Plant tissues and organs
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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

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

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Plant tissues and organs Plant tissues and organs Presentation Transcript

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