Refer to figures handed out in class.

Meristematic: Cells which retain ability to undergo cell division, small, large nucleus/ cytoplasm ratio, alive at maturity, only primary cell wall present.

Parenchyma: Cells which contain chloroplast or leucoplast for storage, support body cells by turgor pressure, alive at maturity, only primary cell wall present.  Large cells with large cytoplasm/ nucleus ratio.

Collenchyma: Cells which  support  herbaceous tissue by turgor pressure.  Alive at maturity. Primary cell wall present at maturity. Primary cell walls are thicker at corners which provides support and strength.  Veins of celery are held together by these cells.

Sclerenchyma: Cells which provide strength and support, especially in older woody tissue. Cell wall contains lignin Dead at maturity . Secondary cell wall present. Mature cell’s volume  may have up to 80% secondary cell wall. Pecan shell consist of sclerenchyma.

        Two types of sclerenchyma cells (shape)

                    A) fibers: long and narrow, cotton fibers
                    B) sclerids: round or star shaped, sclerids in pears
 

Epidermal Cells: Cells are located on the outside of plant organs. These cells may be a single layer or several layers thick.  Alive at maturity lacking chloroplasts in most cases. Epidermal cells secrete cutin, a wax like substance, on the outside surfacae which aids the plant in preventing dissication. Modifed epidermal cells have specific functions.

     Guard cells control the opening and closing of stoma in leaves of
      a plant.
      Stomata are openings which  allow  for gas exchange in plants.
 

      Trichomes are hair like structures found on leaves, stems, flowers, etc.
      These structures are multicellular  and may contain secretions to
      prevent insects from eating them, cover surface to aid in the loss
                   of water  vapor.

       Root Hairs are unicellular epidermal cells located at the tips of all
        roots.  They function in increasing the  absorption of water by the
         root.
 

                         Cork: Cells are dead at maturity, have secondary  growth, cell walls
                         contain suberin to prevent desiccation of inner tissue
 

Xylem Tissue consists of  four cell types:

Refer to figures handed out in class.

                         tracheid: main water conducting cells, usually found in
                         gymnosperms but  not  angiosperms

                         vessel member: main water conducting cells, usually found in
                         angiosperms   but  not gymnosperms

                         sclerenchyma fiber: strong support, same as above

                         parenchyma: soft support, same as above

     Trachery Elements

                 No perforation plates: pits pairs with pit membranes of primary cell wall
                 present.

                  Secondary cell wall forms three types of tracheary elements.

                     Annular – ring like(shape)
                     Helical
                     Scaliform
                                             Study Figures in Text

     Vessel Members

                      Perforation plates on ends: pit pairs on sides

                      Pits may be circular or bodered (rim of extra cellulose.
 

                     Pit Pairs.

                                      Study Figures in Text
 
                    Vessel elements are shorter and wider with one or two perforations.
 
 

Phloem Tissue consists of  four cell types:
 

                         sieve tube cell: conducts food (photosynthates), contains cytoplasm
                         but no  nucleus at maturity

                         companion cell: maintains itself and the sieve tube cell

                            (sieve tube cell and companion cell are formed from the same
                              mother cell and therefore are always together)

                         parenchyma: soft support and storage, same as above

                         sclerenchyma fiber: strength, support, same as above

                         sclerenchyma sclerid: strength, support, same as above

                                       Study Figures in Text

                 Review Plasmodesmata – Cytoplasmic bridges which pass through cell wall.

Primary xylem and phloem are directly derived from the procambium.

In an older root or stem the procambium will form a vascular cambium between the primary xylem and phloem which will form secondary xylem and phloem.
 
 
 

Review the seeds students germinated in the laboratory.

Germinating seeds are heterotrophic. From which do the molecules for energy and synthesizing organic molecules come?

Cotyledons and or Endosperm

Chemical Composition of Specific Seeds of Economic Importance

Species                       Family               Nature of                                Percent Content
                                                         Reserve tissue        Carbohydrate     Protein   Lipid
________________________________________________________________________
Maize                       Gramineae           Endosperm                51 - 74                10         5
(Zea mays)

Wheat                      Gramineae          Endosperm                 60-75                   13        2
 (Triticum vulgare)
Pea                            Legume               Cotyledon                   34-46                   20       2
 (Pisum sativum)
Peanut                                                   Cotyledon                  12-33                20-30 40-50
 (Arachis hypogaea)
Soybean                    Legume               Cotyledon                   14                        37       17
 (Glycine sp)
 
 
 

Matching questions will include matching the  description, function, location in plant to these various types of plant cells. In the second laboratory you observed many of these cell types in living tissue and on prepared slides. Study the cards which were located at the various stations.

 You may want to look at some of these www sites to exam various cell and tissue types. Click on cells and tissues when you get to the site. Surf through the files and look at all cell types listed above.
  http://koning.ecsu.ctstateu.edu/Plant_Physiology/celltypes.html