Lab: Plant Structure: the Plant Body: Part Three
ROOTS:
The root functions in the absorption of water and minerals, storage of excess food, plant propagation, and the anchorage of the plant in the soil.
- Examine the photograph below of a prepared slide of the root cross section. Notice that the section is circular in outline since it was cut across the root. The vascular tissue of the root is concentrated in a single vascular bundle or stele in the center of the root.
- How does this compare to the number of vascular bundles in the stem?
A layer of cells called the endodermis surrounds the stele. Xylem is found towards the center of the stele and phloem towards the outside of the stele.
- How does this compare to their arrangement in the stem?
Parenchyma located outside of the vascular bundle is referred to as the cortex, as it is in the stem. These cells primarily store the products of photosynthesis, sugar, in the polysaccharide starch. The outer surface of the root is covered with epidermis.
Photographs of stained slides of Ranunculus root cross section.
The root continues to elongate by continued cell division in a meristematic region at its tip. The cells produced then elongate and mature into the specialized tissues of a mature plant (e.g., xylem, epidermis).
- Examine the photograph of a slide of the buttercup (Ranunculus) root tip; this section is cut along the length of the root tip (longitudinal section).
Perform this drag and drop activity to identify the various parts indicated.
- Notice that the cells in the meristematic region tend to be relatively small and box-shaped with prominent nuclei. Careful examination of this region will reveal that many of the cells are in the process of dividing mitotically.
The meristematic region is protected in the root by the presence of a root cap.
- How is the meristematic region protected in the stem tip?
- In which of these regions would you expect to find the specialized cells of vascular tissue?
- In which of these regions are the cells genetically identical? Why?
 Lab: Plant Structure 100 points
Submit your completed lab to the Lab: Plant Structure assignment link for grading. For information on how this assignment will be graded, please visit the Course Information section.
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