Phloem and Principal Water-conducting Elements
Exercise (Histology)
- Give at least three distinguishing features of these groups of cells. Apical meristems have the following features: (1) a “border” of cells; (2) they follow order or shape; and (3) some cells are darker (indicating that they undergo mitosis).
- Identify the tissue. The tissue is a vascular cambium.
- Is the epidermis uniseriate or multiseriate? In the cross section of a young root of Helianthus, the epidermis is uniseriate.
- What do you call the outgrowths of the epidermis? These are called trichomes.
- What is their function? They function mainly for support and protection of the leaf or stem which contains the epidermis.
- Classify the types of epidermal outgrowths in the above plants: bristle, scale, simple hair, glandular, branching, stellate
- Draw and identify the tracheary elements: reticulate, annular, pitted, scalariform, helical
- Differentiate the sieve tubes from the companion cells. The sieve tubes in the phloem are composed of long, narrow cells which lack a nucleus, ribosomes, and some other cellular components; they transport sugars and other organic nutrients. Companion cells have nuclei and ribosomes that also serve the sieve-tube cells but do not themselves take part in conduction.
- What are the principal water-conducting elements of the xylem? The two principal water-conducting elements of the xylem are the tracheids and the vessel elements.
