FOLIAR MORPHOLOGY AND ANATOMY OF THE GIGANTOPTERID PLANT DELNORTEA ABBOTTIAE,FROM THE LOWER PERMIAN OF WEST TEXAS

Delnortea is a monotypic genus (type-species: D. abbottiae) of Lower Permian gymnosperms based on leaves from uppermost Leonardian deltaic sediments exposed in the Del Norte Mountains, West Texas. The leaves are simple, symmetrical, mostly oblong or elliptical, and vary in length from 1.2 to about 35 cm. The petioles are short and stout, with a basally enlarged abscission zone. The margins are crenate, with a narrow, indurated border. Venation is in 4 orders: the secondaries and tertiaries are robust, unbranched, and pinnately arranged in a precise “herringbone” pattern, with the secondaries ending in the marginal sinuses; the quaternaries divide sparingly and fuse with others to form a dense reticulum of small meshes. Permineralized petiole and midrib material reflects a bifacial cambium, shown by a semicircular vascular arc, irregularly divided into several collateral bundles with secondary xylem and phloem. Delnortea is referable to the Gigantopteridaceae, a probably artificial family of gymnosperms incertae sedis with important venation features in common, but without known diagnostic reproductive organs. With Delnortea, the North American gigantopterids now include 5 genera, but Gigantopteris itself is lacking. Delnortea holds a relatively advanced evolutionary position among the American gigantopterids; its leaf morphology and gymnospermous anatomy entail intriguing points of comparison with Gnetum. The limited geographic and stratigraphic ranges and morphological distinctiveness of the American gigantopterids and associated taxa attest to rapid evolution and dispersal from a small area of origin in the southwestern United States during Leonardian time.     

GIgantonoclea: an enigmatic Permian plant from North China

Gigantonoclea is a distinctive and enigmatic plant from the Permian of North China proper, with an unusual frond architecture and a pollen organ and vascular structure which are unique; it demonstrates a sudden rise and a rapid extinction. This paper reviews previous work on Asian gigantopterids and describes new material from the Upper Permian of Shanxi Province, including a new type of pollen organ (Jiaochengia lagrelii) and two new species of frond (Gigantonoclea crenataG. pubescens). Jiaochengia shows opposite, dissected and rather modified microsporophylls, laxly aggregating into an independent organ, which is markedly different from ‘Gigantotheca’ from Fujian. This presents evidence of heterogeneity among Asian gigantopterids and partly supports a relationship with the Carboniferous Callistophytales. Jiaochengia sporangia have what may be the first record of a waxy covering on the outer surface of a fossil plant, which is interpreted to have functioned to repel water, to protect against fungal attack and to scatter light. According to Hickey's rule, the venation of true Gigantonoclea fronds consists of three orders of main veins (rachis, midvein and secondary veins) and two orders of anastomosing veins (tertiary veins and veinlets). Certain putative ‘Gigantonoclea’ species from South China and some peripheral areas of North China do not have this type of venation and are thus excluded from the genus. Frond dimorphism is common among gigantopterids in both North and South China and can be compared with the amphibious variation from submerged to emergent leaves in extant aquatic plants. G. pubescens has a thick, bi-layered adaxial cuticle with an indumentum covering with dense papillae and trichomes bases, and deeply sunken, papillate stomata, suggesting that it favoured more arid conditions. An observed gradient from pubescent to glabrate or even glabrous gigantopterid cuticle structures between North and South China suggests a change from xeric, mesic to humid habitats.     

STUDIES ON THE LEAF OF POPULUS DELTOIDES (SALICACEAE): MORPHOLOGY AND ANATOMY

Mature field- and growth-chamber-grown leaves of Populus deltoides Bartr. ex Marsh. were examined with light and scanning electron microscopes to determine their vasculature and the spatial relationships of the various orders of vascular bundles to the mesophyll. Three leaf traces, one median and two lateral, enter the petiole at the node. Progressing acropetally in the petiole these bundles are rearranged and gradually form as many as 13 tiers of vascular tissue in the petiole at the base of the lamina. (Most leaves contained seven vertically stacked tiers.) During their course through the midrib the tiers “unstack” and portions diverge outward and continue as secondary veins toward the margin on either side of the lamina. As the midvein approaches the leaf tip it is represented by a single vascular bundle which is a continuation of the original median bundle. Tertiary veins arise from the secondary veins or the midvein, and minor veins commonly arise from all orders of veins. All major veins–primaries, secondaries, intersecondaries, and tertiaries–are associated with rib tissue, while minor veins are completely surrounded by a parenchymatous bundle sheath. The bundle sheaths of tertiary, quaternary, and portions of quinternary veins are associated with bundle-sheath extensions. Minor veins are closely associated spatially with both ad- and abaxial palisade parenchyma of the isolateral leaf and also with one or two layers of paraveinal mesophyll that extend horizontally between the veins. The leaves of growth-chamber-grown plants had thinner blades, a higher proportion of air space, and greater interveinal distances than those of field-grown plants.     

中国吴茱萸属(广义)叶结构特征及其分类学意义北大核心CSCD

该研究以中国产芸香科广义吴茱萸属18种3变种为材料,于体视显微镜下观察叶结构特征。结果发现:(1)吴茱萸属叶脉为羽状脉。(2)二级脉有花环状弓形脉和简单弓形脉两种类型,极少数存在内二级脉,间二级脉存在或缺失。(3)三级脉不规则网状或极少数弱贯穿,边缘三级脉环状。(4)四级脉不规则网状或自由分支。(5)五级脉不规则网状或自由分支,脉间区发育差或中等,游离端小脉末端简单或管状异形,边缘末级脉大多数不完整,极少数环状。(6)基于重要的外部形态学特征和叶结构特征观察结果,编制了广义吴茱萸属植物的分组检索表。研究表明,吴茱萸属这些类群的二级脉与更高级脉序形成的结构极为稳定,同时又存在种间差异,故广义吴茱萸属植物叶结构特征可以为更准确地鉴定一些疑难种和混淆种提供佐证,具有重要的系统分类学价值。     

Foliar anatomy of Gigantonoclea guizhouensis (Gigantopteridales) from the Upper Permian of Guizhou Province,China

The present paper details the anatomy of permineralized foliar specimens of Gigantonoclea guizhouensis Gu and Zhi (Gigantopteridales) from the Upper Permian of western Guizhou Province in southwest China. In addition to reticulate venation, these fossil leaves possess a number of interesting anatomical features including: multicellular spines on the midrib, hypodermal sclerenchyma ribs, U- or V-shaped xylem in the midrib and secondary veins, tracheids with various secondary wall thickening patterns, paracytic stomata on the abaxial surface, epidermal cells with sinuous anticlinal walls, and secretory cavities in the mesophyll. Based on anatomical features, a liane habit is suggested, and the systematic differences among Gigantonoclea guizhouensis, Gigantopteridium, and the North American taxon Delnortea are underscored.     

Probable mechanical transmission of a virus-like agent from rose rosette disease-infected multiflora rose to Nicotiana species

As part of efforts to identify the causal agent of the rose rosette disease (RRD) of multiflora rose (Rosa multiflora Thunb.), root tip extracts from both symptomatic and nonsymptomatic roses were used to mechanically inoculate leaves of Nicotiana glutinosa. Pale green spots were observed along the margins of the major leaf veins only on leaves inoculated with extracts prepared from symptomatic rose plants. Light microscopy revealed abnormal development of the palisade and spongy mesophyll cells in the symptomatic tissue, although no virus‐like particles (VLPs) were observed by electron microscopy. However, VLPs were observed in cells from tissue adjacent to the leaf veins and bordered by the pale green spots. Inoculation of N. benthamiana with extracts from symptomatic N. glutinosa initially did not result in visible symptoms on N. benthamiana inoculated leaves. However, approximately 4 wk post inoculation, splitting of leaf tissue across and along major leaf veins in expanding leaves occurred. In later stages of leaf expansion some leaves split in regions not associated with veins. Light microscopy of thick sections revealed separation between palisade cells and groups of small dead cells in the mesophyll tissue of expanding systemically infected leaf blades. Electron microscopy revealed crystalline arrays in the cytoplasm of mesophyll cells. No abnormal cellular changes were observed in plants inoculated with extracts prepared from nonsymptomatic rose plants.     

The Jambi gigantopterids and their place in gigantopterid classification

The gigantopterids are a pan‐palaeotropical Late Palaeozoic (to Early Mesozoic) plant group with unknown affiliations. Two gigantopterid species, both sole representatives of their respective genera, are known from the Early Permian Mengkarang Formation of Jambi (Sumatra, Indonesia). Through an emendation of the Jambi gigantopterids, based on the old and newly collected material, and a subsequent analysis of the leaf morphology of several gigantopterid genera, we conclude that the Jambi species are similar to the other gigantopterids, but do not appear to be related to them directly. We propose a possible scenario for the evolution of gigantopterid leaf morphology, based on marginal leaf growth, with implications for the validity of the gigantopterids as a natural group. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 161 , 302–328.     

Preliminary palaeobotanical notes on the Early Cretaceous Cintura Formation (Sonora,Mexico)

The Cintura Formation of Albian–Cenomanian age in the Cabullona Basin yielded an important fossil flora, including palynomorphs, leaf impressions and fossil trunks. At the base of the Marquechi Member a poorly preserved palynomorph assemblage is recognised. The palynological assemblage is dominated by gymnosperms, mainly by cheirolepidiacean genus Classopollis. A noteworthy feature is the presence of angiosperm pollen grains of the genera Clavatipollenites, Retimonocolpites and Tucanopollis. A rich, diverse and well-preserved macroflora of leaf impressions has been observed in the uppermost part of this formation belonging to the San Juan Member. There are at least eight morphospecies of leaves including an abundance of taxa with possible botanical affinities to the family Sapindaceae. The angiosperm pollen grains together with the sapindalean leaves constitute the oldest record of such remains in Mexico.     

Studies onArtemisia afra Jacq.: The phloem in stem and leaf

Summary The structure of the phloem was studied in stem and leaf ofArtemisia afra Jacq., with particular attention being given to the sieve element walls. Both primary and secondary sieve elements of stem and midvein have nacreous walls, which persist in mature cells. Histochemical tests indicated that the sieve element wall layers contained some pectin. Sieve element wall layers lack lignin. Sieve elements of the minor veins (secondary and tertiary veins) lack nacreous thickening, although their walls may be relatively thick. These walls and those of contiguous transfer cells are rich in pectic substances. Transfer cell wall ingrowths are more highly developed in tertiary than in secondary veins.     

中国大羽羊齿植物分叉蕨叶的首次发现--兼论亚洲与北美大羽羊齿植物之异同

东亚与北美大羽羊齿植物间的主要差异在于蕨叶的结构：北美大羽羊齿植物的蕨叶为单叶或二歧分叉叶,而东亚的大羽羊齿植物以往只知为羽状复叶或不分叉的单叶,因之,二歧分叉蕨叶在中国的发现具有十分重要的意义,它使东亚与北美大羽羊齿植物之间的关系变得更为密切,虽然其间仍存在不实质性的差异,同时,对东亚和北美华夏羊齿Cathaysiopteris之间的异同作了较详的讨论。     

MUSOPSIS N. GEN.: A BANANA-LIKE LEAF GENUS FROM THE EARLY TERTIARY OF EASTERN NORTH GREENLAND

A fossil flora from the Late Paleocene-Early Eocene Thyra Ø Formation of eastern North Greenland (paleolatitude 77° N) has yielded monocotyledon leaf impressions with characters seen only in the closely related modem species in the families of Heliconiaceae, Musaceae, and Strelitziaceae. The combination of large costae widths and parallel, nonanastomosing, lateral veins that depart at right angles from the costae in the fossil material are features present only in leaves of extant species from these families. Three basic venation patterns also are recognized in the modem species of these families, but except for the genera Strelitzia and Phenakospermum, none of these patterns are present exclusively in any one family. Musopsis n. gen. is created for the fossil material from Greenland, but it is considered a form genus due to the lack of gross morphological features that can be used for separating leaves of the modem genera in Heliconiaceae, Musaceae, and Strelitiziaceae. It is the first known Arctic occurrence of fossil leaf material resembling this modem group of taxa.     

Do holly leaf spines really deter herbivory?

Summary Although spinose teeth of holly leaves have been widely cited as an example of a physical defense against herbivores, this assumption is based largely on circumstantial evidence and on general misinterpretation of a single, earlier experiment. We studied the response of third and fifth instar larvae of the fall webworm, Hyphantria cunea Drury, a generalist, edge-feeding caterpillar, to intact American holly leaves and to leaves that had been modified by blunting the spines, by removing sections of leaf margin between the spines, or by removing the entire leaf margin. The results suggest that the thick glabrous cuticle and tough leaf margin of Ilex opaca are more important than the spinose teeth in deterring edge-feeding caterpillars. Microscopic examination of mature leaves revealed that the epidermis is thickened at the leaf margin, and that the leaf is cirucumscribed by a pair of fibrous veins. In simple choice tests neither domesticated rabbits nor captive whitetailed deer discriminated between spinescent holly foliage and foliage from which spines were removed. Nevertheless, we found little evidence of herbivory by mammals in the field, either on small experimental trees or in the forest understory. While it is possible that spinose teeth contribute to defense by reducing acceptibility of holly relative to other palatable plant species, we suggest that the high concentrations of saponins and poor nutritional quality of holly foliage may be more important than spines in deterring vertebrate herbivores. The degree of leaf spinescence and herbivory was compared at different heights with the tree canopy to test the prediction that lower leaves should be more spinescent as a deterrent to browsers. Leaves on lower branches of mature forest trees were slightly more spinescent than were upper leaves, and juvenile trees were slightly more spinescent than were mature trees. However, there was no relationship between degree of spinescence and feeding damage. The greater spinescence of holly leaves low in the canopy is probably an ontogenetic phenomenon rather than a facultative defense against browsers.The investigation reported in this paper (No. 87-7-8-77) is in connection with a project of the Kentucky Agricultural Experiment Station and is published with the approval of the Dirctor     

贵州小檗属植物(小檗科)叶脉序研究

采用制作叶脉标本和透明叶标本的方法,对贵州产28种2变种小檗属植物叶脉特征进行比较研究。结果表明:贵州小檗属植物的脉序类型有5种:半达缘羽状脉、花环状半达缘羽状脉、简单弓形羽状脉、花环状弓形羽状脉和混合型。叶脉分支一般有五级:1一级脉构架均为羽状脉,粗度有很粗、粗、中等粗细和纤细四种类型,分支方式包括单轴分支和合轴分支;2粗二级脉构架中有分支达缘或分支均不达缘,与中脉夹角变化各异,内二级脉存在或缺失,细二级脉半达缘、真曲行或简单弓形,间二级脉类型复杂多变但频度种间有差异;3三级脉贯串型、结网型或分支型;4四、五级脉网状或自由分支且常混合在一起。脉间区从发育差到良好,小脉从不分支到不均等分支等各种类型均有,叶缘末级脉缺失、不完整、钉状和环状。大部分种类叶缘具齿,每1cm齿数目和齿内腺点的特性等特征在不同种类间有区别,具有鉴定价值,但齿其它特征复杂多变或种间区别较小,同时齿内脉性状也不稳定。此外,齿的有无会对脉序类型产生影响。小檗属植物叶脉类型存在种间差异,具有重要的分类学价值,叶脉类型的变化和复杂程度显示了该属植物的进化特点;叶齿的有无和齿特征具有分类学和系统学意义。基于叶脉特征的研究结果并结合重要的外部形态学特征编制了贵州小檗属植物的分种检索表。研究结果可为小檗属植物分类寻找新的依据并探讨其系统学意义。     

湖北楠木属一新变种——裂叶白楠

报道了楠木属一新变种——裂叶白楠[Phoebe neurantha(Hemsl.)Gamble var.lobophylla Y.J.Fei]。该变种(裂叶白楠)与白楠[Phoebe neurantha(Hemsl.)Gamble]的区别在于叶片中部到距叶尖1/3处叶片宽度陡然变窄,若有强健侧脉支持则叶片发生裂刻,若无,叶片变狭长,两种变异均存在叶片先端变狭,且呈狭长弯镰状;叶脉下陷更深,侧脉与主脉的夹角逐渐变大,最终呈羽状分布,且越靠近叶尖侧脉分布越密集,单侧侧脉数为25~40;裂刻处叶缘无革质化,粗糙且常具细毛。且这些性状能够稳定遗传给下一代。凭证模式标本现藏于武汉植物园标本馆(编号Y.J.Fei002,HIB)。     

The Knotted leaf blade is a mosaic of blade,sheath, and auricle identities

The dominant Knotted-1 mutations in maize alter development of the leaf blade. Sporadic patches of localized growth, or knots, and fringes of ectopic ligule occur along lateral veins of mutant leaf blades. In addition, bundle sheaths do not completely encircle lateral veins on mutant leaf blades. We have compared mutant leaf blades with wild-type leaves to determine the precise nature of the perturbed regions. Our analysis includes characterization of epidermal cell shapes, localization of photosynthetic proteins and histology of the leaf. We show that mutant leaf blades are a mosaic of leaf organ components. Affected regions of mutant leaf blades resemble either sheath or auricle tissue in both external and internal features. This conversion of blade cells represents an acropetal shift of more basal parts of the leaf blade region and correlates with previously identified ectopic expression of the Knotted-1 protein in the leaf blade. We propose that inappropriate expression of Kn1 interferes with the process of establishment of cell identities, resulting in early termination of the normal blade development program or precocious expression of the sheath and auricle development programs. © 1994 Wiley-Liss, Inc.     

Leaf morphology of a facultative rheophyte,Farfugium japonicum var.luchuense (Compositae)

The gross morphology and anatomy of leaves in a facultative rheophyte,Farfugium japonicum var.luchuense, were examined in order to clarify how the two characters are correlated with one another and how the facultative rheophyte differs from obligate rheophytes in leaf morphology and anatomy. Most rheophytes of the variety have narrowly cuneate leaf base, while most inland plants usually have truncate to cordate one, although the habitat-morphology correlation is not so clear. The leaf shape or the divergence angle of leaf base is strongly correlated with the number of primary veins and intervein-distance dependent on the number of cells intervening between veins. This makes a marked contrast to many reported cases of obligate rheophytes in which the leaf shape is strongly correlated with cell size. There is a rough tendency that narrower leaves of rheophytes have a thicker cuticular layer. However, the cell size and the volume (area) of intercellular space differ only slightly with the leaf shape.     

五种红树植物叶片结构的比较研究

以木榄(Bruguiera gymnorrhiza)、桐花树(Aegiceras corniculatum)、拉关木(Laguncularia racemosa)、海芒果(Cerbera manghas)、杨叶肖槿(Thespesia populnea)五种红树植物为材料,采用常规石蜡切片法对它们的叶片横切面结构进行显微观察,比较真红树植物和半红树植物叶片结构的特点及变化规律,研究红树植物叶对盐浸环境的适应性。结果表明:除杨叶肖槿为异面叶、掌状网脉外;拉关木为等面叶、羽状脉,其它三种植物为异面叶、羽状网脉;五种材料具4级叶脉,3级、4级脉具明显维管束鞘。木榄、桐花树、拉关木、杨叶肖槿1级脉为半周韧无限维管束,海芒果1级脉为外韧无限维管束。五种材料叶肉具有分泌腔,除海芒果外,具有含晶体细胞;木榄、桐花树有内皮层,拉关木有贮水组织;桐花树、海芒果有含单宁细胞;桐花树、拉关木、杨叶肖槿有盐腺。这五种植物的叶片结构体现出不同植物对盐浸环境适应性的特征。相比较而言,真红树植物的特化结构较半红树植物多。     

Photosynthetically versatile thin shade leaves: A paradox of irradiance-response curves

Thick sun leaves have a larger construction cost per unit leaf area than thin shade leaves. To re-evaluate the adaptive roles of sun and shade leaves, we compared the photosynthetic benefits relative to the construction cost of the leaves. We drew photosynthetically active radiation (PAR)-response curves using the leaf-mass-based photosynthetic rate to reflect the cost. The dark respiration rates of the sun and shade leaves of mulberry (Morus bombycis Koidzumi) seedlings did not differ significantly. At irradiances below 250 μmol m⁻² s⁻¹, the shade leaves tended to have a significantly larger net photosynthetic rate (P _N) than the sun leaves. At irradiances above 250 μmol m⁻² s⁻¹, the P _N did not differ significantly. The curves indicate that plants with thin shade leaves have a larger daily CO₂ assimilation rate per construction cost than those with thick sun leaves, even in an open habitat. These results are consistently explained by a simple model of PAR extinction in a leaf. We must target factors other than the effective assimilation when we consider the adaptive roles of thick sun leaves.     

Testing the optimal defense hypothesis in Stryphnodendron adstringens (Fabaceae,Mimosoideae) leaves: the role of structure,number, position and nectar composition of extrafloral nectaries

Stryphnodendron adstringens is a common Cerrado tree that possesses extrafloral nectaries (EFNs) on its leaves, which are located at the base and apex of the rachis and along the secondary veins. The position of EFNs and their nectar production can be affected by defense strategies because plant organs possess different values and herbivory vulnerability. Here we aimed to elucidate anatomy, histochemistry, nectar composition and EFN number on leaves of S. adstringens in the light of the optimal defense hypothesis. We found a convergence on anatomy and histochemical characterization because the three studied types of EFNs have epidermis, secretory parenchyma and vascular tissue, showing phenolic compounds and polysaccharides in the secretory parenchyma cells. The nectar contained glucose, fructose and sucrose, which attract ants of the Camponotus and Cephalotes genus. We found differences in the number of EFNs along the secondary veins and in the nectar composition between EFNs located at the base and apex of the rachis of the leaf. The number of EFNs on the secondary veins increases from the base to the apex, suggesting a strategy to induce ant patrolling over the entire leaf region. EFNs at the base secreted more nectar, which should be related to the protection of the leaf base, which is the part most vulnerable to herbivore attack and the most valued organ. We concluded that EFNs of S. adstringens are anti‐herbivore defenses whose pattern matches the predictions of the optimal defense hypothesis.     

LEAVES OF ARCHAEOSIGILLARIA VANUXEMII,A DEVONIAN LYCOPOD FROM NEW YORK

The leaf of mid Devonian Archaeosigillaria vanuxemii from Gilboa, N.Y. is known to have a thick conical base. This study demonstrates by the uncovering technique the attachment of leaves to the stem, the flattened lamina that is deltoid in outline with a toothed margin, and an apex prolonged into a hair. Comparisons are made with specimens from Kazakhstan. The morphology of leaves of other species of Archaeosigillaria and the slowly accumulating data on leaves of Devonian lycopods are discussed.