摘要:

The pollen of fourteen species ofStenandriumNees from Africa and Madagascar has been examined using light microscopy, scanning electron microscopy and selectively with transmission electron microscopy. The pollen exhibits an interesting range of variation. Four pollen types are described. Pollen Type I is usually prolate, tricolpate and has colpi without margines. In one collection ofStenandrium humile(Mabberley 995) irregular 4–6-colpatc grains occur. Pollen Type II is oblate spheroidal to prolate spheroidal, 3–6-colpate with irregular apertures. Pollen Type III is perprolate, tricolpate and the colpi have prominent margines. Abnormally-shaped grains were found in one collection ofStenandrium afromontanum(Lovett & Congdon 3068). Pollen Type IV is prolate to perprolatc, tricolpate with prominent margines and mesocolpial ridges. Because of the high level of abnormality encountered, material from each species, according to availability, was tested for the presence or absence of cytoplasmic contents. Pollen lacking cytoplasm was found in several collections. The reasons for this and for the presence of irregular pollen grains are not known at present, although chromosomal abnormalities are suggested as a possible cause. The pollen morphology is discussed in relation to the sectional classification of Vollesen and with respect to relationships within the Acantheae. In particular, a close relationship withCrossandraSalisbury is suggested. The results of a brief survey of the pollen morphology of selectedStenandriumspecies from South America are discussed.

ISSN:0017-3134    

DOI:10.1080/00173139309436413

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

G. Erdtman,Handbook of Palynology, 2nd edition, 1992 (Ed. S. Nilsson & J. Praglowski), 676 pages and numerous illustrations. Munksgaard.

ISSN:0017-3134    

DOI:10.1080/00173139309436414

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

This study is on the different pollen types exhibited by the Sudanese Cassias having intra-specific pollen polymorphismCassia italica(Mill.) Lam., C.sennaL., C.sieberianaDC. andC. nigricansVahl). Quantitative and qualitative characters of modern samples ofC. italicapollen grains and stamens are presented in an attempt to evaluate the possible source(s) of the pollen polymorphism. LM and SEM were used. Three types of stamens and at least three pollen types were recognized in C.italica. The three types of stamens differ in size, general outline, apex, base, surface ornamentation, anther dehiscence and fertility. The pollen grains contained in these three types of stamens show continuous variation with respect to their exine sculpturing. The extremes of such variation are classed as pollen types I and II, whereas the intermediates, which are hardly identifiable with LM, are all designated pollen type III. These three pollen-types occur with varying percentages in the fertile stamens (i.e. long and medium stamens).

ISSN:0017-3134    

DOI:10.1080/00173139309436415

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Pollen wall morphogenesis ofPolystachia pubescens(Orchidaceae) was observed with light and transmission electron microscopy.Polystachia pubescenshas pollinia which consist of isobilateral calymmate tetrads. Three sporoderm types are present within the pollinium: type 1 (forming the surface of the pollinium), with large homogeneous exine “flakes”, lacking columellae, footlayer and endexine, with a fibrous intermediate layer and a bilayered intine; type 2, which is found between tetrads within the pollinium, and whose exine is represented by small exine globules only, but otherwise is equivalent to sporoderm type 1; and type 3, found within the tetrads and solely consisting of the bi-layered intine. The whole pollinium is enveloped by a polysaccharidic film (“envelope”) which originates from tapetal and sporocyte cell walls and is formed after the tapetum has degenerated shortly before anthesis. Young microspores are separated by callose. The exine and the outer layer of the intine are formed simultaneously, while the inner layer of the intine is formed after the generative cell has become detached from the pollen wall. No primexinc could be found. The fibrous intermediate layer supporting the exine in sporoderm type 1 and type 2 derives from the “special mother cell wall”, whose callosic nature can be detected as far as the first mitosis.

ISSN:0017-3134    

DOI:10.1080/00173139309436416

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A method is proposed for calibrating modern pollen data in terms of remote sensing data. It includes numerical techniques familiar to the pollen analyst, remote sensing data and a simple although robust technique of model testing. The method allows the calibration of equations to predict radiometric data in regions (such as Southern Patagonia) where the paucity of modern climate data is a major obstacle for research in palaeoclimatology. Remote sensing data from the National Oceanic and Atmospheric Administration (NOAA-9) Advanced Very High Resolution Radiometer (AVHRR) [Channels 1 (.58 to .68 μm) and 2 (.725 to 1.1 μm)], were used to calculate albedo values. These values were used to (1) calculate simple ratio (SR) and Normalized Difference Vegetation Index (NDVI), and (2) to calibrate them in terms of the modern pollen spectra of 74 sites of Southern Chubut, Santa Cruz and Tierra del Fuego, to produce predictive models. The data sets were then split so that one half of the data predicted the radiometric data of the other half. The predicted data of channels 1 and 2 were then used to calculate predicted SR and NDVI values, thus opening new dimensions for paleoenvironmental research. Observed and predicted data have distinctive values in the forest, humid and arid steppes, and coastal locations. The models can be used to reconstruct the history of vegetation, particularly in the arid region.

ISSN:0017-3134    

DOI:10.1080/00173139309436417

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

By means of regression analysis theCladosporiumandAlternariaspore counts for 1980–89 for Stockholm are explored and modelled at 6-hour intervals in order to find the relationship between spore presence and climate for the same time periods. Six different weather parameters are used. ForCladosporiumdaily mean temperature and daily precipitation seem to be consistently significant. The presence ofAlternariaappears to be more complex. There is a tendency forAlternariaspore concentrations to increase with the daily precipitation, wind velocity and total cloud cover. The models are evaluated statistically.

ISSN:0017-3134    

DOI:10.1080/00173139309436418

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The most common airborne algae are recognized as a community of aeroalgae, and their morphological attributes and dimensions are associated to an average aerodynamic structure, called ideal airborne algae. The principal atmospheric factors producing the dispersion and viability of alga are briefly introduced. For the first time, in a systematic and consequent way, preprocessors of atmospheric parameters are used in aerobiology. The research indicates, at least statistically, that the synthesis of specific parameters in preprocessors is of a greater relevance for the dispersion of algae (and physically equivalent particles) than each one of the meteorological parameters by themselves. This synthesis introduces a theoretical — practical level of elaboration that allows a greater deepness of analysis. In this case, the adequate preprocessors of atmospheric movements are the turbulent kinetic energy and the evaporation. Another fundamental factor is the atmospheric pollution. In the southern metropolitan area of Mexico City the ozone represents an acceptable index of the levels of pollution limiting the viability of airborne algae. Under the assumption of a (steady) given supply of algae, a possible model of concentrations of algae in the atmosphere is constructed based on statistical considerations, aimed to predictions of those concentrations.

ISSN:0017-3134    

DOI:10.1080/00173139309436419

出版商:Taylor & Francis Group    

年代:1993

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:10.1080/00173139309436412

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor