BIO13- 1st LE- SECRETORY STRUCTURES (EXTERNAL)

• • Salt Glands 
  • found in halophytes. 
  • No direct connection to the vascular bundles.
  • Secrets ions to regulate the salt content of plant shoots.
• • Hydathodes
  • Structures that discharge the liquid water with various dissolved substances from the interior of the lead to its surface (guttation).
  • Usually located at leaf tips or margins.
  • Has four structures: Terminal tracheids, epithem, sheath, and openings called water pores
• • Epithem (Hydathodes)- composed of thin-walled, chloroplast deficient parenchyma cells located above or distal to the vein endings.
• Sheath (Hydathodes)- a continuation of the bundle sheath that extends to the epidermis
• • Nectaries
  • Structures that release an aqueous fluid (nectar) with a high sugar content (sucrose, fructose, glucose). Has two types: floral nectaries, and extrafloral nectaries
  • released through a modified stomata which is always open. Nectar is also produced by secretory cells.
• Floral nectaries- directly associated with pollination
• Extrafloral nectaries-  not usually associated with pollination. Attracts ants with its nectar so that the ants can protect them from herbivores. (protection).
• • Nectariferous tissue (Nectaries)- tissue composing the nectary (epidermis + specialized parenchyma)
• Secretory cells in Nectaries: Dense cytoplasm, small vacuoles, numerous mitochondria, ER highly developed, and numerous golgi bodies
• • Colleters
  • Structures giving off sticky secretions that are insoluble in water. 
  • Develop on young foliar organs and the secretions cover the entire bud. 
  • A protective coating for the dormant bud and protects a developing meristem and young, differentiating leaves or stipules.
  • Has different types: Common standard type, Reduced standard, Dendroid, and Brushlike
• • Osmophores
  • Secretes fragrance.
  • Consists of glandular tissues, usually several layers in depth. 
  • Stomata occurs on its surface.
• • Glandular Trichomes
  • Releases lipophilic substances such as terpenoids (essential oils and resins), fats, waxes. 
• • Terpenoids (Glandular Trichomes)- this deters the herbivores, and attracts pollinators.