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Corn root ls
x40. Note the larger more rectangular cells in the region
of elongation beyond the root cap and apical meristem.
Onion root tip ls
x100. You can see the root cap and a portion of the
apical meristem. The outer part of the root cap is shown
sloughing off which it does to protect the apical
meristem as the root burrows its way through the soil.
Fern root tip
x40. Non seed plants such as ferns often have shoot and
root apical meristems with a single large central apical
Young dicot root
x40 with 3 xylem lobes in the central vascular cylinder.
The purple structures are starch storing leucoplasts in
parenchyma cells of the root cortex.
Young dicot root
vasuclar cylinder x100. The arrow indicates a
non lignified "passage cell" in the endodermis.
Such cells lack secondary cell walls and permit the
passage of water and minerals between the xylem and
cortex. Nearby endodermal cells that are lignified do not
permit such passage.
Protoxylem and phloem in
a young dicot root x400. You can see staining
red two of the three protoxyem lobes of this root.
Primary phloem (arrow) and vascular cambia are visible.
The metaxylem cells in the center have not yet developed
secondary cell walls and thus stain green. Later in the
development of this root the metaxylem cells will form a
secondary cell wall.
(Buttercup) root xs x40. There are four xylem
lobes in this "typical dicot root" similar to
roots illustrated in most biology textbooks. Purple
staining structures are starch containing leucoplasts in
cells of the cortex.
root vascular cylinder x400. In this specimen
the metaxylem (central last maturing xylem) has fully
formed lignified secondary cell walls. From the top
center down you can see the cortex, endodermis,
pericycle, phloem, vascular cambium, and xylem.
root xs x40. This is a 300 million year old
petrified fern root that looks very much like modern
dicot roots. You can see from the outside toward the
center indications of a cortex, endodermis, phloem, and 5
Orchid root xs
x100. A two layered cortex surrounds the central vascular
cylinder. The arrow indicates a passage cell in the
endodermis immediately outside of a group of xylem cells.
Orchid root vascular
cylinder x400. The arrow indicates a passage
cell in the otherwise lignified endodermis. Cells with
thin red staining walls inside the passage cells are
xylem. Cells with thick red staining walls are fibers.
There are small green staining patches of phloem with
each group of fibers, alternating in position with xylem
Monocot root xs
x40. You can see a pith surrounded by a vascular
cylinder, cortex, and a root hair-bearing epidermis. A
branch root originates at the outer part of the vascular
cylindar. The large white circular areas are tube-shaped
holes in the root that function like vessels in water
Monocot root vascular
tissue x400. Moving from the top down you can
see the cortex, endodermis, 3 groups of red staining
protoxylem with phloem inbetween each group, and pith.
The hole in the outer pith is tube-shaped and functions
like a vesses in water conduction.
(Willow) branch root x40, pushing through the
cortex of its parent root.
root origin x100. You can see the
"X" shaped xylem of the parent root in cross
section and a longitudinal section of the branch root on
the right. The branch root originates at the pericycle of
the parent root, just outside the parent root's primary
Tulip tree woody root xs
x12. This woody root with secondary xylem and phloem
looks very much like a woody stem. The branch root on the
left originating near the center of the parent identifies
this photograph as a woody root rather than a woody stem.
Tulip tree root secondary
tissues xs x40. From the bottom to the top you
can see secondary xylem with vessels and rays, the
vascular cambium, secondary phloem, and cortex.
root hair x400. Root hairs are extensions of
epidermal cells as seen in this root ls.
Clover root nodule
x40. Nodules like this in legume plant roots are about
the size of small peas. They contain symbiotic nitrogen
fixing bacteria in their center cells. The bacteria, with
the help of hemoglobin (yup, the same stuff found in
animal blood) apparently made by the plant, convert
atmospheric N2 gas into nitrate and nitrite ions that the
plant can use.
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