STEM ANATOMY

• The primary stem refers to the _____ (non-woody) stem, which has not undergone secondary growth (the growth that produces bark and wood)

  herbaceous
• TRUE OR FALSE

  Some species (all monocots and some eudicots) remain herbaceous for their entire lives, maintaining the primary stem. 

  TRUE
• Other species of eudicots initially form a primary stem but later become woody, replacing the primary stem with the secondary stem.
• Is the dermal tissue that surrounds and protects the stem. The epidermis typically consists of one layer of cells.

  Epidermis
• A waxy ______ on the outside of these cells limits water loss.

  cuticle
• These are the most numerous and least differentiated of the cells in the epidermis.

  Epidermal cells
• Pores in the epidermis called _____ (singular: stoma) allow for gas exchange.

  Stomata
• Each stoma is bordered by a pair of ________, which regulate stomatal opening. 

  Guard cells
• While stomata are present in stems, they occur at higher densities in leaves.
• They help to reduce transpiration (the loss of water by aboveground plant parts), increase solar reflectance, and store compounds that defend the leaves against predation by herbivores.

  Trichomes 
• Ground tissue fills much of the stem, forming the cortex directly within the epidermis and the pith (if present) in the center.
• The outermost portion of the cortex is usually a few layers of what cells?

  collenchyma cells
• The cortex and pith consist of what cells?

  Parenchyma cells
• Vascular tissues in the stem

  Steles
• The first arrangement (_____) is present in a few eudicots, such as basswood (Tilia).

  Solenostele
• In the solenostele, the vascular tissue appears as a continuous ring (______)

  vascular cylinder
• The interfascicular regions (_____) of parenchyma cells that separate vascular tissue are thus extremely narrow.


  pith rays
• The second arrangement (_____) is present in most eudicots such as sunflower (Helianthus) and buttercup (Ranunculus).

  eustele
• In the eustele, vascular tissue is clustered into distinct _________ arranged in a ring, allowing for thicker interfascicular regions in between them

  vascular bundles
• The third arrangement (______) is present in most monocots, such as corn (Zea mays) and a few eudicots.

  atactostele
• In the ______, vascular bundles are scattered throughout the stem 

  atactostele
• Identify the following:

  A) Eustele (most eudicots)

  B) Primary phloem fibers

  C) Phloem

  D) Xylem

  E) Ground tissue

  
• The cells of embryonic tissue called the ______ (see Meristems) divides to produce primary xylem internally and primary phloem externally.

  procambium
• In some vascular bundles, some procambial cells remain and form the ______ in the center of the vascular bundle.

  fascicular cambium
• Once the stem has finished lengthening, sclerenchyma fibers called ____________ are produced just outside of the primary phloem.

  primary phloem fibers
• The primary phloem fibers of each vascular bundle are sometimes called ________ (bundle caps)

  phloem caps
• If primary phloem fibers surrounded the entire vascular bundle, they form a _________.

  bundle sheath
• _________ connect leaves and stems. 

  Vascular bundles
• The strands of vascular tissue that connect the leaves to the stem are called _______

  Leaf traces
• Just above leaf traces are portions of stem without vascular tissue called ________.

  Leaf trace gaps
• Branch traces connect axillary shoots to the main stem, leaving _______ just above them

  branch trace gaps