Comparative morphology of leaf epidermis in the Chloranthaceae

Leaf epidermis of 23 samples representing 16 species of all the four extant genera of the Chloranthaceae, i.e. Sarcandra, Chloranthus, Ascarina and Hedyosmum , were investigated under both light microscope and scanning electron microscope. Characters of leaf epidermis in this family, such as pattern of epidermal cells, type of stomata, shape of guard cell pairs and cuticular ornamentation, are usually constant in species and thus of great significance in understanding the relationships between and within genera. The previous viewpoints with either Hedyosmum or Chloranthus shown as having the closest affinity with Ascarina seem to be unreasonable. The phylogeny indicated by DNA sequence analysis, which suggested that Ascarina be the sister group of Sarcandra and Chloranthus , and Hedyosmum the sister of the above three genera, is well supported. Within Chloranthus , the traditional division of the genus on the basis of habit seems to be quite unnatural. Evidence from leaf epidermis, just as that from stem anatomy and cytology as well as sequence analysis of ITS region, strongly suggests the separation of the genus into two groups according to the characteristics of androecial organs.     

Anti-herbivore structures of Paulownia tomentosa: morphology, distribution, chemical constituents and changes during shoot and leaf development

Background and Aims: Recent studies have shown that small structures on plant surfacesserve ecological functions such as resistance against herbivores.The morphology, distribution, chemical composition and changesduring shoot and leaf development of such small structures wereexamined on Paulownia tomentosa. Methods: The morphology and distribution of the structures were studiedunder light microscopy, and their chemical composition was analysedusing thin-layer chromatography and high-performance liquidchromatography. To further investigate the function of thesestructures, several simple field experiments and observationswere also conducted. Key Results: Three types of small structures on P. tomentosa were investigated:bowl-shaped organs, glandular hairs and dendritic trichomes.The bowl-shaped organs were densely aggregated on the leavesnear flower buds and were determined to be extrafloral nectarines(EFNs) that secrete sugar and attract ants. Nectar productionof these organs was increased by artificial damage to the leaves,suggesting an anti-herbivore function through symbiosis withants. Glandular hairs were found on the surfaces of young and/orreproductive organs. Glandular hairs on leaves, stems and flowerssecreted mucilage containing glycerides and trapped small insects.Secretions from glandular hairs on flowers and immature fruitscontained flavonoids, which may provide protection against someherbivores. Yellow dendritic trichomes on the adaxial side ofleaves also contained flavonoids identical to those secretedby the glandular hairs on fruits and flowers. Three specialtypes of leaves, which differed from the standard leaves inshape, size and identity of small structures, developed nearyoung shoot tips or young flower buds. The density of smallstructures on these leaf types was higher than on standard leaves,suggesting that these leaf types may be specialized to protectyoung leaves or reproductive organs. Changes in the small structuresduring leaf development suggested that leaves of P. tomentosaare primarily protected by glandular hairs and dendritic trichomesat young stages and by the EFNs at mature stages. Conclusions: The results indicate that P. tomentosa protects young and/orreproductive organs from herbivores through the distributionand allocation of small structures, the nature of which dependson the developmental stage of leaves and shoots.     

Comparative morphology of the leaf epidermis in Schisandra (Schisandraceae)

The leaf epidermis of 127 samples representing ten species within Schisandra Michaux. and one species of the related genus, Kadsura Kaempf. ex Juss., was investigated using light and scanning electron microscopy. Many characters of the leaf epidermis in Schisandra , such as pattern of epidermal cells, type of stomata, shape of guard cell pairs and cuticular ornamentation, are usually constant within species and thus make good characters for studying the relationship between and within genera. A new character, rim number, of the outer stomatal rim in the genus is introduced. It is shown that double outer stomatal rims occur only in evergreen Schisandra species, whereas a single rim occurs in deciduous species. This character supports the classification of Schisandra into two subgenera based on habit and androecial organs. This classification is also supported by additional morphological and molecular taxonomic characters. Kadsura coccinea (Lem.) Smith A. C. is the most primitive taxon in the related genus Kadsura . The outer stomatal rim of this species also has double rims. Combined with morphological and molecular evidence, this suggests that Schisandra and Kadsura are closely related and may share a recent common ancestor.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 148 , 39–56.     

Uptake and distribution of abscisic acid in Commelina leaf epidermis

Closure of stomata by abscisic acid (ABA) was studied by floating leaf epidermal strips of Commelina communis L. in PIPES buffer (pH 6.8) containing a range of KCl concentrations. Control apertures were greatest at high concentrations of the salt, and the effects of ABA, in terms of closure, were most pronounced below 100 mol m^-3 KCl. Stomata opened on strips floated on buffer plus 50 mol m^-3 KCl and closed within 10 min when transferred to the same medium plus 0.1 mol m^-3 ABA. [2-¹⁴C]ABA was used to study uptake and distribution of the hormone by the epidermal strips. It was calculated that no more than 6 fmol ABA were present per stomatal complex at the time of closure, although uptake continued thereafter. Microautoradiography indicated that radioactivity from [2-¹⁴C]ABA accumulated in the stomatal complex at or near the guard cells within 20 min. TLC was used to examine the state of the label after 1 h incubation. Efflux of label from preincubated tissue appeared to occur in three phases (t_1/2=7.2 s, 4.0 min, 35.2 min). Efflux was correlated with stomatal re-opening. The results confirm that ABA can accumulate in the epidermis of C. communis.Abbreviation ABA Abscisic acid     

杜鹃花属照山白叶表皮及花粉形态的研究

利用光学显微镜和扫描电子显微镜对杜鹃花属植物照山白的叶表皮及花粉形态进行了观察,该种的叶表皮细胞表面光滑,胞间界限明显;叶上下表皮均有盾状鳞,上表皮仅有针状毛;气孔器仅见于下表皮,分布稀疏,副卫细胞和保卫细胞表面光滑。扫描电镜下可见该种的花粉为四合花粉,呈正四面体排列,具三沟,表面纹饰为负网状雕纹,局部区域有大颗粒状突起。     

Floral phyllotaxis in basal angiosperms: development and evolution

To date, molecular developmental studies have focused on vegetative rather than floral phyllotaxis because vegetative shoot apices are technically more tractable than floral apices in model plants. In contrast to evolutionary changes in the phyllotaxis of vegetative shoots, however, changes in floral phyllotaxis appear to have played a major role in angiosperm evolution. Consolidation of a whorled floral phyllotaxis in derived groups allowed synorganization of floral organs and further adaptive radiations. In basal angiosperms, floral phyllotaxis is more flexible. To study these phenomena, we need clarification of the complex relations of both spiral and whorled phyllotaxis with divergence angles, plastochrons, spiral versus simultaneous initiation of organs, parastichies, orthostichies, organ series, and whorls. Improved resolution of phylogenetic relationships and increased knowledge of the diversity of floral phyllotaxis will allow us to trace evolutionary changes in floral phyllotaxis in ever more detail. Already, such surveys have confirmed that floral phyllotaxis was unusually labile early in angiosperm evolution. Whether the original floral phyllotaxis in angiosperms was spiral or whorled is equivocal, but it appears that spiral floral phyllotaxis in Magnoliales and Laurales is derived rather than primitive.     

The question of cotyledon homology in angiosperms

The flowering plants (Magnoliophyta) are separated into two large classes distinguished by the morphology of their embryos. The embryos of monocots (class Liliopsida) have a single terminal cotyledon, while the embryos of dicots (class Magnoliopsida) usually have two lateral cotyledons. The cotyledons of monocots and dicots also differ in form, and there are no true intermediates. In addition, the third leaf of Nymphaealean seedlings appears to be identical to the single cotyledon of monocots. From this it is concluded that the cotyledons of monocots and dicots are not homologous. In addition, dissimilarity of cotyledons and succeeding leaves in dicots, together with recent genetic studies, suggests that the two cotyledons of dicots are not homologous with the succeeding leaves of the same plant. This interpretation is consistent with the view that the Nymphaealean embryo’s third leaf is homologous to the first leaf (cotyledon) of monocots. Because dicotyledonous embryos are common among seed plants and are present in the Gnetopsids, the most likely scenario is that the dicots share a widespread seed plant symplesiomorphy and that the monocots have lost this character state. A less parsimonious hypothesis of monocotyledonous embryos as plesiomorphic for angiosperms is also discussed. Genetic analysis of early embryo development in a variety of vascular plants may be the only way to conclusively determine the evolutionary origin of the distinctive difference between monocot and dicot embryos.     

Comparative morphology of leaf epidermis in the genus Lithocarpus and its implication in leaf epidermal feature evolution in Fagaceae

Leaf epidermal features are considered to be taxonomically important in Fagaceae. In this study, we examined and compared leaf epidermal features of 112 specimens, representing 105 species and one variety of Lithocarpus from China and adjacent areas and Notholithocarpus densiflorus. As a result of the different interpretations of terms in previous studies, trichome terminology in Lithocarpus and its relatives was re-assessed aiming to reveal the trichome evolutionary patterns in Fagaceae. Twelve types of trichomes and five types of trichome bases were detected in Lithocarpus, among which the broad-based trichome (BBT) is newly reported. Stomata in Lithocarpus are restricted to the cyclocytic type and their size range is 28.6 ± 8.2 μm × 26.5 ± 9.3 μm. The distribution of epidermal features in Lithocarpus revealed three distinct morphological groups: glabrous, BBT, and appressed parallel tufts (APT). The importance of epidermal features across Fagaceae for taxon delimitation is evaluated. Species of Lithocarpus can be accurately identified by the presence of APT or flat epidermal cells combined with non-dark stained subsidiary cells and non-cutinized trichome bases only, or in addition, fasciculate trichome bases. The phylogenetic distribution of epidermal features and their evolutionary trends in Fagaceae is also discussed.     

Comparative morphology of the leaf epidermis in Fritillaria (Liliaceae) from China

The leaf epidermis of 16 species and one putative species of Fritillaria was examined using light microscopy (LM) and scanning electron microscopy (SEM). The results showed that the stomatal and other epidermal features were constant within species. Epidermal cells of Fritillaria under LM were usually polygonal and anticlinal cell walls were straight or curved. In a few species they were irregular, with sinuous anticlinal cell walls. The cuticular membrane of Fritillaria was usually striated, and the wax ornamentations were flaked, granular or concomitant. Based on leaf epidermal characteristics, the subdivision of Fritillaria is discussed, and the statistical t‐test method was used to ascertain the significance level of the differences in the stomata of each species. All orientations of the stomatal poles in Fritillaria were the same, and this phenomenon was named ‘stomatal orientation’. The stomatal characteristics support the origin of section Fritillaria in China from two floristic elements. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 160 , 93–109.     

Stomatal architecture and evolution in basal angiosperms

Stomatal architecture-the number, form, and arrangement of specialized epidermal cells associated with stomatal guard cells-of 46 species of basal angiosperms representing all ANITA grade families and Chloranthaceae was investigated. Leaf clearings and cuticular preparations were examined with light microscopy, and a sample of 100 stomata from each specimen was coded for stomatal type and five other characters contributing to stomatal architecture. New stomatal types were defined, and many species were examined and illustrated for the first time. Character evolution was examined in light of the ANITA hypothesis using MacClade software. Analysis of character evolution, along with other evidence from this study and evidence from the literature on fossil angiosperms and other seed plant lineages, suggests that the ancestral condition of angiosperms can be described as anomo-stephanocytic, a system in which complexes lacking subdidiaries (anomocytic) intergrade with those having weakly differentiated subsidiaries arranged in a rosette (stephanocytic). From this ancestral condition, tangential divisions of contact cells led to the profusion of different types seen in early fossil angiosperms and Amborellaceae, Austrobaileyales, and derived Chloranthaceae, while the state in Nymphaeales is little modified. Formation of new, derived types by tangential division appears to be a recurrent theme in seed plant evolution.     

中国梅花草属植物的叶表皮特征及其系统学意义

利用光学显微镜和扫描电镜对梅花草属Parnassia 30种植物的叶表皮进行了观察。结果表明:气孔器普遍存在于叶的下表皮,少数种的上表皮也有分布,均为无规则型。叶表皮细胞形状为多边形或不规则形;垂周壁式样可区分为近平直、浅波状和波状。在扫描电镜下,叶表皮气孔器外拱盖内缘为近平滑、浅波状或波状;一些种的保卫细胞两端有加厚;角质膜条纹状,有的条纹隆起,有的条纹上附有颗粒或小孔穴。气孔器类型及下表皮细胞形状的一致性表明梅花草属是一个自然分类群;sect. Saxifragastrum叶表皮特征具有多样性显示该组可能是一个复合群;突隔梅花草P. delavayi属于subsect. Xiphosandra,其气孔下陷,与其细胞学特征相似,支持独立为一组;此外,气孔器的分布、保卫细胞两端加厚、气孔器外拱盖内缘形态以及角质膜等特征对该属部分种的区分有一定的参考价值。     

Floral variation and floral genetics in basal angiosperms

Recent advances in phylogeny reconstruction and floral genetics set the stage for new investigations of the origin and diversification of the flower. We review the current state of angiosperm phylogeny, with an emphasis on basal lineages. With the surprising inclusion of Hydatellaceae with Nymphaeales, recent studies support the topology of Amborella sister to all other extant angiosperms, with Nymphaeales and then Austrobaileyales as subsequent sisters to all remaining angiosperms. Notable modifications from most recent analyses are the sister relationships of Chloranthaceae with the magnoliids and of Ceratophyllaceae with eudicots. We review "trends" in floral morphology and contrast historical, intuitive interpretations with explicit character-state reconstructions using molecular-based trees, focusing on (1) the size, number, and organization of floral organs; (2) the evolution of the perianth; (3) floral symmetry; and (4) floral synorganization. We provide summaries of those genes known to affect floral features that contribute to much of floral diversity. Although most floral genes have not been investigated outside of a few model systems, sufficient information is emerging to identify candidate genes for testing specific hypotheses in nonmodel plants. We conclude with a set of evo-devo case studies in which floral genetics have been linked to variation in floral morphology.     

The evolution of floral biology in basal angiosperms

In basal angiosperms (including ANITA grade, magnoliids, Choranthaceae, Ceratophyllaceae) almost all bisexual flowers are dichogamous (with male and female functions more or less separated in time), and nearly 100 per cent of those are protogynous (with female function before male function). Movements of floral parts and differential early abscission of stamens in the male phase are variously associated with protogyny. Evolution of synchronous dichogamy based on the day/night rhythm and anthesis lasting 2 days is common. In a few clades in Magnoliales and Laurales heterodichogamy has also evolved. Beetles, flies and thrips are the major pollinators, with various degrees of specialization up to large beetles and special flies in some large-flowered Nymphaeaceae, Magnoliaceae, Annonaceae and Aristolochiaceae. Unusual structural specializations are involved in floral biological adaptations (calyptras, inner staminodes, synandria and food bodies, and secretory structures on tepals, stamens and staminodes). Numerous specializations that are common in monocots and eudicots are absent in basal angiosperms. Several families are poorly known in their floral biology.     

Early leaf miners and the ground plan of the lepidopteran larval trunk: Caterpillar morphology of the basal moths Heterobathmia,Eriocrania, and Acanthopteroctetes

The larval trunk morphology including chaetotaxy, locomotory structures, and trunk musculature of Heterobathmia pseuderiocrania, Eriocrania cicatricella, and Acanthopteroctetes unifascia is described using conventional light, polarization, and scanning electron microscopy. The ground plan morphology of the lepidopteran larva and neolepidopteran caterpillar is discussed in light of the life history succession from free soil dwelling organism to endophagous and finally to a primarily free living, angiosperm associated organism. I suggest that the larval morphology is argued to be strongly influenced by the shift in number of surfaces present in the larval environment. Especially the environment of the endophagous species, where the upper surface of the leaf mine is linked to the presence of dorsal locomotory structures such as the retractable calli and dorsal friction patches is proposed to have had a significant impact on the morphology and locomotory mechnism of the lepidopteran caterpillar. The chaetotaxy of the lepidopteran ground plan is found to be simple, consisting only of primary and secondary tactile setae and segmental proprioceptors. The presumption of Gerasimov ([1935] Zool Anz 112:177–194) that MXD1 of the prothorax is a shifted mesothoracic MD setae is supported. I suggest that the serial arrangement of the proprioceptors MD1, present on all trunk segments except the prothorax, and a trisetous MV group on all the thoracic segments is part of the lepidopteran larval ground plan. The absence of apodeme structures associated with trunk musculature in the nonglossatans suggests that this is an autapomorphic character of the Lepidoptera and it is further found to have been influential in the evolution of the typical caterpillar trunk. The attachments of the thoracic muscles directly to the trunk integument, suggest that the apodemal structures ancestral to the Amphiesmenoptera have been reduced in the Lepidoptera. Within the non‐Neolepidoptera, the lifehistory shift may have resulted in reduction of the dorsal locomotory structures, such as calli. The abdominal musculature and structural similarities further suggest that the ventral calli are structural predecessors to the crotchet bearing proleg of the “typical caterpillar.” J. Morphol. 274:1239–1262, 2013. © 2013 Wiley Periodicals, Inc.     

Bacterial leaf symbiosis in angiosperms: host specificity without co-speciation

Bacterial leaf symbiosis is a unique and intimate interaction between bacteria and flowering plants, in which endosymbionts are organized in specialized leaf structures. Previously, bacterial leaf symbiosis has been described as a cyclic and obligate interaction in which the endosymbionts are vertically transmitted between plant generations and lack autonomous growth. Theoretically this allows for co-speciation between leaf nodulated plants and their endosymbionts. We sequenced the nodulated Burkholderia endosymbionts of 54 plant species from known leaf nodulated angiosperm genera, i.e. Ardisia, Pavetta, Psychotria and Sericanthe. Phylogenetic reconstruction of bacterial leaf symbionts and closely related free-living bacteria indicates the occurrence of multiple horizontal transfers of bacteria from the environment to leaf nodulated plant species. This rejects the hypothesis of a long co-speciation process between the bacterial endosymbionts and their host plants. Our results indicate a recent evolutionary process towards a stable and host specific interaction confirming the proposed maternal transmission mode of the endosymbionts through the seeds. Divergence estimates provide evidence for a relatively recent origin of bacterial leaf symbiosis, dating back to the Miocene (5-23 Mya). This geological epoch was characterized by cool and arid conditions, which may have triggered the origin of bacterial leaf symbiosis.     

Orbicules in angiosperms: Morphology, function, distribution, and relation with tapetum types

Orbicules, or Ubisch bodies, are sporopollenin particles lining the inner tangential and sometimes also the radial tapetal cell walls. They occur only in species with a secretory tapetum. The surface ornamentation of orbicules and pollen of the same species is often strikingly similar. Although orbicules were discovered more than a century ago, these structures remain enigmatic since their function is still obscure. Proposed hypotheses about their possible function are discussed. We also deal here with topics such as the possible allergenicity of orbicules and their representation in the fossil record. The use of orbicule characters for systematics is reviewed. The distribution of orbicules throughout the angiosperms, based on a literature review from the first report until today, is shown in a list with 314 species from 72 families. Those species found in the literature without orbicules are presented together with their tapetum type. We plotted this information on a dahlgrenogram to visualize the distribution of orbicules. Orbicules occur in all subclasses of the angiosperms. Their occurrence is not correlated with certain modes of pollination or habitats.

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Résumé  Les orbicules, ou corps d’Ubisch, sont des particules de sporopollénine couvrant la surface intérieure tangentiale et parfois la surface radiale des cellules du tapétum. On ne les retrouve que dans les espèces possédant un tapétum sécréteur. L’ornementation superficielle des orbicules et celle du pollen d’une même espèce est souvent remarquablement similaire. Malgré le fait que les orbicules ont été découvert il y a plus d’un siècle, ces structures restent énigmatiques et leur fonction est toujours méconnue. Les hypothèses proposées concernant la fonction éventuelle des orbicules sont commentées dans cet article. Nous avons également traité des sujets tels que les éventuels effets allergènes des orbicules ainsi que leur présence dans les strates fossiles. L’utilisation de caractères orbiculaires dans la systématique est analysée. Nous présentons une liste de 314 espèces appartenant à 72 familles possédant des orbicules, sur base d’une analyse de la litérature à partir de la première observation jusqu’au présent. Pour les espèces rapportées dans la litérature qui ne possèdent pas d’orbicules, nous présentons aussi leur type de tapétum. Nous avons projeté cette information sur un Dahlgrenogramme afin de visualiser la distribution des orbicules. Nous les retrouvons dans toutes les sous-classes des angiospermes. Leur présence n’est pas correlée avec certains modes de pollinisation ou avec divers types d’habitat.

     

Congruence,non‐homology,and the phylogeny of basal turtles

Joyce, W.G. and Sterli J. 2010. Congruence, non‐homology, and the phylogeny of basal turtles.–Acta Zoologica (Stockholm) Modern cladistic analysis is characterized by the assembly of increasingly larger data sets coupled with the use of congruence as the final test of homology. Some critics of this development have recently called for a return to more detailed primary homology analysis while questioning the utility of congruence. This discussion appears to be central to the debate regarding the phylogenetic relationships of basal turtles, as the large data sets developed by us have been criticized recently for utilizing poorly constructed characters and including too many homoplasy‐prone characters. Our analysis of this critique reveals that (1) new information regarding poorly understood taxa has a greater impact on the outcome of turtle phylogenies than the characters under dispute; (2) most current turtle phylogenies differ in taxon sampling, not character sampling, and so it appears illogical to condemn a particular analysis for its character sampling; (3) even evolutionary taxonomists should agree that key characters utilized to resolve basal turtle relationships cannot be thought to be ‘infallible’; (4) whereas various criteria provide positive evidence for homology, only congruence provides positive evidence for non‐homology; and (5) a stalemate between conflicting camps within a congruence frame work is preferable to the ad hoc dismissal of data sets, because authoritative statements are untestable.