摘要:

The pollen of the four genera of the Thymelaeaceae occurring in the Cape Floristic Region was studied with the LM, SEM and TEM. All four genera have spherical, pantoporate pollen grains and inGnidia, LachnaeaandStruthiolathe grains have a typicalCroton‐pattern similar to that of the majority of genera in the Thymelaeaceae. The exine of these three genera comprises triangular, supratectal subunits attached to a reticulum or semitectum, which is connected with short columellae to the nexine. InPasserinathe supratectal subunits are lacking. Instead, the reticulum is ornamented with sparsely distributed spinules and can be described as supra‐microechinate. Polymorphism with regard to pollen size was found in some specimens of three of theLachnaeaspecies, but since it was not consistent for all the specimens of the three species concerned, the phenomenon of polymorphism is ascribed to temporary ecological conditions. The structure of the tectum ofGnidia, LachnaeaandStruthiolais very similar and reveals a continuum of variation so that the palynology seems not to be of any taxonomic value within the three genera. The pollen morphology revealed a closer relationship betweenGnidia, LachnaeaandStruthiolawhich show aCroton‐pattern, whereasPasserinawith the subunits lacking, confirms the present idea of placing it in a separate subtribe.

ISSN:0017-3134    

DOI:10.1080/00173139809362667

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The pollen grains, the pistil, growth of the pollen tube and its pathway are described inBorago officinalisandHeliotropium europaeum.The exine is thick in both taxa but it is covered with dense gemmae inBorago.The intine seems to be thicker and contains more proteins inBoragothan inHeliotropium.Starch is very abundant in the latter while it is lacking in the former. The style is hollow inBoragowith a stylar canal running from the stigma to the ovary, while inHeliotropiumit is broadly cone‐shaped with papillae located at the base of the cone (the “stigmatic ring") and not at the top of the style as usual. InBoragostigmatic papillae are unicellular, skittle‐shaped and have a thick pectocellulosic wall and an equally thick cuticular layer, while inHeliotropiumthe stigmatic papillae are unicellular, elongated cone‐shaped with a thin pecto‐cellulosic wall and have an apparently reduced cuticular layer. The stigmatic exudate is very abundant on the stigmas ofHeliotropiumeven before anthesis while it is absent on those ofBoragoexcept when allo‐pollination occurs. Pollen tube growth has been followed from stigma to ovules in both taxa.

ISSN:0017-3134    

DOI:10.1080/00173139809362668

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The pollen grains of seven species of the genusSicydiumSchlechtendal (Cucurbitaceae, Zanonioideae, Zanonieae, Sicydiinae) are described and illustrated using both light and scanning electron microscopes. The species included in the study were:S. araguenseSteyermark et Trujillo, S.daviliaeLira,S. diffusumCogn.,S. gracileCogn.,S. schiedeanumSchlechtendal,S. tamnifolium(H.B.K.) Cogn., andS. tuerckheimiiJ. D. Smith. The analysis of the palynological information obtained showed that the shape and dimensions of the pollen grains, and the distance between colpi, are characters that could be a very useful complement for the identification ofSicydiumspecies.

ISSN:0017-3134    

DOI:10.1080/00173139809362669

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The spores ofBruchia uleana, B. uruguensis, Eobruchia bruchioides, Trematodon ambiguus, T. aureus, T. brevifolius, T. longlcollis, T. reflexusandT. vaginatuswere studied by light and scanning electron microscopy. The spore wall of the family Bruchiaceae includes sclerine (the distinction between exine and perine may be difficult to define) and intine. The aperture may be surrounded or not by one or more rings of ornamentation elements. Two basic types of spore were recognized: one characterized by a gemmoid surface and the other with elongated processes and two types of ornamentation in the apertural region. The spores of the taxa studied support the separation of the Bruchiaceae from the Dicranaceae.

ISSN:0017-3134    

DOI:10.1080/00173139809362670

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Peroxidase isozyme profiles of the pollen collected from the immature and mature anthers (before and after anthesis) of seven tropical plant taxa from eastern India were studied in order to understand the development of Peroxidase isozyme activity with the maturity of the pollen. Considerable variation in the enzyme profiles was observed in all cases, except inSaccharum spontaneumwith the individual isoforms showing a tendency to increase in their concentration and staining properties and with the simultaneous appearance of new bands, in certain cases, on maturity.Saccharum spontaneumshowed no variation in its isozyme profile even on maturity.

ISSN:0017-3134    

DOI:10.1080/00173139809362671

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The flowering patterns ofUlmus pumilaandFraxinus excelsiorwere studied during the 1990 growing season in order to investigate their pollen dispersion curves. The use of airborne pollen records as predictors of flowering of allergenic trees was evaluated. A sampling method to describe quantitative flowering phenophases was applied. A Burkard trap recorded airborne pollen in the city of Mar del Plata. The phenological sampling method showed that floral phenophase development is not always synchronous between trees. The variability registered was larger forF. excelsiorthan forU. pumila.A delay between flowering and the airborne pollen recorded was not noticed forUlmus.The greatest amount ofUlmuspollen came from the local vegetation, mainly fromU. pumila. Fraxinuspollen was recorded for a longer period after theF. excelsiorflowering season the ended.Fraxinuspollen income came fromF. excelsiorbut also fromF. americanaandF. excelsiorvar.aureathat flower later. An immediate decrease in airborne concentration was noticed for both pollen types following rain. When relatively strong rainfall was registered a decrease in the number of open flowers occurred only inF. excelsior.

ISSN:0017-3134    

DOI:10.1080/00173139809362672

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Many palynological investigations require the comparison of large collections of samples and here the optimization of the effort is crucial. A method to determine the pollen sum according to the intrinsic characteristics of the site pollen composition is proposed. Different variables such as pollen spectra, typological lists, richness, diversity, intra‐ and inter‐sites affinities, are alternatively analyzed in order to determine the minimum sample size and the results are compared. An example of this methodology is developed for the airborne pollen from an agroecosystem in the Pampean grasslands. Increasing pollen counts from 150 to above 2700 does not yield different results among the dominant and subdominant types, which account for 70%‐80% of the pollen sum. Both diversity estimates and similarity among sites are not significantly affected when quantitative coefficients are employed. As pollen counts increase, there is an increment in the number of types, but the types added with counts over 150 are always rare, their overall relative frequency never exceeding 6%. The minimum sample size obtained as shown here provides the necessary information to reconstruct the major pollen fraction of the site and it provides reliable estimates of the typologie diversity and the affinities among sites.

ISSN:0017-3134    

DOI:10.1080/00173139809362673

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A continuous sampling of airspora in Singapore was carried out over a period of 5 years at 3 different sites. Fungal spores were found to be numerically dominant, comprising between 86.0–89.4% of the total airspora which also consisted of spores of fern and pollen grains. Conidia ofCladosporiumwere the most abundant fungal spore type, followed by the ascospores ofDidymosphaeriaand the conidia ofCurvularia, DrechsleraandPithomyces.Variations in fungal spore counts were discernible. Two periods of high spore densities were observed annually; in the months of February‐March, and October‐November. Minor peak periods were observed occasionally in April and July‐August. The seasonal trends of the 5 most common fungi generally coincided with these same peak periods for spore counts. Correlation analysis showed that fungal spore counts were influenced by meteorological factors, especially temperature and relative humidity. In particular,Didymosphaeriaascospore counts were positively correlated with relative humidity and total daily rainfall, and inversely correlated with temperature and wind speed. Conversely,Curvularia, DrechsleraandPithomycesspore counts decreased with increases in relative humidity and precipitation. The spore counts ofCurvulariaandCladosporiumwere also positively correlated with temperature, while those ofDrechslerawere positively correlated with wind speed. This study revealed the existence of a rich fungal airspora in Singapore.

ISSN:0017-3134    

DOI:10.1080/00173139809362674

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In the course of an aerobiological survey of Kerala State, India, using a Rotorod sampler, four spores in one sample collected at Palode, Thiruvananthapuram district were identified as ascospores of a member of the Meliolaceae. These occurred in only very small concentrations (0.93 spores m−3air). Meliolaceae ascospores are formed in ascomata, although these may develop an irregular ostiole and their dispersal mechanism has not been determined. The role of airborne spores in enabling dispersal of the fungus in forests and grasslands is discussed in relation to previous hypotheses of rain splash and insect dispersal.

ISSN:0017-3134    

DOI:10.1080/00173139809362675

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0017-3134    

DOI:10.1080/00173139809362666

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor