MIDTERMS

• What is the primary function of the stem in plants?

  Conduction of materials
• What are the aerial parts supported by the stem?

  Leaves, fruits, and flowers
• What is one of the functions of the stem related to growth?

  Production of leaves, branches, and new shoots
• What is a function of the stem related to energy?

  Food storage
• Which type of stems can perform photosynthesis?

  Green stems
• What are the external anatomical features of a stem?

  • Nodes: Joint line structures where leaves develop
  • Internodes: Spaces between nodes
  • Leaf Axis: Angle formed by the leaf with the stem
  • Buds: Growing portions of the stem
  • Apical/Terminal Buds: At the tips of stems
  • Axillary/Lateral Buds: At the nodes of the stem
• What is the role of leaf primordia in a stem?

  They are the beginnings of the leaves surrounding the bud's mass of cells
• What do bud scales do in a stem?

  They protect the apical meristems
• What is the function of apical meristems?

  Region of actively dividing cells
• What is the maturation region in a stem?

  It contains primary tissues with a common structure and function
• What are the types of stele in stems?

  • Prostostele: Phloem surrounds the xylem
  • Siphonosteles: Tubular with pith at the center
  • Eusteles: Vascular bundles of primary phloem and xylem
• How are stems classified based on location?

  • Acoulescent: No obvious stem above ground
  • Caulescent: Obvious stems above ground
• How are stems classified based on the direction of growth?

  • Erect: Ascends perpendicularly
  • Ascending: Rises obliquely
  • Decumbent: Reclining to the ground
  • Prostrate/Procumbent: Lying flat
  • Creeping: Pressed to the ground and rooting at nodes
  • Scandent/Climbing: Ascends using support
• What are the characteristics of herbaceous stems?

  • Lack secondary growth
  • Primary tissues present: epidermis, cortex, endodermis, vascular bundles, vascular cambium, pith
• What are the characteristics of monocot stems?

  • Vascular bundles scattered
  • No pith
  • No secondary growth
  • Growth in diameter depends on primary tissues
• What are the characteristics of dicot stems?

  • Vascular bundles arranged in a ring
  • Presence of pith
  • Vascular cambium present
  • Secondary tissues poorly developed
• What defines woody stems?

  • Formation of secondary tissues
  • Conducting tissues in concentric circles
• What is the role of vascular cambium in woody stems?

  It produces secondary xylem and phloem, increasing stem thickness
• What comprises the majority of a typical tree's structure?

  Secondary xylem/wood
• What is sapwood?

  The outer few rings of xylem that transport water and nutrients
• What is heartwood?

  Older dark rings near the center that support the tree
• What constitutes the bark of a tree?

  • Secondary phloem: Transports water and organic solutes
  • Periderm: Replaces the epidermis during secondary growth
• What are the three tissues comprising the periderm?

  • Phellogen: Cork cambium producing periderm
  • Phellem: Cork cells that waterproof and protect
  • Phelloderm: Secondary cortex with living parenchymatous cells
• What is wood primarily composed of?

  Cellulose and lignin
• What is summerwood in the context of annual rings?

  Outer band of each ring made of smaller, thicker-walled cells formed in summer
• What is springwood?


  Inner band of each ring made of larger cells formed in spring
• What are the microscopic structures of wood?

  • Transverse/Cross-section: Annual rings as concentric circles
  • Vascular ray: Band of cells for transverse conduction
  • Tangential section: Longitudinal section not cut through the center
  • Radial section: Cut through the center parallel with vascular rays
• What is the function of xylem in plants?

  Upward conduction of water and dissolved nutrients
• What causes sap to move upward in plants?

  Transpiration pull and root pressure
• What is transpiration pull?

  Loss of water through stomates and lenticels
• How does temperature affect transpiration?

  Higher temperature increases the rate of absorption
• What is cohesion in the context of water molecules?

  Holding together like substances
• What is root pressure?

  Result of osmotic uptake of water into the vascular elements of the root
• What is guttation?

  Excretion of droplets of water from hydathodes in leaves
• What is the function of phloem in plants?

  • Distributes products of photosynthesis via translocation
  • Involves mass flow/pressure flow theory
• What is the role of active transport in phloem function?

  Moves solutes into the sieve tubes of the phloem vessel
• What happens when solute concentration increases in sieve elements?

  They become hypertonic and attract water from nearby xylem
• What is the result of water moving into the sieve elements of the phloem?

  It creates turgor pressure
• What is the function of phloem in plants?

  To distribute the products of photosynthesis via translocation
• What does the mass flow or pressure flow theory explain?

  The flow of solutes in mass due to turgor pressure in cells