Trichome Bases Research Articles

Citric acid-assisted accumulation of Ni and other metals by Odontarrhena muralis: Implications for phytoextraction and metal foliar distribution assessed by μ-SXRF

Odontarrhena muralis is one of the most promissing plant species for Ni phytomining, and soil amendments can further increase its Ni phytoextraction ability. Here we investigated whether Ni phytomining/phytoremediation using this Ni hyperaccumulator can benefit from applying citric acid to a serpentine soil that is naturally enriched in Ni (>1000 mg kg−1). Synchrotron micro X-ray fluorescence (μ-SXRF) was used to image Ni and other metal distributions in whole fresh leaves of O. muralis. Leaf Ni accumulation in plants grown on citric acid-amended soil increased up to 55% while Co, Cr, Fe, Mn, and Zn concentrations were 4-, 14-, 6-, 7- and 1.3-fold higher than the control treatment. O. muralis presented high bioconcentration factors (leaf to soil concentration ratio) to Ni and Zn whereas Cr was seemingly excluded from uptake. The μ-SXRF images showed a uniform distribution of Ni, preferential localization of Co in the leaf tip, and clear concentration of Mn in the base of trichomes. The citric acid treatments strongly increased the Co fluoerescence intensity in the leaf tip and altered the spatial distribution of Mn across the leaf, but there was no difference in Ni fluorescence counts between the trichome-base region and the bulk leaf. Our data from a serpentine soil suggests that citrate treatment enhances Ni uptake, but Co is excreted from leaves even in low leaf concentrations, which can make Co phytoming using O. muralis unfeasible in natural serpentine soils.

MORPHOFUNCTIONAL CHARACTERISTICS OF LEAVES AND FRUITS IN MALOIDEAE (ROSACEAE): b. THE ROLE OF SURFACE TISSUES IN THE FORMATION OF RESISTANCE TO FUNGAL DISEASES

Background. Resistance to the effects of plant biotic stressors is determined by a set of factors. Among them, the leading protective role is often assigned to the physiological and biochemical characteristics of the surface tissues. However, one cannot ignore the specificity of the microstructural organization of the plant surface, since the nature of interactions in phytopathogenic organisms is more complex than the chemical impact. Meanwhile, the information accumulated to date about the structure of the surface tissues of the vegetative and reproductive organs of plants, and the interface of mycobiota, is fragmentary.Objective. Mature leaves and fruits taken from representatives of the subfamily Maloideae Werber (Malus domestica Borkh., Pyrus communis L., Cydonia oblonga Mill. and Mespilus germanica L.) were selected for the study.Materials and methods. Samples for the research were taken from the middle part of the crown of model trees in 3 replications. In recent years, scanning electron microscopy (SEM) with cryofixation is considered the most promising technique and is used to analyze the surface of biological organisms and identification of species. It is particularly informative in the case of organisms with complex surface micromorphology and for studying the biodiversity of pathogens. However, in this work we combined the methods of light, electron (SEM, TEM) and confocal microscopy. The samples were also studied using phytopathological and histochemical techniques. Condensed polyphenols were detected using K2Cr2O7 and FeCl3 as well as 4-(Dimethylamino)cinnamaldehyde (DMACA, Sigma-Aldrich).Results. On the basis of the obtained phytopathological materials and published data an overview of fungal diseases afflicting leaves and fruits of M. domestica, P. communis, C. oblonga and M. germanica was made. It has been established that a common feature of the Maloideae fruits is the accumulation of condensed polyphenols, which play an important protective role against biotic stressors, in the cells of the pericarp’s outer tissues. Anatomical and morphological characteristics of passive immunity, or horizontal resistance to fungal pathogens, include the specific nature of waxy and cuticular deposits, features of the formation of cuticular folds and peristomatic rings in the stomata area and microstrands at the base of trichomes, thickness of the cuticle and cork tissue, and the development of lenticels on fruits.Conclusion. The studied model plants suffer from a sufficiently wide range of diseases with different etiologies; among them, the most widespread and harmful are mycoses. In view of this, their resistance to fungal pathogens correlates with the specificity of the leaf and fruit surface microstructure and the content of phenolic substances (polyphenols) in the cells of the pericarp’s surface tissues.

A new species of Ormosia (Leguminosae) from the middle Miocene of Fujian, Southeast China and its biogeography

The Leguminosae are the third-largest angiosperm family with crucial floristic and ecological importance in major biomes, especially in tropical rainforests. However, reliable fossils of the family are not common in East Asia, rendering a poor understanding of the diversification and biogeographic history of the Leguminosae in this region. In this paper we described a new species of Ormosia (Leguminosae: Papilionoideae) based on compressed fruits (legumes) from the middle Miocene of Fujian in southeastern China. Ormosia zhangpuensis sp. nov. is an obovate to broadly elliptical fruit with acuminate apex, and constricted, neck-like base. Each fruit contains one single seed. External cuticle of pericarp has trichome bases and randomly oriented, anomocytic stomata. The studied fossils provide a new evidence for the diversity of the Leguminosae in East Asia during the Neogene. Fossil records also indicate that Ormosia had expanded its distribution southwards, probably in response to the global climatic cooling during the Cenozoic.

PHARMACOGNOSTIC AND HPTLC BASED COMPARATIVE STUDY ON LEAVES OF MERREMIA EMARGINATA BURM. F. AND CENTELLA ASIATICA (L.) URBAN

Objective: In this study, an attempt was made to generate information based on botanical, physicochemical and HPTLC data needed for proper identification and authentication of M. emarginata and C. asiatica belonging to two different families.
 Methods: Botanical study comprises of macroscopy, microscopy and powder microscopy of leaves of both crude drugs. The physicochemical parameters such as water-soluble extractive, alcohol soluble extractive and loss on drying at 105℃, total ash, acid insoluble ash, and volatile oil were determined according to standard methods. HPTLC studies of chloroform extracts of leaves of both drugs were conducted at 254 nm, 366 nm and 575 nm after derivatisation using vanillin-sulphuric acid and the results were documented.
 Results: The present study reveals that microscopy and most of the physicochemical parameters of both the plant materials are different. Anatomy of the leaves showed two main characteristic differences. First plenty of trichome with trichome base and calcium oxalate crystal is common in M. emarginata, which is not observed in C. asiatica. Both plants have different venation patterns and leaf constants. The total ash content and the solubility in alcohol and water for leaves of C. asiatica are higher than that of M. emarginata. The HPTLC fingerprinting pattern obtained for both drugs are different.
 Conclusion: All the results obtained from this study help in determining differences and similarities of leaves of M. emarginata and C. asiatica and thereby preventing adulteration and substitution and emphasizing the importance of standardization.

Exceptionally well-preserved Early Cretaceous leaves of Nilssoniopteris from central Mongolia

AbstractTwo new Early Cretaceous (Aptian-Albian) species of fossil bennettitalean leaves are described from central Mongolia and assigned to the genus Nilssoniopteris. Nilssoniopteris tomentosa F.Herrera, G.Shi, Tsolmon, Ichinnorov, Takahashi, P.R.Crane, et Herend. sp. nov., isolated from bulk sediment samples collected for mesofossils in the Tevshiingovi Formation at the Tevshiin Govi opencast coal mine, is distinctive in having a dense, well-developed indumentum composed of branched, flattened multicellular trichomes on the abaxial leaf surface. This species provides the first direct evidence of complex multicellular trichomes in Bennettitales and adds to the evidence of leaf anatomical features in the group that were probably advantageous in increasing water use efficiency and/or perhaps had other functions such as deterring insect herbivory. Comparison with other well-preserved leaves of Bennettitales, including Nilssoniopteris shiveeovoensis F.Herrera, G.Shi, Tsolmon, Ichinnorov, Takahashi, P.R.Crane, et Herend. sp. nov., collected as hand specimens from the Khukhteeg Formation at the Shivee Ovoo locality, suggests that the trichome bases seen commonly on the abaxial cuticle of bennettitalean leaves bore trichomes with very low fossilization potential. In some cases these trichomes may have been shed as the leaves matured, but in other cases they probably decayed during diagenesis or were destroyed during the standard processes by which fossil leaf cuticles are prepared.

Trichomes and naphthoquinones protect Streptocarpus dunnii Hook.f. against environmental stresses

Streptocarpus dunnii Hook.f. (Gesneriaceae) grows wild in South Africa in rocky terrain and at high altitude. It possesses unique patterns of growth, is acaulescent, unifoliate and monocarpic and produces unique naphthoquinones. Morphological examinations of Streptocarpus species have tended to concentrate on germination, cotyledon anatomy and development of the primary leaf (phyllomorph) while mature phyllomorphs are rarely examined. This study sought to examine the morphology of the mature phyllomorph and to more accurately determine the type and site of naphthoquinone(s)excretion. Plants were developed from invitro plantlets originating from authenticated seeds and allowed to grow in a peat-based potting compost for a year, under ambient room conditions. Mature lamina samples were examined morphologically by light, stereo and scanning electron microscopy. Results showed anisocytic stomata only on the abaxial epidermis, with numerous non-glandular and glandular trichomes on both epidermises, especially at the proximal end of the phyllomorph. Energy-dispersiveX-ray analysis indicated both trichome types to be rich in potassium. Glandular trichomes were more abundant on the abaxial surface, especially at non-glandular trichome bases over veins and adjacent to stomata in lamina areas between veins. These trichomes were shown for the first time to be the source of the naphthoquinones in S.dunnii. Chromatographic and FT-IR analyses confirmed the glandular secretions as being mainly (±)-dunnione. Results suggest that mature phyllomorphs with densely packed epidermal trichomes and a restricted distribution of stomata are adaptations by this plant to dehydration stress, while dunnione-type naphthoquinones may function in the amelioration of oxidative stress whether of biotic or abiotic origin.

Absorption of foliar-applied Zn in sunflower (Helianthus annuus): importance of the cuticle, stomata and trichomes.

The pathways whereby foliar-applied nutrients move across the leaf surface remain unclear. The aim of the present study was to examine the pathways by which foliar-applied Zn moves across the sunflower (Helianthus annuus) leaf surface, considering the potential importance of the cuticle, stomata and trichomes. Using synchrotron-based X-ray florescence microscopy and nanoscale secondary ion mass spectrometry (NanoSIMS), the absorption of foliar-applied ZnSO4 and nano-ZnO were studied in sunflower. The speciation of Zn was also examined using synchrotron-based X-ray absorption spectroscopy. Non-glandular trichomes (NGTs) were particularly important for foliar Zn absorption, with Zn preferentially accumulating within trichomes in ≤15 min. The cuticle was also found to have a role, with Zn appearing to move across the cuticle before accumulating in the walls of the epidermal cells. After 6 h, the total Zn that accumulated in the NGTs was approx. 1.9 times higher than in the cuticular tissues. No marked accumulation of Zn was found within the stomatal cavity, probably indicating a limited contribution of the stomatal pathway. Once absorbed, the Zn accumulated in the walls of the epidermal and the vascular cells, and trichome bases of both leaf sides, with the bundle sheath extensions that connected to the trichomes seemingly facilitating this translocation. Finally, the absorption of nano-ZnO was substantially lower than for ZnSO4, with Zn probably moving across the leaf surface as soluble Zn rather than nanoparticles. In sunflower, both the trichomes and cuticle appear to be important for foliar Zn absorption.

Leaf epidermal descriptors applied to the taxonomy of Lauraceae, including new anatomical characters

The difficulty of identifying Lauraceae species is well known. The leaf epidermis of 18 species from the Federal District, Brazil, was analyzed to test more characters as an aid to the taxonomy of this family. New anatomical characters are proposed here, such as sinus number, internal angles and number of sides of the common epidermal cells, their arrangement around the trichome base, and the shape and width of the subsidiary cells in relation to the guard cells. Epidermal characters that can aid in the identification of the studied species are: the contour of the common cells on both leaf surfaces and their anticlinal wall width, number of sides of the polygonal cells, sinus number, presence of angles greater than 180°, presence and type of indumentum, common cells with radial arrangement around the trichome base, stomatal position relative to the rest of the epidermis and width of the subsidiary cells in relation to the guard cells. Glabrous and glabrescent leaves are distinguished. Two species have unique characters: Aniba heringeri, with papillae on the abaxial surface, and Cryptocarya moschata, with peculiar horseshoe-shaped subsidiary cells. Characters of the epidermis together with the external leaf morphology are sufficient to distinguish the studied species. Additionally, we report for the first time the occurrence of Mezilaurus crassiramea and Ocotea diospyrifolia for the flora of Federal District, Brazil.

Stinging hair morphology and wall biomineralization across five plant families: Conserved morphology versus divergent cell wall composition.

Stinging hairs are striking examples of plant microengineering-the plant equivalent of the hypodermic syringe. The requisite mechanical properties are mostly achieved by cell wall mineralization. Stinging hairs of Urtica dioica (Urticaceae) are known to be mineralized with silica and calcium carbonate and those of Loasaceae also with calcium phosphate, but no comparative study has been provided across different taxa with stinging hairs. Light microscopy and scanning electron microscopy (SEM) with cryo-SEM and energy-dispersive x-ray spectroscopy were used to analyze morphology and biomineralization of stinging hairs of 43 species from the families Caricaceae, Euphorbiaceae, Loasaceae, Namaceae, and Urticaceae. Stinging hair morphology is similar across the taxa studied, in striking contrast to the divergent patterns of biomineralization. Trichome bases are mostly calcified, sometimes silicified, the shafts are mostly calcified, and the apices silicified (Urticaceae), and contain calcium phosphate (Caricaceae, Namaceae), both silica and calcium phosphate (some Loasaceae), or no minerals (Cnidoscolus, Euphorbiaceae). Some stinging hairs are superficially thinly coated with silica over a cell wall otherwise mineralized with calcium carbonate or calcium phosphate. Mineralization patterns are surprisingly diverse and involve three different biominerals deposited in different parts of individual trichomes with calcium phosphate a common component. The physical properties of different wall regions of the stinging trichomes are thus fine-tuned to optimize their function via modulation of wall thickness and differential element deposition. Similar function is apparently achieved through divergent wall compositions.

Two new species ofNilssoniopteris(Bennettitales) from the Middle Jurassic of Sandaoling, Turpan-Hami Basin, Xinjiang, NW China

AbstractTwo new species ofNilssoniopterisof the order Bennettitales,Nilssoniopteris hamiensisZhao and Deng, new species andNilssoniopteris crassiaxisZhao and Deng, new species, are established from the Xishanyao Formation (Middle Jurassic) of Sandaoling Coal Mine in Hami, Xinjiang, China, based on leaf macromorphology and cuticular features.Nilssoniopteris hamiensisn. sp. is characterized by its varied leaf shapes and trichome bases of 1–4 cells on the abaxial epidermis.Nilssoniopteris crassiaxisn. sp. is characterized by its broad midrib (especially near the leaf base) and trichome bases of 1–3 cells on the abaxial epidermis. Both species possess unique venation patterns that are not only simple and free, but also forked and merged to form closed loops. These anastomosing veins are even more complicated inN.crassiaxisn. sp. in that the veins can fork once, twice, or even three times, the forked veins can later merge with each other or with an adjacent vein to form a closed loop, which may later further disjoin. The generic diagnosis ofNilssoniopterisis thus accordingly emended, particularly in the venation pattern. In addition, the stratigraphic and geographical distributions of all 45 JurassicNilssoniopterisspecies worldwide have been summarized and analyzed to better understand their brief evolutionary history, indicating thatNilssoniopterismight be able to grow not only in subtropical regions as the living cycads are, but also in warm climatic regions.

Mineralized trichomes in Boraginales: complex microscale heterogeneity and simple phylogenetic patterns.

Boraginales are often characterized by a dense cover of stiff, mineralized trichomes, which may act as a first line of defence against herbivores. Recent studies have demonstrated that the widely reported silica and calcium carbonate in plant trichomes may be replaced by calcium phosphate. The present study investigates mineralization patterns in 42 species from nine families of the order Boraginales to investigate detailed patterns of mineralization and the possible presence of a phylogenetic signal in different mineralization patterns. The distribution of biominerals was analysed by scanning electron microscopy (SEM) including cryo-SEM and energy-dispersive X-ray analyses with element mapping. The observed distribution of biominerals was plotted onto a published phylogeny of the Boraginales. Three colours were selected to represent the principal elements: Si (red), Ca (green) and P (blue). Calcium carbonate was present in the mineralized trichomes of all 42 species investigated, silica in 30 and calcium phosphate in 25; multiple mineralization with calcium carbonate and silica or calcium phosphate was found in all species, and 13 of the species were mineralized with all three biominerals. Trichome tips featured the most regular pattern - nearly all were exclusively mineralized with either silica or calcium phosphate. Biomineralization of the trichome shafts and bases was found to be more variable between species. However, the trichome bases were also frequently mineralized with calcium phosphate or silica, indicating that not only the tip is under functional constraints requiring specific patterns of chemical heterogeneity. The complete absence of either silica or phosphate may be an additional feature with systematic relevance. This study demonstrates that complex, site-specific and differential biomineralization is widespread across the order Boraginales. Calcium phosphate, only recently first reported as a structural plant biomineral, is common and appears to be functionally analogous to silica. A comparison with the phylogeny of Boraginales additionally reveals striking phylogenetic patterns. Most families show characteristic patterns of biomineralization, such as the virtual absence of calcium phosphate in Cordiaceae and Boraginaceae, the triple biomineralization of Heliotropiaceae and Ehretiaceae, or the absence of silica in Namaceae and Codonaceae. The complex chemical and phylogenetic patterns indicate that trichome evolution and functionalities are anything but simple and follow complex functional and phylogenetic constraints.

Preinfection process in cocoa fruits by Moniliophthora roreri

Moniliophthora roreri (Cif & Park) (Evans et al 1978) infects cocoa ( Theobroma cacao L) fruits causing great losses. A study was conducted of the pathogen-host relationships on the fruit considering fungal spore distribution, germination, germ tube formation and infection using Scanning Electron Microscopy, Sixty-day-old fruits, inoculated and not inoculated, of cv. Pound-7 (susceptible) and UF-296' (moderately resistant) were collected from two sites of Costa Rica's low humid tropic, La Lola and Turrialba, Conidia were found mostly at the base of trichomes. Spores germinated similarly on both cultivars. Germination occurred through a polar germination pore or alternatively through the lateral spore wall 7-8 hr after inoculation of the fruits. The number of germinated spores was low, Germtube infection of the fruit via stomata was not common, Preliminary evidence suggests infection via direct penetration of epidemal cells and trichomes. Hyphae that emerged from the trichomes spread and infected other sites in the epidermis, including trichomes, stomata, injuries and other epidermal cells, Apressorium-like structures or terminal swellings on germ tubes were observed occassionally.

Leaf epidermal features of Quercus Group Ilex (Fagaceae) and their application to species identification

Leaf epidermal features are useful for elucidating the taxonomy and systematics of oak species. Quercus Group Ilex has a wide distribution mainly in subtropical areas of Eurasia with rich fossil records since the Oligocene, but no comprehensive study has ever been conducted on its diversity of leaf epidermal features. We compared the leaf epidermal features of 37 species of Quercus Group Ilex and Q. suber from Group Cerris using light microscopy (LM) and scanning electron microscopy (SEM). A total of five trichome types (including three glandular and two non-glandular types) and two trichome base types were found. Leaf epidermal features of Group Ilex show typical xeromorphic features. The stomatal complexes are stephanocytic. The leaf trichome types and trichome base types are stable at inter- and intra-species levels. The trichomes, stomatal sizes and density and the ray arm lengths show a wide variation during developing stages within species. The leaf epidermal features show a highly convergent pattern in the genus Quercus based on tree-mapping analysis, except for the multiple epidermal layers on the adaxial surface supports the monophyletic origin of section Heterobalanus. Cluster analysis of leaf epidermal characters infers two morphological subgroups within Group Ilex: (1) the capitate and (2) the branched uniseriate. The trichomes and trichome base types, and their density are useful for species identification, which can improve the accuracy of assigning fossil leaves to their nearest living relatives in Group Ilex.

Leaf Cuticle Microstructure of Machilus maomingensis sp. nov. (Lauraceae) from the Eocene of the Maoming Basin, South China

AbstractMachilus maomingensis Jin et Tang, sp. nov. from the Eocene Youganwo Formation of the Maoming Basin, South China, is studied in detail from the perspective of the leaf architecture and the excellently preserved cuticle. The leaf margin is entire, the primary venation is pinnate; 6 to 8 secondary veins are present and the major secondary venation is eucamptodromous. Stomata are paracytic and occur on the lower epidermis. Trichome bases are unicellular. Oil cells are present in the upper epidermis. The new fossil species described has features of the Lauraceae, particularly of the extant genus Machilus Rumphius ex Nees, and it is most similar to Machilus chinensis (Bentham) Hemsley, an extant species distributed in southern China and Vietnam. Hence, Machilus maomingensis sp. nov. is inferred to live in a warm and humid climate. The discovery of the present fossil indicates that Machilus has existed in South China from at least the Eocene.

Protein profile and protein interaction network of Moniliophthora perniciosa basidiospores

BackgroundWitches’ broom, a disease caused by the basidiomycete Moniliophthora perniciosa, is considered to be the most important disease of the cocoa crop in Bahia, an area in the Brazilian Amazon, and also in the other countries where it is found. M. perniciosa germ tubes may penetrate into the host through intact or natural openings in the cuticle surface, in epidermis cell junctions, at the base of trichomes, or through the stomata. Despite its relevance to the fungal life cycle, basidiospore biology has not been extensively investigated. In this study, our goal was to optimize techniques for producing basidiospores for protein extraction, and to produce the first proteomics analysis map of ungerminated basidiospores. We then presented a protein interaction network by using Ustilago maydis as a model.ResultsThe average pileus area ranged from 17.35 to 211.24 mm2. The minimum and maximum productivity were 23,200 and 6,666,667 basidiospores per basidiome, respectively. The protein yield in micrograms per million basidiospores were approximately 0.161; 2.307, and 3.582 for germination times of 0, 2, and 4 h after germination, respectively. A total of 178 proteins were identified through mass spectrometry. These proteins were classified according to their molecular function and their involvement in biological processes such as cellular energy production, oxidative metabolism, stress, protein synthesis, and protein folding. Furthermore, to better understand the expression pattern, signaling, and interaction events of spore proteins, we presented an interaction network using orthologous proteins from Ustilago maydis as a model. Most of the orthologous proteins that were identified in this study were not clustered in the network, but several of them play a very important role in hypha development and branching.ConclusionsThe quantities of basidiospores 7 × 109; 5.2 × 108, and 6.7 × 108 were sufficient to obtain enough protein mass for the three 2D-PAGE replicates, for the 0, 2, and 4 h-treatments, respectively. The protein extraction method that is based on sedimentation, followed by sonication with SDS-dense buffer, and phenolic extraction, which was utilized in this study, was effective, presenting a satisfactory resolution and reproducibility for M. perniciosa basidiospores. This report constitutes the first comprehensive study of protein expression during the ungerminated stage of the M. perniciosa basidiospore. Identification of the spots observed in the reference gel enabled us to know the main molecular interactions involved in the initial metabolic processes of fungal development.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-016-0753-0) contains supplementary material, which is available to authorized users.

Epidermal morphology and ecological significance of Glossopteris pubescens nom. nov. from the Brazilian Permian (Sakmarian)

A Brazilian glossopterid species is reassigned and redescribed based on cuticular analysis. The original name (Guerra-Sommer, 1992) is illegitimate because it is a later homonym of Glossopteris papillosa Srivastava (1969). Thus, the new name Glossopteris pubescens is erected as a replacement for G. papillosa Guerra-Sommer. The leaf adpressions come from a tonstein layer within a Sakmarian coal seam (U/Pb age 291±1.3Ma) of the Faxinal Coalfield, southern Paraná Basin, Brazil (Rio Bonito Formation). Leaf fragments macerated in Schulze's solution yielded larger cuticle fragments than those previously described, totaling over 100 analyzed leaves. The unique ornamentation of the lower side of the lamina comprises simple trichomes and trichome base complexes densely concentrated on the venation system. These epidermal structures are interpreted under the light of new paleoecological data for the Faxinal Coalfield which include humidity oscillations, wildfire occurrences and influence of volcanic activity. These paleoenvironmental factors are suggested to have played a main role in the development of the xeromorphic cuticle structures which possibly had a multitask function during both dry and wet cycles, mainly as protection of stomata against excessive humidity and air dust.

A New Species of Eriosema (Leguminosae, Papilionoideae, Phaseoleae) from Mato Grosso do Sul, Brazil, with a Secretory Structure Novel to the Genus

Eriosema grearii, a new species for the genus (Leguminosae, Papilionoideae, Phaseoleae, Cajaninae), is described and illustrated. Similar to E. heterophyllum, it differs from it morphologically by the free (vs. joined) stipules, lax flowers distributed along the inflorescence axis (vs. congested and concentrated at its apex), inflorescences not opposite to the leaves (vs. opposite), and leaflets with secretory cells at the base of trichomes (vs. absence of secretory cells at the base of trichomes). A survey of the leaflet secretory structures revealed that E. grearii has distinct secretory structures, referred here as secretory-base trichomes, and reported for the first time for the Phaseoleae tribe. An identification key for the Eriosema species in Mato Grosso do Sul, where the new species occurs, is provided.

First record of charcoalified sphenopterid mesofossils from the Serpukhovian (Mississippian, early Carboniferous) Jingyuan (Tsingyuan) Formation in Gansu Province, western China

Anatomical characteristics of three charred mesofossils are described from the Serpkhovian Jingyuan (Tsingyuan) Formation (Mississippian, early Carboniferous) in the Ciyao Section, Baiyin City, Gansu Province, western China. They are attributed to three types based on morphology, corresponding to the well-known, late Palaeozoic (uppermost Devonian–Permian) sphenopterid foliage. All of these three morphologic types of mesofossils have similar epidermal characteristics: the differentiation of costal and intercostal fields in both upper and lower epidermis, the same shape of the epidermal cells, similar simple stomata with only two bean-shaped guard cells but without subsidiary cells, the same distribution and orientation of stomata in the upper epidermis, and trichome bases in the costal fields of the lower epidermis. It is inferred that, based on the similarity of the anatomical characteristics, these three types of mesofossils could be derived from the same species of parent plant, although it appears that there are some differences in morphology. The presence of trichome bases in the costal fields of upper epidermis of the fossils is most probably an ecological adaptation to insect activity as observed in extant plants. Our record of charcoalified mesofossils for the first time demonstrates the occurrence of Mississippian wildfire in the North China Block, then located in eastern Pangaea, appearing as a tropical island in Palaeotethys Ocean.

Infection of Maize by Clavibacter michiganensis subsp. nebraskensis Does Not Require Severe Wounding.

Goss's bacterial wilt and leaf blight of maize is caused by Clavibacter michiganensis subsp. nebraskensis. Infested residue is the primary source of inoculum and infection occurs via wounds caused by sand blasting, hail, or wind damage. The pathogen survives as an epiphyte on maize leaves and, because the disease has been observed on plants in the field with no obvious wounding, we wondered whether infection by epiphytic C. michiganensis subsp. nebraskensis and disease development could occur in the absence of severe wounding. Consequently, greenhouse experiments were done to evaluate disease development in the absence of wounding in ambient and increased humidity conditions. Maize plants at the V4 to V5 crop development stage were spray inoculated with a suspension of C. michiganensis subsp. nebraskensis (108 cells ml-1). Leaf blight incidence was assessed on whole plants and individual leaves; epiphytic populations of C. michiganensis subsp. nebraskensis were monitored by dilution plating of leaf washes; and epiphytic C. michiganensis subsp. nebraskensis colonization was visualized using scanning electron microscopy (SEM). Goss's leaf blight symptoms were observed on nonwounded plants in ambient (37.0% plant incidence) and increased humidity conditions (60.0% plant incidence). Populations of epiphytic C. michiganensis subsp. nebraskensis survived and increased on maize leaves, particularly at increased humidity. We observed C. michiganensis subsp. nebraskensis colonizing maize leaves in localized sites that included epidermal junctions, cuticle depressions, in and around stomata, and at the base of trichomes. Single cells and aggregates of C. michiganensis subsp. nebraskensis were observed within substomatal chambers using SEM. These data indicate that severe wounding is not necessary for C. michiganensis subsp. nebraskensis infection of maize, and stomata or trichomes may serve as entry points for the bacterium.

Fossil leaves of Banksia, Banksieae and pretenders: resolving the fossil genus Banksieaephyllum

The genus Banksieaephyllum, originally erected for cuticle-bearing fossil leaves of subtribe Banksiinae (Proteaceae subfamily Grevilleoideae, tribe Banksieae), is reassessed. Of the 18 described species, nine are accepted within Banksia, including Banksieaephyllum obovatum Cookson & Duigan, which is synonymised with B. laeve Cookson & Duigan on the basis of new cuticular preparations. Two other species are transferred to Banksieaefolia gen. nov., a genus erected for Banksieae of uncertain affinities, and which presently includes only fossils that probably belong to subtribe Musgraveinae. The seven other Banksieaephyllum species lack definitive characters of Proteaceae (i.e. brachyparacytic stomata and annular trichome bases) and do not have Banksieae-type cylindrical trichome bases. These species are, therefore, not accepted as Proteaceae and are transferred to Pseudobanksia gen. nov., together with another fossil Banksia-like leaf species, Phyllites yallournensis Cookson & Duigan. Lectotypes are chosen for Banksia fastigata H.Deane, Banksieaephyllum acuminatum Cookson & Duigan, Banksieaephyllum angustum Cookson & Duigan and Banksieaephyllum laeve Cookson & Duigan. Implications arising from the re-assessment of Banksieaephyllum include clarification of biome conservatism in Banksieae; Banksia has long had an association with relatively open, sclerophyllous vegetation, and Musgraveinae with rainforest. Pseudobanksia and Banksia share convergent traits, but in contrast to Banksia, Pseudobanksia failed to survive the drying climates and increased fire-frequencies of the Neogene.