摘要:

Three features of developing pollen grains may facilitate the uptake of materials: (1) tubules (∼ 10 nm in diameter) at the surface of the exine, (2) wall tubules (7–18 nm in diameter), and (3) channels through the exine (irregular in shape, but generally between 50 and 300 nm in diameter). The tubules ofAegicerasoccur in tufts on the surface of the exine and extend from the exine to the tapetal cell surface. A glycocalyx (1,2-glycols and acidic groups) is associated with the tubules, and we suggest that the tubules and glycocalyx may be a specialization of a unit membrane on the exine surface. The wall tubules ofNupharare found in the outer part of the exine and extend from the nexine-2 to the tectum, including the tips of spines. Evaginations of the plasma membrane penetrate the exine of young microspores ofEpilobiumand their trails remain as channels in the mature exine. We show that lanthanum nitrate can pass directly through the substance, not only the channels, of the exine in microspores ofEpilobium.

ISSN:0017-3134    

DOI:10.1080/00173137009429851

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

At the released stage, the residual cell plates and “spore chambers” of the microspore tetrads ofIpomoea purpurea,are the most resistant elements of the callosic special wall. The spore chamber walls show a regular geometric pattern, visible in phase contrast or fluorescence, which constitutes a hollow template or “mould” for the first spore wall or primexine matrix. This matrix forms a network of polygonal meshes at the angles and along the sides of which the probacula and spines of the future exine are embedded until formation of a “foot layer”. In the mature exine, large spines are absent from some of the angles. Their distribution is not random but definite, and is directly related to the primary patterning of the spore chamber. Important developmental stages occur, and the general patterning of the exine is established, whilst the callosic special wall is still present. This indicates that it plays an essential rôle in pollen ontogeny.

ISSN:0017-3134    

DOI:10.1080/00173137009429852

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The temporary occurrence of the callose plate between the generative and vegetative cells in pollen grains was observed in 82 angiosperm species and 4 gymnosperm species. The period of isolation of the generative cell by callose, determined as the “callose stage”, includes the early interphase of the generative nucleus. The significance of the “callose stage” in the differentiation process of generative cells is discussed. The opinion is expressed that the temporary occurrence of a callose plate may explain why some authors only observe a double plasma membrane separating the generative and vegetative cells of the pollen grain, while others observe a wall-like structure between these membranes.

ISSN:0017-3134    

DOI:10.1080/00173137009429853

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

During the development of intine in spores ofLycopodium annotinumthe inner nuclear membrane develops extrusions into the area enclosed by the nuclear envelope. The outer nuclear membrane may then form bulges which seem to be distended cisternae of the endoplasmic reticulum, and which contain the constricted vesicles mentioned above. Such cisternae have been observed also in the cytoplasm between nucleus and wall. It seems that the vesicles enclosed in the endoplasmic reticulum are ultimately emptied into the developing intine.

ISSN:0017-3134    

DOI:10.1080/00173137009429854

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Thirty-nine bee pollen loads collected in Kangra, were analyzed, during a period of three months. Eight loads were found to be mixed and the rest unifloral. In all, twenty pollen types were recognised in the loads, which included some of the anemophilous types, namely, Gramineae, Cyperaceae, Palmae, Chenopodiaceae and Urticaceae.

ISSN:0017-3134    

DOI:10.1080/00173137009429855

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Forty-nine species of spores and non-saccate pollen grains are described from the Permian of the northern Perth Basin. One new genus, 12 new species, and four new combinations are proposed. The stratigraphic distribution of each species is given.

ISSN:0017-3134    

DOI:10.1080/00173137009429856

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Following the recent official rejection of proposals for conservation of the generic nameHystrichosphaera,the diagnosis of its senior synonymSpiniferitesis expanded in order to incorporate additional information gained since 1850 and all species according with the expanded diagnosis are listed (24 species are transferred toSpiniferites).The cyst-family name “Hystrichosphaeraceae” is replaced by the new name “Spiniferitaceae”.

ISSN:0017-3134    

DOI:10.1080/00173137009429857

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue

ISSN:0017-3134    

DOI:10.1080/00173137009429850

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor