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Plant tissues and organs


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..presentation made by our professor at bicol university with regards to plants tissues and organs

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Plant tissues and organs

  2. 2. Plant Cell Types (Support and Storage) <ul><li>Parenchyma cells are the most numerous type of cell in young plants. </li></ul><ul><li>Parenchyma cells usually have thin walls and large central vacuoles. </li></ul><ul><li>The photosynthetic cells in leaves are parenchyma cells filled with chloroplasts. These cells are called mesophyll cells. </li></ul><ul><li>Some parenchyma cells store lipids or starch (potatoes). </li></ul><ul><li>Other parenchyma cells serve as “packing material” and play a vital role in supporting the stem especially in nonwoody stems. </li></ul>
  3. 3. <ul><li>Collenchyma cells are supporting cells that lay down primary cell walls that are thick in the corners. </li></ul><ul><li>Collenchyma cells provide support to leaf petioles, nonwoody stems, and growing organs. </li></ul><ul><li>These cell types compose the cortex and pith tissues of the root and stems. </li></ul>
  4. 4. <ul><li>Sclerenchyma cells are the main supporting cells of a plant. They have a thick secondary cell wall that contains a substance called lignin, a component of wood. Therefore they are found in woody plants. </li></ul>
  5. 5. <ul><li>There are two types of sclerenchyma cells : elongated fibers and variously shaped sclereids. </li></ul><ul><li>Fibers often organize into bundles. (They are common components of xylem.) </li></ul><ul><li>Sclereids may pack together very densely. (Sclereids are found in fruits such as pears and this give them their gritty texture.) They are often referred to as “stone cells”. </li></ul>
  6. 6. Plant Cell Types Vascular (Transport) <ul><li>Xylem </li></ul><ul><li>The xylem conducts water from roots to above ground plant parts. It contains conducting cells called tracheary elements . </li></ul><ul><li>Tracheids are evolutionarily more ancient tracheary elements found in gymnosperms. </li></ul><ul><li>Both tracheary elements and tracheids undergo apoptosis(die) and do their jobs as empty cells (only the cell walls remain). </li></ul>
  7. 7. Tracheids and vessel elements: Water conducting cells <ul><li>Vessel elements are the water “pipeline” system in flowering plants, also formed from dead cells. Flowering plants have both tracheids and vessel elements. </li></ul><ul><li>Vessel elements are generally larger in diameter than tracheids and are laid down end-to-end to form hollow tubes . </li></ul>
  8. 8. Sieve-tube members: Food onducting Cells <ul><li>Phloem </li></ul><ul><li>Cells of the phloem are alive when they do their job, unlike those of the xylem. </li></ul><ul><li>The characteristic cell of the phloem is the sieve tube member . </li></ul><ul><li>Cells of the phloem are arranged end-to-end and form long sieve tubes, which transport carbohydrates and other materials. </li></ul>
  9. 9. <ul><li>The plasmodesmata in sieve tube members enlarge as they mature, resulting in end walls that look like sieves. </li></ul><ul><li>At functional maturity, a sieve tube is filled with sieve tube sap (water, sugars, and other solutes). </li></ul><ul><li>The sieve tube members have adjacent companion cells. </li></ul><ul><li>Companion cells retain all their organelles and may regulate the performance of and support the sieve tube members. </li></ul>
  10. 10. Plant Tissues <ul><li>A tissue is an organization of cells that work together as a functional unit. </li></ul><ul><li>Parenchyma cells make up parenchyma tissue, which is a simple tissue. </li></ul><ul><li>Xylem and phloem are complex tissues; they are composed of a number of different cell types. </li></ul><ul><li>Tissues are grouped into tissue systems that extend throughout the body of the plant to form the various organs of the plant. </li></ul><ul><li>There are three plant tissue systems: vascular, dermal, and ground. </li></ul>
  11. 11. Plant Tissues
  12. 12. THREE TISSUE SYSTEMS IN PLANT <ul><li>Vascular Tissue </li></ul><ul><li>The vascular tissue system includes the xylem and phloem ; it is the conductive or “plumbing” system of the plant. </li></ul><ul><li>The phloem transports carbohydrates from sites of production (sources such as leaves) to sites of utilization for energy or where it is being stored (sinks) elsewhere in the plant. </li></ul>
  13. 13. Vascular Tissue <ul><li>The xylem distributes water and mineral ions taken up by the roots to the stem and leaves . </li></ul>
  14. 14. Dermal Tissue <ul><li>The dermal tissue system is the outer covering of the plant . </li></ul><ul><li>All parts of the young plant body are covered by an epidermis, which is a single layer or multiple layers of cells. </li></ul><ul><li>The epidermis contains epidermal cells and other specialized cells such as guard cells. </li></ul><ul><li>The shoot epidermis secretes a layer of wax-covered cutin, the cuticle, which helps retard water loss from stems and leaves. </li></ul>
  15. 15. Ground Tissue <ul><li>The ground tissue system makes up the rest of a plant and consists primarily of parenchyma tissue. </li></ul><ul><li>Ground tissue functions primarily in storage, support, photosynthesis, and the production of defensive and attractant substances (oils and toxins). </li></ul>
  16. 16. Meristems generate cells for new organs(Plant Stem Cells) <ul><li>In plants the growth of roots and stems is indeterminate and is generated from specific regions of active cell division. </li></ul><ul><li>The localized regions of cell division in plants, called meristems , are forever embryonic. They have the ability to produce new cells indefinitely. </li></ul><ul><li>The cells of meristematic tissues are analogous to the stems cells found in animals. </li></ul><ul><li>When a meristem cell divides, one daughter cell develops into another meristem cell, and the other differentiates into a more specialized cell. The meristem gives rise to all plant cell and tissue types. </li></ul>
  17. 17. <ul><li>There are two types of meristems : </li></ul><ul><ul><li>Apical meristems give rise to the primary plant body, which is the entire body of many plants. </li></ul></ul><ul><ul><li>Lateral meristems give rise to the secondary plant </li></ul></ul><ul><ul><li>body. </li></ul></ul><ul><li>The stems and roots of some plants form wood and become thick; it is the lateral meristems that give rise to the tissues responsible for this thickening. </li></ul><ul><li>Apical meristems are located at the tips of roots and stems and in buds. </li></ul><ul><li>Shoot apical meristems supply the cells that extend stems and branches. </li></ul><ul><li>Root apical meristems supply the cells that extend roots. </li></ul><ul><li>Apical meristems are responsible for primary growth, which leads to elongation and organ formation. </li></ul>
  18. 18. Location of Meristematic Tissues
  19. 19. Primary Growth of Root <ul><li>Root Cap Thimble-like covering which protects the delicate apical meristem </li></ul><ul><li>Produced from cells derived from the root apical meristem </li></ul><ul><li>Secretes polysaccharide slime that lubricates the soil </li></ul><ul><li>Constantly sloughed off and replaced </li></ul>
  20. 20. <ul><li>Apical Meristem Region of rapid cell division of undifferentiated cells </li></ul><ul><li>Most cell division is directed away from the root cap </li></ul><ul><li>Quiescent Center Populations of cells in apical meristem which reproduce much more slowly than other meristematic cells </li></ul><ul><li>Resistant to radiation and chemical damage </li></ul><ul><li>Possibly a reserve which can be called into action if the apical meristem becomes damaged </li></ul>
  21. 21. <ul><li>The Zone of Cell Division - Primary Meristems Three areas just above the apical meristem that continue to divide for some time </li></ul><ul><li>Protoderm - outermost primary meristem - produces cells which will become dermal tissue </li></ul><ul><li>Ground meristem - central primary meristem - produces cells which will become ground tissue </li></ul><ul><li>Procambium - innermost primary meristem - produces cells which will become vascular tissue </li></ul>
  22. 22. <ul><li>The Zone of Elongation Cells elongate up to ten times their original length </li></ul><ul><li>This growth pushes the root further downward into the soil </li></ul><ul><li>The Zone of Maturation Region of the root where completely functional cells are found </li></ul>
  23. 23. The leaf vein stalk lamina midrib
  24. 24. The Leaf – Cross-section <ul><li>Midrib - extension of the stalk into the leaf </li></ul><ul><li>Vein Branch-off from the midrib </li></ul><ul><li>Lamina - the blade of the leaf </li></ul><ul><li>Stalk - attaches the leaf to the stem </li></ul>midrib vein lamina
  25. 25. Waxy Cuticle & Epidermis <ul><li>The waxy cuticle is a thin layer atop the epidermis. </li></ul><ul><li>Its function is to reduce the water lost from the leaf. </li></ul><ul><li>In arid conditions this cuticle layer can be quite thick. </li></ul><ul><li>Epidermis cells contain no chloroplasts – not true of the stoma cells. </li></ul><ul><li>They form layers on the upper and lower surfaces of the leaf. </li></ul><ul><li>Their function is to prevent water getting out and stopping unwanted substances/organisms getting in . </li></ul>cuticle epidermis
  26. 26. Palisade Mesophyll Layer <ul><li>The palisade mesophyll layer is where most of the photosynthesis occurs in the leaf. </li></ul><ul><li>The palisade cells contain a lot of chloroplasts to help them perform this photosynthesis. </li></ul><ul><li>The palisade cells are closely packed together to maximize light absorption. </li></ul><ul><li>In the leaf cross-section we can see the palisade cells are only found in the upper part of the leaf . </li></ul>
  27. 27. Spongy Mesophyll Layer <ul><li>The cells in the spongy mesophyll layer are not as closely packed as the cells in the palisade mesophyll layer . </li></ul><ul><li>This creates air spaces inside the leaf to enable gases to move in and out . </li></ul><ul><li>There are not as many chloroplasts in the spongy mesophyll cells as there are in the palisade mesophyll cells – but photosynthesis still occurs in the spongy mesophyll layer . </li></ul>
  28. 28. Stomata <ul><li>There are holes found in leaves called stoma </li></ul><ul><li>These holes allows gases to diffuse in and out of the leaves </li></ul><ul><li>The stoma are formed by two highly specialized epidermis cells . </li></ul><ul><li>These cells, called guard cells , are the only epidermis cells that contain chloroplasts. </li></ul><ul><li>The stoma open and close depending upon the requirements of the plant. </li></ul><ul><li>It is through these stoma that water leaves the leaf, the process that powers transpiration . </li></ul>
  29. 29. <ul><li>During photosynthesis carbon dioxide diffuses in and oxygen diffuses out </li></ul><ul><li>When the stomata are closed,often at night or in a humid environment, this stops gases diffusing in and out of the leaf </li></ul>Open stomata Close stomata
  30. 30. <ul><li>FLOWERS </li></ul><ul><li>A flower is were the reproductive parts of the plant is held. Many parts are inside of a flower. The major parts are: -Stamen -Stigma -Pistil -Filament -Ovary -Eggs -Pollen/Sperm -Anther </li></ul>
  31. 31. Flowers <ul><li>Flower Parts </li></ul><ul><li>Pistil </li></ul><ul><ul><li>Female part of plant </li></ul></ul><ul><ul><li>Containing: </li></ul></ul><ul><ul><ul><li>Stigma </li></ul></ul></ul><ul><ul><ul><li>Style </li></ul></ul></ul><ul><ul><ul><li>Ovary </li></ul></ul></ul>
  32. 32. <ul><li>The pistil is the term for all the female parts of a flower. Each pistil includes an ovary (where the eggs are produced; the female reproductive cells, a style (a tube on top of the ovary), and a stigma (which the pollen sticks to during fertilization). </li></ul>
  33. 33. <ul><li>Stamen </li></ul><ul><ul><li>Male reproductive part </li></ul></ul><ul><ul><li>Contains </li></ul></ul><ul><ul><ul><li>Anther </li></ul></ul></ul><ul><ul><ul><li>Filament </li></ul></ul></ul><ul><li>The male parts of the flower help fertilize the egg of </li></ul><ul><li>the flower. </li></ul><ul><li>These parts are usually in a place that can be easily moved by insects and animals. </li></ul>
  34. 34. <ul><li>Sepals </li></ul><ul><ul><li>Small green structures on the base of a flower that protect the flower bud </li></ul></ul><ul><li>Petals </li></ul><ul><ul><li>Highly colored part of the flower, may contain perfume and/or nectar glands </li></ul></ul>
  35. 35. Parts of the Seed <ul><li>Embryo </li></ul><ul><ul><li>Growing part of seed containing: </li></ul></ul><ul><ul><ul><li>Plumule – “Shoot” </li></ul></ul></ul><ul><ul><ul><li>Hypocotyl – Stem </li></ul></ul></ul><ul><ul><ul><li>Radicle – “Root” </li></ul></ul></ul><ul><li>Endosperm </li></ul><ul><ul><li>Tissue that provides nutrition for the developing seed </li></ul></ul><ul><li>Cotyledon </li></ul><ul><ul><li>Food Storage </li></ul></ul><ul><li>Seed Coat </li></ul><ul><ul><li>Protective outer covering of the seed </li></ul></ul>
  36. 36. Parts of the Seed
  37. 37. <ul><li>Testa -outer covering of the seed; protects the embryo </li></ul><ul><li>Hilum - the scar on the seedcoat; place where the seed was attached to the ovary </li></ul><ul><li>Endosperm-the food supply of the baby plant. </li></ul>