Search

Bulbophyllum is the most species-rich orchid genus. Recent molecular data groups certain of its species into a monophyletic ' Cirrhopetalum alliance'. Within this alliance are a monophyletic section Cirrhopetaloides and a non-monophyletic section Cirrhopetalum. Floral morphology and scent are partially conserved phylogenetically compared to the molecular data. Here, floral morphology, histochemistry, anatomy, and floral volatile organic compounds (VOCs) of selected Bulbophyllum species are analysed to assess whether there are structural or chemical differences that support separation into the two sections, to update available VOC data from this genus, and to consider evolutionary adaptations in the ' Cirrhopetalum alliance'. We found that ' Cirrhopetalum alliance' flowers differ from some sections of Bulbophyllum in the structure of cells lining the longitudinal groove on the labellum or lip and report, for the first time in Bulbophyllum , a type of atypical oleiferous trichome probably involved in VOC production. We show a clear difference in floral VOC profiles between B. bicolor (sect. Cirrhopetaloides) and four other Bulbophyllum species, three previously assigned to sect. Cirrhopetalum , but VOC profiles do not support separation into the two sections. The lack of congruence between already established molecular phylogeny, floral anatomy, and VOC data suggests that VOC differences are due to recently and independently evolved pollinator specificity. We therefore show that there is no clear separation of these sections based on floral anatomy, histochemistry, or VOC profiles. [ABSTRACT FROM AUTHOR]

The zygnematophytes are the closest relatives of land plants and comprise several lineages that adapted to a life on land. Species of the genus Serritaenia form colorful, mucilaginous capsules, which surround the cells and block harmful solar radiation, one of the major terrestrial stressors. In eukaryotic algae, this 'sunscreen mucilage' represents a unique photoprotective strategy, whose induction and chemical background are unknown. We generated a de novo transcriptome of Serritaenia testaceovaginata and studied its gene regulation under moderate UV radiation (UVR) that triggers sunscreen mucilage under experimental conditions. UVR induced the repair of DNA and the photosynthetic apparatus as well as the synthesis of aromatic specialized metabolites. Specifically, we observed pronounced expressional changes in the production of aromatic amino acids, phenylpropanoid biosynthesis genes, potential cross-membrane transporters of phenolics, and extracellular, oxidative enzymes. Interestingly, the most up-regulated enzyme was a secreted class III peroxidase, whose embryophyte homologs are involved in apoplastic lignin formation. Overall, our findings reveal a conserved, plant-like UVR perception system (UVR8 and downstream factors) in zygnematophyte algae and point to a polyphenolic origin of the sunscreen pigment of Serritaenia , whose synthesis might be extracellular and oxidative, resembling that of plant lignins. [ABSTRACT FROM AUTHOR]

Background Land plants commonly produce red pigmentation as a response to environmental stressors, both abiotic and biotic. The type of pigment produced varies among different land plant lineages. In the majority of species they are flavonoids, a large branch of the phenylpropanoid pathway. Flavonoids that can confer red colours include 3-hydroxyanthocyanins, 3-deoxyanthocyanins, sphagnorubins and auronidins, which are the predominant red pigments in flowering plants, ferns, mosses and liverworts, respectively. However, some flowering plants have lost the capacity for anthocyanin biosynthesis and produce nitrogen-containing betalain pigments instead. Some terrestrial algal species also produce red pigmentation as an abiotic stress response, and these include both carotenoid and phenolic pigments. Scope In this review, we examine: which environmental triggers induce red pigmentation in non-reproductive tissues; theories on the functions of stress-induced pigmentation; the evolution of the biosynthetic pathways; and structure–function aspects of different pigment types. We also compare data on stress-induced pigmentation in land plants with those for terrestrial algae, and discuss possible explanations for the lack of red pigmentation in the hornwort lineage of land plants. Conclusions The evidence suggests that pigment biosynthetic pathways have evolved numerous times in land plants to provide compounds that have red colour to screen damaging photosynthetically active radiation but that also have secondary functions that provide specific benefits to the particular land plant lineage. [ABSTRACT FROM AUTHOR]

Life on land exposes plants to varied abiotic and biotic environmental stresses. These environmental drivers contributed to a large expansion of metabolic capabilities during land plant evolution and species diversification. In this review we summarize knowledge on how the specialized metabolite pathways of bryophytes may contribute to stress tolerance capabilities. Bryophytes are the non-tracheophyte land plant group (comprising the hornworts, liverworts, and mosses) and rapidly diversified following the colonization of land. Mosses and liverworts have as wide a distribution as flowering plants with regard to available environments, able to grow in polar regions through to hot desert landscapes. Yet in contrast to flowering plants, for which the biosynthetic pathways, transcriptional regulation, and compound function of stress tolerance-related metabolite pathways have been extensively characterized, it is only recently that similar data have become available for bryophytes. The bryophyte data are compared with those available for angiosperms, including examining how the differing plant forms of bryophytes and angiosperms may influence specialized metabolite diversity and function. The involvement of stress-induced specialized metabolites in senescence and nutrient response pathways is also discussed. [ABSTRACT FROM AUTHOR]

Objective Cartilage and bone damage in RA are associated with elevated IL-1β. The effects of IL-1β can be reduced by biological therapies that target IL-1β or TNF-α. However, the mechanisms responsible for increased IL-1β and the effect of anti-TNF-α have not been fully elucidated. Recently, sterile-α and armadillo motif containing protein (SARM) was identified as a negative regulator of toll-like receptor (TLR) induced IL-1β secretion through an interaction with the inflammasome. This study set out to investigate SARM during TLR-induced IL-1β secretion in RA peripheral blood monocytes and in patients commencing anti-TNF-α treatment. Methods Monocytes were isolated from RA patients and healthy controls; disease activity was measured by DAS28. IL-1β secretion was measured by ELISA following TLR1/2, TLR4 and TLR7/8 stimulation. The mRNA expression of SARM1 , IL-1β and the components of the NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome were measured by quantitative PCR. SARM protein expression was measured by western blotting. Results TLR1/2 activation induced elevated IL-1β in RA monocytes compared with healthy controls (P = 0.0009), which negatively correlated with SARM1 expression (P = 0.0086). Lower SARM expression also correlated with higher disease activity (P = 0.0246). Additionally, patients responding to anti-TNF-α treatment demonstrated a rapid upregulation of SARM, which was not observed in non-responders. Conclusion Together, these data highlight a potential contribution from SARM to RA pathophysiology where decreased SARM may lead to elevated IL-1β associated with RA pathogenesis. Furthermore, the data additionally present a potential mechanism by which TNF-α blockade can modify IL-1β secretion. [ABSTRACT FROM AUTHOR]

Most members of the Neotropical orchid subtribe Maxillariinae lack floral rewards (e.g. nectar, food-hairs, resin or wax) and attract pollinators by food- or sexual-deceit. Of those that produce floral rewards, relatively few produce resin. Members of the Mexican and Central American Camaridium cucullatum complex are considered to be entirely rewardless. Here, we demonstrate that they produce lipoidal or resin-like labellar secretions. They are also characterized by the possession of a prominent, and often brightly coloured, thickened transverse ridge located at the base of the column, above the point of attachment to the labellum. Although the transverse ridge is considered a putative synapomorphy for members of the C. cucullatum complex, a similar structure was observed in the related genus Nitidobulbon. Anatomy and secretory activity of the labella and presumed transverse ridges of both taxa are investigated and compared by means of light and fluorescence microscopy, in conjunction with histochemistry and scanning and transmission electron microscopy. Of the representatives of core Maxillariinae investigated, only members of the C. cucullatum complex possessed a transverse ridge, strengthening claims for this synapomorphy. The similar structure in Nitidobulbon comprised the proximal part of the column. Because both these structures were non-secretory and located in juxtaposition to the secretory region of the labellum, where their bright colours contrasted with those of the perianth segments, it is proposed that they act as focal points, guiding insect visitors further into the flower, and thus facilitating pollination. It is also hypothesized that they compensate for a lack of obvious nectar-guides on the labellum, or where these are obfuscated by heavy secretions of resin. Because the transverse ridge was not prominent in some members of the C. cucullatum complex, and not always easily distinguishable from superficially similar structures in related genera (e.g. Nitidobulbon), we recommend it be used in taxonomy only in conjunction with other more reliable characters. [ABSTRACT FROM AUTHOR]

Species traditionally considered to constitute the non-pseudocopulatory Maxillaria section Rufescens have recently been transferred to the pseudocopulatory genus Mormolyca, based on molecular phylogenetic analysis. The labellum of species assigned to the latter taxon, however, differs from that of species assigned to Maxillaria section Rufescens s.s. on morphological, anatomical, biochemical and ultrastructural grounds. Thus, whereas species of Mormolyca s.s. have insectiform, pilose-hirsute labella, the trichomes of which produce no food-reward and no resin, the non-insectiform labella of species of Maxillaria section Rufescens s.s. are papillose and their clavate papillae secrete copious resin and are frequently rich in starch. Furthermore, fragrance production in these two groups appears to involve a different set of organelles, with resin and fragrance seemingly produced by the same organelles in Maxillaria section Rufescens s.s. All these differences are ultimately related to the dissimilar pollination syndromes of the two taxa. [ABSTRACT FROM AUTHOR]

Cytomegalovirus (CMV) infection sometimes causes large expansions of CMV-specific T cells, particularly in older people. This is believed to undermine immunity to other pathogens and to accelerate immunosenescence. While multiple different CMV proteins are recognized, most publications on age-related T-cell expansions have focused on dominant target proteins UL83 or UL123, and the T-cell activation marker interferon-γ (IFN-γ). We were concerned that this narrow approach might have skewed our understanding of CMV-specific immunity at older ages. We have, therefore, widened the scope of analysis to include in vitro-induced T-cell responses to 19 frequently recognized CMV proteins in "young" and "older" healthy volunteers and a group of "oldest old" long-term survivors (>85 years of age). Polychromatic flow cytometry was used to analyze T-cell activation markers (CD107, CD154, interleukin-2 [IL-2], tumor necrosis factor [TNF], and IFN-γ) and memory phenotypes (CD27, CD45RA). The older group had, on average, larger T-cell responses than the young, but, interestingly, response size differences were relatively smaller when all activation markers were considered rather than IFN-γ or TNF alone. The oldest old group recognized more proteins on average than the other groups, and had even bigger T-cell responses than the older group with a significantly larger central memory CD4 T-cell component. [ABSTRACT FROM AUTHOR]

Background:  Parallel upregulation of several T-cell effector functions (ie, polyfunctionality) is believed to be critical for the protection against viruses but thought to decrease in large T-cell expansions, in particular at older ages. The factors determining T-cell polyfunctionality are incompletely understood. Here we revisit the question of cytomegalovirus (CMV)-specific T-cell polyfunctionality, including a wide range of T-cell target proteins, response sizes, and participant ages.Methods:  Polychromatic flow cytometry was used to analyze the functional diversity (ie, CD107, CD154, interleukin 2, tumor necrosis factor, and interferon γ expression) of CD4+ and CD8+ T-cell responses to 19 CMV proteins in a large group of young and older United Kingdom participants. A group of oldest old people (age >85 years) was included to explore these parameters in exceptional survivors. Polyfunctionality was assessed for each protein-specific response subset, by subset and in aggregate, across all proteins by using the novel polyfunctionality index.Results:  Polyfunctionality was not reduced in healthy older people as compared to young people. However, it was significantly related to target protein specificity. For each protein, it increased with response size. In the oldest old group, overall T-cell polyfunctionality was significantly lower.Discussion:  Our results give a new perspective on T-cell polyfunctionality and raise the question of whether maintaining polyfunctionality of CMV-specific T cells at older ages is necessarily beneficial. [ABSTRACT FROM AUTHOR]

Floral food-rewards of B ulbophyllum range from nectar to protein-rich mucilage and lipid-rich labellar secretions. For the first time, the structure of the labellum and the secretory process are investigated for four African B ulbophyllum species. The most specialized type of labellar organization occurred in B . schinzianum, the deep, narrow, median longitudinal groove consisting of palisade-like secretory cells flanked by trichomes containing lipid droplets, and the copious secretion containing sugar. This groove was absent or poorly defined, shallow and wide, in the remaining taxa, the scant secretion containing lipid. All taxa possessed a striate cuticle lacking cracks and pores, and micro-channels were present, cuticular blisters occurring only in B . schinzianum. The labellum contained storage parenchyma ( B . lupulinum) or mesophyll-like parenchyma ( B . schinzianum), but in section M egaclinium ( B . falcatum and B . maximum), these were replaced by aerenchyma. In B . schinzianum, the form of the labellar groove, sweet fragrance and sugary secretion suggest pollination by Hymenoptera, the food-reward and fragrance indicating that pseudocopulation is unlikely. Conversely, the form of the labellum of taxa having smaller flowers, and the lipid-rich secretion, suggests pollination by small flies. The labellar aerenchyma may facilitate this process or even aid wind-assisted pollination. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 179, 266-287. [ABSTRACT FROM AUTHOR]

Systemic Lupus Erythematosus (SLE) can affect multiple organ systems, including the central (CNS) and/or peripheral nervous system. Individuals with nervous system involvement (termed Neuropsychiatric SLE or NPSLE) can present with nonspecific symptoms such as cognitive dysfunction. It is difficult to ascertain whether this is a direct consequence of lupus disease activity on the brain. Intraindividual variability, measured through trial-to-trial reaction time variation, has been proposed as a behavioral marker of CNS integrity.We compared 14 NPSLE, 20 non-NPSLE, and 27 age-matched healthy participants using multiple variability metrics. Variability was increased in NPSLE compared with non-NPSLE participants, and was increased throughout the distribution rather than there being a selective increase in extreme reaction times. Variability metrics were strongly intercorrelated providing convergent evidence that the different metrics are tapping similar processes. The results suggest that there is ongoing disruption to cognitive processing in NPSLE and may indicate small fluctuations in attention. [ABSTRACT FROM AUTHOR]

Anthocyanin biosynthesis is regulated by a transcription factor complex. Here, it is determined that the potential bHLH partners in this complex function in a hierarchy to control each other and the anthocyanin biosynthesis pathway.The anthocyanin biosynthetic pathway is regulated by a transcription factor complex consisting of an R2R3 MYB, a bHLH, and a WD40. Although R2R3 MYBs belonging to the anthocyanin-activating class have been identified in many plants, and their role well elucidated, the subgroups of bHLH implicated in anthocyanin regulation seem to be more complex. It is not clear whether these potential bHLH partners are biologically interchangeable with redundant functions, or even if heterodimers are involved. In this study, AcMYB110, an R2R3 MYB isolated from kiwifruit (Actinidia sp.) showing a strong activation of the anthocyanin pathway in tobacco (Nicotiana tabacum) was used to examine the function of interacting endogenous bHLH partners. Constitutive expression of AcMYB110 in tobacco leaves revealed different roles for two bHLHs, NtAN1 and NtJAF13. A hierarchical mechanism is shown to control the regulation of transcription factors and consequently of the anthocyanin biosynthetic pathway. Here, a model is proposed for the regulation of the anthocyanin pathway in Solanaceous plants in which AN1 is directly involved in the activation of the biosynthetic genes, whereas JAF13 is involved in the regulation of AN1 transcription. [ABSTRACT FROM PUBLISHER]

Background and Aims Floral secretions are common in Bulbophyllum Thouars, and the labella of a number of Asian species are said to produce secretions rich in lipids that act as food rewards for insect pollinators. Although some of these reports are based on simple histochemical tests, a much greater number are anecdotal and, hitherto, neither the ultrastructure of the labellum nor the secretory process has been investigated in detail. Furthermore, sophisticated histochemical approaches have generally not been applied. Here, both the labellar structure and the secretory process are investigated for four species of Asian Bulbophyllum sect. Racemosae Benth. & Hook. f., namely Bulbophyllum careyanum (Hook.) Spreng., B. morphologorum Kraenzl., B. orientale Seidenf. and B. wangkaense Seidenf., and compared with those of unequivocal lipid-secreting orchids. Methods Labellar, secretory tissue was investigated using light microscopy, scanning electron microscopy, transmission electron microscopy and histochemistry. Key Results The adaxial median longitudinal groove of the labellum contained secretory tissue comprising palisade-like epidermal cells, similar to those of certain lipid-secreting Oncidiinae Benth. However, these cells and their secretions gave positive results mainly for protein and mucilage, and their organelle complement was consistent with that of cells involved in protein and mucilage synthesis. Sub-cuticular accumulation of secretion resulted in cuticular distension and blistering. The sub-epidermal layer of isodiametric parenchyma contained starch and, like the epidermal cells, ultrastructure consistent with mucilage synthesis. Lipids were mainly confined to the cuticle, and hardly any intracellular lipid droplets were observed. Conclusions It is proposed that mucilage is produced by dictyosomes present in the palisade-like epidermal cells. Mucilage precursors may also be produced by these same organelles in sub-epidermal cells and are thought to pass along the symplast via plasmodesmata into the adjoining palisade-like secretory cells, which contain abundant arrays of rough endoplasmic reticulum. Here, they become chemically modified and form a protein-rich, mucilaginous secretion that, following vesicle-mediated transport across the cytoplasm, traverses the cell wall and accumulates in blisters formed from the distended cuticle. Rupture of these blisters releases the secretion onto the labellar surface. However, in certain species, there is some evidence that the secretion may traverse the cuticle via cuticular pores, and micro-channels may permit the passage of fragrance. Hydrolysis of sub-epidermal starch probably generates the carbohydrate and, together with mitochondria, much of the energy required for the secretory process. This anatomical organization resembles that found in certain lipid-secreting, Neotropical species of Bulbophyllum and Oncidiinae, but since the chemical composition of their secretions is different, and these taxa occur on a separate continent and have different insect pollinators, parallelism of floral anatomy is likely. [ABSTRACT FROM PUBLISHER]

Background and Aims Recently, molecular approaches have been used to investigate the phylogeny of subtribe Oncidiinae, resulting in the re-alignment of several of its genera. Here, a description is given of the structure of the floral elaiophores (oil glands) of four species formerly assigned to Oncidium Sw. Those of Vitekorchis excavata (Lindl.) Romowicz & Szlach., Cyrtochilum meirax (Rchb.f.) Dalström and a species of Oncidium displaying floral dimorphism, namely O. heteranthum Poepp. & Endl. var. album, are compared with that of Gomesa longipes (Lindl.) M.W. Chase & N.H. Williams, whose epithelial elaiophores are typical of many Oncidiinae, in order to extend our understanding of elaiophore diversity within this subtribe. Methods Floral elaiophore structure was examined and compared at anthesis for all four species using light microscopy, scanning electron microscopy, transmission electron microscopy and histochemistry. Key Results In all species investigated, with the exception of C. meirax, the floral elaiophore occurs on the labellar callus and is of the intermediate type, possessing both glabrous and trichomatous regions. By contrast, although all four species produce lipid secretions, C. meirax lacks an obvious elaiophore. In each case, the secretory tissue is represented by a single-layered epidermis of cuboidal cells (trichomatous and/or atrichomatous). Palisade cells are absent. The secretion may be wax- or oil-like and is usually produced by smooth endoplasmic reticulum (SER). However, in C. meirax, where rough endoplasmic reticulum (RER) predominates, oil accumulates as plastoglobuli within elaioplasts. These plastoglobuli are then discharged into the cytoplasm, forming oil bodies. In some species, oil usually accumulates within vesicles at the plasmalemma or in the periplasmic space before traversing the cell wall and accumulating beneath the cuticle, sometimes with distension of the latter. Gomesa longipes is unusual in its production of a heterogeneous secretion, whereas Vitekorchis excavata is equally remarkable for the protuberances found on the walls of its secretory cells. Conclusions Anatomically, the secretory tissues of all four species, despite currently being assigned to four different genera, are remarkably similar and indicative of homoplasy. This supports previous investigations of the floral elaiophore in Oncidiinae, which showed that the same elaiophore characters may be shared by different clades, but not always by species of the same genus. Consequently, elaiophores are considered to be of limited value in investigating the phylogeny of this subtribe. Furthermore, floral dimorphism does not greatly modify elaiophore structure in the fertile flowers of Oncidium heteranthum var. album. Based on the presence or absence of well-defined elaiophores, the nature of the secretion and the cell ultrastructure, it is likely that floral oil may be produced in Oncidiinae in one of two ways: by the ER (mainly SER) or by plastids, most notably elaioplasts. Once the oil is discharged into the cytoplasm as oil bodies or oil droplets, there is little difference between the subsequent stages of oil secretion; the oil traversing the cytoplasm (often vesicle-mediated) and cell wall before accumulating beneath the cuticle. [ABSTRACT FROM PUBLISHER]

Plants require sophisticated regulatory mechanisms to ensure the degree of anthocyanin pigmentation is appropriate to myriad developmental and environmental signals. Central to this process are the activity of MYB-bHLH-WD repeat (MBW) complexes that regulate the transcription of anthocyanin genes. In this study, the gene regulatory network that regulates anthocyanin synthesis in petunia (Petunia hybrida) has been characterized. Genetic and molecular evidence show that the R2R3-MYB, MYB27, is an anthocyanin repressor that functions as part of the MBW complex and represses transcription through its C-terminal EAR motif. MYB27 targets both the anthocyanin pathway genes and basic-helix-loop-helix (bHLH) ANTHOCYANIN1 (AN1), itself an essential component of the MBW activation complex for pigmentation. Other features of the regulatory network identified include inhibition of AN1 activity by the competitive R3-MYB repressor MYBx and the activation of AN1 , MYB27 , and MYBx by the MBW activation complex, providing for both reinforcement and feedback regulation. We also demonstrate the intercellular movement of the WDR protein (AN11) and R3-repressor (MYBx), which may facilitate anthocyanin pigment pattern formation. The fundamental features of this regulatory network in the Asterid model of petunia are similar to those in the Rosid model of Arabidopsis thaliana and are thus likely to be widespread in the Eudicots. [ABSTRACT FROM AUTHOR]

Background and Aims A significant proportion of orchid species assigned to subtribe Oncidiinae produce floral oil as a food reward that attracts specialized bee pollinators. This oil is produced either by glabrous glands (epithelial elaiophores) or by tufts of secretory hairs (trichomal elaiophores). Although the structure of epithelial elaiophores in the Oncidiinae has been well documented, trichomal elaiophores are less common and have not received as much attention. Only trichomal elaiophores occur in the genus Lockhartia, and their distribution and structure are surveyed here for the first time. Methods Flowers of 16 species of Lockhartia were studied. The location of floral elaiophores was determined histochemically and their anatomical organization and mode of oil secretion was investigated by means of light microscopy, scanning electron microscopy and transmission electron microscopy. Key Results and Conclusions – All species of Lockhartia investigated have trichomal elaiophores on the adaxial surface of the labellum. Histochemical tests revealed the presence of lipoidal substances within the labellar trichomes. However, the degree of oil production and the distribution of trichomes differed between the three major groups of species found within the genus. All trichomes were unicellular and, in some species, of two distinct sizes, the larger being either capitate or apically branched. The trichomal cuticle was lamellate, and often appeared distended due to the subcuticular accumulation of oil. The labellar trichomes of the three species examined using transmission electron microscopy contained dense, intensely staining cytoplasm with apically located vacuoles. Oil-laden secretory vesicles fused with the plasmalemma and discharged their contents. Oil eventually accumulated between the cell wall and cuticle of the trichome and contained electron-transparent profiles or droplets. This condition is considered unique to Lockhartia among those species of elaiophore-bearing Oncidiinae studied to date. [ABSTRACT FROM AUTHOR]

Most species of Maxillaria s.l. are rewardless and employ deceit pollination strategies. Some, however, reward pollinators with nectar, resins or pseudopollen (farina). Pseudopollen is yellow-white in colour and is usually composed of food-laden cells formed by detachment or fragmentation of moniliform labellar hairs. As the pollen of epidendroid orchids is bound in pollinia, it is not accessible to pollen-foraging insects. It has thus been proposed that potential insect pollinators, deceived by the resemblance of pseudopollen to the nutritious, powdery pollen of other angiosperms, gather it and feed it to their larvae. Mimicry here, however, may not be as simple as supposed. This study compares the pseudopollen of selected species of Maxillaria s.s., namely Maxillaria grandis, M. grayi, M. huebschii and M. roseola (all members of the M. grandiflora complex), M. lepidota ( M. arachnites complex) and M. buchtienii ( M. splendens complex), using light microscopy ( LM), fluorescence microscopy, histochemistry, scanning electron microscopy ( SEM) and transmission electron microscopy ( TEM), and comments on its evolutionary significance. Some members of the M. grandiflora complex produce pseudopollen-forming hairs, the cells of which contain potential food rewards in the form of an intravacuolar protein body and abundant starch grains. Others produce pseudopollen that is devoid of protein bodies, but contains abundant starch, and others produce pseudopollen that lacks protein bodies and contains negligible amounts of starch. Maxillaria lepidota and M. buchtienii fall into the second and third categories, respectively. Lipid droplets, when present, usually occur in minute quantities. These observations suggest that a dual deceit strategy operates in some species, as pseudopollen not only mimics powdery pollen, but in many instances lacks a food reward. Cryptic evolutionary changes to pseudopollen content may confer biological advantage by reducing expenditure of material and energy in food reward production, while trichome micromorphology simultaneously encourages pollinator visits. The presence or absence of particular foods may, in turn, result in pollinator selection. Conversely, in the absence of food rewards, insect behaviour is unlikely to be reinforced, possibly to the detriment of the orchid. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 173, 744-763. [ABSTRACT FROM AUTHOR]

Background and Aims Recently, molecular approaches have been used to investigate the phylogeny of Oncidiinae. This has resulted in the transfer of taxa previously considered to be species of Oncidium Sw. into Gomesa R. Br. and the re-circumscription of both genera. In this study, the structure of the floral elaiophore (oil gland) is described and compared for Gomesa echinata (Barb. Rodr.) M.W. Chase & N.H. Williams, G. ranifera (Lindl.) M.W. Chase & N.H. Williams, Oncidium amazonicum (Schltr.) M.W. Chase & N.H. Williams and O. oxyceras (Königer & J.G. Weinm.) M.W. Chase & N.H. Williams in order to determine whether phylogenetic revision is supported by differences in its anatomy. Methods The floral elaiophore structure was examined and compared at three developmental stages (closed bud, first day of anthesis and final stage of anthesis) for all four species using light microscopy, fluorescence microscopy, scanning electron microscopy, transmission electron microscopy and histochemistry. Key results In all species investigated, the floral elaiophore occurs on the labellar callus and is of the epithelial type, comprising cuboidal to palisade-like, secretory epidermal cells and a layer of sub-epidermal cells, both tissues enclosing ground parenchyma supplied with collateral vascular bundles and containing idioblasts, often with raphides or phenolic contents. A bi-layered cuticle comprising an outer, lamellate and an inner, reticulate layer is present, and sub-cuticular accumulation of secreted material results in distension of the cuticle. Secretion-filled cavities are present at anthesis in the elaiophore cell walls and, in most species, the outer, tangential walls of the elaiophore have small, peg-like projections that protrude into the cytoplasm. In all taxa examined, the elaiophore organelle complement, especially the smooth endoplasmic reticulum (SER), is typical of lipid-secreting cells. Conclusions In terms of location, morphology, anatomy and ultrastructure, the floral elaiophores of both Gomesa and Oncidium species examined are very similar, and distinction between these genera is not possible based on elaiophore features alone. Furthermore, many of these elaiophore characters are shared with representatives of other clades of Oncidiinae, including the Ornithocephalus clade. Consequently, elaiophores are considered homoplasious and of limited value in investigating the phylogeny of this subtribe. [ABSTRACT FROM AUTHOR]

Background and Aims The pollination biology of very few Chloraeinae orchids has been studied to date, and most of these studies have focused on breeding systems and fruiting success. Chloraea membranacea Lindl. is one of the few non-Andean species in this group, and the aim of the present contribution is to elucidate the pollination biology, functional floral morphology and breeding system in native populations of this species from Argentina (Buenos Aires) and Brazil (Rio Grande do Sul State). Methods Floral features were examined using light microscopy, and scanning and transmission electron microscopy. The breeding system was studied by means of controlled pollinations applied to plants, either bagged in the field or cultivated in a glasshouse. Pollination observations were made on natural populations, and pollinator behaviour was recorded by means of photography and video. Key Results Both Argentinean and Brazilian plants were very consistent regarding all studied features. Flowers are nectarless but scented and anatomical analysis indicates that the dark, clavate projections on the adaxial labellar surface are osmophores (scent-producing glands). The plants are self-compatible but pollinator-dependent. The fruit-set obtained through cross-pollination and manual self-pollination was almost identical. The main pollinators are male and female Halictidae bees that withdraw the pollinarium when leaving the flower. Remarkably, the bees tend to visit more than one flower per inflorescence, thus promoting self-pollination (geitonogamy). Fruiting success in Brazilian plants reached 60·78 % in 2010 and 46 % in 2011. Some pollinarium-laden female bees were observed transferring pollen from the carried pollinarium to their hind legs. The use of pollen by pollinators is a rare record for Orchidaceae in general. Conclusions Chloraea membrancea is pollinated by deceit. Together, self-compatibility, pollinarium texture, pollinator abundance and behaviour may account for the observed high fruiting success. It is suggested that a reappraisal and re-analysis of important flower features in Chloraeinae orchids is necessary. [ABSTRACT FROM AUTHOR]

Flowers of most species formerly included in Maxillaria are rewardless. Some, however, reward pollinators with nectar or pseudopollen, whereas the labella of a relatively small number of taxa produce lipoidal floral rewards that include resins and waxes. To date, the labellar secretory tissues of few species have been examined in detail, and some rewardless species having glossy labella are thought to mimic taxa that produce lipoidal rewards. Here, the labellar anatomy of a range of resin-secreting, wax-secreting and putative resin-mimic species is compared using light microscopy, fluorescence microscopy, scanning electron microscopy, transmission electron microscopy and histochemistry, in order to investigate how such secretory tissues may have evolved. Comparisons are also made with other resiniferous and wax-secreting Maxillariinae s.s., and with rewardless control species and the oil-secreting elaiophores of certain Oncidiinae. The labella of all Maxillariinae species investigated displayed similar anatomy, the differences largely being restricted to the adaxial epidermis and subepidermal layer. The labellar secretory epidermis of resiniferous Maxillariella elatior was composed of epithelial palisade cells, whereas that of other resin- and wax-secreting species investigated consisted of secretory papillae or trichomes. Putative resin-mimic species also produced resin, albeit in small quantities, and, here, the epidermal cells were cuboidal or rectangular in section. Secreted material on the labellar surface of control species was probably fragrance residues. Resin was often heterogeneous, and fluorescence microscopy revealed that its composition could change throughout the course of anthesis. Although the resiniferous floral tissues of Maxillariinae s.s. may be epithelial or trichomal, and thus closely resemble the epithelial and trichomal elaiophores of oil-secreting Oncidiinae, they differ in a number of important ways, necessitating the use of more exact descriptive terminology when distinguishing between oil-, resin- and wax-secreting floral structures. Similarity between the resin- or wax-secreting floral structures of Maxillariinae s.s and the oil-secreting elaiophores of Oncidiinae is probably a result of parallelism. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 170, 405-435. [ABSTRACT FROM AUTHOR]

Background and Aims A significant number of species assigned to the Neotropical orchid sub-tribe Oncidiinae reward insect pollinators with oil produced in floral glands termed elaiophores. The latter may be glabrous (epithelial elaiophores) or hirsute (trichomal elaiophores). Although the detailed anatomy and ultrastructure of epithelial elaiophores have been studied for a number of genera, such as Oncidium Sw., Gomesa R. Br. and Trichocentrum Poepp. & Endl., hitherto, trichomal elaiophores have been investigated only for a single species of Oncidiinae, Ornithocephalus ciliatus Lindl. Furthermore, this is the only representative of the Ornithocephalus clade to be investigated to date. Here, an examination is made of the elaiophore anatomy and ultrastructure of a further four species currently assigned to this clade (Ornithocephalus gladiatus Hook., Phymatidium falcifolium Lindl., Zygostates grandiflora (Lindl.) Mansf. and Zygostates lunata Lindl.) and the results compared with those obtained for other Oncidiinae. Methods Elaiophore structure was examined for all species at three stages of flower development: closed bud, first day of anthesis and final stage of anthesis, using light microscopy, fluorescence microscopy, scanning electron microscopy, transmission electron microscopy and histochemistry. Key Results Elaiophores of O. gladiatus occur upon the lateral lobes of the labellum and display characters intermediate between those of typical epithelial and trichomal elaiophores, in that they are largely glabrous, consisting mainly of cuboidal epidermal cells, but bear short, unicellular hairs proximally. By contrast, the elaiophores of all the other species investigated occur on the callus and are of the trichomal type. In P. falcifolium, these unicellular hairs are capitate. In all species, oil secretion commenced at the closed floral bud stage. Ultrastructurally, the mainly trichomal elaiophores of the four representatives of the Ornithocephalus clade closely resembled the epithelial elaiophores of other Oncidiinae, in that their cells displayed an organelle complement typical of lipid-secreting cells. However, in some taxa, a number of noteworthy characters were present. For example, the elaiophore cuticle of O. gladiatus and P. falcifolium was bi-layered, the outer layer being lamellate, the inner reticulate. The cuticle of Z. grandiflora and Z. lunata was also lamellate, but here, a reticulate layer was absent. Accumulation of secreted oil resulted in the localized distension of the cuticle. Cuticular cracks and pores, however, were absent from all species. The walls of the secretory cells of Z. grandiflora were also atypical in that they had short protuberances or ingrowths, and contained cavities which are thought to be involved in the secretory process. Conclusions Of the species investigated, most displayed similar anatomical organization, their trichomal elaiophores occurring on the labellar callus. They, thus, differ from many other members of the Oncidiinae, where epithelial elaiophores are found either on the callus, or on the lateral lobes of the labellum. However, ultrastructurally, all elaiophores, whether those of representatives of the Ornithocephalus clade, or those of other oil-secreting Oncidiinae, possessed a similar complement of organelles, regardless of whether the elaiophores were trichomal or epithelial. In view of the latter, and the similar chemical composition of oils derived from all Oncidiinae investigated to date, it is probable that position and type of elaiophore, and possibly the structure of the overlying cuticle, play an important role in pollinator selection in these oil-secreting orchids. [ABSTRACT FROM AUTHOR]

As part of a study to explore diversity and disparity in Early Devonian terrestrial vegetation, several hundreds of sporangia with in situ spores have been isolated from a Lochkovian locality in Shropshire. These include a small number (seven) of sporangia showing dehiscence into four valves and containing permanent sculptured dyads, belonging to the Cymbohilates horridus complex and C. cymosus, which are recorded in coeval dispersed spore assemblages. A further, previously described, mesofossil comprises an incomplete sporangium containing C. horridus that terminates a naked isotomously branching stem with stomata. The valvate sporangia are placed in a new genus, Partitatheca, containing four species, P. splendida (type), P. horrida, P. densa and P. cymosa, their names reflecting the names of the dispersed spore species and varieties. Complex ultrastructure in the walls of the dyads is similar to that in earlier dyads in the Dyadospora complex where it provides evidence for a hepatic affinity of the earliest embryophytes, but the new taxa present a combination of bryophyte and tracheophyte characters and are considered to represent a new embryophyte lineage. General discussion includes the development of dyads, more particularly their relevance to understanding the diversity in meiotic processes, and the disappearance of dyads from the dispersed spore record prior to the Middle Devonian. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 168, 229-257. [ABSTRACT FROM AUTHOR]

Background and Aims Capanemia Barb. Rodr. comprises seven species that mostly inhabit the Brazilian Atlantic Rain Forest domain. The genus currently consists of two sections: Capanemia Cogn. and Planifolia Pabst, distinguished on the basis of leaf shape. We compare the floral morphology and anatomy of all species to determine whether separation into sections is supported by floral characters. Methods Both fresh flowers and herbarium specimens were investigated, and column and pollinarium features, together with the presence or absence of floral rewards, recorded. Anatomical features were examined using both light microscopy and scanning electron microscopy. Key Results and Conclusions With the sole exception of Capanemia therezae, all species shared a distinctive set of floral characters. Flowers were mostly white or yellowish-white and fragrant, and column wings were positioned parallel to the labellum, concealing the stigmatic cavity. Pollinaria had proportionally long tegular stipes and clavate to reniform pollinia, whereas the labellum possessed a conspicuous indument of trichomes, but was devoid of nectar or any other secretion that might function as a food-reward. Capanemia therezae, however, was exceptional in having greenish, unscented flowers with short, rounded and divergent column wings and an exposed stigmatic cavity. Its pollinaria had proportionally short tegular stipes and round pollinia, whereas the labellum lacked trichomes. Droplets of nectar were evident on the adaxial surface of the labellum, adjacent to the callus. Floral features did not support the currently accepted sectional division of Capanemia. If ongoing phylogenetic studies demonstrate that both sections are indeed monophyletic, then these taxa should be distinguished solely on the basis of foliar features. [ABSTRACT FROM AUTHOR]

Background and Aims Molecular evidence indicates that the Neotropical sub-tribe Zygopetalinae is sister to Maxillariinae. Most members of the latter sub-tribe have deceit pollination strategies, but some species produce rewards such as nectar, pseudopollen, resin and wax, and are pollinated by a range of pollinators that include stingless bees (Meliponini), wasps and hummingbirds. By contrast, relatively little is known about the pollination of Zygopetalinae species. However, some are pollinated by fragrance-gathering, male euglossine bees or employ nectar deceit strategies. The aim of this study is to describe the labellar micromorphology of Zygopetalinae and to compare it with that of Maxillariinae sensu lato (s.l.) as part of an ongoing project to record the range of labellar characters found within the tribe Maxillarieae, and to assess whether these characters represent synapomorphies or homoplasies resulting from similar pollination pressures. Methods The labella of 31 species of Zygopetalinae, including Cryptarrhena R. Br. and representatives of the Zygopetalum, Huntleya and Warrea clades, were examined using light microscopy and scanning electron microscopy, and the range of labellar characters was recorded. These characters were subsequently compared with those of Maxillariinae s.l. which formed the subject of our previous investigations. Key Results and Conclusions The labellar micromorphology of Zygopetalinae is less diverse than that of Maxillariinae and does not reflect the currently accepted phylogeny of the former sub-tribe based on molecular studies. Instead, the relative uniformity in labellar micromorphology of Zygopetalinae is probably due to homoplasies resulting from similar pollinator pressures. Labellar trichomes are relatively uncommon in Zygopetalinae, but occur in certain members of both the Zygopetalum and Huntleya clades. Trichomes are unbranched, uniseriate and multicellular with rounded apices, or unbranched and unicellular, with tapering, pointed and flexuose apices. Hitherto, unicellular trichomes of this kind have been observed only for euglossophilous orchid taxa, and the adoption of a relatively limited range of pollination strategies by Zygopetalinae may have resulted in reduced investment in micromorphological labellar characters. [ABSTRACT FROM AUTHOR]

Background and Aims To date, the structure of the nectary spur of Aeridinae has not been studied in detail, and data relating to the nectaries of ornithophilous orchids remain scarce. The present paper compares the structural organization of the floral nectary in a range of Aeridinae species, including both entomophilous and ornithophilous taxa. Methods Nectary spurs of Ascocentrum ampullaceum (Roxb.) Schltr. var. aurantiacum Pradhan, A. curvifolium (Lindl.) Schltr., A. garayi Christenson, Papilionanthe vandarum (Rchb.f.) Garay, Schoenorchis gemmata (Lindl.) J.J. Sm., Sedirea japonica (Rchb.f.) Garay & H.R. Sweet and Stereochilus dalatensis (Guillaumin) Garay were examined by means of light microscopy, scanning electron microscopy and transmission electron microscopy. Key Results and Conclusions The diverse anatomy of the nectary is described for a range of Aeridinae species. All species of Ascocentrum investigated displayed features characteristic of ornithophilous taxa. They have weakly zygomorphic, scentless, red or orange flowers, display diurnal anthesis, possess cryptic anther caps and produce nectar that is secluded in a relatively massive nectary spur. Unicellular, secretory hairs line the lumen at the middle part of the spur. Generally, however, with the exception of Papilionanthe vandarum, the nectary spurs of all entomophilous species studied here (Schoenorchis gemmata, Sedirea japonica, Stereochilus dalatensis) lack secretory trichomes. Moreover, collenchymatous secretory tissue, present only in the nectary spur of Asiatic Ascocentrum species, closely resembles that found in nectaries of certain Neotropical species that are hummingbird-pollinated and assigned to subtribes Maxillariinae Benth., Laeliinae Benth. and Oncidiinae Benth. This similarity in anatomical organization of the nectary, regardless of geographical distribution and phylogeny, indicates convergence. [ABSTRACT FROM AUTHOR]

Phylogenetic analysis indicates that Lycastinae should be incorporated into a more broadly defined Maxillariinae. This is supported by several anatomical features, including the presence of sunken, glandular trichomes in both Lycastinae and Maxillariinae s.s. Until recently, these were known only from vegetative organs, but have since been reported from flowers of Maxillaria dichroma. One character currently used to distinguish between Lycaste and Sudamerlycaste is the distribution of floral trichomes. In this article, we test the reliability of this character, describe the floral micromorphology of Lycaste and Sudamerlycaste and investigate whether their flowers bear sunken hairs. Their floral micromorphology is compared with that of other genera currently assigned to Maxillariinae s.l. Flowers of Lycaste and Sudamerlycaste bear conical or obpyriform papillae and unbranched and unequally branched multicellular trichomes. Contrary to previous reports that trichomes are confined to the column in Sudamerlycaste, they also occur in the tepal axils. Labellar trichomes, although often present in Lycaste, are lacking in Sudamerlycaste. In Lycaste sections Lycaste and Aromaticae, floral trichomes tend to be unbranched, whereas section Intermediae has both unbranched and branched hairs. Branched hairs are more common in Sudamerlycaste. Some hairs are tracheoidal, pitted and lignified. These mainly occur in section Lycaste and, to a degree, in section Intermediae, but are absent from section Aromaticae and most species of Sudamerlycaste. Branched column hairs, present in Sudamerlycaste, are absent from all sections of Lycaste, and tracheoidal column hairs occur only in Sudamerlycaste. Sunken floral hairs are absent from both genera. Trichome structure and distribution may prove useful in distinguishing between these taxa and in elucidating the intergeneric relationships of Maxillariinae s.l.© 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, , 409-421. [ABSTRACT FROM AUTHOR]

The Lc petunia system, which displays enhanced, light-induced vegetative pigmentation, was used to investigate how high light affects anthocyanin biosynthesis, and to assess the effects of anthocyanin pigmentation upon photosynthesis. Lc petunia plants displayed intense purple anthocyanin pigmentation throughout the leaves and stems when grown under high-light conditions, yet remain acyanic when grown under shade conditions. The coloured phenotypes matched with an accumulation of anthocyanins and flavonols, as well as the activation of the early and late flavonoid biosynthetic genes required for flavonol and anthocyanin production. Pigmentation in Lc petunia only occurred under conditions which normally induce a modest amount of anthocyanin to accumulate in wild-type Mitchell petunia [Petunia axillaris×(Petunia axillaris×Petunia hybrida cv. ‘Rose of Heaven’)]. Anthocyanin pigmentation in Lc petunia leaves appears to screen underlying photosynthetic tissues, increasing light saturation and light compensation points, without reducing the maximal photosynthetic assimilation rate (Amax). In the Lc petunia system, where the bHLH factor Leaf colour is constitutively expressed, expression of the bHLH (Lc) and WD40 (An11) components of the anthocyanin regulatory system were not limited, suggesting that the high-light-induced anthocyanin pigmentation is regulated by endogenous MYB transcription factors. [ABSTRACT FROM PUBLISHER]

Background and Aims: Until recently, there was no consensus regarding the phylogenetic relationships of the Neotropical orchid genera Scuticaria Lindl. and Dichaea Lindl. However, recent evidence derived from both gross morphological and molecular studies supports the inclusion of Scuticaria and Dichaea in sub-tribes Maxillariinae and Zygopetalinae, respectively. The present paper describes the labellar micromorphology of both genera and seeks to establish whether labellar characters support the assignment of Scuticaria and Dichaea to these sub-tribes. [ABSTRACT FROM PUBLISHER]

The elaiophores of Trichocentrum cavendishianum (Bateman) M.W. Chase & N.H. Williams, Oncidium loefgrenii Cogn., and Gomesa recurva R. Br. display considerable morphological and anatomical diversity. Oil secretion by flowers of T. cavendishianum and O. loefgrenii can be related to the presence of saddle-like, labellar elaiophores and the labellar callus, respectively, whereas, in G. recurva, although oil is present, no obvious structure appears to be involved in its secretion. In the first two species, the secretory tissue consists of palisade-like cells, whereas, in G. recurva, these cells are oval. Many Oncidiinae are thought to mimic members of the Malpighiaceae, and the elaiophores of that family also contain palisade-like cells that may indicate evolutionary convergence. As oils accumulate below the elaiophore cuticle, that of T. cavendishianum becomes distended, whereas that of the other two species does not. Full discharge of oil from the elaiophores of T. cavendishianum probably occurs only after the cuticle is ruptured by a visiting insect, and this may contribute towards pollinator selection. © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 155, 135–148. [ABSTRACT FROM AUTHOR]

The Rosea1, Rosea2, and Venosa genes encode MYB-related transcription factors active in the flowers of Antirrhinum majus. Analysis of mutant phenotypes shows that these genes control the intensity and pattern of magenta anthocyanin pigmentation in flowers. Despite the structural similarity of these regulatory proteins, they influence the expression of target genes encoding the enzymes of anthocyanin biosynthesis with different specificities. Consequently, they are not equivalent biochemically in their activities. Different species of the genus Antirrhinum, native to Spain and Portugal, show striking differences in their patterns and intensities of floral pigmentation. Differences in anthocyanin pigmentation between at least six species are attributable to variations in the activity of the Rosea and Venosa loci. Set in the context of our understanding of the regulation of anthocyanin production in other genera, the activity of MYB-related genes is probably a primary cause of natural variation in anthocyanin pigmentation in plants. [ABSTRACT FROM AUTHOR]

This article investigates the role played by exhibitions of Finnish design in both promoting exports and coordinating ideas about Finnish national identity abroad in the period c. 1953-65. The work concentrates on two exhibitions held in Britain, 'Modern Art in Finland' (1953-4) and 'Finlandia' (1961-2), which were a representative part of a much larger project of overseas exhibitions of Finnish Design in the post-war period. The first section of the paper, set against an economic backdrop, presents an analysis of the development of export markets for Finnish design in the 1950s and early 1960s. This is followed by an interpretation of the two exhibitions in terms of the ideas about Finland, Finns and Finnish products that were being propagated by the exhibitions' Finnish organizers and the way these were digested, recycled and modified by British critics. [ABSTRACT FROM AUTHOR]

Finmar Ltd. was a wholesale company founded to market Alvar Aolto's plywood furniture ion the UK. This paper looks at the operation of the company from its start in 1934 to the beginning of the Second World War. By treating Aalto's furniture as a simple commodity, using economic data (particularly trade figures), information from company archives in Finland and the UK, and specialist journal coverage, the work attempts to establish and understand soles patterns for goods marketed in the UK as 'time furniture of the future for the homes if today'. [ABSTRACT FROM AUTHOR]

Finmar Ltd., a wholesale firm, was one of the major importers of Scandinavian furniture to the UK in the period 0934-65. This article looks at the operation of the company after the Second World War, from 0949 to 1952, charting the goods that were imported, consumption patterns, and the restrictions the firm faced, in order to show how the UK market for Scandinavian furniture developed. Although Finmar had imported Alvar Aalto's plywood furniture from Finland before the war, its source of goods changed to Denmark in 1949 when the company was sold to a Dane, Paul Stemann. Under his direction the company expanded rapidly, starting with Danish factory-made versions of Windsor chairs that fitted the Utility regulations, and was, by the time the Utility regulations were dropped, selling a much greater range of goods too number of large, London-based department stores ouch as Heal's and Liberty's. [ABSTRACT FROM AUTHOR]

We previously isolated a cDNA clone, pTIP13, whose homologous mRNA rapidly declined in abundance in the tips of harvested asparagus (Asparagus officinalis L.) spears [King and Davies (1992) Plant Physiol. 100: 1661]. In order to identify factors regulating the postharvest deterioration of asparagus, we have now sequenced the pTIP13 cDNA, derived the encoded amino acid sequence and determined the cellular location of pTIP13 mRNA by in situ hybridization. pTIP13 encodes a derived protein that is rich in proline (22.3%), but also has a high content of lysine (15.2%) and threonine (14.1%). The proline residues are located in motifs at the amino-terminal region of the protein. The carboxyl-terminal region of the derived protein has a high leucine content and shares >64% amino acid identity with derived proteins identified from cDNA clones to cell wall protein precursor mRNAs obtained from soybean hypocotyls, alfalfa roots, and tomato fruit. Genomic Southern analysis suggests that pTIP13 is encoded by a single-copy gene in asparagus. pTIP13 mRNA was localized to specific cell types in the young bracts of the asparagus spear tip. The results provide new information on the complexity of tissue responses in the tips of asparagus spears following harvest. [ABSTRACT FROM AUTHOR]