Objective:

     Study the anatomical tissue systems that function primarily in the storage of water and elaborated reserves.

I.  Water Storage Tissues

     There appear to be two basic classes of water storage tissues.  Those that store water reserves primarily in centralized vacuoles of cells and those that store water in association with mucilage within the cytoplasm.  Record one of the following examples in your lab exercise sheet.

     A.  Make free hand sections the multiple epidermis of Peperomia (10.01) leaves that have been removed from the stem over a period of days and allowed to dehydrate to various degrees by placing them on a secluded part of a bench top to observe the ordered collapse of the multiple epidermis.  Rehydrate a dehydrated leaf by placing the petiole in a water reservoir.  Observe how the water storage tissue recovers from their collapse.  Does air enter the cells as water is lost from them?

     B.  The outer layer of cells of Linum seeds is a typical example of a mucilage water storage tissue.  During seed germination large amounts of water are taken up by the mucilage cells which protects the plant against desiccation.  Examine the outer layer of Linum seeds in the dehydrated condition, then place a number of seeds in a water reservoir and observe over time what happens as water is absorbed by the mucilage cells.

     C.  The pith region of Tilia (3.05,3.055) stems contain groups of densely staining mucilage cells that store water.   Locate these in the transverse sections of Tilia stems.   Is there any organizational relationship between these mucilage cells of the primary or secondary xylem?

II.  Elaborated Reserve Storage

     Much of the material that plants produce via photosynthesis and other anabolic processes are not immediately incorporated into plant cell structure, but rather are stored in crystalline or globular form in specialized cells or tissues.  These reserve materials are utilized later via catabolic processes after the plant has undergone a period of dormancy, either as a specialized vegetative reproductive form or as an embryo enclosed within a seed.  Another function of some stored elaborated reserve tissue takes is in the form of attracting animals to the plants fruit, thereby facilitating seed dispersal. Examine the reserve storage tissues in the following plants by means of free hand sections.  Record two of the following examples in your lab exercise sheet

     A.  Beta (10.02) roots and Allium bulb scale leaves store amides and proteins dissolved in the cytoplasm plus sugar (glucose) in the cytoplasm.  Exposure of sections to alcohol will result in precipitation of the amides and proteins from the cytoplasm.   You can confirm the presence of glucose by eating a sample!

      B.  Tubers of Solanum store amides and proteins dissolved in the cytoplasm plus crystalline starch.

      C.  Cotyledons of Pisum (10.03) and Phaseolus (10.04) embryos store protein in the form of aleurone grains and crystalline starch.  Compare the distribution of these stored substances with that in Zea (10.05) endosperm.

     D.  Cotyledons of Glycine and the endosperm of Ricinus seeds store protein in the form of aleurone grains and fatty oils in the form of
             droplets.  The caruncle on the Ricinus seed has high fatty oil content which may attract  animals to it to aid in dispersal.

     E.  Various fleshy fruits such as Malus pomes store sugars (glucose, fructose) which encourage  herbivory thereby aiding seed dispersal.  You can  verify the presence of sugar by taste.
 

SECRETORY SYSTEMS

Objective:

     Examine the specialized anatomy involved in internal and external secretion.

I.  Secretion of Water

     The accumulation of water in intercellular space in leaves is potentially disastrous to plants if it occurs to such an extent that liquid saturation occurs since the transpiration stream would thereby be inhibited.  The familiar phenomenon of guttation prevents this from happening during the night in several species of plants.

     1.  Examine sections of Brassica oleraceae (11.02) leaves to learn the typical anatomical features of hydathodes.  Identify terminal tracheids, epithem  and guard cells of the water pore.  Record your observations in your lab exercise sheet
 

II.  Secretion of Other Substances

     Many categories of plant structures or cells reveal secretory functions or activity.  Likewise the product of the protoplasmic function varies widely.  Although the significance of the product to the function of the plant is often obscure, recognition of structural features and relationships is often significant in a heuristic sense.  Record two of the following examples in your lab exercise sheet

     A.  Oil cells - enlarged and usually "clear" cells in stems of Cinnamonium (11.03).

     B.  Oil cavities - enlarged sacs in citrus rind, and early development as revealed in the ovary of the flower (11.04,11.05).  Lysigenous origin appears to be evident, but  recent studies have indicated that the cellular debris is an artifact  introduced during fixation.  Free hand sections indicate that these cavities have a schizogenous origin.

     C.  Glandular cells - stigma and style of Citrus flower (11.05).

     D.  Digestive glands of insectiverous plants such as the pitcher plant (11.06) and venus fly trap (11.07).

     E.  Intercellular canals - resin canals or ducts in leaves (3.09,3.095)  and stems (3.06,3.061,3.0652.09) of Pinus.  Note epithelium; origin is       schizogenous. Also in dicot stem, Rhus (11.09), Poison Ivy.

     F.  Osmophors

         Identify osmophors in flowers collected in green house (e.g. Orchidaceae, Araceae spadix) by immersing them in solution of neutral red.
 

Prepared Slides                      Fresh Material

   Peperomia (10.01)                       Peperomia leaves
   Beta (10.02)
   Tilia (3.05,3.055)                      Opuntia stems
   Pisum (10.03)                           Linum seeds
   Phaseolus (10.04)                       Beta root
   Zea (10.05)                             Allium bulb
                                           Solanum tuber

                                        Soaked and dry seeds of:
                                           Pisum
                                           Phaseolus
                                           Zea
                                           Glycine
                                           Ricinus

                                        Malus pomes
Material

Prepared Slides                           Fresh Material

   Cinnamonium (11.03)                       Fuchsia leaves
   Citrus (11.04,11.05)                     Brassica oleraceae leaves
                                            Citrus fruit
   Pinus                                    Orchidaceae flowers
     Stems (3.06,3.061,3.065)                           Araceae flowers
     Wood (2.09)                            Taraxacum
     Roots                                  Nerium
     Leaves (3.09,3.095)                    Ficus
                                            Allium bulb
   Rhus (11.09)
   Cannabis (3.24)
   Nerium (11.11)
   Euphorbia (3.25)
   Asclepias (11.13,3.22)
   Lactuca (3.23)
   Brassica (11.02)
   Pitcher Plant (11.06)
   Venus Flytrap (11.07)
   Taraxacum (11.15)