Anatomy of Flowering Plants

Different tissues

  • A tissue is made up of group of cells which are similar / dissimilar in shape that has common origin and function.
  • Two types of tissue are (i) meristematic and (ii) Permanent
  • Characteristics of meristematic tissues
    ⇒ Only 1° cell wall is present
    ⇒ Metabolically active with no reserve food
    ⇒ No inter cellular space with compact tissue.
  • On the basis of location, meristem is of three types (i) Apical (Tip of root/shoot; length of the plants and 1° growth); (ii) Inter calary meristem (increase the length of plant organs); Eg: Base of Internode [grass, bamboo]; Base of node [min]; leaves [Pins] and (iii) Lateral meristem (increase the width / girth / Thickness)
  • On the basis of plane of division; meristem is of three types
    ⇒ Rib/Tile (Cortex / pith formation)
    ⇒ Plate (leaf blade)
    ⇒ Mass (endosperm / embryo)
  • Three theories to support optical meristem formation are (i) Apical cell theory (Karl Nageli). Histogen theory (Hanotein) and Tunica corpus theory (Schmidt)
  • According to histogen theory
    (i) Dermatogen : give rise to epidermis
    (ii) Periblem : give rise to hypodermis, cortex and endodermis
    (iii) Plerome, formation of stile.
    In monocot
    (iv) Calyptrogen : root cap.
  • According to tunica corpus theory
    (i) Tunica - forms epidermis
    (ii) Corpus - rest other than epidermis.
  • Permanent tissue is of three types (i) Simple (ii) Complex and (iii) Special.
  • Simple tissues are made up of similar cells that have common function
  • Parenchyma is very primitive and its firstly evolude
  • Characteristics:
    ⇒ All plant parts are obtained from it.
    ⇒ Central vacuole to store food
    ⇒ Possess Inter Cellular spaces
    ⇒ Eg. Flesh of a fruit
  • Parenchyma modifications
    (i) Prosenchyma (rigidity / strength)
    (ii) Aerenchyma (aquatic)
    (iii) Chlorenchyma [Palisade / spongy]
    (iv) Mucilage
  • Collenchyma which originates from ground meristem is a living mechanical tissue. Which has a localized deposition of pecto cellulose or Hemicellulose to provide tensile strength, to perform photo synthesis and flexibility.
  • Occurrence:
    ⇒ Herbaceous dicotyledonous
    ⇒ Absent in plants after secondary growth
  • Three types of collenchyma thickening are
    ⇒ Angular (Tomato stem)
    ⇒ Lamellate (Stem of sun flower)
    ⇒ Lacunate (stem of cucurbita)
  • Sclerenchyma is a dead tissue which is the main mechanical tissue that give rise to pits. Sclerenchyma is of 2 types (i) Sclereids and (ii) Fibers.
  • Types of sclereids:
    → Stone cells / Brachysclereids / grit cells Eg: Coconut, mango, almond, walnut
    → Trichosclereids Eg: Floating leaves.
    → Astrosclereid Eg: Vicloria, Nelumbo, Nymphae.
    → Osteo sclereids Eg: Hakea, Osmanthus.
  • Sclerenchymatous fibers are the congest cell in plant body which looks tapering that are interlocked to provide mechanical strength.
  • Fibers
Xylary fibers Bast / phloem fibers
→ hard → Flexible
→ not useful → Commercially useful
→ eg. munj (saccharum munja) → eg. (Cannabis sativa, crotalaria juncea)
  • Complex permanent tissues contain more than one type cell. Which work as one unit to perform heterogeneous function. These tissues are absent in gametophytes.
  • Xylem and phloem are 2 important complex tissues
Tracheids Vessels
Present in Xylem of Vascular plants Present in Xylem of flowering plants
Present in all vascular plants Only present in Angiosperms ; Gymnosperms
Eg: ephedra, gnetum, welwitschia)
Contain narrow lumen Contain wide lumen
Imperforated cells perforated cells
Primitive conducting element Advanced conducting element
  Angiosperm: In Dracaena, Yucca, Daziharia and Drimyl, vessels are absent.
sieve tube companion cells
Rigid cell wall necessary to support pressure gradients which lacks nucleus. Perform many genetic / metabolic functions of sieve tube cells
Separated from one another by sieve plates that help to ensure a steady flow of gap in phloem Contain many mitochondria supporting active transport with in folding plasma membrane.
  •  During autumn season - β(1 - 3) glucan starts depositing on the pores of sieve elements that form thick layer called as callus pad and it is dissolved is following spring.
  • Companion cell has thin wall with large nucleus that is present in angiosperm.
    [Exception : Austrobaileya]
  • Sieve tube contain P-protein, which series a seal against leakage in case of injury.
  • Sieve tube and companion cell are called siter cells and they both arise from single mother cell.
  • In gymnosperm, Albuminous / strasburger cells are present instead of companion cell.
  • Special Tissues: Special tissue or secretory tissue is of 2 types (i) lactiferous tissue and (ii) glandular tissue
  • Lactiferous tissue [highly branched thin walled cells filled with milky juice called latex]
    * latex vessels (articulated vessel) (Eg: Papaver, papaya, Argsmone)
    * latex cells (non articulated latex ducts) (Eg: Calotropis, Euphorbia, Nerium)
  • Glandular tissue may be unicellular (or) multi cellular glands
  • Unicellular → Example [urtica - dioica]
  • Multi cellular glands can be either External / Internal glands.
  • Glandular hairs (Eg: Drosera) and Nectar glands constitute external glands.
  • Digestive glands (utricularia, Drosera); mucous secreting leaves (betel leaves) oil glands (sunflower) constitute internal glands.

View this video for the topic from 0:42 to 51:42

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