Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Plant Tissues The Form and Function of Plants Learning objectives • Students are able to discuss the plant body – root & shoot systems • Students are able to describe the different kinds of plant tissues The "Typical" Plant Body 1) The Root System -Anchor the plant in the soil -Absorb water and nutrients -Conduct water and nutrients -Food Storage 2) The Shoot System -Elevates the plant above the soil -Photosynthesize -Reproduce -Disperse food & conduct water Tissues of the plant body • A tissue is a group of cells that forms a structural and functional unit • Some plant tissues are simple, whereas others are complex Simple & Complex Tissues • Simple – one kind of cell • Complex – two or more kinds of cells Three tissue systems (in vascular plants) based on functions 1. Dermal tissue system 2. Ground tissue system 3. Vascular tissue system Ground tissue -photosynthesis -storage -support Vascular tissue -conduction of materials Dermal tissue -protections (based on functions) The ground tissue system • Composed of 3 simple tissues 1. Parenchyma – thin primary cell walls 2. Collenchyma – unevenly thickened primary cell walls 3. Sclerenchyma – both primary and thick secondary cell walls Parenchyma cells -Unspecialized, living, and metabolizing cells (found throughout the body) -Functions: photosynthesis, storage, secretions, and differentiation when injured Collenchyma cells -Uneven primary cell walls (occur as long strands near stem surfaces and along leaf veins) -Function: support (flexibility) Sclerenchyma cells - often dead cells & thickening secondary cell walls (occur several areas of the plant body) - 2 types of sclerenchyma cells: Sclereids & Fibers -Function: support the body Fibers -Long & tapered cells -Often occur in groups Sclereids -Short & varied in shape The vascular tissue system • Composed of two complex tissues 1. Xylem conducts water and dissolved minerals 2. Phloem conducts food materials Xylem • Composed of Tracheids, vessel elements, parenchyma cells, fibers • Conducting cells are tracheids & vessel elements collectively called tracheary element Tracheids and Vessel Elements as water conducting cells pit Tracheids -Water pass through pits -Less efficient than vessel elements Vessel elements -Hollow with perforations at end walls -Wider & shorter than tracheids -One cell stacked on top of the other -Water movement: updown & sideway Tracheary Elements (Conducting Sclerenchyma) Perforations (Only vessel elements) Bordered pit Annular Helical 2nd 2nd cellScalariform Reticulate 2nd Pitted 2nd cell cell walls walls 2nd cell walls cell walls walls A & B = bordered pit 1 = secondary wall 2 & 3= primary wall 4 = pit membrane 5 = pit 6 = border Xylem Vessel member: angiosperm Tracheid: Gymnosperm Phloem • Composed of Sieve-tube elements, companion cells, parenchyma cells, fibers • Conducting cells are sieve-tube elements Food materials are conducted in solution – that is, dissolved in water through the sieve-tube elements Sieve-Tube Members as Food Conducting Cells Sieve-tube elements –long & thin cells -stacked end on end with sieve plants -Alive at maturity but many organelles, including nucleus absent 1 Sieve tube member Which makes up vessel of phloem. They loss of most organelles but are still alive 2 Companion cell A cell adjacent to the sieve tube cell that keep the sieve cell tube alive Dermal tissue system • Consists of two complex tissues: epidermis & periderm • Function: protective covering In herbaceous plants • The dermal tissue system is a layer of epidermis Epidermis as a complex tissue • Generally contain no chloroplasts • Transparent to light • Coated by cuticle • Some modified into guard cells • Some modified into trichome • Some modified into root hairs Trichome Root hair Guard cells in leaf In woody plants • Epidermis initially produced but split apart when 2nd growth occurred • Epidermis replaced by several layers of periderm Tissue system 1. Ground tissue system 2. Vascular tissue system 3. Dermal tissue system Tissues Cell types Parenchyma tissue Parenchyma cells Collenchyma tissue Collenchyma cells Sclerenchyma tissue Sclerenchyma cells (sclereids, fibers) Xylem Tracheids, vessel elements, parenchyma cells, fibers Phloem Sieve-tube elements, companion cells, parenchyma cells, fibers Epidermis Parenchyma cells, guard cells, trichomes Periderm Cork cells, cork cambium cells, cork parenchyma References • เอกสารประกอบการสอนหัวข้อ Plant Tissue โดย Dr. Vasakorn Bullangpoti มหาวิทยาลัยเกษตรศาสตร์ • Berg, L. R. 2008. Introductory Botany: Plants, people, and the environment. 2nd ed. Thomson Brooks/ Cole. 622 pp. • Mauseth, J. D. 2009. Botany: an introduction to plant biology. 4th ed. Jones and Bartlett Publishers, LLC. 624 pp.