Parenchyma

• Parenchyma:

  Living protoplasts – living at maturity

  • can resume meristematic activity and give rise to new cells
  • totipotent
  • Principal seat of essential cellular activities
• Parenchyma:

  Thin primary walls – important in wound healing, regeneration, formation of adventitious organs, union of grafts

  • Usually no secondary cell walls
  • Primary pit fields present
• Parenchyma:

  Unspecialized morphologically and physiologically – may change functions or combine several different ones
• parenchyma cells are not meristematic unless they undergo trans-differentiation.
• Parenchyma cells are fundamental, it is the foundation of the plant ontogenetically (spores and gametes are parenchymatous in nature), and phylogenetically (charophytes are parenchymatous).
• Origin and Distribution

  1. Ground meristem - gives rise to the cells of the pith, pith ray cortex, mesophyll, and ground tissue of reproductive structures.
• Procambium/Vascular cambium - parenchyma cells associated with the primary and secondary vascular tissues are formed by the procambium and the vascular cambium, respectively
• Cork cambium - may also arise from the phellogen in the form of phelloderm, and it may be increased in amount by diffuse secondary growth
• Parenchyma cells are Ubiquitous (seen in every parts of the plant body)
• Parenchyma is Polyhedral (many sides or facets, but no single pattern of shape)
• Isodiametric: ground tissues of stem and root

  
• Lobed: gymnosperm mesophyll (ground tissue of leaves)

  
• Irregular/branched: spongy mesophyll (of dicots)

  
• Elongated: prosenchyma of the palisade mesophyll (of dicots)

  
• Cell types - Parenchyma perform a wide variety of functions because they attain specialization in terms of function
• Cell type: Chlorenchyma

  1. cells contain numerous chloroplast that functions in photosynthesis
  2. highly vacuolated and with an extensive system of intercellular spaces
  3. widely seen in mesophyll but may also be found in the cortex of stem, secondary xylem tissue, and pith

  
• Cell type: Secretory

  1. Dense protoplast, rich in ribosomes, numerous Golgi-bodies, and ER
  2. Found in secretory ducts and secretory channels

  
• Cell type: Storage cells:

  1. Starch storing
  2. Protein and Oil storing
  3. Pigment storing
  4. Crystal storing
  5. Water storing
• starch-storing parenchyma cells: abundant amyloplasts, common in roots

  
• protein and oil-storing: common in seeds

  
• pigment-storing: abundant chromoplast, and anthocyanin filled vacuoles. common in flowers and fruits

  
• 'crystal-storing: common in flowers and fruits

  
• water-storing: commonly found in tissues of succulent plants

  
• Cell type: Transfer Cells

  • cells that contain cell wall ingrowths
  • increases the surface area of the plasma membrane
  • commonly seen in phloem tissues, function in the transfer of solutes

  
• Cell type: Aerenchyma

  • parenchyma tissues that are characterized to have prominent intercellular spaces
  • common in angiosperm that grows in aquatic/semi-aquatic habitats/waterlogged soils
  • intercellular spaces formed through

  
• Cell type: Idioblast

  • Specialized cells that contain certain substances
  • May contain resin (Pinus), crystals (druse in Begonia), oil, pigments, tannins, and excretory structures
  • Also have different morphology relative to the cells surrounding them

  
• The former may vary because of the cells' respective function