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The vascular plant body is strongly differentiated
at all levels of organization and contains many
distinct cell types, tissues, and organs. To survive
in a terrestrial habitat, plants must coordinate
the assimilatory activities of two spatially distant
but nutritionally interdependent regions: aerial
shoots that harvest light energy and CO 2 , and
subterranean roots that take up water and mineral
nutrients. Although mechanical and spatial factors
are also involved, the physiological requirements
of this interdependence are met primarily by transport
of materials throughout the plant body.
The distinction
between short-distance transport and long-distance
transport is somewhat arbitrary. Long-distance
transport via bulk flow in the vascular tissues
is the basis of functional interaction between
plant organs, and it is the principal topic of
this chapter. However, I will also address short-distance,
nonvascular transport in the tissues that surround
the conducting cells because these tissues play
a central role in controlling the movement of
solutes and water into and out of the vasculature.
At these shorter distances, diffusive transport
becomes increasingly important.
Many specialized
tissues participate in the transport of nutrients
and metabolites throughout the plant body. Some
of the basic features of vegetative plant anatomy,
with emphasis on the vascular system, are illustrated
in Figure 15.1.
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