摘要:

The pollen of 30 species, five subspecies and one possible hybrid ofCrossandraSalisbury, together with that of one species ofCrossandrellaC. B. Clarke, was examined with light microscopy, scanning electron microscopy and selectively with transmission electron microscopy. A remarkable range of exine stratification was discovered and this was used as the basis for the delimitation of six pollen types. Pollen Types I-V are found inCrossandraand Pollen Type VI inCrossandrella. The relationships between these Pollen Types and the sectional classification ofCrossandraare discussed. The pollen of one species,Crossandra flava, was found to be highly variable, with both ridged and unridged pollen, and some abnormally shaped sterile pollen grains. Three evolutionary trends are recognised in the pollen morphology ofCrossandraandCrossandrellaand these are discussed, together with functional aspects.

ISSN:0017-3134    

DOI:10.1080/00173139009427749

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Pollen of 30 species representing the generaKoenigia, PersicariaandAconogononwas examined by light microscopy and scanning electron microscopy. Pollen descriptions are given for each genus. Earlier palynological investigations of each genus are listed. Each of the genera is characterized by a particular surface structure (spinulose inKoenigia, semitectate reticulate inPersicaria, and with microspinules inAconogonon), but the number and arrangement of the apertures varies considerably, showing interesting parallels in the three genera. All three genera follow the pollen evolutionary model called ‘successiformy’. A few evolutionary and phytogeographically interesting intermediates between these three genera are discussed.

ISSN:0017-3134    

DOI:10.1080/00173139009427750

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Pollen morphology of southern African Lauraceae (Cassytha, Cryptocarya, Dahlgrenodendron, Ocotea) and members of the generaBeilschmiedia, Eusideroxylon, Hypodaphnis, LinderaandPotoxylonwas studied by means of light and scanning electron microscopy. Pollen morphologically the various genera could readily be distinguished from each other, but few interspecific differences were found. To assess the taxonomic significance of pollen characters in Lauraceae, evidence from the literature was also considered and compared with the infrafamilial classification proposed by Kostermans. On the basis of mainly shape and exine sculpture, four pollen types are distinguished in Lauraceae. Pollen type A (grains spheroidal, apolar, spinulose) has been only recorded in the tribes Perseeae, Cinnamomeae, Litseeae and Hypodaphneae; pollen type B (oblate/peroblate, isopolar, slightly to strongly verrucate) occurs only in the Cryptocaryeae; pollen type C (spheroidal, apolar, strongly verrucate/spinuloid) is characteristic of the subfamily Cassythoideae, whereas pollen type D (spheroidal, para-isopolar, striate) is known only inDahlgrenodendron, a monotypic genus and perhaps best placed in a tribe of its own. Hence each of the tribes proposed by Kostermans (1957) proved to be homogeneous as to pollen type. Detailed analyses of the shape and surface ornamentation of lauraceous pollen grains hold considerable promise as a potential source of taxonomic evidence to be employed on the generic and higher levels.

ISSN:0017-3134    

DOI:10.1080/00173139009427751

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Pollen of the Chilean plantPeumus boldusMolina was compared with that of the Australian plantPalmeria scandensF. Muell. (Monimiaceae) under SEM and TEM. Both have apolar, radiosymmetric, globose-spherical, inaperturate spinulose pollen of medium (Peumus) and small (Palmeria) size. The spinules appear to have been built up by successive layers of cylindrical strands of material 100–250 nm (Peumus) and 100–150 nm diameter (Palmeria). The tectum comprises interwoven cylindrical strands, smaller than those of the spinules. Ion/atom beam etching inPalmeriarevealed that each strand resembled a tightly coiled spring of similar size to models for exine units proposed by J. R. Rowley and co-workers. Under TEM the spinules appeared homogeneous in section. It was concluded that this was because material cementing the strands was of similar electron density to the strands themselves. For, prolonged ion/atom beam etching of spinules revealed substructure indicating the presence of the strands. In both genera the exine is two-zoned, with an inner zone of rod-shaped, more or less radially aligned sporopolleninous elements, with, inPalmeriasome innermost circumferentially aligned sporopolleninous elements too. A foot layer and endexine are absent. BothPeumusandPalmeriahave a two-zoned intine with an outer zone containing tubular material. It is concluded that pollen morphology does not support the recent segregation ofPeumusandPalmeriainto different subfamilies.

ISSN:0017-3134    

DOI:10.1080/00173139009427752

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The pollenof Limnanthes douglasiiwas reinvestigated in order to clarify certain disagreements. Contrary to former authors the (single) tetrahedral/decussate tetrad and the microspore orientation is interpreted as follows: the ring-like aperture region of the spherical monads/young microspores runs parallel to the equator, but is slightly shifted towards the distal face. A smaller polar area is found distally, while a larger one is located proximally. As a result of our interpretation of the pollen orientation, the pollen grains must be described as zonosulcate. The unusual arrangement of relatively thick and thin intine regions gives rise to a quite uncommon harmomegathic effect. Dry pollen is hooked, while expanded pollen is irregularly ellipsoidic or kidney-shaped. The unique pollen characters suggest an isolated taxonomic position of this family.

ISSN:0017-3134    

DOI:10.1080/00173139009427753

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Apocynaceae pollen and anthers (unacetolyzed) were analysed with a Cambridge S 200 scanning electron microscope equipped with an energy dispersive X-ray (EDX) unit. Pollen grains collected from herbarium sheets show a very similar distribution of their elemental content. In most cases, complete dried anthers and single pollen grains gave the same results.

ISSN:0017-3134    

DOI:10.1080/00173139009427754

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Ultrastructural analysis of the microspores from the Pennsylvanian lycophyte coneSelaginellites crassicinctusreveals a structural organization which is comparable to modern representatives ofIsoetesandSelaginella. The most prominent similarities include the presence of a para-exospore—a layer external to and largely free from the exospore, but with a similar ontogeny and staining characteristics—and a proximal multilamellated region situated at the innermost region of the exospore in the center of each interradial area. A more rigorous comparison of specific structural features indicates a higher degree of similarity withSelaginella, particularlyS. selaginoides. These results are somewhat anomalous in light of the suggested affinity ofPaurodendron, the axis which presumably bore this cone, with the Isoetales. These results stand in support of the existence of a recently proposed group of Carboniferous lycophytes which are structurally intermediate between the rhizomorphic and herbaceous types.

ISSN:0017-3134    

DOI:10.1080/00173139009427755

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The daily concentration of airborne pollen has been recorded in central Stockholm during the period 1 March-31 August, 1977–1986, using a Burkard seven-day recording volumetric spore trap placed c. 20 m above ground level. Total annual catches and phenology of arboreal pollen are presented, attaching importance to five frequent deciduous taxa namelyCorylus, Alnus, Ulmus, BetulaandQuercus. The annual arboreal pollen count is numerically presented in a bar diagram together with non-arboreal, unidentified and estimated missing data. The arboreal count dominates and has varied from 10513 in 1986 to 39552 in 1985. The non-arboreal pollen contribution to the annual sum has varied from 10 to 30% and does not correlate to the rise and fall of the arboreal sum. Annual pollen sums inBetulaandUlmusshow a certain tendency towards a two-year cycle whilePinusshows a tendency towards a three-year cycle. The phenology is presented on a decadal (10-day) mean basis and shown as a percentage of the yearly sum for each taxon. The flowering seasons in decadal percentages year by year forCorylus, Alnus, Ulmus, BetulaandQuercusis compared to the 10-year decadal average. Rank correlation statistics are used to define within which decade a pollen type dominates the pollen spectrum. Using our study alone, which is based only on pollen concentration calculations, it is not possible to forecast either the total annual catch or the phenology of the following year.

ISSN:0017-3134    

DOI:10.1080/00173139009427756

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

This paper describes a pollen survey from Turin based on 25 taxa of interest. The survey took place between 1981 to 1988 recording pollen types and amounts.

ISSN:0017-3134    

DOI:10.1080/00173139009427757

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Pollen grains ofShorea robustaGaertn. (Dipterocarpaceae) were examined with light and scanning electron microscope. The pollen grains are tricolpate with reticulate sculpture with some of the muri discontinuous, giving a canaliculate appearance. The relation between pollen production and dispersal ofShorea robustareveals that the huge numbers of pollen grains produced is associated with entomophily. The pollen grains have a poor dispersion power as indicated by substantial decline in percentage away from source trees. An extremely low percentage of sal (Shorea robusta) pollen deposited in ground soil within and outside and forest despite the high pollen production which may be attributed to microbial as well as chemical degradation. This information can be utilized for the precise evaluation of pollen diagram in terms of past vegetation and climate from tropical deciduous forests in the Indian sub-continent.

ISSN:0017-3134    

DOI:10.1080/00173139009427758

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor