Roots, Stem, Leaves

• Primary functions of the root (three total)

  • Anchorage
  • Absorption
  • Hormone production
• Taproot


  Described to be swollen and prominent. Oftentimes, the primary root is bigger than the lateral root.
• Adventitious roots


  Roots derived from non-root tissues
• Fibrous root system


  Roots that are commonly found in monocots
• Angiosperms are a general term for plants that produce fruits and classify eudicots and monocots into one group.
• Root cap


  Structure that protects the roots from damage when growing underground
• Mucigel


  Lubricating substance secreted by the root cap, made of glycoprotein and pectin
• Root hairs


  Structure that increases the surface area of the root, and is NOT a lateral root
• Primary name for the root epidermis

  • Rhizodermis
  • Epiblem
• The root epidermis does not develop a cuticle because roots are underground and not at risk of water loss
• Cells in the root epidermis

  • Trichoblast
  • Atrichoblast
• Quiescent center/zone


  Part of the root which is generally inactive, but activates and divides when the root cap is broken and the Root Apical Meristem ceases meristematic activity while still growing
• Regions of the internal structure of a root (longitudinal cross section)

  • Zone of elongation
  • Zone of division
  • Zone of maturation
  • Root cap OR columella
• Cells in the zone of elongation


  • Ground tissue
  • Procambium
  • Protoderm
• Columella


  Specialized structure composed of a large amount of amyloplasts that is capable of gravisensing
• Amyloplasts in the columella are important for gravisensing by weighing down the plant
• Endodermis


  Innermost cortical region, which is heavily lignified
• Casparian strip


  Composed of lignin and suberin
• Routes of movement within the root

  • Apoplastic (across cell wall)
  • Symplastic (pass through the plasmodesmata)
  • Transmembrane (apoplast to cell protoplasm // apoplast and symplast route combined)
  • Endodermal (symplastic within endodermis)
• Differences between Eudicot and Monocot roots

  • Eudicot: Xylem forms solid mass at center, surrounded by phloem. No pith. Presence of proto and meta phloems and xylems. Central region is the vascular bundle.
  • Monocot: Pith at center. Xylem and phloem are scattered in ground tissue
• Functions of the shoot system


  • Orient the shoot
  • Conduits of vascular tissue
• Epicotyl


  The stem develops from this structure of the seed
• Secondary growth


  Stem is classified into three groups, but when it comes to structure, can be split due to the presence/absence of this
• Lignophytes are a plant group distinguished for the presence of lignin in the stem
• Internodes


  Region between nodes that are produced due to intercalary growth
• Lenticels


  Corky eruptions on the bark that allow gas exchange
• Epidermis


  Dermal tissue that covers the stem exterior, covered in a waxy cuticle layer
• Pith


  Central region of eudicot and made of pure & weak parenchyma cells
• The pith is crushed or destroyed when the eudicot matures
• Stem vascular bundle arrangements

  • Collateral bundle (phloem abaxial to xylem)
  • Bicollateral bundle (primary phloem can be found on both inner and outer sides of xylem)
• Interfascicular cambium


  Dissected ring formation of vascular bundles in eudicot
• Tissues that produce a false woody stem in monocot stems due to anomalous growth

  • Sclerenchyma tissue
  • Fibrous strands
• Initials


  Cells produced by the vascular cambium that increase diameter
• Bifacial division


  Type of division where the vascular cambium is pushed and slips in cells generated, thereby increasing size
• Translocation


  Process for phloem to load and unload photosynthates
• Tracheary elements


  Conducting cells of xylem, including tracheids and vessel elements
• The vascular cambium is closed for monocot and herbaceous eudicots when transitioning from primary to secondary growth state
• Growth rings can be used to tell the age of a tree, with bigger rings indicating a good year and smaller rings indicating a bad year
• Secondary growth xylem


  Wood is produced by the multiyear accumulation of this
• Origins of the cork cambium (phellogen)

  • Superficial phellogen → epidermis or cortex
  • Deep-sided phellogen → phloem
  • Root phellogen → pericycle