Plant Morphologists Research Articles

Eco-evo-devo of plant stomata: the diversity of stomatal development and its evolution

Stomata have long been playing an important role since plant ancestor invaded the land. The stomatal guard cells are produced by a simple developmental process, in which the meristemoids, stomatal-lineage stem cells, undergo asymmetric divisions prior to differentiation. Since the 2000s, stomatal development has been lively studied in the model plant Arabidopsis, which led to the elucidation of its molecular basis, particularly the pivotal role of three stomatal key transcription factors, namely SPEECHLESS, MUTE, and FAMA. On the other hand, when looking at non-model plants, people will notice that the developmental process of stomata is considerably diverged among species. While such diversity in stomatal development has been well documented by plant morphologists from early times, its molecular basis and ecological significance remained poorly known. In recent years, however, accumulating knowledge in model plants and the development of research technologies applicable to non-model plants have made stomata accessible to studies of ecological evolutionary developmental biology (eco-evo-devo). This review provides an overview of the diversity in the form and development of stomata in land plants, introduces the eco-evo-devo research applied on stomata, such as (1) the research on the unique stomatal complex in grass species, and (2) our recent work on the intrageneric diversity of stomatal development in Callitriche (Plantaginaceae), and discusses the prospects of this emerging field.

The world’s smallest Campanulaceae: Lysipomia mitsyae sp. nov.

AbstractBotanists and plant morphologists have long been fascinated by how certain species can exhibit such reduced morphologies that even their identification to genus‐ or family‐level becomes difficult. Such was the case with Lysipomia mitsyae sp. nov., an exceptionally small plant discovered in the Peruvian Andes which bears lobelioid characteristics but differs in size by an order of magnitude from the current smallest members known from the entire Campanulaceae and lacks diagnostic characters allowing it to be reliably placed to genus‐level. Molecular analyses of trnL‐F, composed of a representative Lobelioideae sampling, place the samples within the genus Lysipomia, requiring that amendments be made to the description of the genus. Supplementary ITS analyses of a representative generic sampling indicate a close relationship to Lysipomia sphagnophila and L. multiflora. We here describe the world’s smallest Campanulaceae, Lysipomia mitsyae sp. nov., and discuss its phylogenetic and systematic relationships to the other members of the genus. Its highly reduced morphology, which has given it status as the smallest Campanulaceae and, quite possibly, the world’s smallest eudicot, is discussed in the light of current knowledge on the physiological and anatomical constraints on alpine plant growth and survival.

Meristem identity and phyllotaxis in inflorescence development.

Inflorescence morphology is incredibly diverse. This diversity of form has been a fruitful source of inquiry for plant morphologists for more than a century. Work in the grasses (Poaceae), the tomato family (Solanaceae), and Arabidopsis thaliana (Brassicaceae) has led to a richer understanding of the molecular genetics underlying this diversity. The character of individual meristems, a combination of the number (determinacy) and nature (identity) of the products a meristem produces, is key in the development of plant form. A framework that describes inflorescence development in terms of shifting meristem identities has emerged and garnered empirical support in a number of model systems. We discuss this framework and highlight one important aspect of meristem identity that is often considered in isolation, phyllotaxis. Phyllotaxis refers to the arrangement of lateral organs around a central axis. The development and evolution of phyllotaxis in the inflorescence remains underexplored, but recent work analyzing early inflorescence development in the grasses identified an evolutionary shift in primary branch phyllotaxis in the Pooideae. We discuss the evidence for an intimate connection between meristem identity and phyllotaxis in both the inflorescence and vegetative shoot, and touch on what is known about the establishment of phyllotactic patterns in the meristem. Localized auxin maxima are instrumental in determining the position of lateral primordia. Upstream factors that regulate the position of these maxima remain unclear, and how phyllotactic patterns change over the course of a plant's lifetime and evolutionary time, is largely unknown. A more complete understanding of the molecular underpinnings of phyllotaxis and architectural diversity in inflorescences will require capitalizing on the extensive resources available in existing genetic systems, and developing new model systems that more fully represent the diversity of plant morphology.

Charles Darwin and the origins of plant evolutionary developmental biology.

Much has been written of the early history of comparative embryology and its influence on the emergence of an evolutionary developmental perspective. However, this literature, which dates back nearly a century, has been focused on metazoans, without acknowledgment of the contributions of comparative plant morphologists to the creation of a developmental view of biodiversity. We trace the origin of comparative plant developmental morphology from its inception in the eighteenth century works of Wolff and Goethe, through the mid nineteenth century discoveries of the general principles of leaf and floral organ morphogenesis. Much like the stimulus that von Baer provided as a nonevolutionary comparative embryologist to the creation of an evolutionary developmental view of animals, the comparative developmental studies of plant morphologists were the basis for the first articulation of the concept that plant (namely floral) evolution results from successive modifications of ontogeny. Perhaps most surprisingly, we show that the first person to carefully read and internalize the remarkable advances in the understanding of plant morphogenesis in the 1840s and 1850s is none other than Charles Darwin, whose notebooks, correspondence, and (then) unpublished manuscripts clearly demonstrate that he had discovered the developmental basis for the evolutionary transformation of plant form.

Characters as groups: a new approach to morphological characters in phylogenetic analysis

A new method for working with morphological characters is described and explored in experiments using human participants. The method uses direct comparison and sorting of images to produce hierarchical character‐cladograms. A character‐cladogram is a graphical representation of a single character that serves as a hypothesis of phylogeny based on that character. Each dichotomy in the character‐cladogram represents a character state. Character states are unnamed, thus avoiding problems that arise through the application of verbal labels. Experiments with human participants are used to explore the conditions under which direct comparison produces reliable (consistent from investigator to investigator) and valid (in agreement with an independent estimate of phylogeny) characters. Participants were drawn from students taking a course in plant diversity at UNC Greensboro, and professional plant morphologists attending the Botany 2004 meetings. The students were randomly assigned to trained and untrained groups. Training was carried out using a method that has been shown to change a participant’s mode of visual processing from analytic (the mode used by visual novices) to holistic (an additional mode only employed by visual experts). Morphologists (no specialists of the taxonomic group) were included in the study to investigate the effects of disciplinary expertise on the ability to describe character‐cladograms. They received no additional training beyond that available to them as disciplinary experts. The results suggest an improvement in both reliability and validity after the training regime. We found no support for the idea that the morphologists differed from untrained students in their ability to produce reliable or valid character‐cladograms. Disciplinary expertise may not translate into the ability to make reliable and valid assessments of similarity in an unfamiliar visual domain. Based on these results, we suggest a method for creating morphological characters and character states.

Encasement in plant morphology: an integrative approach from genes to organisms

Recent advances in molecular genetics are prompting developmental plant morphologists to refine the theoretical context of their field. For example, at the level of the action of certain developmental genes, the distinction between recognized structural categories (i.e., stem and leaf) are not obvious. This issue has also been analyzed by morphologists from qualitative and quantitative perspectives and has lead to similar conclusions. Consequently, the classical approach to morphology with a typological view of organ categories is no longer sufficient to explain the set of all possible forms. However, within the context of a dynamic morphology, where processes of development such as growth rate, duration, and distribution are considered, a more encompassing view of the generation of form can be achieved. We therefore propose that classical morphology is a subset of dynamic morphology. The main goal of this paper is to show how new concepts and methods of viewing plant morphology allow us to build a conceptual theoretical framework that may have a predictive value with respect to morphological characteristics as well as molecular properties of organs. The main premise of this commentary, within the context of dynamic morphology, is that the plant consists of an encasement of structures or a nesting of partially similar units. Common developmental processes are in operation at each structural level and variations in the modalities of these processes lead to the development of specific structures. Repeating polymorphic sets (RPS) represent an extension of this perspective on plant development and have the potential to predict the existence of new, perhaps unknown forms. The idea of repeating polymorphic sets can also be extended to outline the activity of specific developmental genes to explain how a wide variety of those genes are interrelated during development to specify form.

Phytomorphology Golden Jubilee Issue 2001: Trends in Plant Sciences. Edited by N S Rangaswamy. Delhi (India): International Society of Plant Morphologists. $75.00 (hardcover); $60.00 (paper). vii + 586 p; ill.; no index. ISSN: 0031–9449. 2001.

Previous articleNext article No AccessPlant SciencesPhytomorphology Golden Jubilee Issue 2001: Trends in Plant Sciences. Edited by N S Rangaswamy. Delhi (India): International Society of Plant Morphologists. $75.00 (hardcover); $60.00 (paper). vii + 586 p; ill.; no index. ISSN: 0031–9449. 2001.PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Quarterly Review of Biology Volume 79, Number 1March 2004 Published in association with Stony Brook University Article DOIhttps://doi.org/10.1086/421632 Views: 2Total views on this site PDF download Crossref reports no articles citing this article.

Structure of the Casparian strip: an artwork knitted by cells

Summary: The structure of the Casparian strip was first described by the German botanist Robert Caspary in the 19th century. The function of the Casparian strip as an apoplastic barrier for solute transport is now fairly well understood. However, up to now the formation and the development of the Casparian strip is still an open question not only for plant physiologists but also for plant morphologists. Therefore, in the following I will try to rise some new questions and I will try to point out some new experimental approaches, which will be necessary in future in order to find answers to these questions concerning Casparian strip formation and development.

Methods for distinguishing carbonized specimens of the presumed cephalopod aptychusSidetes(Spathiocaris) from the plantProtosalvinia(Foerstia)

The purpose of this note is to point out the similarities betweenProtosalvinia (Foerstia)andSidetes (Spathiocaris)and to discuss characters that can be used to distinguish the two taxa.ProtosalviniaClarke, 1885 (Figure 1.1-1.4), also commonly referred to by the junior subjective synonymFoerstia, is a plant fossil that is frequently noted as occurring in Upper Devonian black shale sequences of North America. This taxon has been of great interest to stratigraphers, paleoecologists, plant taxonomists, and plant morphologists over the years (see, for example, Winslow, 1962, p. 7, p. 22, fig. 3; Barron and Ettensohn, 1981, p. 30-31; Matthews, 1983; and Romankiw et al., 1988). Most workers in recent years have consideredProtosalviniato be a marine alga, but there is also evidence for a land plant affinity (Romankiw et al., 1988).

A new technique for making plant epidermal imprints using various domestic adhesives

SUMMARYA simple, quick and easy method for making leaf surface imprints for microscopic studies by using cheap and easily available non‐toxic domestic adhesives is described. The most satisfactory results were obtained, in order of preference, by using ‘Quickfix’, ‘Stickfast’, ‘Fevicol’, ‘D.P.X. (mountant)’, ‘Camel paste’, ‘Cello‐tape’ and ‘Araldite’. These were used on the epidermis of vegetative and floral organs of a number of plants (living and dried). A semi‐transparent film was allowed to dry, which was then stripped off and mounted on a clean slide. This film records very fine structural details which are evident from the photomicrographs presented. With the help of this technique, the form, distribution and orientation of stomata, size of guard cells and their movement, size of stomatal pores, stomatal development, cell‐wall nature, stomatal frequency and indices and venation pattern can easily be studied. Repeated imprints can be made from the same surface of an organ. This method should be of great use to plant morphologists and anatomists.

Reticulate Cuticle on Leaf Epidermis in Hevea brasiliensis Muell.

VARIATIONS of the surface patterns of cuticles have attracted the attention of both plant morphologists and physiologists. The formation and the functions of cuticle have been previously discussed1–3. Electron microscopic studies have revealed much greater details4,6. Observations under the light microscope show three main types of cuticles, namely, lamellate, striate and reticulate1,6,7, and the effects of cell growth are mentioned as chief causes for the formation of different types1,4. Of these three, occurrence of the lamellate cuticle appears to be more common than the other two. Different genera that possess striated cuticles have been listed3,7.

The inferior ovary. II

Within the last 12 years knowledge concerning the inferior ovary has been extended, but controversy has not terminated. As the result of anatomical studies, appendicular inferior ovaries have been reported in various genera of the following families: Agavaceae, Araliaceae, Begoniaceae, Bromeliaceae, Caprifoliaceae, Celastraceae, Compositae, Cornaceae, Ericaceae, Orchidaceae and Rubiaceae, and inJuglans of the Juglandaceae. The receptacular cup type, with ascending and recurrent budles in the wall, present inDarbya seems to be characteristic of the Santalaceae as a whole, of the Loranthaceae, ofCarya andAnnamocarya of the Juglandaceae, and of the Cactaceae. True inferior ovaries, in which the outer structures are fused with the ovary, should be distinguished from perigynous cups, as are found inRosa andCalycanthus. Recently the value of using the anatomical method in solving the problem of the structure of the inferior ovary has been questioned because of facts which have come out of modern studies in histogenesis and morphogenesis. It should be emphasized, however, that these facts are concerned with ontogeny. Plant morphologists have found that vascular anatomy, when used in comparative studies, has been a most valuable tool in the reconstruction of plant phylogenies, and they see no valid reason why it is not conclusive in the determination of the nature of the inferior ovary wall.

Society of Plant Morphologists

Society of Plant Morphologists

RELATIONAL PLANT MORPHOLOGY

ALTHOUGH occasional protests have been made by plant morphologists for many years against the inflexible framework of morphological concepts to which they have felt compelled to adhere in interpreting their experimental data, little attempt has been made to discard the defective outlook of traditional morphology in favour of something more adequate. Implicit in most botanical text-books and accepted by the majority even of research workers is the notion that morphology consists largely of the establishment of categories, such as chromosome, cell, vessel, periblem, pericycle, root, stem, leaf and stipule, into which all the diversity of plant structure has to be forced ; and structures as dissimilar as cotyledons, stamens and carpels, which happen to fall in the same pigeon-hole, in this case labeled 'leaf', are then described as related by the bond of 'homology'.

Morphological Interpretation of Floral Anatomy

IN the recent issue of the New Phytologist1, Mrs. Agnes Arber, in a paper dealing with the above subject, raises certain points which are of fundamental importance to all plant morphologists. She discusses the use of anatomical evidence in phylo-genetic morphology and comes to conclusions which are directly opposed to one of the well-established doctrines of modern comparative morphology. To the question, “Are we to consider it proven that the vascular bundles are more conservative than the external form, so that vestigial organs may be represented by their bundles, when all external trace of these organs has disappeared”, her answer is that “we have no alternative but to discard the doctrine of the conservatism of the vascular bundles”. Proceeding further, she says, “there seems to be no escape from the conclusion that there is a complete absence of positive evidence for the vestigial survival of vascular tissue after the organ which it supplied has ceased to exist”. She admits that the general nature of the vascular scheme may have a certain systematic value and may serve to some extent as an indicator of trends in race history, but in her opinion there appears to be no basis, say, for the statement of Bower2 that “anatomical characters and of the vascular system are apt to tardily follow evolutionary progress and thereafter to persist as vestigia” (italics mine).