Anatomy Of Flowering Plants

• Plants have cells as the basic unit, which are organised into tissues and then into organs
• Angiosperms, specifically monocots and dicots, show anatomical differences
• • Stomatal apparatus includes stomata, guard cells, and subsidiary cells
• Epidermal tissue system:

  • Forms the outermost covering of the plant body
  • Comprises epidermal cells, stomata, trichomes, and root hairs
  • Epidermis is single-layered and made up of elongated, compactly arranged cells
  • Epidermal cells have a small amount of cytoplasm and a large vacuole
  • Cuticle is a waxy layer on the outside of the epidermis that prevents water loss
  • Stomata regulate transpiration and gaseous exchange
  • Guard cells regulate the opening and closing of stomata
  • Subsidiary cells are specialised cells near guard cells
• Ground tissue system:

  • Consists of all tissues except epidermis and vascular bundles
  • Includes parenchyma, collenchyma, and sclerenchyma
  • Parenchymatous cells are found in cortex, pericycle, pith, and medullary rays
  • Mesophyll is the ground tissue in leaves and contains thin-walled chloroplast-containing cells
• Vascular tissue system:

  • Consists of phloem and xylem
  • Vascular bundles in dicotyledonous stems have cambium for secondary growth (open vascular bundles)
  • Vascular bundles in monocotyledonous stems lack cambium (closed vascular bundles)
  • Radial arrangement of xylem and phloem in roots
  • Conjoint type of vascular bundles in stems and leaves with phloem located on the outer side of xylem
• Dicotyledonous root anatomy:

  • Epiblema is the outermost layer with unicellular root hairs
  • Cortex consists of thin-walled parenchyma cells
  • Endodermis has barrel-shaped cells with casparian strips
  • Pericycle is thick-walled and initiates lateral roots and vascular cambium
  • Pith is small or inconspicuous
  • Conjuctive tissue lies between xylem and phloem
  • Stele includes all tissues on the inner side of the endodermis
• Monocotyledonous root anatomy:

  • Similar to dicot root but with more xylem bundles (polyarch)
  • Large and well-developed pith
  • No secondary growth in monocot roots
• Dicotyledonous stem anatomy:

  • Transverse section shows specific features
• Dicotyledonous Stem:

  • Epidermis is the outermost protective layer of the stem
  • Root hair, Cortex, Endodermis, Protoxylem, Metaxylem, Pith, Phloem present
  • Hypodermis consists of collenchymatous cells below the epidermis
  • Cortex consists of parenchymatous cells with intercellular spaces
  • Endodermis is rich in starch grains and referred to as the starch sheath
  • Pericycle present on the inner side of the endodermis and above the phloem as semi-lunar patches of sclerenchyma
  • Medullary rays between vascular bundles
  • Vascular bundles arranged in a ring with endarch protoxylem
• • Pith consists of parenchymatous cells with large intercellular spaces
• Monocotyledonous Stem:

  • Sclerenchymatous hypodermis
  • Scattered vascular bundles surrounded by sclerenchymatous bundle sheath
  • Conjoint and closed vascular bundles
  • Absence of phloem parenchyma
  • Water-containing cavities present within the vascular bundles
• Dorsiventral (Dicotyledonous) Leaf:

  • Epidermis covers upper and lower surfaces with a conspicuous cuticle
  • Mesophyll between epidermis layers, made up of palisade parenchyma and spongy parenchyma
  • Palisade parenchyma made up of elongated cells arranged vertically
  • Spongy parenchyma loosely arranged below palisade cells
  • Vascular system includes vascular bundles in veins and midrib
  • Vascular bundles surrounded by thick-walled bundle sheath cells
• Isobilateral (Monocotyledonous) Leaf:

  • Stomata present on both surfaces of the epidermis
  • Mesophyll not differentiated into palisade and spongy parenchyma
  • Presence of bulliform cells in grasses
  • Parallel venation with similar sizes of vascular bundles
• Plant Tissues:

  • Classified into meristematic (apical, lateral, intercalary) and permanent (simple, complex)
  • Functions include assimilation of food, storage, transportation of water, minerals, and mechanical support
  • Tissue systems: epidermal, ground, vascular
  • Epidermal tissue system made of epidermal cells, stomata, and epidermal appendages
  • Ground tissue system divided into cortex, pericycle, and pith
  • Vascular tissue system formed by xylem and phloem
  • Vascular bundles conduct and translocate water, minerals, and food material
• Monocotyledonous and dicotyledonous plants:

  • Marked variation in internal structures
  • Differ in type, number, and location of vascular bundles
  • Secondary growth in most dicotyledonous roots and stems