Lab 4 -- Dicot Roots
Here are a few of the photos taken by students in class based on their
from very young pea or bean (dicot) roots. Labels have been added
to a few of
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
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 - three xylem poles and three phloem groups.
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.
The next three images show root branching out from one
of the xylem poles.
Lastly, we have a nice view of some root
hairs extending out from the epidermis.