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Hairs on
plants are extremely variable in
their presence across species, location on plant
organs, density (even within a
species), and therefore
function. However, several basic
functions or advantages of having surface hairs can be listed:
Defence
against herbivores:
It is
likely that in many cases, hairs interfere with the feeding of at least
some small herbivores and,
depending upon stiffness and irritability to the "palate", large
herbivores as well.
Reduction of
frost damages:
Hairs on plants growing in areas subject to
freeze keep the
frost away from the living surface
cells.
Protection from
wind:
In windy locations, hairs
break-up the flow of air across the
plant surface, reducing
evaporation.
Reflection of
solar radiation:
Dense coatings of hairs reflect
solar radiation,
protecting the more delicate tissues
underneath in hot, dry,
open habitats.
Absorption of
moisture from
dew and
fog: In locations
where much of the available moisture comes from cloud drip, hairs
appear to enhance this process.
The
surface
appearance of plant's
organs,
such as
stems
and
leaves,
are mainly characterized by the presence of trichomes and many terms are
used in reference to the presence, form, and appearance of them.
See:
surface features.
There are several terms dealing whit hairs the most basic are
glabrous (lacking hairs) and
pubescent (having hairs),
following some of the more common terms. Plant hairs may be
unicellular or
multicellular,
branched or
unbranched. Multicellular hairs
may have one or several layers of cells.
Branched hairs can be dendritic
(tree-like), tufted, or stellate
(star-shaped).
Any of the various types of hairs may be
glandular. |
