Stems

• What are the types of stems based on growth direction?

  • Erect: Grows straight and perpendicular to the ground.
  • Ascending: Rises obliquely from the ground.
  • Decumbent: Lies flat with upright tips.
  • Prostrate/Procumbent: Lies completely flat.
  • Creeping: Grows flat and roots at nodes.
  • Scandent/Climbing: Climbs by attaching to structures.
• What are the types of stems based on location?

  
  

  Aboveground Stems:

  • Tendrils: Support in climbing plants.
  • Stolons/Runners: Horizontally oriented for vegetative reproduction.
  • Thorns: Protection against grazers.
  • Cladodes/Cladophylls: Modified for photosynthesis.
  • Culms: Hollow or solid with nodes and internodes.
  • Succulent Stems: Store water.

  Underground Stems:

  • Bulb: Large, roundish bud with thickened scales.
  • Corm: Stubby, fleshy stem that stores nutrients.
  • Rhizomes: Grow horizontally, develop roots and buds.
  • Tubers: Swollen regions that store food and bear "eyes."
• Types based on Texture

  Herbaceous:

  • Soft, fleshy texture.
  • Often short-lived.
  • Example: Lettuce

  Woody:

  • Hard, permanent tissues covered in bark.
  • Example: Oak trees

  Suffrutescent:

  • Partially woody, typically only at the base.
  • Example: Lavender
• Types based on Visibility

  Acaulescent:

  • No obvious stem above ground.
  • Only leaves are visible.
  • Example: Grasses.

  Caulescent:

  • Stem is visible above ground.
• Herbaceous Stems:

  • Lack secondary growth (do not develop wood or bark).
  • Small diameter, soft, and flexible.
  • Buds lack protective scales.
  • Covered with epidermis.
  • Lives for only one growing season.

  Woody Stems:

  • Have secondary growth (develop wood or bark).
  • Diameter increases over time due to growth rings.
  • Covered with periderm (bark).
  • Can live year after year (perennial).
• The first stem that arises from a seed is derived from the epicotyl, which is an embryonic shoot within the seed.
• A stem is a collection of integrated tissues that form the structural framework of a plant. It is typically organized into nodes and internodes.

  • Nodes: Points on the stem where leaves, buds, and flowers attach.
  • Internodes: The spaces or segments between nodes.
• Where is the terminal bud located on a stem?

  At the tip of the stem
• What are axillary buds also known as?

  Lateral buds
• Where are axillary buds found?

  In the axils between leaves and stems
• What are bud scales?

  Modified leaves that cover dormant terminal buds
• What is the function of bud scales?

  To protect both lateral and terminal buds
• What do bud scale scars indicate?

  They develop when bud scales fall off
• What is a leaf scar?

  A mark showing where the leaf was once attached to the stem
• What are bundle scars?

  Tiny bumps or dots in a leaf scar representing broken ends of vascular bundles
• What are lenticels?

  Sites of loosely arranged cells allowing gas exchange
• • Rays are chains of parenchyma cells that radiate from the center of the woody stem, formed by the vascular cambium.
  • Serve as pathways for the lateral transport of water
• Wood Types:

  • Sapwood: The younger, light-colored secondary xylem closest to the bark, actively involved in water conduction.
  • Heartwood: The older, darker central wood that is typically non-conducting and serves a supportive role.