).…”

Section: Floral Morphology and Anatomymentioning

confidence: 99%

Ecology and Evolution of Reproduction in Milkweeds

Wyatt¹,

Broyles²

1994

Annu. Rev. Ecol. Syst.

156

112

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Asclepiadaceae are the dicot counterparts to the Orchidaceae, which also transmit their pollen grains in large groups within pollinia. Unlike many terrestrial, nectar-producing orchids, however, milkweeds are characterized by low fruit-set, typically averaging 1-5%. Transfer of hundreds of pollen grains as a unit makes it possible to quantify pollinator activity and male and female reproductive success more directly and more easily in milkweeds than in plants with loose pollen grains. It also leads to the production of fruits whose seeds all share a single father, thus simplifying paternity analysis. Recent anatomical work has demonstrated that three of the five stigmatic chambers of milkweed flowers transmit pollen tubes to one of the two separate ovaries, whereas the other two chambers transmit only to the second ovary. Milkweed flowers are long-lived and produce copious nectar, which flows from nectaries within the stigmatic chambers to fill the hoods, which serve as reservoirs. Nectar also serves as the germination fluid for pollen grains, but concentrations above 30% inhibit germination. Most milkweeds are genetically self-incompatible and express an unusual late-acting form of ovarian rejection. Some weedy milk weeds, however, are self-compatible, and levels of self-insertion of pollinia are apparently high in these, as well as in self-incompatible, species. Early

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A Morphological Study of Certain Asclepiadaceae

Cited by 38 publications

References 0 publications

The origin of the ovule

The origin of the ovule

Structural, Functional and Phylogenetic Aspects of the Colleter

Ecology and Evolution of Reproduction in Milkweeds

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