Life Cycle - Plants (3B)
Lab 

   
OBJECTIVES:
  • Comparing cellulose from different plant products.
  • Exploring the uses of plants.

VOCABULARY:

  • cellulose
  • wood
MATERIALS:

Students compare products made from cellulose.

 

BACKGROUND:

Cell walls are made primarily of cellulose but there are also other substances like hemicelluloses, minerals, tannins, resins, pigments, proteins, mucilages, and gums that can be found in plant cell walls. Cell walls are porous, allowing an exchange with substances outside the cell wall. Cellulose has a straight chain structure, forming strong fibers that are ideal cell-wall structural materials and useful in making products.

Cellulose is used commercially in making paper, rayon, explosives, cellophane, buttons, and many other materials. Cellulose comprises approximately 80 per cent of the dry weight of wood, and forests are the source of many valuable articles in addition to lumber. Plant fibers are twisted together to manufacture thread or yarn from which fabrics are woven. The fibers are obtained primarily from the cotton, flax, or hemp plants.

Lumber is mainly cellulose. There are two zones of wood on a tree, the sapwood, a light-colored outer zone and the heartwood, surrounding a generally darker-colored zone. The sapwood functions in sap conduction and food storage, the heartwood is used for mechanical support. Sapwood will eventually turn into heartwood. Heartwood is the more durable portion of lumber.

PROCEDURE:

  1.  In this lab, students will look at six different products made from cellulose and will determine if there are any characteristics that can help identify the items that came from plants. Students will need to look at the material with a microscope or good hand lens. You can either use the module or get six different specimens of materials made from plants.
      
  2. Many specimens show evidence that they have been derived from plants. Cotton fibers or threads will show a twisting in the fiber which can be seen with a microscope. Lumber shows portions of growth rings which are often visible to the naked eye. Dried moss, which is used as a decoration for artificial plants, still has a green color and has its structure except for the roots. Different types of hemp or rope-like decorations show elongated fibers. Paper, however, doesn't show much evidence that it can from plants, but that is mainly because the wood pulp from which it was derived has been pulverized and squashed to hide any connection to plants.

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