Phloem and Secretory Vesicles

• Secretory structures:

  • External- secretes substances outside the plant
  • Internal- secretes substances inside the plant
• State whether external or internal: x/i

  1. salt glands- x
  2. nectaries (floral and extrafloral)- x
  3. tannin idioblast- i
  4. osmophores- x
  5. secretory ducts and cavities- i
  6. stinging hairs- x
  7. colleters- x
  8. hydathodes- x
  9. laticifer- i
  10. mucillage cells- i
  11. oil cells- i
  12. myrosin cells- i
  13. glandular trichomes- x
  14. crystal containing cell- i
  15. digestive glands- x
• salt glands (external)

  • found in plants in saline habitat
  • located on plant surface
  • regulate salt content
  • holocrine secretion
• nectaries (external)

  • nectar- aqueous fluid with high sucrose/ glucose/ fructose content
  • secretion through stomatal pores and glandular trichomes (if present)
• floral nectaries

  • directly associated with pollination
  • attract pollinators
  • e.g., intrastaminal, septal
• extrafloral nectaries

  • occur on vegetative parts
  • represented by glandular hairs/ epidermis
  • attract animals for defense
• osmophores (external)

  • floral fragrance glands/ " scent glands "
  • attract flowers' pollinators
  • precursor for sex pheromone
• glandular trichomes (external)

  • secrete lipophilic substances (terpenoids, fats, waxes)
  • deter herbivores
  • attract pollinators
• colleters (external)

  • mucilaginous/ resinous, water-insoluble fluid, terpene
  • found in bud scales, young leaves
  • emergences of epidermal and subepidermal tissues
• stinging hairs (external)

  • produce toxic substances
• digestive glands (external)

  • digest insects that get caught
  • found in carnivorous plants
• hydathodes (external)

  • secrete water via guttation
  • loose arrangement of parenchyma cells
• internal secretory cells

  • large cells
  • produce and store chemicals to deter foraging animals
  • e.g., pellucid glands (Rutaceae)
  • includes crystal-containing cells, myrosin cells, oil cells, mucillage cells, tannin idioblast
• secretory ducts and cavities (internal)

  • secrete substances into intercellular spaces
  • secretory cavities: short secretory spaces
  • secretory ducts: long secretory spaces
  • usually found associates with vascular tissues
• laticifers (internal)

  • cells/series of connected cells containing latex- may be found in cortex, phloem, or pith.
  • articulated laticifers/ laticiferous vessels- fused cells
  • non-articulated laticifers/ laticiferous cells- single cells with unlimited growth
  • cytoplasm containing carbohydrates, oils, alkaloids, organic acids, enzymes, rubber
  • white or colorless
  • deter grazing animals