Origin of sperm cell association in the “male germ unit” ofBrassica pollen

Charzyńska, Maria; Murgia, M.; Milanesi, Claudio; Cresti, Mauro

doi:10.1007/bf01623975

Cited by 23 publications

(13 citation statements)

References 17 publications

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“…This concept has since been extended to bicellular pollen, in which a close association between the GC and the VN is characteristic of numerous species. The events of MGU formation at earlier stages of pollen development have been reported previously in tricellular (Russell et al 1988;Charzynska et al 1989) but not bicellular pollen.…”

Section: Introductionmentioning

confidence: 72%

“…Although this may also occur in other plants, we are unaware of any previous reports suggesting the disappearance of an established association during development. This suggests that physical associations between the GC and VN are not invariant, and therefore differ from the structural connections occurring between the two brother sperm cells, which are maintained from their inception during GC cytokinesis (Charzynska et al 1989). Other systems without GC-VN associations in the mature pollen grains frequently display associations after germination (Hippeastrum, Mogensen 1986a, b; Rhododendron, Theunis et al 1985, Kaul et al 1987).…”

Section: Association Between the Gc And Vnmentioning

confidence: 99%

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Male cytoplasmic diminution and male germ unit in young and mature pollen of Cymbidium goeringii: a 3-dimensional and quantitative study

Russell

1992

Sexual Plant Reprod

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Pollinia of Cymbidium goeringii (Orchidaceae) were examined at a young stage (approx. 2 weeks before anthesis) and at anthesis using transmission electron microscopy, computer-assisted serial reconstruction and quantitative cytology. At the young stage, the generative cell (GC) has a spherically shaped main body with a large nucleus and 1 to 4 cytoplasmic extensions (up to 10 gm long) physically associated with a groove on one side of the vegetative nucleus (VN). By anthesis, some GCs lose their cytoplasmic extensions, becoming spherical. The GC surface becomes highly wrinkled, the distance between the GC and the VN increases and the two may separate completely. Enucleated cytoplasmic bodies (ECBs) are apparently generated by the GC, as evidenced by their similar ultrastructural appearance and distribution near the GC. ECBs are likely produced from two sites: the GC surface and the tips of cytoplasmic extensions of the GC. Vesicle-containing bodies (VCBs) may be generated from the lateral surface of the GC and may also represent a degeneration stage of ECBs, finally fusing with lipid bodies. Heritable organelles are rare and usually absent in the GC of Cymbidium." 0.176 mitochondria and 0.0042 plastids per GC were observed at the young stage and no mitochondria and 0.019 plastids at anthesis. Of 16 cellular parameters examined during GC development, all decreased with the exception of the surface area and volume of ECBs/ VCBs (which remained stable) and GC vacuoles (which increased). Significant decreases in 11 parameters presumably relate to dehydration of the pollen and male cytoplasmic diminution.

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Section: Introductionmentioning

confidence: 72%

Section: Association Between the Gc And Vnmentioning

confidence: 99%

Male cytoplasmic diminution and male germ unit in young and mature pollen of Cymbidium goeringii: a 3-dimensional and quantitative study

Russell

1992

Sexual Plant Reprod

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“…Grant et al (1986) have described microspore development in B. napus from the premeiotic stage up to the first pollen mitoOffprint requests to: M. Cresti sis stage. The final maturation events in the pollen grain have been presented by Charzynska et al (1989a). Most of the attention, however, has been given to the ultrastructure and organization of the sperm cells of the mature Brassica pollen grain (Dumas et al 1985;McConchie et al 1985McConchie et al , 1987Tuohy et al 1987;Charzynska et al 1989b).…”

Section: Introductionmentioning

confidence: 99%

Brassica napus pollen development during generative cell and sperm cell formation

Murgia

Detchepare

Went

et al. 1991

Sexual Plant Reprod

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Brassica napus pollen development during the formation of the generative cell and sperm cells is analysed with light and electron microscopy. The generative cell is formed as a small lenticular cell attached to the intine, as a result of the unequal first mitosis. After detaching itself from the intine, the generative cell becomes spherical, and its wall morphology changes. Simultaneously, the vegetative nucleus enlarges, becomes euchromatic and forms a large nucleolus. In addition, the cytoplasm of the vegetative cell develops a complex ultrastructure that is characterized by an extensive RER organized in stacks, numerous dictyosomes and Golgi vesicles and a large quantity of lipid bodies. Microbodies, which are present at the mature stage, are not yet formed. The generative cell undergoes an equal division which results in two spindle-shaped sperm cells. This cell division occurs through the concerted action of cell constriction and cell plate formation. The two sperm cells remain enveloped within one continuous vegetative plasma membrane. One sperm cell becomes anchored onto the vegetative nucleus by a long extension enclosed within a deep invagination of the vegetative nucleus. Plastid inheritance appears to be strictly maternal since the sperm cells do not contain plastids; plastids are excluded from the generative cell even in the first mitosis.

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“…The other sperm cell (Sua) is connected to the Svn by a common cell junction, more recently described as being comprised of channels passing between the two cells (Charzynska et al 1989). We have now observed that in the pollen tube this connection is made up of finger-like membrane evaginations similar to the sperm ccll connections in Rhododendron (Taylor et al 1989).…”

Section: The Male Germ Unitmentioning

confidence: 57%