Presence of the protruding oncus is affected by anther dehiscence and acetolysis technique

Kuang, Yuanwen; Kirchoff, Bruce K.; Liao, Jingping

doi:10.1080/00173134.2012.660984

Cited by 8 publications

(14 citation statements)

References 28 publications

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“…The compact inner zone of the intine below the protruding oncus (Figure 13C) concurs with the description of the “inner microfibrillar cellulosic layer” of the oncus from which the pollen tube emerges in germinating pollen grains of Corylus avellana (Betulaceae) and Eucalyptus rhodantha (Myrtaceae) [10], [11]. In contrast to the observations of Kuang et al [9], in V. infausta after anther anthesis, the protruding onci remain conspicuous, though somewhat shrunken. We suspect this apparent “shrinkage” of the protruding onci may be due to harmomegathic change [11], [35]–[37] reflecting the hydration status of the pollen grains.…”

Section: Resultssupporting

confidence: 88%

The Epidermal Cell Structure of the Secondary Pollen Presenter in Vangueria infausta (Rubiaceae: Vanguerieae) Suggests a Functional Association with Protruding Onci in Pollen Grains

2014

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Secondary pollen presentation is a well-known phenomenon in the Rubiaceae with particularly conspicuous pollen presenters occurring in the tribe Vanguerieae. These knob-like structures are formed by a modification of the upper portion of the style and stigma, together known as the stylar head complex. In the flower bud and shortly before anthesis, the anthers surrounding the stylar head complex dehisce and release pollen grains which adhere to the pollen presenter. The epidermal cells of the pollen presenter facing the anthers are radially elongated with a characteristic wall thickening encircling the anticlinal walls of each cell towards the distal end. These cells were studied in the pollen presenter of Vangueria infausta using electron and light microscopy in conjunction with histochemical tests and immunohistochemical methods. Other prominent thickenings of the cell wall were also observed on the distal and proximal walls. All these thickenings were found to be rich in pectin and possibly xyloglucan. The terms “thickenings of Igersheim” and “bands of Igersheim” are proposed to refer, respectively, to these wall structures in general and those encircling the anticlinal walls of each cell near the distal end. The epidermal cells have an intricate ultrastructure with an abundance of organelles, including smooth and rough endoplasmic reticulum, Golgi apparatus, mitochondria and secretory vesicles. This indicates that these cells are likely to have an active physiological role. The pollen grains possess prominent protruding onci and observations were made on their structure and development. Walls of the protruding onci are also rich in pectin. Pectins are hydrophilic and known to be involved in the dehydration and rehydration of pollen grains. We hypothesise that the thickenings of Igersheim, as well as the protruding onci of the pollen grains, are functionally associated and part of the adaptive syndrome of secondary pollen presentation, at least in the Vanguerieae.

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Section: Resultssupporting

confidence: 88%

The Epidermal Cell Structure of the Secondary Pollen Presenter in Vangueria infausta (Rubiaceae: Vanguerieae) Suggests a Functional Association with Protruding Onci in Pollen Grains

2014

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“…Apertural intine protrusions occurring in different taxa and their differences among these structures are summarised in Kuang et al (2012).…”

Section: Function Of the Protruding Oncusmentioning

confidence: 99%

“…Protruding onci undergo structural changes at different developmental stages and are usually invisible at the anthesis phase. Kuang et al (2012) assumed that the harmomegathic effect, which occurs after anther anthesis, is likely to correlate to these changes. However, no detailed evidence has been put forward.…”

mentioning

confidence: 99%

“…A protruding oncus is a projection of intine in the pollen aperture found in many Rubiaceae plants (Kuang et al 2008(Kuang et al , 2012. Ultrastructure changes of the protruding onci during pollen development in Uncaria hirsuta Havil.…”

mentioning

confidence: 99%

“…Ultrastructure changes of the protruding onci during pollen development in Uncaria hirsuta Havil. were described in detail (Kuang et al 2012). Protruding onci undergo structural changes at different developmental stages and are usually invisible at the anthesis phase.…”

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confidence: 99%

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Calcium distribution during pollen development ofUncaria hirsutaHavil. (Rubiaceae), with special reference to the function of the protruding oncus

Kuang

Liao

2014

Grana

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Calcium distribution in the developing anthers of Uncaria hirsuta was studied with the potassium pyroantimonite method. The amount and distribution of calcium precipitates change along with the developing anthers and pollen grains in U. hirsuta. Calcium distribution is closely correlated with the anther wall differentiation, exine and intine formations. In mature pollen grains, abundant calcium is in intine, protruding onci and nucleus. A generative cell has more calcium than a vegetative cell does. The calcium storage is likely to contribute to pollen germination, and mitosis of the generative cell. Ubisch bodies formed at the same period with the pollen exine development, and some of them are in close contact with the exine. Abundant calcium is present in the Ubisch bodies, protruding onci and tapetum. These results might support the idea that Ubisch bodies and protruding onci participate in calcium transportation during pollen development. The protruding oncus is likely to have function of calcium or other ions transportation, although further experiment and additional data are required to confirm this. The present study also provides confirmatory evidence to the previous knowledge that calcium participates in regulation of cell differentiation, degradation in each layer of anther wall cells, and pollen development.

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Histochemical and ultrastructural analysis of tapetum and sporoderm development in relation to precocious pollenkitt production of Garcinia dulcis (Roxb.) Kurz

Sutthinon,

Meesawat,

Ulrich

et al. 2024

Protoplasma

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Presence of the protruding oncus is affected by anther dehiscence and acetolysis technique

Cited by 8 publications

References 28 publications

The Epidermal Cell Structure of the Secondary Pollen Presenter in Vangueria infausta (Rubiaceae: Vanguerieae) Suggests a Functional Association with Protruding Onci in Pollen Grains

The Epidermal Cell Structure of the Secondary Pollen Presenter in Vangueria infausta (Rubiaceae: Vanguerieae) Suggests a Functional Association with Protruding Onci in Pollen Grains

Calcium distribution during pollen development ofUncaria hirsutaHavil. (Rubiaceae), with special reference to the function of the protruding oncus

Histochemical and ultrastructural analysis of tapetum and sporoderm development in relation to precocious pollenkitt production of Garcinia dulcis (Roxb.) Kurz

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