Paula J. Rudall

Royal Botanic Gardens, Kew · Comparative Plant and Fungal Biology

Flowers are deceptively simple structures, characterized by a determinate primary axis that bears organs in condensed concentric zones in a strict structural and temporal sequence. Few species have escaped these constraints, but those that have can provide insights into the evolutionary history of flowers if placed in the appropriate phylogenetic a...

Background and Aims Structural colour is responsible for the remarkable metallic blue colour seen in the leaves of several plants. Species belonging to only ten genera have been investigated to date, revealing four photonic structures responsible for blue leaves. One of these is the helicoidal cell wall, known to create structural colour in the lea...

The genus Iris as a critical taxon in establishing an integrated approach to Italian plant biodiversity Abstract Colasante, M., Fadda, A., Rudall, P. J. & Tarquini, F.: The genus Iris as a critical taxon in establishing an integrated approach to Italian plant biodiversity.-Fl. Medit. 31 (Special Issue): 213-239. 2021.-ISSN: 1120-4052 printed, 2240-...

Afrothismia is a genus of non-photosynthetic mycoheterotrophs from the forests of continental tropical Africa. Multiple phylogenetic inferences using molecular data recover the genus as sister to a clade comprising mycoheterotrophic Thismiaceae and the photosynthetic family Taccaceae, contrary to earlier placements of Afrothismia and Thismiaceae wi...

Background: Oriented patterning of epidermal cells is achieved primarily by transverse protodermal cell divisions perpendicular to the organ axis, followed by axial cell elongation. In linear leaves with parallel venation, most stomata are regularly aligned with the veins. This longitudinal patterning operates under a strong developmental constrai...

The magnoliid clade encompasses 18 extant families arranged in four orders, plus several extinct taxa, including some of the most ancient angiosperm fossils. The clade is characterized by paracytic stomata with a distinct pair of lateral subsidiary cells that flank the guard cells, though other stomatal types are also reported, including anomocytic...

Simple Summary: Our frequently deployed approach to optimally circumscribing species requires large-scale field sampling within and between populations for large numbers of morphometric characters, followed by multivariate ordinations to objectively seek discontinuities (or, failing that, zones of limited overlap) among sets of populations consider...

Introduction Understanding the complex inflorescence architecture and developmental morphology of common buckwheat (Fagopyrum esculentum) is crucial for crop yield. However, most published descriptions of early flower and inflorescence development in Polygonaceae are based on light microscopy and often documented by line drawings. In Fagopyrum and...

Afrothismia is a genus of non-photosynthetic mycoheterotrophs from the forests of continental tropical Africa. Multiple phylogenetic inferences using molecular data recover the genus as sister to a clade comprising mycoheterotrophic Thismiaceae and the photosynthetic family Taccaceae, contrary to earlier placements of Afrothismia and Thismiaceae wi...

Structural color is poorly known in plants relative to animals. In fruits, only a handful of cases have been described, including in Viburnum tinus where the blue color results from a disordered multilayered reflector made of lipid droplets. Here, we examine the broader evolutionary context of fruit structural color across the genus Viburnum. We ob...

Plants combine both chemical and structural means to appear colorful. We now have an extensive understanding of the metabolic pathways used by flowering plants to synthesize pigments, but the mechanisms remain obscure whereby cells produce microscopic structures sufficiently regular to interfere with light and create an optical effect. Here, we com...

Kew’s Jodrell Laboratory was established in 1876 as a centre for botanical research in disciplines including plant physiology, anatomy and embryology, palaeobotany and mycology. Despite relatively little available funding, its location in one of the world’s largest botanic gardens and close to several well-curated plant collections has ensured its...

Conical epidermal cells occur on the tepals (perianth organs, typically petals and/or sepals) of the majority of animal-pollinated angiosperms, where they play both visual and tactile roles in pollinator attraction, providing grip to foraging insects and enhancing colour, temperature and hydrophobicity. To explore the evolutionary history of conica...

The grass family (Poaceae) includes cereal crops that provide a key food source for the human population. The food industry uses the starch deposited in the cereal grain, which develops directly from the gynoecium. Morphological interpretation of the grass gynoecium remains controversial. A bistigmatic grass gynoecium has two sterile carpels, each...

Molecular phylogenetic analyses have revealed a superclade of mesangiosperms with five extant lineages: monocots, eudicots, magnoliids, Ceratophyllum and Chloranthaceae. Both Ceratophyllum and Chloranthaceae are ancient lineages with a long fossil record; their precise placement within mesangiosperms is uncertain. Morphological studies have suggest...

Premise: The sporoderm of seed-plant pollen grains typically has apertures in which the outer sporopollenin-bearing layer is relatively sparse. The apertures allow regulation of the internal volume of the pollen grain during desiccation and rehydration (harmomegathy) and also serve as sites of pollen germination. A small fraction of angiosperms un...

The family Rapateaceae represents an early-divergent lineage of Poales with biotically pollinated showy flowers. We investigate developmental morphology and anatomy in all three subfamilies and five tribes of Rapateaceae to distinguish between contrasting hypotheses on spikelet morphology and to address questions on the presence of nectaries and gy...

Significance Helicoidal architectures are widespread in nature; several species adopt this structure to produce brilliant colorations. Such chiral architectures are usually left-handed in plants, with the only exception found in the cell walls of epicarp cells of Pollia condensata , where both handednesses are observed. Here, we aim to understand t...

The genus Iris as a critical taxon in establishing an integrated approach to Italian plant biodiversity Abstract Colasante, M., Fadda, A., Rudall, P. J. & Tarquini, F.: The genus Iris as a critical taxon in establishing an integrated approach to Italian plant biodiversity.-Fl. Medit. 31 (Special Issue): 213-239. 2021.-ISSN: 1120-4052 printed, 2240-...

• Background and Aims. Floral developmental studies are crucial for understanding the evolution of floral structures and sexual systems in angiosperms. Within the monocot order Poales, both subfamilies of Eriocaulaceae have unisexual flowers bearing unusual nectaries. Few previous studies have investigated floral development in subfamily Eriocauloi...

Background and Aims The gymnosperm order Cycadales is pivotal for our understanding of seed-plant phylogeny because of its phylogenetic placement close to the root node of extant spermatophytes and its combination of both derived and plesiomorphic character states. Although widely considered a ‘living fossil’ group, extant cycads display a high deg...

Premise: There is little direct evidence linking floral development and pollination biology in plants. We characterize both aspects in plain and ornamented flowers of Trimezieae (Iridaceae) to investigate how changes in floral ontogeny may affect their interactions with pollinators through time. Methods: We examined floral ontogeny in 11 species...

Helicoidally arranged layers of cellulose microfibrils in plant cell walls can produce strong and vivid coloration in a wide range of species. Despite its significance, the morphogenesis of cell walls, whether reflective or not, is not fully understood. Here we show that by optically monitoring the reflectance of Pollia japonica fruits during devel...

To mark the commencement of Dennis Stevenson’s status as Senior Curator Emeritus at New York Botanical Garden, we present a brief and subjective overview of his academic achievements to date. We highlight his deep and scholarly background in plant morphology, his adherence to cladistic methodologies for testing hypotheses of organismal relationship...

Circumscriptions of both the genus Gymnadenia and the 11–27 species that it contains are highly controversial. These Eurasian terrestrial orchids are nectar-rewarding and pollinated primarily by Lepidoptera. Opinions expressed on the number of species occurring in the British Isles range from one to four, though there exists broad agreement that at...

Succulence is widely interpreted as an adaptation to drought, usually associated with CAM and xeromorphic features among arid-adapted plants. However, this syndrome can also be observed in species typical of mesic and even hydric environments. The leaf-succulent genus Crassula (Crassulaceae) occurs in contrasting habitats in all nine biomes of sout...

Plastid sequences have long dominated phylogeny reconstruction at all time depths, predicated on a usually untested assumption that they accurately represent the evolutionary histories of phenotypically circumscribed species. We combined detailed in situ morphometrics (124 plants) and whole-plastome sequencing through genome skimming (71 plants) in...

The ovule and its developmental successor, the seed, together represent a highly characteristic feature of seed plants that has strongly enhanced the reproductive and dispersal potential of this diverse group of taxa. Ovules encompass multiple tissues that perform various roles within a highly constrained space, requiring a complex cascade of genes...

Understanding plant anatomy is not only fundamental to the study of plant systematics and palaeobotany, but is also an essential part of evolutionary biology, physiology, ecology and the rapidly expanding science of developmental genetics. This modernised new edition covers all aspects of comparative plant structure and development, arranged in a s...

Viburnum tinus is an evergreen shrub that is native to the Mediterranean region but cultivated widely in Europe and around the world. It produces ripe metallic blue fruits throughout winter [1]. Despite its limited fleshy pulp [2], its high lipid content [3] makes it a valuable resource to the small birds [4] that act as its seed-dispersers [5]. He...

Gilliesieae are a South American tribe of Amaryllidaceae characterized by high floral diversity. Given different taxonomic interpretations and proposals for generic and specific relationships, a representative phylogenetic analysis is required to clarify the systematics of this group. The present study provides a framework for understanding phyloge...

Anecdotal theories about traditional uses of Polynesian woods in relation to social and religious practices were tested using comparative wood identification. The woods used to make 135 figure carvings from the Hawaiian archipelago were identified and compared with 23 figure carvings from elsewhere in Polynesia (especially Tahiti and the Marquesas)...

The rattan genus Korthalsia Blume (Arecaceae: Calamoideae: Calameae) is widespread in the Malesian region. Among the 28 accepted species are 10 species that form intimate associations with ants. The ants inhabit the conspicuous ocreas that are produced by these species, using them as domatia to care for their young and aphids. As a foundation for f...

Angiosperms that are biotically pollinated typically produce flowers with bright and contrasting colours that help to attract pollinators and hence contribute to the reproductive success of the species. This colourful array contrasts with the much less multicoloured reproductive structures of the four living gymnosperm lineages, which are predomina...

• Background and Aims: The gymnosperm order Gnetales, which has contentious phylogenetic affinities, includes three extant genera (Ephedra, Gnetum, Welwitschia) that are morphologically highly divergent and have contrasting ecological preferences: Gnetum occupies mesic tropical habitats, whereas Ephedra and Welwitschia occur in arid environments. L...

The developmental morphology and genetics of the orchid flower is described in order to explore the evolutionary 'no man's land' that separates the Extended Synthesis from the Modern Synthesis. The gynostemium, ubiquitous among orchids and developed through congenital fusion (and dorsal suppression) of fertile reproductive organs, is an unbreakable...

Background and aims: Hydraulic studies are currently biased towards conifers and dicotyledonous angiosperms; responses of arborescent monocots to increasing temperature and drought remain poorly known. This study aims to assess xylem resistance to drought-induced embolism in palms. Methods: We quantified embolism resistance via P50 (xylem pressu...

Premise of research. The evolutionary origin of the seed habit coincided with profound physiological and structural changes associated with underlying developmental patterns. A coenocyte is formed during megagametophyte development in many vascular plants, including some lycophytes and all spermatophytes; this structure compares closely with simila...

The flora of the southwestern Australian biodiversity hotspot is rich in endemic species, many of which remain to be discovered or properly described; estimates of species diversity and levels of endemism should take into account the possible occurrence of cryptic species. Here we explore taxonomic diversity in a Western Australian lineage belongin...

Plants have evolved a multitude of adaptations to survive extreme conditions. Succulent plants have the capacity to tolerate periodically dry environments, due to their ability to retain water in a specialized tissue, termed hydrenchyma. Cell wall polysaccharides are important components of water storage in hydrenchyma cells. However, the role of t...

Reproductive structures of both genders of Wollemia nobilis were investigated, including both wild-type and teratological cones. Typically, both pollen cones and seed cones in this species are terminal on first order branches. At maturity, wild-type pollen cones are pendulous and cylindrical; wild-type seed cones are broad and ellipsoidal in shape....

Stomata play a critical ecological role as an interface between the plant and its environment. Although the guard‐cell pair is highly conserved in land plants, the development and patterning of surrounding epidermal cells follow predictable pathways in different taxa that are increasingly well understood following recent advances in the development...

The digitate-tubered clade (Dactylorhiza s.l. plus Gymnadenia s.l.) within subtribe Orchidinae is an important element of the North-temperate orchid flora and has become a model system for studying the genetic and epigenetic consequences of organism-wide ploidy change. Here, we integrate morphological phylogenetics with Sanger sequencing of nrITS a...

Background and aims: Fleshy structures that promote biotic dispersal by ingestion have evolved many times in seed plants. Within the yew family Taxaceae sensu lato (six genera, including Cephalotaxus), it remains controversial whether the characteristic fleshy structure surrounding the seed is interpreted as a novel outgrowth of the base of the ov...

The phylogenetic relationships and phylogeography of two relatively rare Macaronesian Lactuca species, Lactuca watsoniana (Azores) and L. palmensis (Canary Islands), were, until this date, unclear. Karyological information of the Azorean species was also unknown. For this study, a chromosome count was performed and L. watsoniana showed 2n = 34. A p...

• The petals of Eschscholzia californica (California Poppy) are robust, pliable and typically coloured intensely orange or yellow due to the presence of carotenoid pigments; they are also highly reflective at certain angles, producing a silky effect. • To understand the mechanisms behind colour enhancement and reflectivity in California Poppy, whic...

Both wild-type and teratological seed cones are described in the monoecious conifer Glyptostrobus pensilis and compared with those of other Cupressaceae sensu lato and other conifers. Some Cupressaceae apparently possess a proliferation of axillary structures in their cone scales. In our interpretation, in Glyptostrobus each bract of both typical a...

The petals of Eschscholzia californica (California poppy) are robust, pliable and typically coloured intensely orange or yellow owing to the presence of carotenoid pigments; they are also highly reflective at certain angles, producing a silky effect. To understand the mechanisms behind colour enhancement and reflectivity in California poppy, which...

Oxygyne Schltr. (Thismiaceae) is a rare and little-known genus of achlorophyllous mycoheterotrophic perennial herbs with one of the most remarkable distributions of all angiosperm plant genera globally, being disjunct between Japan and West–Central Africa. Each species is known only from a single location, and in most cases from a single specimen....

Understanding the origin and early diversification of the flowering plants (angiosperms) represent primary goals in biology. However, despite extensive knowledge of angiosperm biology and biodiversity, much remains to be determined about their evolutionary origin, partly because many of their characteristic (some supposedly diagnostic) features pro...

Background and aims: Recent tissue-level observations made indirectly via flow cytometry suggest that endoreplication (duplication of the nuclear genome within the nuclear envelope in the absence of subsequent cell division) is widespread within the plant kingdom. Here, we also directly observe ploidy variation among cells within individual petals...

Two decades have passed since DNA evidence first demonstrated an intimate relationship between the circumboreal species 'Coeloglossum' viride and the temperate Eurasian genus Dactylorhiza s.s. Most subsequent molecular phylogenies showed 'C.' viride to diverge after the D. incarnata group. The law of monophyly therefore dictated inclusion in Dactyl...

Background and aims: Helicocytic stomata are characterized by an inward spiral of mesogenous cells surrounding a central stomatal pore. They represent a relatively rare feature that occurs in some drought-tolerant angiosperm species. In some Begonia species with thick leaves, the stomata are not only helicocytic but also clustered into groups that...

Naturally durable heartwoods, where available, continue to be used as support structures in environments considered hazardous, particularly in ground contact. However, durability of heartwoods against wood decay microorganisms varies. Therefore, it is important to evaluate heartwood products for their in-service performance in order to maximise ben...

We provide a detailed comparative study of floral ontogeny and vasculature in Xyridaceae, including Xyris, Abolboda and Orectanthe. We evaluate these data in the context of a recent well-resolved phylogenetic analysis of Poales to compare floral structures within the xyrid clade (Xyridaceae and Eriocaulaceae). Xyrids are relatively diverse in both...

Diverse forms of nanoscale architecture generate structural colour and perform signalling functions within and between species. Structural colour is the result of the interference of light from approximately regular periodic structures; some structural disorder is, however, inevitable in biological organisms. Is this disorder functional and subject...

Androdioecy is the rarest sexual system among plants. The majority of androdioecious species are herbaceous plants that have evolved from dioecious ancestors. Nevertheless, some woody and androdioecious plants have hermaphrodite ancestors, as in the Annonaceae, where androdioecious genera have arisen several times in different lineages. The majorit...

Although the majority of taxonomic studies of European orchids treat Pseudorchis as a monotypic genus, some observers have argued that the apparently circumboreal segregate P. straminea should also be treated as a full species. Here, we compare detailed in vivo measurements of 55 plants from nine populations of P. albida in Britain with ten plants...

Premise of the study: Leaves of monocots are typically linear with parallel venation, though a few taxa have broad leaves. Studies of stomatal patterning and development in monocots required updating in the context of rapidly improving knowledge of both the phylogenetic and development-genetic context of monocots that facilitate studies of charact...

The bright and intense blue-green coloration of the fruits of Margaritaria nobilis (Phyllanthaceae) was investigated using polarization-resolved spectroscopy and transmission electron microscopy. Optical measurements of freshly collected fruits revealed a strong circularly polarized reflection of the fruit that originates from a cellulose helicoida...

Transmission Electron Microscop; Margaritaria nobilis fruit anatomy; Anatomy of Pericarp; Microscopy of Pericarp; Hyperspectral Microscopy

The bright and intense blue-green coloration of the fruits of $\textit{Margaritaria nobilis}$ (Phyllanthaceae) was investigated using polarization-resolved spectroscopy and transmission electron microscopy. Optical measurements of freshly collected fruits revealed a strong circularly polarized reflection of the fruit that originates from a cellulos...

Premise of research. The pantropical magnoliid family Lauraceae has an extensive macrofossil record that dates back to the Early Cretaceous. However, flower anatomy among extant species is relatively poorly known. We investigate flower structure and development in six Neotropical genera to elucidate the homologies of the floral parts, especially th...

Background and aims: The stomata of Equisetum - the sole extant representative of an ancient group of land plants - are unique with respect to both structure and development, yet little is known about details of ultrastructure and patterning, and existing accounts of key developmental stages are conflicting. Methods: We used light and electron m...

Premise of the study: A diverse range of pollen morphologies occurs within the large, paraphyletic legume subfamily Caesalpinioideae, especially among early-branching lineages. Previous studies have hypothesized an association between surface ornamentation and pollination syndrome or other aspects of pollen function such as desiccation tolerance a...

We report the first bona fide graminid spikelet inclusions found in Eocene Baltic amber. The most informative anatomically preserved specimen is assigned to the genus Rhynchospora Vahl (Cyperaceae), whereas two others show affinities with sedges (Cyperaceae) or grasses (Poaceae). Examination of historic descriptions of putative graminid inclusions...

Background and Aims. A recently described Brazilian species, Lacandonia brasiliana, shares with its longer established putative sister species from Mexico, L. schismatica, inverted floral patterning (carpels surrounding stamens) that is almost unique among angiosperms. We present a detailed ontogenetic study of L. brasiliana for comparison with oth...

Imaging the helicoidal structure with high resolution with TEM can be challenging. Here in Figure S1 we show how the same fixation procedure can fail to reveal the helicoidal structure of the cell wall of Margaritaria nobilis fruits when as stained fresh; Anatomy of Margaritaria nobilis fruit. (a,b,c) Transverse section of a fresh fruit shown at di...

Imaging the helicoidal structure with high resolution with TEM can be challenging. Here in Figure S1 we show how the same fixation procedure can fail to reveal the helicoidal structure of the cell wall of Margaritaria nobilis fruits when as stained fresh; Anatomy of Margaritaria nobilis fruit. (a,b,c) Transverse section of a fresh fruit shown at di...

Poplars (Populus sp.) and willows (Salix sp.) are well known woody plants common throughout the northern hemisphere, both with fully sequenced genomes. They bear compact unisexual inflorescences known as “catkins.” Closely related genera of the “salicoid clade” within the family Salicaceae include the Asian genera Bennettiodendron, Idesia, Itoa, Po...

Relatively little is known about species‐level genetic diversity in flowering plants outside the eudicots and monocots, and it is often unclear how to interpret genetic patterns in lineages with whole‐genome duplications. We addressed these issues in a polyploid representative of Hydatellaceae, part of the water‐lily order Nymphaeales. We examined...

In most seed plants, cotyledons formed within the seed act as haustorial organs, as well as playing a key role in releasing the shoot apex from the seed coat on germination. Emergence of the shoot apex often results from asymmetric intercalary growth of the cotyledon bases. This process avoids the principal spatial constraint on germination in seed...

Premise of research. Family relationships in the monocot order Liliales have been revised recently, so that the order now consists of 10 families of geophytes and climbers, with unusually diverse pollen morphology. Corsiaceae are sometimes placed as sister to all other Liliales, probably allied with Campynemataceae. Relationships of the wild card f...

PREMISE OF THE STUDY: The small primarily Australian commelinid monocot family Centrolepidaceae displays remarkably high structural diversity that has been hitherto relatively poorly explored. Data on Centrolepidaceae are important for comparison with other Poales, including grasses and sedges. METHODS: We examined vegetative and reproductive morp...

Poaceae pollen grains are notoriously difficult to use as a tool for eco-palynological studies due to their relatively uniform morphology. This article uses light and scanning electron microscopy to describe the pollen morphology of 31 species of Malagasy grasses, including 11 endemic species and seven endemic genera that are described here for the...

The marine world is incredibly rich in brilliant and intense colours. Photonic structures are found in many different species and provide extremely complex optical responses that cannot be achieved solely by pigments. In this study we examine the cuticular structure of the red alga Chondrus crispus (Irish Moss) using anatomical and optical approach...

• In angiosperms, several carpel tissues are specialized to facilitate pollen-tube elongation to achieve fertilization. We evaluated the possible evolutionary pathways of the diverse female reproductive tracts in Nyctaginaceae.• We studied the anatomy of a range of species representing different tribes, using light, fluorescence, scanning electron,...

Premise of research. The highly specialized grass inflorescence varies with respect to phyllotaxis, with the reproductive meristem forming primary lateral branches that are either spirally arranged or distichous. The Brazilian bamboo Eremitis is highly unusual in that it has a dimorphic inflorescence, typically composed of an apical gynecandrous wh...

Background and Aims. This paper concludes our series of publications comparing island and mainland speciation in European butterfly-orchids, by studying the morphology, phylogenetics and reproductive biology of the controversial circum-arctic species Platanthera (Limnorchis) hyperborea—the most frequent of seven Icelandic orchids. We draw particula...

AimMany plant families have a disjunct distribution across the southern Pacific Ocean, including the mycoheterotrophic family Corsiaceae, which provides a prime example of this biogeographical pattern. A better grasp of the family's evolutionary relationships is needed to understand its historical biogeography. We therefore aimed to (1) test the un...

Opportunistic observations of the longest-standing British population of Orchis militaris L. suggest that bumblebees (Bombus spp.) may have become the primary pollinators of the orchid at the site. We document pollination by (female) workers of B. pratorum and males of the brood parasite B. vestalis. Placement of the pollinaria on the bodies of the...