Pollen morphology of the tribes Eritrichieae and Cynoglosseae (Boraginaceae) in the Iberian Peninsula and its taxonomic significance

DÍEZ, M. J. & VALDÉS, B., 1991. Pollen morphology of the tribes Eritrichieae and Cynoglosseae (Boraginaceae) in the Iberian Peninsula and its taxonomic significance.
The pollen morphology of 33 species of Boraginaceae from the Iberian Peninsula belonging to the tribes Eritrichieae and Cynoglosseae has been studied by light and scanning electron microscopy. The results confirm the eurypalinous character of this family, in which a large number of species can be recognized by their pollen characters.
The pollen of these two tribes is basically heterocolpate, a type which is very uncommon in the angiosperms, with 6, 8 or 10 apertures, sometimes with ectoapertures anastomosed at the equator (ectocingulum), or diorate, minute or small in size, outline elliptic or rectangular-elliptic in equatorial view, with or without a constriction at the equator, exine 0.5-1.0 urn thick and the tectum psilate with granules around the colpi. The similarity in shape and apertural system found in several genera such as Asperugo, Gyrocarion and Omphalodes, and some species of Myosotis, does not permit the two tribes to be distinguished on pollen characters. The generic limits of Cynoglossum and the infrageneric classification of Myosotis are discussed.     

A phylogenetic analysis of morphological and molecular characters of Boraginaceae: evolutionary relationships,taxonomy, and patterns of character evolution

The angiosperm family Boraginaceae includes ca. 1600 species distributed among ca. 110 genera. Some floral features are constant within the family, but many vegetative, floral, pollen, and nutlet traits vary. Utilizing 224 species of Boraginaceae and related taxa, five matrices were constructed with various combinations of morphological characters, three chloroplast DNA regions, and one nuclear ribosomal DNA region. Phylogenetic analyses were conducted for these matrices, and patterns of character evolution were examined. Boraginaceae is resolved as monophyletic, with Wellstedia as its sister. Codon is sister to Boraginaceae + Wellstedia. Although most of the investigated morphological characters have a low consistency index, particular character states are synapomorphies for large clades in each of the tribes of the family. In Boraginaceae, the breeding system heterostyly evolved at least 12 times, which is the largest number of origins resolved in any family; therefore Boraginaceae can serve as a model for the evolution and development of heterostyly. Nutlet ornamentation is most diverse in Cynoglosseae and Trichodesmeae, while pollen and floral features are most variable in Boragineae and Lithospermeae. Phylogenetic relationships and patterns of character evolution identified in the present study set the stage for future work creating an updated taxonomic system of Boraginaceae.     

Pollen Morphology of Xyridaceae Systematic (Poales) and its Potential

Xyridaceae are a predominantly tropical family of five genera that exhibit two pollen morphologies often considered to be of taxonomic importance. Xyris comprises about 95% of the species and is characterized by medium to large, elliptic, sulcate pollen grains. The other pollen class is spheroidal grains without an evident aperture. Many of the species with spheroidal grains have remarkably large and ornamented pollen found to be species specific in earlier research. A scanning electron microscopy investigation of 23 taxa representing all genera with spheroidal pollen revealed new data to further distinguish the genera based on pollen characters. Reliable specific pollen characters need to be evaluated in a statistical study.     

桦木科植物花柱适应风媒传粉的特征

植物体为适应自己的传粉系统, 表现出高度的适应特征。风媒花植物为适应风传播花粉, 要形成特殊的结构, 以扩大接受花粉粒的面积。利用扫描电镜观察了桦木科(Betulaceae)6属18种植物花柱的形态及花粉粒在花柱上的萌发过程, 探讨了桦木科植物花柱适应风媒传粉的特征。结果表明, 桦木科植物的二心皮(铁木、云南鹅耳枥稀为三心皮)雌蕊具柱状花柱, 柱头不发达, 花柱表皮细胞长条状, 纵向排列紧密。传粉时, 花柱表皮细胞能执行柱头的功能, 接受花粉粒, 为花粉粒萌发提供场所和萌发条件。桦木科植物花柱有2种类型: 一种是花柱表皮细胞能形成乳突, 花粉管经乳突细胞进入花柱; 另一种是花柱表皮细胞不形成乳突, 花粉管经过花柱表皮细胞或胞间隙进入花柱。无论花柱表皮细胞是否形成乳突, 乳突的形态、大小以及花粉管和乳突的结合方式等在族间、属间、属内种间存在差异。与基部被子植物相比, 桦木科植物的花柱呈现适应风媒传粉的进化特征。桦木科植物花柱表皮细胞形成的乳突与基部被子植物柱头乳突功能相同, 是桦木科植物风媒传粉的适应策略。     

Stigma form and surface in relation to self-incompatibility in the Onagraceae

The Onagraceae is unique among families of comparable size in the heterogeneity of stigma form and physiology. Studies of the receptive surfaces of stigmas from representatives of all genera of the family have shown that a range of types exists from papillate to non-papillate, and from "wet", bearing a free-running secretion, to "dry", lacking such a secretion, most genera falling in the former category. Self-incompatibility is wholly restricted to wet-stigma species, and direct and circumstantial evidence indicates that it is always likely to be of the gametophytic type, as in certain Oenothera species that have been the subjects of detailed genetical and physiological research. Whilst Oenothera and most other self-incompatible species in the family appear to reject incompatible pollen mainly in the stigma surface layers, the precise site is subject to both genetical and environmentally-determined variation. Intraspecific polymorphy in sex function is known in the genus Fuchsia , most species of which have wet stigmas. Female sterility in the functionally male flowers of certain species of this genus appears simply to be due to a failure to produce adequate stigma secretion. All species of the dry-stigma genera in the family are self-compatible, but not all are inbreeding because of the existence of other mechanisms enforcing outcrossing. The stigmas of some possess certain unique features, apparently related to water conservation. Possible evolutionary trends in the family and in the breeding and pollination systems are briefly discussed in the light of what is now known of pollen-stigma relationships.     

Structural analysis of stigma development in relation with pollen–stigma interaction in sunflower

Structural analysis of stigma development in sunflower highlights the secretory role of papillae due to its semi-dry nature. Production of lipid-rich secretions is initiated at the staminate stage of the flowers in stigma development and increases at the receptive stage, coinciding with an extensive development of elaioplasts and endoplasmic reticulum network in the basal region of the papillae. Transfer cells, earlier identified only in the wet type of stigma, are also present in the transmitting tissue of the sunflower stigma. Attainment of physiological maturity by the stigmatic tissue, accompanying development from bud to pistillate stage, appears to affect the initial steps of pollen–stigma interaction. The nature of self-incompatibility in Helianthus has also been investigated in relation with pollen adhesion, hydration and germination. Pollen adhesion to the stigma is a rapid process in sunflower and stigma papillae exhibit greater affinity for pollen during cross pollination as compared to self-pollination. Components of the pollen coat and the pellicle on the surface of stigmatic papillae are critical for the initial phase of pollen–stigma interaction (adhesion and hydration). The lipidic components of pollen coat and the proteinaceous and lipidic components from the surface of the papillae coalesce during adhesion, leading to the movement of water from stigma to the pollen, thereby causing pollen hydration and its subsequent germination. Pollen germination (both in self-and cross-pollen) on the stigma surface and the growth of the pollen tube characterize the flexibility of self-incompatibility in sunflower. Compatible pollen grains germinate and the pollen tube penetrates the stigma surface to enter the nutrient-rich transmitting tissue. The pollen tube from incompatible pollen germination, however, fails to penetrate the stigmatic tissue and it grows parallel to the papillae. Present findings provide new insights into structural and functional relationships during stigma development and pollen–stigma interaction.     

POLLEN-PISTIL INTERACTIONS IN TRISTYLOUS PONTEDERIA SAGITTATA (PONTEDERIACEAE). I. FLORAL HETEROMORPHISM AND STRUCTURAL FEATURES OF THE POLLEN TUBE PATHWAY

Heteromorphic characters and structural features of the pollen tube pathway are described in tristylous Pontederia sagittata to assess their influence on the pollination process and in mediating self-incompatibility behavior. Heteromorphic characters that distinguish the floral morphs include style length, stigma depth, stigmatic papillae length, stylar parenchyma cell length, area of the stylar canal, stamen height, anther size, and pollen size. Unlike several distylous species that have been investigated, the exine of pollen in P. sagittata was not strongly differentiated among the pollen types, and no differences in stigma cytochemistry were apparent. Features common to the floral morphs were a wet stigma, a hollow trilobed stylar canal separating into two sterile and one fertile canal, and a single anatropous ovule with a highly elaborated integumentary obturator. The similarity in structural features of the pollen tube pathway of P. sagittata to those found in monocotyledonous taxa with gametophytic self-incompatibility suggests that phylogenetic constraints may have influenced the evolution of trimorphic incompatibility in the Pontederiaceae.     

Pollen presenters in the flowering plants–form and function

Pollen presenters are specific floral structures, other than anthers, from which pollen is distributed for cross fertilization between flowers. They occur in only five families of monocotyledons and 20 families of the dicotyledons. Presenters in 15 families are described here. In the largest plant family (Asteraceae) all taxa have pollen presenters, while in others (e.g. Myrtaceae) they occur in only some species in a few genera. Most presenters are associated with the gynoecium and there is a wide range of forms involving hairs or outgrowths of the stylar tissue. Despite the placement of self pollen close to the stigma most taxa are outcrossing and avoid self fertilization by protandry, with the stigma being covered at anthesis, or by precise placement of pollen so that is does not contact the stigma. Likely selective advantages in the development of pollen presenters include greater accuracy in pollen transfer than in the normal anther to stigma movement and avoidance of interference between male and female organs in the flower. In some groups there is enhanced ability for female choice because effective pollen delivery enables a choice from among many pollen grains, while in others pollen presenters enhance male reproductive success. Study of the pollination biology of plants requires a knowledge of which plants have pollen presenters and a full understanding of the structures in the flower which are associated with the pollen presentation action.     

The Pollen-stigma Interaction: Pollen-tube Penetration in Crocus

In a compatible pollination in Crocus, pollen tube tips enterthe stigma papillae after the enzymic erosion of the cuticle,and the tubes continue downward growth towards the ovary betweenthe cuticle and the underlying pectocellulosic wall. The cuticleof the receptive zone of the stigma papilla is chambered, thechambers containing a secretion accumulated during the maturationof the stigma. Pollen exudates contain various acid hydrolases,but are incapable alone of eroding stigma cutin. Furthermore,there is no penetration when the proteins of the wall-held stigmasecretions are degraded enzymically. These facts are taken toindicate that the pollen contributes a ‘cutinase’precursor which is activated by a factor or factors held inthe stigma secretion. Pollens of certain Cruciferae producetubes capable of penetrating the Crocus stigma cuticle, suggestingthat notwithstanding the taxonomic remoteness of Cruciferaeand Iridaceae the enzyme activation systems are quite similar.     

THE TRANSMITTING TRACT IN GLADIOLUS. I. THE STIGMA AND THE POLLEN-STIGMA INTERACTION

The stigma papillae in Gladiolus are of the “dry” type and are highly vacuolated cells with an organelle-rich peripheral cytoplasm. The cell wall of each papilla is overlain by a distinctive cuticle possessing an irregularly scalloped inner margin. Between the cell wall and cuticle is a layer of amorphous sub-cuticular material. Lipids are detected on the papilla surface. A pollen grain will hydrate and germinate only on a papilla and not on any other (non-papillate) portion of the stigma. The pollen tube penetrates the papilla cuticle, which is forced away from the papilla cell wall by sub-cuticular pollen tube growth. As the cuticle lifts away, the sub-cuticular material disperses. At the base of the papilla, the pollen tube grows onto the adaxial non-papillate surface of the stigma lobe. At this site, the cuticle has been lifted away from the underlying cells by release of a mucilaginous substance from the latter, and the pollen tube grows within this substance beneath the detached cuticle. The cytological features of Gladiolus papillae are compared with other stigma papillae described in the literature. Also, a review of the literature, as well as some of the findings of the present study, suggest that certain prevalent interpretations of dry stigma structure and function may be open to question.     

Early history of theJuglandaceae

The major radiation of theJuglandaceae occurred during the early Tertiary as recorded by the proliferation of juglandaceous pollen and the appearance of fruits representing extinct and extant genera of the family. Juglandaceous pollen types of the Paleocene were predominantly triporate and exhibited a greater diversity in patterns of exinous thinning than occurs in the family today. Analyses of in situ pollen from early Tertiary juglandaceous inflorescences confirms the taxonomic value of certain patterns of exinous thinning. Data from co-occurring fruits and pollen indicate that relatively unspecialized, isopolar triporate pollen of the type presently confined to the tribeEngelhardieae also occurred in other tribes of the family during the Paleocene. Pollination has been mostly anemophilous throughout the Tertiary. Both wind and animal fruit-dispersal syndromes were established early in the radiation of the family but a greater diversity of wind-dispersed genera has prevailed.     

Pollen morphology of some species belonging to Codonoprasum and Allium sections of Allium (Liliaceae-Alliaceae) genus

Pollen morphology of 14 Allium L. species grown in Turkey, that belong to the sections Codonoprasum and Allium, were investigated under LM (light microscopy) and by SEM (scanning electron microscopy). However, the pollens of 5 species were investigated under TEM (transmission electron microscopy). Detailed pollen morphological characteristics are given for Allium in the family on the basis of the results presented here together with data from the literature. The genera Allium homogeneous in both aperture type and exine ornamentation. It is suggested that some palynological characters, such as aperture type and the presence of an operculum, could be of taxonomic value at the section level.     

The stigmatic orifice in Cassia,Senna, and Chamaecrista (Caesalpiniaceae): morphological variation,function during pollination,and possible adaptive significance

In species of Cassia, Senna, and Chamaecrista an orifice leading into a stigmatic cavity is present at the tip of the style. The size of the orifice, the occurrence and morphology of surrounding trichomes or papillae, and the occurrence of a drop of secretion at its outlet were recorded in 17 species belonging to the three genera of the subtribe Cassiinae. Much of the observed variation in these characters apparently reflects different modes of pollen capturing and varying degrees of secretion exposure. In some of the species studied no secretion was noticeable at the entrance to the stigmatic cavity. The unusual type of stigma in the Cassiinae does not fit into any of the recognized main groups of angiosperm stigmas. It is conjectured that in the buzz-pollinated Cassiinae species with small stigmatic orifices, the secretory material is retained within the stigmatic cavity, to be extruded by vibratory movements of the style induced by a buzzing bee. It is also hypothesized that in the wet tropics, concealment of secretory materials within a cavity prevents their washing away or dilution by rain. Furthermore, in the Cassiinae, the considerable variation in features of the style and of the stigma may function as mechanisms isolating between sympatric, visitor-sharing, concurrently blooming species.     

Caractères ultrastructuraux du pollen de quelques Podostémales. Affinités avec les Rosidae évoluées

The order Podostemales are two pantropical families of aquatic plants living in running water: Tristichaceae (five genera, ten species) and Podostemaceae (35 genera, 200 species). Pollen of the 26 genera and 62 species studied is characterized by: a granular infratectum in which the granules are sometimes organized as columellae like units, and a lamellar and/or granular endexine in all pollen types, single or in dyads. Most of the apertural characters and the ornamentation of the exine allow us to distinguish the previously established taxonomic groups: Weddellinoideae have tricolporate rugulo-areolate, pollen with a smooth apertural membrane; in Tristichoideae, pollen is periporate and the microspines of the tectum and of the apertural membrane are massive; in Podostemaceae, the tectal spines with their broad bulbous base are formed from numerous masses of sporopollenin, the endexine is microfibrillar at the base, the apertural membrane is constituted of structured ectexinous masses, and the endexine is granular at the aperture. Presence of the tricolporate pollen type associates the Podostemales with the higher eudicotyledons. Most of the pollen characters of Podostemales and their variations are found among advanced Rosidae (Hamamelidales, Polygalales, Santalales, Violales, Euphorbiaceae).     

Stigma morphology in distylous and non-heterostylous species ofVillarsia (Menyanthaceae)

Stigma morphology was examined with the SEM in 14 of the 16 species ofVillarsia. In nine of the ten distylous species studied, stigmas of the floral morphs were strongly dimorphic in length, shape, configuration of the receptive surface, and in the size and density of their papillae. Thrum stigmas ofVillarsia, in contrast to those of most other distylous species, are not simply smaller versions of the conspecific pin stigmas, but generally exhibit an array of morph-specific characters. Thrum stigma lobes may be broader than those of pins, they may have undulate margins, lobes subdivided into secondary lobes, papillae more extensively distributed than in pins, and various combinations of these traits occur. The traits that distinguish thrum from pin stigmas achieve an increase in the receptive area and may enhance more efficient pollen capture by the shorter and less accessible thrum stigmas. The morphogenesis of the stigma shape dimorphism appears to involve processes more complex than inhibition of elongation in thrum styles. InVillarsia, the stigma dimorphisms are species-specific. No correlations were found between morphologies of the stigma and the different breeding systems in distylous species. Stigmas of the four non-heterostylous species examined resemble the thrum stigma type found in most distylousVillarsia species.     

Flower morphology and pollen germination in the genus Capsella (Brassicaceae)

Evolutive changes in mating systems are often accompanied by changes in flower morphology, such as the reduction in size or even loss of petals, changes in production of volatiles, pollen/ovule ratio, the position between anthers and stigma and the germination time of pollen after pollination. These changes have been merged under the term “selfing syndrome” and often result in new taxonomic species. The evolutionary shift frequently happens parallel within many families and genera, for example within the Brassicaceae family. Within the genus Capsella, which is closely related to the molecular model species pair Arabidopsis lyrata (SI)/A. thaliana (SC), we studied self-incompatible and self-compatible species. SC species C. rubella and C. bursa-pastoris produce in comparison with the SI species C. grandiflora (i) smaller petals as the result of decreased cell division and only less of decreasing cell volume, (ii) less production of pollen in one flower, (iii) show a lesser incision between the two valves of the fruits, in combination with a shorter style, and (iv) have a much quicker fertilization of SC pollen after pollination. Crossing success between the diploid species, between different provenances of the tetraploid C. bursa-pastoris, and between the two diploid species and particular individuals of the self-incompatible C. grandiflora has been proven.     

丛藓科植物叶细胞疣和乳突的光镜观察及其分类学意义

选择中国丛藓科中具有代表性的4亚科、11属、13种,利用光学显微镜对其叶细胞的疣和乳突进行形态、大小、数量、疏密及形成等方面的观察和比较,为探讨并确定丛藓科中部分物种的系统位置提供依据。结果表明:中国丛藓科13个种植物的叶细胞疣和乳突在形态上主要分为圆疣、分叉疣和乳头状突起共3个类型,不同物种的疣和乳突在形态特征和分布上都存在一定程度的差异;通过对不同资料相应物种疣和乳突描述的比较,纠正了一些物种疣和乳突的描述错误,并提出疣和乳突的区分方法:观察叶片横切,疣是细胞壁的局部加厚或凸起,数量变化较大,而乳突是细胞壁和腔整体的膨起,每细胞仅具一个乳突。研究认为,疣和乳突是丛藓科物种叶细胞表面的稳定结构,具有重要的辅助分类功能,可利用其差异对丛藓科属间和种间的物种进行划分。     

ANATOMY AS AN AID TO CLASSIFYING THE CYPERACEAE

During a period of about 10 years the systematic anatomy of the vegetative organs of more than 280 species belonging to 90 genera of the taxonomically complex family Cyperaceae have been examined, some of them for the first time. Abstracts of about 250 published articles relating to the anatomy of the Cyperaceae have also been prepared. The combined results of this investigation and literature survey are to appear as Vol. 5 of a reference book entitled Anatomy of the Monocotyledons. In the present article particulars are given of the anatomical characters which have proved to be among the most important as an aid in classifying the tribes and genera within the family. Special attention has been devoted to silica-bodies in surface-view preparations of the leaf epidermis. In transverse sections of the lamina, the relationship between genera and species in which there are dorsiventral, isobilateral, pseudodorsiventral, and cylindrical leaves, respectively, appears to be of special interest. Selected conclusions concerning the affinities between tribes and between certain genera and the tribes to which they belong within the Cyperaceae are presented. The relationship of the Cyperaceae to other families is briefly discussed.     

The family classification of the Anoplura

Fifteen families of Anoplura are recognized and defined, one with two sub-families, and a key is provided for their identification. The included genera are listed for each family, together with the relevant type-species as well as the mammalian hosts. Phylogenetic relationships between the families are discussed, and an extensive historical review and analysis of the available taxonomic characters is presented.