Anatomy

• Dicotyledonous (Dorsiventral) Leaf


  Leaf type in dicot plants
• Monocotyledonous (Isobilateral) Leaf


  Leaf type in monocot plants
• Components of Epidermal Tissue System

  • Epidermal cells
  • Stomata
  • Epidermal appendages (trichomes and emergences)
• Epidermal Tissue System


  • Forms the outermost covering of the whole plant body
  • Derived from protoderm
• Stomata


  • Openings found in the epidermis of most aerial plant parts, especially leaves
  • Composed of two bean-shaped guard cells that enclose the stomatal pore
• Guard cells


  • Generally much smaller in size compared to other epidermal cells
  • Outer walls are thin, inner walls are highly thickened
  • Possess chloroplasts and regulate opening and closing of stomata
• Subsidiary/accessory cells

  • Surround the guard cells in some species
  • Differ morphologically from other epidermal cells
• Stomatal apparatus

  • Includes the stomatal aperture, guard cells, and surrounding subsidiary cells
• Stomata in monocots

  • Guard cells are dumb-bell shaped
  • Mostly found on the upper epidermis of leaves
  • In some hydrophytes, found on upper surface to avoid water contact
• Epidermal Appendages (Outgrowths)


  • Trichomes (epidermal hairs)
  • Emergences (prickles)
• Trichomes

  • Multicellular epidermal outgrowths on plant parts
  • May be branched or unbranched
  • May be secretory in nature
  • Help in reducing transpiration
• Emergences (Prickles)


  • Multicellular, stiff and sharp epidermal outgrowths containing some inner tissues
  • Protect against water loss and grazing
  • Help in climbing in some plants
• Functions of Epidermal Tissue System


  • Provide protective covering
  • Reduce water loss
  • Prevent entry of harmful organisms
  • Help in absorption, secretion, and excretion
• Components of Ground Tissue System

  • Hypodermis
  • Cortex
  • Endodermis
  • Pericycle
  • Medullary rays
  • Pith
• Mitochondria produce energy through aerobic respiration.
• Hypodermis


  • Region just below the epidermis, outer part of cortex
  • Contains one, two or few continuous or discontinuous layers of collenchyma (in dicots) or sclerenchyma (in monocots)
  • Protective and mechanical in function
• Cortex

  • Thin-walled region between epidermis and endodermis
  • Contains parenchyma, collenchyma and sclerenchyma tissues
  • Distinct layer in dicots, not in monocots
  • Contains starch grains, oil, tannins, crystals
  • May develop chloroplasts and become photosynthetic (chlorenchyma)
  • In hydrophytes, may be aerenchymatous (spongy with air spaces)
  • Contains special cells like sclereids, resin ducts, oil glands, laticifers
• Endodermis


  Layer between cortex and vascular cylinder
• Dicotyledonous root

  • Presence of root hairs
  • Endodermis with Casparian strips
  • Absence of pith
  • Radial bundles less than eight
  • Presence of each xylem
• Monocotyledonous root

  • Presence of root hairs
  • Endodermis with passage cells
  • Presence of pith
  • Radial bundles more than eight
  • Xylem exarch
  • Presence of an exodermis
• Differences between dicot root and monocot root

  • Cortex is well-developed in monocot root
  • Endodermis is more prominent with Casparian thickenings in dicot root
  • No secondary growth occurs in monocot root (except in some plants)
  • Conjunctive tissue around metaxylem vessel is sclerenchymatous in monocot root
  • Pith is large in monocot root
• Dicotyledonous stem

  • Epidermis is the outermost protective layer with cuticle and may bear trichomes and stomata
  • Hypodermis is a layer of collenchymatous cells below epidermis providing mechanical strength
  • General cortex is parenchymatous with intercellular spaces and chloroplasts
  • Endodermis is a single layer of barrel-shaped cells surrounding the stele
  • Pericycle is present on the inner side of phloem with sclerenchymatous bundle caps and parenchymatous cells
• Hard bast is the semi-lunar patches of sclerenchymatous cells in the pericycle associated with phloem of the vascular bundle
• The epidermal tissue system forms the outermost covering of the whole plant body. It is derived from protoderm
• Each stomata is composed of two bean shaped cells called guard cells which encloses stomatal pore
• the guard cells are surrounded by subsidiary cells or accessory cells which differ morphologically from other epidermal cells
• The epidermal hairs present on the stem are called trichomes
• when the xylem and phloem alternate with each other separated by parenchymatous cells
• in dicots cambium is present between xylem and phloem