s a n
a
m y
as 85 per cent of plants may
owe all or some of their nutrient
uptake capacity to mycorrhizae.”
Symplastic vs Apoplastic Movement
of Water and Nutrients in Roots
Once inside the roots or root cells, water and dissolved
nutrients travel through different root pathways in one of
two ways — either symplastic movement or apoplastic
movement. Most water and nutrients move through the
roots via apoplastic movement. When this happens,
water does not actually enter the cells, but travels
through the passages between cells. Think of this as
a hallway connecting bedrooms. This is easier than
traveling by symplasticity. With symplastic movement,
water and nutrients must cross over a cell membrane to
enter into the cytoplasm, a gelatinous material inside the
cell. Water and nutrients must then travel upwards by
moving through the cell walls. Think of this as gaining
access to bedrooms through the adjoining walls instead
of taking the hallway.
Mycorrhizae: Roots’ Fungal Friend
Worthy of inclusion, though not a component of root anatomy or
function proper, is mycorrhizae. This lauded beneficial fungus
attaches itself to plant roots in a symbiotic embrace that can
exponentially increase the reach of any particular root system.
As many as 85 per cent of plants may owe all or some of their
nutrient uptake capacity to mycorrhizae. The fungus not only
gets fed while attaching itself to root systems, but acts as a
force multiplier by increasing the reach of plant roots and the
surface area of the root system. The hyphae, or tentacles of
the fungus, are much smaller than even the root hairs and can
therefore mine into much smaller crevices in search of nutrients.
In addition to the basic and more complex functions described
earlier, roots also serve to aerate the soil they are anchored in
and can pull the plant closer to the dirt for protection from the
elements. All of these and more are functions of roots in the care
and feeding of the shoots.
To recap the process of water and
nutrient uptake, we can reduce it to
four basic steps:
• Step 1: Water and dissolved
nutrients enter the roots through
the root hairs by the process of
osmosis or root force.
• Step 2: Water and dissolved
nutrients then cross over the root
cortex either through symplastic
or apoplastic movements.
• Step 3: Water and dissolved
nutrients enter the xylem.
• Step 4: Water and dissolved
nutrients are sent up into the
plant stem in the transpiration
stream to deliver needed nutri-
tion to all the shoots of the plant.
These processes will go on so
long as the plant is alive, and
water and nutrients can be found
in the soil. Periods of drought will
slow down these actions and,
in some cases, encourage root
growth as plants seek deeper
sources of water and nutrition.
Maximum Yield
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