6/10/2023 0 Comments Plant stem![]() Although, more and more epigenetic regulators have been shown to control plant stem-cell fate, only a few studies demonstrate how they are recruited and how they change the chromatin structure and transcriptional regulation of pluripotency factors. It is now clear that, in addition to gene regulatory networks of pluripotency factors and phytohormone signaling, epigenetics play a crucial role in initiation, maintenance and determination of plant stem-cells. Hence, in contrast to the widely-held assumption that all plant cells have the ability to reproduce a complete organism, only few cell types are pluripotent in practice, raising the question how pluripotent stem-cells differ from differentiated cells. In tissue cultures, after detached plant organs are transferred to rooting or callus induction medium (G5 or CIM), vasculature-associated pluripotent cells (VPCs) immediately start proliferation to form adventitious roots or callus, respectively, while other cell types of the organ explants basically play no part in the process. After ablation of stem-cell niches, pluripotent meristematic cells can establish new stem-cells, whereas the removal of the whole meristem destructs the regeneration process. In plants, stem-cells are located in specific niches of the shoot and root apical meristems (SAMs and RAMs). Pluripotent stem-cells are slowly dividing cells giving rise to daughter cells that can either differentiate to new tissues and organs, or remain stem-cells. Lushan Botanical Garden, Chinese Academy of Sciences, Jiujiang, China.The general features of the woody stem illustrated in Figure 13.1 will be characteristic for a particular plant species. In contrast to herbaceous stems that die at the end of the growing season, woody stems are permanent structures that grow in length and girth (diameter) each year and produce bark as a protective covering. Descriptions of morphological characteristics are illustrated at this link to Grasses, Sedges and Rushes. the leaves may be reduced to just a rounded sheath. can look very grass-like with leaf blades while in Juncus spp. Rushes differ from grasses in that stems are not jointed (no nodes) and are typically filled with pith. Sedges ( Carex spp.), differ from grasses and rushes in that the stems are triangular (V-shaped) in cross section at the base (“sedges have edges”), have a solid pith, and are not jointed. The base of the leaf circles around the stem forming a series of overlapping sheaths. The culm (stem) of a grass plant ( Poa spp.) is hollow with pith only at the jointed nodes. The stems are generally filled with a soft spongy tissue called pith, that stores and transports nutrients. Herbaceous (non-woody) stems with solid or hollow stems are typical of forbs (eudicots), grasses, and grass-like plants called rushes and sedges (monocots). Depending on the type of plant, stems may be woody or herbaceous, and solid or hollow in cross section. Plant stems with vascular tissue support leaves and reproductive structures such as flowers. Ī morphological description usually starts with the structure of a plant. ![]() ![]() Some regional databases are available at these links to the Kwantlen Polytechnic University Plant Database, Oregon State University Landscape Plants, and University of British Columbia E-Flora BC. ĭigital databases and apps typically use the morphology of stems, leaves, flowers, and fruit to identify unknown plants. You can view it online here: Herbarium: How to Press Plants Īn example of an institutional herbaria is available at this link to the University of British Columbia Beaty Biodiversity Museum. Information on the procedure for creating herbarium samples is available at this link to Herbarium: How to Press Plants Ī YouTube element has been excluded from this version of the text. A herbarium is a collection of pressed and dried plants that is systematically arranged for research and plant identification purposes. London, Macmillan Press, 1992.Ī working knowledge of morphological descriptors for plant identification enables the use of dichotomous keys as well as herbarium samples and digital databases. (ed.) The New Royal Horticultural Society Dictionary of Gardening. While the original botanical resource, Species plantarum was published by Carolus Linnaeus in 1753, one of the most comprehensive references currently available for plant morphology is Huxley, A. Morphology is the Greek word for “the study of shape,” and plant morphology is the study of the external plant structures and shapes. Plant identification depends on knowledge of taxonomy and understanding of stem, leaf, bud, flower and fruit morphology. Describe the morphological characteristics of herbaceous and woody stems. ![]()
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