Distribution of several morphologic pollen types of the Cretaceous angiosperms

Records of monosulcate, polychotomosulcate, tricolpate, tricolporate, polyporate, triporate and peculiar types of angiosperm pollen are considered from Cretaceous deposits of the U.S.S.R., West Canada, Australia, Europe, the Atlantic coastal plain of the U.S.A. and Equatorial Africa. One can see morphological similarities of the earliest pollen types from different geographical regions in contrast to later polyporate, triporate and peculiar pollen.Provincialism of the Cretaceous flora is revealed by the early monosulcate and tricolpate pollen types which make their first appearance at different stratigraphical levels and by the endemic later polyporate, triporate and peculiar ones.     

Morphological and ultrastructural diversity of orbicules in Gentianaceae

Minute granules of sporopollenin, called orbicules, can be observed on the innermost tangential and/or radial walls of secretory tapetum cells. Orbicules were investigated in 53 species of 34 Gentianaceae genera using light microscopy, scanning electron microscopy and transmission electron microscopy. This selection covered all different tribes and subtribes recognized in Gentianaceae (87 genera, +/-1650 species). Orbicules were found in 38 species (23 genera) distributed among the six tribes recognized in Gentianaceae. The orbicule typology is based on those described previously in Rubiaceae. Of the six orbicule types described previously, Type II orbicules are lacking. Type III orbicules are most common (17 species). Hockinia Gardner is the only representative with Type I orbicules. The number of representatives with orbicules belonging to the other orbicule types are equally distributed among the species studied: seven species possess Type IV orbicules, six species Type V and six species Type VI. The systematic usefulness of this typology is discussed in comparison with the latest systematic insights within the family, and palynological trends in Gentianaceae. Orbicule data have proven to be useful for evaluating tribal delimitation within Rubiaceae and Loganiaceae s.l.; however, they seem not to be useful for tribal delimitation in Gentianaceae. In the tribes Potalieae and Gentianeae orbicule data may be useful at subtribal level.     

A survey of anthocyanins in fruits of some angiosperms,II

Anthocyanins in the fruits of 41 species belonging to 25 families were investigated paper-chromatographically. Fifteen kinds of anthocyanins, in addition to the previous findings, were newly identified. In addition to cyanidin 3-monoglucoside as the most common anthocyanin, the 3-rutinoside and the 3-sambubioside were found in the fruits with high frequency.     

A survey of anthocyanins in fruits of some angiosperms,I

The anthocyanin pigments in the fruits of fifty-two species belonging to seventeen families of angiosperms were investigated paper-chromatographicallly. They were identified as cyanidin 3-monoglucoside, pelargonidin 3-monoglucoside, cyanidin 3-rutinoside, pelargonidin 3-rutinoside, cyanidin 3-xylosylglucoside, cyanidin 3-xylosylgalactoside, delphinidin 3-xylosylglucoside and delphinidin 3-sophorosido-5-monoglucoside. Of those anthocyanins detected, the most common was cyanidin 3-monoglucoside. In general, the plants belonging to a certain genus contained the same anthocyanin.     

Oil bodies in leaf mesophyll cells of angiosperms: overview and a selected survey

Neutral (storage) oil bodies occur in leaf mesophyll cells of many angiosperms, but their literature has been largely forgotten. We review this literature and provide a survey of 302 species and hybrids from mostly north-central US species representing 113 families. Freehand cross sections of fresh leaves stained with Sudan IV verified the presence of oil. In 71 species from 24 families we observed 1-15 oil bodies per mesophyll cell. The eudicot families Asteraceae, Caprifoliaceae, Lamiaceae, and Rosaceae had the highest number of species with oil bodies, whereas few or no species in the Apiaceae, Betulaceae, Fabaceae, and Scrophulariaceae had them. Only three of 19 monocot species sampled had oil bodies. Repeat sampling of a Malus (crabapple) cultivar and a Euonymus species showed conspicuous oil bodies in mid-summer and also in mid-autumn in both attached and recently shed leaves. Oil bodies in leaf mesophyll cells are conspicuous (visible in hand cross sections using moderate magnification in unstained water mounts) in numerous species, and they occur throughout the growing season in at least some species. Neutral oil bodies in leaf mesophyll cells are not mentioned in contemporary textbooks and advanced works, but they deserve recognition as significant cellular components of many taxa, in which they may be significant sources of commercial oils.     

Morphology and ultrastructure of orbicules in the subfamily Ixoroideae (Rubiaceae)

Orbicules were studied in 43 species belonging to 32 genera of the five tribes of the Ixoroideae (Rubiaceae). The orbicules were investigated with scanning electron microscopy (SEM), light microscopy (LM), and transmission electron microscopy (TEM). Orbicules are present in all species investigated of the tribes Pavetteae, Octotropideae and Coffeeae. In the tribes Gardenieae and Aulacocalyceae orbicules were found in some species, while they were absent in others. 15 species out of 11 genera lack orbicules. Three orbicule types (III, V, and VI) could be distinguished, mainly on the basis of general morphological and ultrastructural variations. Orbicules that belong to type III (0.50-1.29μm) have perforations in their wall, a regular or irregular shape and two or three electron transparent cores. This orbicule type, exclusively found in all Pavetteae species investigated, can be divided into two subtypes. Orbicules of subtype IIIa are present in all genera related to Ixora, and orbicules of subtype IIIb in those genera related to Tarenna. Orbicules of type V (0.97-1.86μm) are present in Himalrandia tetrasperma (Aulacocalyceae), and in all Octotropideae genera investigated, except Feretia. Complexes of more than three individual orbicules characterize this type. They are irregularly shaped and have many perforations as well as sporopollenin granules on the orbicule wall. In all species investigated of tribe Coffeeae, type VI orbicules (0.56-1.60μm) are present. These orbicules are characterized by their embedded position towards the tapetal membrane, their aggregated form and by the presence of perforations as well as sporopollenin granules on their orbicule wall. In the tribe Gardenieae different types of orbicule were found (V, VI and orbicules that cannot be classified in our typology). Our results suggest that orbicule characters in the Ixoroideae may be systematically useful on tribal level.     

Morphology of pollen and orbicules in some Dioscorea species and its systematic implications

Pollen and orbicule morphology of 35 Dioscorea L. species is described based on observations with light microscopy, and scanning and transmission electron microscopy. Pollen and orbicule characters are critically evaluated and discussed in the context of existing hypotheses of systematic relationships within the genus. Pollen is mostly bisulcate (sometimes monosulcate) with a perforate, microreticulate or striate sexine. Our results indicate that pollen data may be significant at sectional rank. The close relationship between sections Asterotricha and Enantiophyllum proposed by Burkill and Ayensu is supported by pollen morphology as all species investigated share bisulcate, perforate pollen with small perforations and a high perforation density. Macromorphological differences between the two compound-leaved sections Botryosicyos and Lasiophyton are also supported by pollen morphology; pollens of these two sections have very different perforation patterns. Orbicules in Dioscorea are mostly spherical and possess a smooth or spinulose surface. The latter is often correlated with a striate sexine.     

Incompatibility in angiosperms

 Since Darwinian times considerable knowledge has accumulated on the distribution, physiology and genetics of self-incompatibility (SI) in higher plants. In the second half of this century the first attempts were made to identify the biochemical bases of SI. These included thediscovery that cutinase enables pollen tube penetration at the surface* of the stigma in Cruciferae, sorting of segregation pollen S-phenotypes by serological techniques, a lock-and-key model of the SI reaction, the first detection and characterisation of SI proteins and the discovery of the role of the tapetum in the determination of pollen phenotypes in homomorphic sporophytic SI. This pioneering work was followed by a worldwide effort to identify and understand the cellular and molecular processes which lead to the recognition and rejection of SI pollen. The present review article summarizes briefly the current state of knowledge in areas essential for the understanding and exploitation of SI and outlines new information that has become available during recent years. Received: 14 March 1997 / Revision accepted: 10 June 1997     

Dichogamy in angiosperms

We obtained information on dichogamy and other aspects of the biology of over 4200 species of angiosperms from several hundred published and unpublished sources. We used this information to describe patterns of occurrence of dichogamy and to test specific hypotheses relating dichogamy to other characteristics of plants or their environments. Protandry was more common than protogyny at the intrafloral level, but the reverse was true at the interfloral level. Patterns of dichogamy varied significantly among major taxa, with protogyny more common among monocotyledons and primitive dicotyledons, and protandry expecially common in the Asteridae. Arctic species tended to be less dichogamous and more protogynous than temperate and tropical species. Aquatic and alpine species were especially protogynous. Patterns of dichogamy varied among sexual systems, with gynomonoecious and gynodioecious species especially protandrous, and monoecious species highly protogynous. Autogamous and self-compatible species were disproportionately protogynous. Flowers of intraflorally dichogamous species were slightly larger than those of adichogamous species, owing to the presence of many autogamous species in the latter group. Species with interfloral protogyny bore much smaller flowers than did species with interfloral protandry. Early-blooming species in north-temperate and polar regions were disproportionately protogynous. Sexual structures that abscised, shriveled or moved after completion of their function tended to be presented first, and those that facilitated the other sexual function were presented second. A negative association existed between type of intrafloral and interfloral dichogamy in diclinous species. Most animal-pollinated flowers were protandrous, except beetle-pollinated and refuge and trap blossoms. Wind pollination was markedly associated with protogyny. Vertical inflorescences visited by upwardly-moving vectors were protandrous.     

A 2-year aeropalynological survey of allergenic pollen in the atmosphere of Kastamonu, Turkey

Knowledge of airborne pollen concentrations and the weather conditions influencing them is important for air quality forecasters, allergists and allergy sufferers. For this reason, a 7-day recording volumetric spore trap of the Hirst design was used for pollen monitoring between January 2006 and December 2007 in Kastamonu, Turkey. A total of 293,427 pollen grains belonging to 51 taxa were recorded during the study period. In the 2?years of study, the period March–August was identified as the main pollination season for Kastamonu. The highest monthly pollen counts were observed in May in both years. Six taxa made up 86.5% of the total amount of pollen recorded in the atmosphere of Kastamonu. These were as follows: Pinaceae (42.9%), Cupressaceae (20.6%), Poaceae (9.7%), Quercus (5.5%) Betula (5.3%) and Carpinus (2.6%). Four of these are considered to be highly allergenic (Betula, Carpinus, Cupressaceae and Poaceae). There were also a greater percentage of highly allergenic taxa found within the city, including Betula pendula that is not part of the local flora. This shows that through urban planting, the public and municipalities can unconsciously create a high risk for allergy sufferers. Daily average pollen counts from the six most frequently recorded pollen types were entered into Spearman’s correlation analysis with meteorological data. Mean daily temperature, relative humidity, daily rainfall and wind speed were found to significantly (p?<?0.05) affect atmospheric pollen concentrations, but the relationships between pollen concentrations and meteorological variables can vary and so there is a need for more local studies of this nature.     

Stomatal patterning in angiosperms

My thesis is that understanding stomatal patterning requires a holistic perspective. Since stomata are structures critical to the survival of terrestrial plants, they need to be viewed in relation to their function and their interface with other structural components. With this outlook, I begin by discussing pattern types, means of measuring them, advantages of each type of measurement, and then present patterning from evolutionary, physiological, ecological, and organ views. I suggest areas where I believe profitable studies might enable us to better understand stomatal patterning. The final sections of the paper review stomatal patterning on angiosperm leaves and present a theory of patterning. With the abundance of molecular information, and coming genomic sequences and new tools, an opportunity exists to dissect the process of how cells are selected to become different from their neighbors and assume a fate critical to plant survival. Understanding this biological process at the molecular level requires comprehending the broad base on which stomatal patterning rests.     

Late-acting self-incompatibility in angiosperms

In most self-incompatible (SI) plants, pollen tube growth in self-pollinated flowers is inhibited on the stigma or in the style. SI systems that operate in the ovary have been assumed to be extremely rare. Evidence from many plant species is presented to show that the SI barriers in the ovary, described here as late-acting SI systems, are quite common. The late-acting SI systems are divided into four categories: (1) ovarian inhibition of incompatible pollen tubes before the ovule is reached; (2) prefertilization inhibition in the ovule; (3) post-zygotic rejection of the embryo, and (4) ovular inhibition for which the cytological details have not been established. Whether or not post-zygotic incompatibility systems can be distinguished from inbreeding depression depends upon the assumptions underlying the genetic models of self-incompatibility. However, four approaches are outlined that could distinguish between active uniform rejections that are presumably evolved responses to inbreeding depression and the passive, variable failures that are commonly understood to be expressions of typical inbreeding depression. Possible advantages of late-acting SI include an extended period of time over which pollen genotypes may be evaluated by the maternal parent and greater flexibility in the choice of male parents. Due to a paucity of data regarding the genetics and physiology of lateacting SI systems, little can be said at this time about the possible diversity of such systems of their evolutionary relationships with classical gametophytic and sporophytic SI. An hypothesis for the operation of post-zygotic SI is described whereby maternal resources to developing embryos are terminated if the embryo (and/or endosperm) fall below a threshold level of heterosis. This hypothesis is a modification of one first proposed by Westoby and Rice in 1982 to explain variable maternal resource allocation to developing embryos.     

Anther plastids in angiosperms

In the anther of angiosperms, all types of plastids are found in the course of pollen development. They are located in the different cell layers of the microsporangium and have various functions that contribute to the formation of the functional male gametophyte. This includes photosynthesis, stomata opening, sugar storage and/or mobilization, lipid synthesis and secretion for pollenkitt formation, as well as serving as a physiological buffer under stress conditions. They are also involved in plastid inheritance, but to different extents, according to the species. The plastid is a semi-autonomous organelle. Plastid division in the anther is synchronous with cell division, except in the vegetative cell during pollen maturation. Furthermore, recent data seem to show that plastids are affected by programmed cell death and DNA degradation, which occur in the whole anther throughout pollen development. However, the timing of plastid disappearance fluctuates in the different cell layers and also depending on species. In vitro, following androgenesis, plastids that originate in the microspore are responsible for the occurrence of albino plantlets in Poaceae. This trait reflects the relative independence of the plastid genome when compared with that of the nucleus. In this family, microspore plastids may become so involved in programmed cell death that they are unable to follow the alternative sporopohytic program. The different pathways of plastid differentiation in neighboring anther cell layers require an accurate regulation of cell development that remains widely unknown in the anther.