Hello Wayne and Tom,
there are some studies in the agricultural literature on this
phenomenon termed hydrotropism referring to the root cap's ability to
sense moisture. For instance:
Delfeena Eapen, María L. Barroso, Georgina Ponce, María E. Campos and
Gladys I. Cassab (2005) Hydrotropism:Root Growth Responses to Water.
Trends in Plant Science
Volume 10, Issue 1, January 2005, Pages 44-50
On often comes across much denser root growth out to one side of a
plant, if there is much more moisture in one side relative to the
other side, like a dripping tap.
There are many more studies looking at root distribution between trees
and shrubs/ grasses in savannahs, that takk about lateral spread for
sparse water and nutrients.
Mycorrhizal associations, as I have read, are very important for
nutrient aquisition, especially immobile Phosphorus. I wonder how
important would they be as a water source; am not aware of any study
that attempts to quantify how much of a tree's water budget would come
from mycorrhizae as opposed to direct root uptake - interesting idea
that ! I have heard about mile long mycorrhizal strands in the Sahara
desert, where one expects that mycorrhizae can take advantage of dew
at dawn better than roots can, owing to their finer thickness, net
like structure and greater surface area.
Cheers
amartya
Visiting Research Associate
Southeastern Environmental Research Center
Florida International University
Miami, FL 33199
Quoting Tom Horton <[email protected]>:
I will suggest that many plants partner with mycorrhizal fungi for
water and mineral acquisition. So the fungi access water and deliver it
via the hyphae directly to the plant hosts. Estimates vary, but about
80% of the world's plant species are mycorrhizal and consideration of
root physiology and soil interactions in the absence of the mycorrhizal
partners is probably misleading.
Tom
At 7:09 AM -0700 9/22/10, Wayne Tyson wrote:
Ecolog:
The following quote has come to my attention:
"To find water, a plant has to position its roots with just as much
precision as it arranges its leaves. If moisture is in very short
supply, then a plant may have to drive a tap root deep into the
ground to reach the water table. Some desert plants have had to
develop root systems that are far deeper than they are tall and
extend laterally a very long way beyond the furthest extent of
their foliage. Even if the environment is well-watered, a plant may
still need to compete with others for this essential commodity, so
it positions a network of roots within a few inches of the soil
surface, where it can gather the rain water before others can."
(Attenborough 1995:48-51)
Attenborough, D. 1995. The Private Life of Plants: A Natural
History of Plant Behavior. London: BBC Books. 320 p.
Can anyone attest to the accuracy of, or refute this statement,
particularly with reference to a plant "finding" water,
"positioning" its roots with "precision," "driving" a tap root to
"reach" the water table, and "positions" a network of roots . . .
"where it can gather the rain water before others can?"
WT
--
It was worth being a bubble just to have held that rainbow thirty seconds.
Carl Sandburg
Thomas R. Horton
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