Lab 4 -- Dicot Roots

Here are a few of the photos taken by students in class based on their hand sections from very young pea or bean (dicot) roots.  Labels have been added to a few of the images.

The first image of the pea root fairly close to the tip.  The cortex and epidermal tissues are present, but the vascular tissue is still in the process of differentiation - so we only see a few protoxylem with their thick walls (triarch patterned pea roots).




The next two images are a little further back from the root tip.  Xylem differentiation is proceeding (exarch) and it looks like some fibers are differentiating near the outer edge of the phloem. There are four xylem poles and four phloem groups in this bean root.



These next three images show xylem development from the protoxylem to the metaxylem.  Don't forget that this is an exarch pattern - you can see the initial differentiation of the first protoxylem elements in groups which will form the tips of the xylem poles - these are triarch arrangements in the pea roots and tetrarch in the bean roots.





This next image show a closeup view of the xylem where you can tell something about the type of secondary walls formed in vessels.



The next three images show root branching out from one of the xylem poles.








If you look far enough back from the root tip you find the differentation of xylem has proceeeded all the way to the center of the stele.

 
Lastly, we have a nice view of some root hairs extending out from the epidermis.