Pollen Morphology of the Periplocoideae, Secamonoideae, and Asclepiadoideae (Apocynaceae)

Verhoeven, R.L.; Venter, H.J.T.

doi:10.2307/3298634

Cited by 38 publications

(25 citation statements)

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“…Rauvolfioideae, considered to be first‐branching (Endress & Bruyns, 2000), have three to four colporate single pollen grains, Apocynoideae have three to four porate, occasionally aperturate or polypantoporate single pollen grains or porate tetrads, and Periplocoideae have four to six porate tetrads, multiporate tetrads, or pollinia composed of porate tetrads (Vinkier & Smets, 2002). The type of pollinium and translator (which together form the pollinarium) in Asclepiadoideae was considered to be the most advanced by Verhoeven & Venter (2001). This implies a trend throughout the family from aperturate to inaperturate pollen.…”

Section: Systematic Distribution Of Inaperturate Pollen In Eudicotsmentioning

confidence: 99%

“…In Secamonoideae and Fockea (Apocynaceae s.l. ), the exine of the walls that separate tetrads on the inside of the pollinium (the proximal walls) consists of only a granular layer (Verhoeven & Venter, 2001). Pollen in orchid pollinia may be exineless, or exineless in the interior of the pollinium (Zavada, 1983).…”

Section: Functional Significance Of Inaperturate Pollenmentioning

confidence: 99%

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Why does some pollen lack apertures? A review of inaperturate pollen in eudicots

Furness

2007

Botanical Journal of the Linnean Society

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Apertures are key characters of pollen grains with systematic importance in angiosperms. They function as sites for pollen tube exit, water uptake, transfer of recognition substances and accommodation of volume changes. Not all pollen has apertures; inaperturate pollen (lacking obvious apertures) characterizes many angiosperm groups, especially in early divergent angiosperms and monocots, but also eudicots. In order to expand our knowledge of the systematic distribution, possible functional significance and development of inaperturate pollen in angiosperms, this review focuses on inaperturate and cryptoaperturate (with hidden apertures) pollen in the large eudicot clade, which comprises about 75% of present-day angiosperm species. It includes new TEM observations of inaperturate pollen from four exemplar taxa selected from different parts of the eudicot phylogeny. Two categories of inaperturate (including cryptoaperturate) pollen occur in eudicots. (1) Sterile attractant or feeding pollen associated with functional dioecy has evolved iteratively at least six times in conjunction with complex breeding systems in the core eudicots.(2) Fertile pollen has evolved numerous times independently throughout eudicots, though generally in a relatively small number of individual taxa. Notable exceptions are the petaliferous crotonoid Euphorbiaceae s.s., in which fertile inaperturate pollen occurs in c. 1500 species, and two subfamilies of Apocynaceae s.l. (Secamonoideae and Asclepiadoideae) with c. 2500 species with fertile inaperturate pollen in pollinia. Fertile inaperturate pollen is sometimes (but not always) associated with an aquatic habit, parasitism, insectivory, heterostyly, anemophily or pollinia. Most fertile inaperturate pollen has a thin exine, or the exine is largely restricted to isolated components (muri, protuberances, subunits) separated by thinner areas which probably function as apertures. In cryptoaperturate pollen, the aperture is covered by continuous exine which probably has a protective function, similar to an operculum. Developmentally, inaperturate pollen is not associated with any particular tetrad type or meiotic spindle orientation (unlike some apertures) due to the absence of a colpal shield of endoplasmic reticulum or other organelles and hence is independent of microsporogenesis type. The lack of a colpal shield during the tetrad stage of development permits complete deposition of first primexine and then exine around each microspore, possibly mediated by the action of the DEX1 protein.

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Section: Systematic Distribution Of Inaperturate Pollen In Eudicotsmentioning

confidence: 99%

Section: Functional Significance Of Inaperturate Pollenmentioning

confidence: 99%

Why does some pollen lack apertures? A review of inaperturate pollen in eudicots

Furness

2007

Botanical Journal of the Linnean Society

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“…a trend is observed from the presence of spherical orbicules in the majority of species belonging to the basal group of subfamilies Rauvolfioideae, Apocynoideae and Periplocoideae (Endress & Bruyns 2000) which are characterised by colporate, orporate single pollen grains, or 3 -6 porate tetrads, towards embedded orbicules in the more advanced genera of Periplocoideae which have multiporate tetrads or pollinia (Table I; Vinckier & Smets 2002b, Nilsson et al 1993, Verhoeven & Venter 2001. Therefore, we suggest that embedded orbicules are a more derived orbicule type.…”

Section: Orbicules In Gentianalesmentioning

confidence: 60%

The manifold characters of orbicules: structural diversity, systematic significance, and vectors for allergens

Vinckier

Cadot

Smets

2005

Grana

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E. 2005. The manifold characters of orbicules: structural diversity, systematic significance, and vectors for allergens. -Grana 44: 300-307. ISSN 0017-3134.In the anthers of flowering plants, gymnosperms, and seed ferns, tiny (¡1 mm) granules might occur on the radial and innermost tangential wall of secretory tapetum cells. These sporopollenin granules develop simultaneously with the pollen exine and are called orbicules or Ubisch bodies. The present paper focuses on two quite different topics associated with orbicules.The morphological and ultrastructural diversity of orbicules in the order Gentianales is summarized, and it is demonstrated that orbicules are a plesiomorphic feature in the order. Furthermore, orbicule characters seemed to be correlated with evolutionary trends in pollen dispersal unit and tapetum type features.In the second part, we report on our investigation of Corylus avellana L. (Hazel) pollen, using immunogold electron microscopy to gain an insight into the possible role that orbicules may play as a vector of pollen allergens. During the pollen season orbicules are dispersed into the atmosphere along with Hazel pollen grains. The localisation of homologues of the new birch pollen allergen Bet v 7 was studied at the subcellular level in Hazel anthers. The results of this study indicate that orbicules and pollen of Hazel might act as very effective vectors for homologues of Bet v 7 and that debris of Hazel anthers represent vectors of allergens after the pollen season.

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“…The apparent genetic simplicity of the trait and the absence of pleiotropic effects support the hypothesis that evolution of tetrads was the first step toward the evolution of pollinia, even though all extant milkweeds have pollinia. In Secamonoideae and in one genus of Asclepiadoideae ( Fockea ), tetrads are evident in the mature pollinia, while in other Asclepiadoideae the tetrad organization is lost as the pollinium matures (Safwat, 1962; dan Dicko‐Zafimahova, 1980; Verhoeven and Venter, 2001; Verhoeven et al, 2003). Tetrads have evolved at least 39 times over angiosperm evolution (Harder and Johnson, 2008).…”

Section: Discussionmentioning

confidence: 99%

Climate niches of milkweeds with plesiomorphic traits (Secamonoideae; Apocynaceae) and the milkweed sister group link ancient African climates and floral evolution

Livshultz

Mead

Goyder

et al. 2011

American J of Botany

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Pollen Morphology of the Periplocoideae, Secamonoideae, and Asclepiadoideae (Apocynaceae)

Cited by 38 publications

References 4 publications

Why does some pollen lack apertures? A review of inaperturate pollen in eudicots

Why does some pollen lack apertures? A review of inaperturate pollen in eudicots

The manifold characters of orbicules: structural diversity, systematic significance, and vectors for allergens

Climate niches of milkweeds with plesiomorphic traits (Secamonoideae; Apocynaceae) and the milkweed sister group link ancient African climates and floral evolution

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