BIO 104 4/12/96

Cell types
     Ground tissue
     1) Parenchyma
          -thin walled
          -location: everywhere
          -function: photosynthesis, respiration, and storage
     2) Collerchyma
          -thickened primary walls
          -location: cortex of stems and leaves
          -function: support for young stems and leaves
     3) Sclerenchyma
          -massive secondary walls-dead at maturity
          -location: leaves; flesh of fruits; seed coats
          -function: hard textures, mechanical support

Vascular Tissue
     1) Xylem
          A) Trachieds
          -pits in walls
          -gymnosperm and angiosperms
          -chief water conducting tissue in gymnosperms
          -conduction of water and solutes; dead at maturity
          B) Vessels
          -pits, end walls that are perforated
          -angiosperms
          -conduction of water and solutes; dead at maturity
     2) Phloem
          -Sieve tube member
               -nucleus lacking at maturity; 
               usually has companion cells with nucleus
               -functions in the conduction of organic solutes

Plasmodesmata:  strands of cytoplasm that connects all the cytoplasm in
a plant together.
     
     Dermal tissue:
          epidermal cells
          -has a cuticle
          -may specialize, due to location
          -gives rise to root hairs in roots

Structures of the Plant
     Root system
     SEE FIGURE 30.22
     -roots grow from the apical meristem
     - the zone of elongation is where the cells expand
     - behind the zone of elongation is the zone of differentiation, this
is where the root hairs are formed which increase surface area and
absorb water and minerals
     -in zone of differentiation passes a cylinder of xylem and phloem
     -cylinder of cells inside the root is called the endodermis in which
passes the xylem and phloem -there is a water proofing on these
endodermal cells called the Casparian strip; so, water doesn't get into the
central cylinder.
          -for water to get to the center cylinder it must use
               plasmodesmata; it must go through cytoplasm not the
               cell wall
          -pericycle is the area between xylem and phloem
          -formation of lateral roots

Stems
     Monocot Stem (Corn)
     -scattered vascular bundles, which contain xylem and phloem
     -no vascular cambium-so very little if any secondary growth
     
     Dicot Stem
     -vascular bundles are in a ring
     -vascular cambium is between the bundles it is responsible for
secondary growth.