The Ray Parenchyma
These images show ray parenchyma cells in the wood
of common beech (Fagus sylvatica). Distinct from
fibers and vessels, parenchyma cells are much more
rounded in shape, and in much of the functional
sapwood, these cells are alive, unlike those of fibers
and vessels, which are dead cells when they are fully
formed. In a tree, the rays make an important living
network through the outer sapwood, making this region
of the wood able to respond to many challenges.
Ray parenchyma play many roles in sapwood per-
formance: sensing, metabolizing, defending,
translocating, and storing non-structural carbo-
hydrates. In the closer-up image, you can see
starch grains as small, rounded pellets, stored up
in a ray cell—a cache of tree food, if you will.
It is quite an investment for a tree to develop an
extensive ray system, but in general, tree species
with a larger ray system in their wood tend to be
those that live longer, come back from decline
more readily, and are less prone to decay.
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