Roots

The first thing to remember about roots is that they're different from stems. A root cross section will be round and will contain more or less the same tissue types as a stem, but the arrangement of those tissues is different.

Objective:

• Recognize organization of the tissue types in roots and compare them with the equivalent tissues in stems.

Specimens: Microscope slides

• Allium root tip mitosis l.s. and Lilium root tip mitosis c.s.: longitudinal and cross section slides of the same thing. The slides are labeled "mitosis" because you see the stained chromosomes in some cells undergoing mitotic division, but for this lab the main point is that these slides show apical meristems in the root.
• Smilax root c.s.
• Ranunculus mature root c.s.
• Ranunculus mature root metazylem c.s.
• Any other root slides that are set out in lab.

Ranunculus (buttercup) root

This is a eudicot with no secondary growth. The vascular tissue phloem and xylem) is in the center, surrounded by a layer of endodermis. The endodermis contains the casparian strip and helps control the movement of water and nutrients into the vascular tissue. We'll look at how this works in lecture. The xylem consists of large, thick-walled cells that are stained red. In eudicots like this one, the xylem forms an X shape in cross section. The phloem consists of smaller, thin-walled cells that are stained blue. The phloem surrounds the xylem. Much of the root outside the endodermis is filed with cortex, a ground tissue.The epidermis helps control the movement of water and nutrients into the root.

Smilax (greenbrier) root

Smilax is a monocot with that grows as a woody bush or vine. This root has the same tissues as the Ranunculus root, with a slightly different arrangement of the vascular tissue in the middle.