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Floral morphological adaptations and composition of secretions aim to ensure reproductive success. Maxillariella is part of the largest subtribe of Orchidaceae, and Maxillariella spp. are important components of the orchid flora of the Neotropics. The aim of this paper was to provide a detailed study of the reproductive biology of three morphologically and geographically distinct species: M. sanguinea, M. variabilis and M. vulcanica. For many years, species in this group were considered rewardless, but several studies have revealed that lips of some species may secrete resins. However, most published research has mainly focused on investigating either micromorphology (SEM, TEM, histochemistry) or fragrance composition (GC–MS). In this study, we make the first attempt to investigate Maxillariella flowers in a more comparative manner by combining both aspects. In all investigated species we reported the presence of resins with lipids, sugars and/or proteins, suggesting a potential role as a food reward. Scant quantities of residues indicate that they are produced periodically in small quantities. Chemical analysis revealed significant differences between species, however, the presence of some compounds was constant. Cycloartenal and cycloartenol (main ingredients of resin and wax-like material in some Maxillariinae) were not been found.

Understanding vascular bundle systems in angiosperms is a challenge. On the one hand, the vascular tissue is extremely important in reconstructing the evolution and survivability of plants, but on the other hand, it forms a complicated three-dimensional system of controversially discussed phylogenetic and ontogenetic origin. To increase clarity, in this paper we briefly summarize histological, phylogenetic and molecular aspects of primary vascular bundle formation in angiosperms, adding histological data on early stages of vascular bundle formation, proposing a concept combining the different views and providing simplified illustrations to improve the understanding of primary vascular systems in angiosperms. Based on the auxin hypothesis, vascular bundle formation is stimulated by the development of leaf primordia. Provascular domains appear at the base of the leaf primordia and develop into two directions (leaf, internode). The low vs. high number of internodal bundles, their circular vs. scattered arrangement and the open vs. closed bundle construction in eudicots vs. monocots can be deduced to be due to processes below the shoot apical meristem. The most important processes distinguishing monocots from eudicots are the isolated bundle initiation outside the primary meristem, the enormous expansion of the leaf bases associated with a high number of vascular bundles and the early onset of primary thickening passively dislocating vascular bundles.

Nodes are interfaces between stems and leaves. Vascular bundles originate here and elongate into leaves and internodes. In Marantaceae, internodal bundles are highly diverse, including inverted bundles in the climbing genus Haumania. The objective of this paper is to characterize bundle forms, their position across the stem and their connection to leaves and short shoots in Haumania spp. and other unrelated African branch-angle climbers in the family (Hypselodelphys, Trachyphrynium). We question whether bundle inversion is a genus-specific trait in Haumania or related to the climbing growth form. Vascular bundles in internodes are scattered across the stem diameter in a characteristic pattern. Four (to five) bundle types follow each other in a centripetal order from highly sclerenchymatic ‘a’-bundles close to the epidermis to ‘d’-bundles in the centre with a low sclerenchyma proportion. Inverted bundles only appear in internodes of Haumania, making this trait a synapomorphy for the genus. The nodes show stem, leaf and short shoot bundles in a remarkably diverse pattern with partitioned phloem clusters and apparently augmented xylem elements. Our preliminary conclusion is that the inversion of bundles happens when leaf and short shoot traces join the main axis bundle layers.

In this commentary, we discuss evidence for the phylogenetic affiliations of Tortotubus protuberans, the subject of Martin Smith's 2016 paper in the Botanical Journal of the Linnean Society entitled, ‘Cord-forming Palaeozoic fungi in terrestrial assemblages’. We agree that the fossilized, branching, somatic filaments probably represent fungal hyphae. We were not convinced by Smith's proposal that T. protuberans represents Dikarya, the clade of fungi that includes most modern moulds, yeasts and mushrooms. To justify classification, Smith relied on structures that are analogous between T. protuberans and modern fungi, and argued ‘that Dikarya can produce the range of morphologies expressed by T. protuberans’. We review available information about homologies of the characteristics of T. protuberans, including mycelial cords, retrograde growth, septal pores and ornamented hyphae. Retrograde growth in T. protuberans is intriguing from an evolutionary developmental point of view, but it differs sufficiently in fine detail when compared with growth patterns in croziers or clamp connections of Dikarya, so that homologies are unclear. Tortotubus protuberans is an important fossil form, but we suggest taking a step back and relating it to the distribution of character evolution through the fungal phylogeny rather than to derived characters of modern taxa.

Scheuchzeria palustris, the only member of Scheuchzeriaceae, is unique among Alismatales in several characters, including flower-subtending bracts with conspicuous laminas and pollen dispersed in permanent dyads. Earlier studies revealed unidirectional flower development in some monocots with massive flower-subtending bracts, but not in Scheuchzeria. Permanent pollen or spore dyads are extremely rare among extant land plants and in no case have they been studied developmentally. The paper provides new data on flower development and the first description of pollen development in Scheuchzeria. Flowers are arranged in a closed raceme. Development of lateral flowers is unidirectional, with delayed initiation of abaxial tepals and stamens. Flowers are often trimerous and pentacyclic, but numerous deviations from this groundplan are observed. Dyad development is investigated from microspore mother cells to mature pollen and their germination by electron microscopy and cytochemical methods. Meiosis is successive. Tetrads are irregular (42%), tetragonal (35%), decussate (13%), linear (7%) and T-shaped (3%). During the tetrad period, the microspores are surrounded by a callose special wall of different thickness. Disintegration of tetrads into two dyads takes place along the plane of the first cytokinesis, where the thickness of the callose wall is maximal. Pollen grains are held together in the dyads due to a simple fusion of tectal layers, this fusion takes place at the late tetrad period. Developmental data did not reveal any possible aperture sites in Scheuchzeria. This favours the hypothesis of complete loss and subsequent regain of apertures in the course of evolution of the ‘tepaloid clade’ of Alismatales.

Understanding pollen germination is of great importance for breeding and conservation. We present a protocol for evaluating culture media for germination of pollen of Elaeis guineensis. Samples were collected in the municipality of Nilo Pecanha (State of Bahia, Brazil). A solution of aniline blue in lactophenol was used to determine viability of pollen grains. Two alternative culture media to evaluate germination rates of pollen grains were tested: M1, Brewbaker and Kwack medium; and M2, BCa medium, with addition of boron and calcium. Both media were used with 20% sucrose at pH 6.5. The pollen grains were dried at room temperature in silica gel for 4 h and later placed on slides containing culture media, kept in a Petri dish with filter paper wetted with distilled water and stored in chamber at 30 °C for 24 h. The greatest viability rate was 94% for fresh pollen grains. Highest germination rates were 26 and 64% for M1 and M2, respectively. There was no positive correlation between viability and germination for either M1 or M2 (Pearson's and Spearman's correlation, respectively). Dried pollen on BCa medium (M2) is useful for in vitro germination experiments of E. guineensis given appropriate concentration of sucrose and ions, pH, temperature and incubation time and in the absence of light.

This paper and this issue attempt to address how, when and why the phenomenal c. 100,000 species of seed plants in tropical America (the Neotropics) arose. It is increasingly clear that an approach focusing on individual major biomes rather than a single aggregate view is useful because of evidence for differing diversification histories among biomes. Phylogenetic evidence suggests that Neotropical-scale diversification patterns are structured more ecologically than geographically, with a key role for phylogenetic niche or biome conservatism. Lower geographical structure reflects the fact that long-distance dispersal, inferred from dated phylogenetic trees, has overcome many supposed dispersal barriers. Overall, high rates of species turnover as inferred from palaeontological and molecular data have been the hallmark of plant evolutionary dynamics in the Neotropics throughout the Cenozoic, with most extant species diversity post-dating the Mid- to Late Miocene, perhaps reflecting the conjunction of both global climatic changes and geological upheavals such as the Neogene uplift of the tropical Andes. Future studies of Neotropical diversification will be facilitated by taxonomically and genetically better sampled phylogenetic analyses, their integration with palaeontological, geological and ecological data, and improved methods to estimate biogeographic history and diversification dynamics at different spatial and temporal scales. Future biome-focused approaches would benefit greatly from better delimitation and mapping of Neotropical biomes. (c) 2012 The Linnean Society of London

Minthostachys (Benth.) Spach (Labiatae) is a South American genus of aromatic shrubs frequently collected as a condiment, for the preparation of tea, or for medicinal purposes. Notoriously difficult species delimitation, conflicting taxonomic treatments of the past, and the lack of a revision with modern methods have hampered the understanding of this ecologically and economically interesting group. The amplified fragment length polymorphism (AFLP) study presented in this paper supplements field and morphological studies within the framework of a taxonomic and systematic revision. AFLP is found to be unsuitable for the reconstruction of the phylogeny of Minthostachys. Although, in some cases, morphologically well-defined species are also genetically distinct, extensive gene flow seems to occur between strikingly different species growing in the immediate vicinity and even between Minthostachys and Clinopodium (Xenopoma) vanum. Samples from the most complicated species, M. mollis, are genetically very heterogeneous and mostly fall into two clusters according to their geographical origin, exhibiting a high discrepancy with the pattern of morphological variation. © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 153, 9–19.

Water relations represent a pivotal nexus in plant biology due to the multiplicity of functions affected by water status. Hydraulic properties of plant parts are therefore likely to be relevant to evolutionary trends in many taxa. Bromeliaceae encompass a wealth of morphological, physiological and ecological variations and the geographical and bioclimatic range of the family is also extensive. The diversification of bromeliad lineages is known to be correlated with the origins of a suite of key innovations, many of which relate directly or indirectly to water relations. However, little information is known regarding the role of change in morphoanatomical and hydraulic traits in the evolutionary origins of the classical ecophysiological functional types in Bromeliaceae or how this role relates to the diversification of specific lineages. In this paper, I present a synthesis of the current knowledge on bromeliad water relations and a qualitative model of the evolution of relevant traits in the context of the functional types. I use this model to introduce a manifesto for a new research programme on the integrative biology and evolution of bromeliad water-use strategies. The need for a wide-ranging survey of morphoanatomical and hydraulic traits across Bromeliaceae is stressed, as this would provide extensive insight into structure–function relationships of relevance to the evolutionary history of bromeliads and, more generally, to the evolutionary physiology of flowering plants.