Bristol, United Kingdom
December 15, 2008
In the face of climate change,
being able to increase crop yields by enabling plants to take up
nutrients and water more efficiently becomes increasingly
important, as fertiliser and water supplies incur significant
energy and environmental costs.
New research from the University
of Bristol, published today in
Nature Cell Biology,
has shown how to increase the length of root hairs on plants,
potentially improving crop yields, as plants with longer root
hairs take up minerals and water more efficiently.
Angharad (Harry) Jones, a PhD student in Biological Sciences at
the University of Bristol, and lead author on the paper, said:
“Each root hair is a single, elongate cell and the length of
each hair depends on having an adequate supply of the plant
hormone auxin. Auxin is used, for example, in hormone rooting
powders to encourage cuttings to root. The difficulty has been
in understanding how auxin is delivered to the root hairs in
order to promote their growth.”
Since auxin cannot be observed directly, Jones used a computer
model built by physicist Eric Kramer at Bard College, USA, to
calculate where auxin was likely to be in plants. The model was
based on current knowledge of auxin transport through and around
the relevant cells.
What the model showed was very surprising: auxin is not
delivered to root hair cells directly, but via the cells next
door which act as canals through which the auxin is transported.
During transport, some of the auxin leaks out, supplying hair
cells with the auxin signal to grow. This new understanding will
be crucial in helping farmers to produce food sustainably and to
reduce fertiliser waste, which can cause severe damage to
ecosystems.
Dr Claire Grierson, senior author on the paper added: “This
important new work is an example of ‘integrative biology’, an
innovative, interdisciplinary approach that uses experimental
results alongside mathematical models and computer simulations
to test ideas that are difficult or impossible to investigate
with experiments alone. This approach has produced
groundbreaking and surprising insights into a biological
mechanism that might otherwise have eluded us.”
The results also suggest that increasing the number of root
hairs is likely to interfere with auxin supply and cause
problems with other important traits like a plant’s response to
gravity and root branching. The new understanding of how to
increase the length of roots hairs, rather than their numbers,
will now avoid these kinds of problems.
It was Charles Darwin and his son Francis who, in 1880, first
discovered that plants direct their growth towards the light.
These observations would later lead to the discovery of auxin.
Auxin transport through
non-hair cells sustains root-hair development.
Angharad R. Jones, Eric M. Kramer, Kirsten Knox, Ranjan
Swarup, Malcolm J. Bennett, Colin M. Lazarus, H. M. Ottoline
Leyser, Claire S. Grierson.
Nature, 15 December 2008.
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A
diagram of the root showing the
arrangement of cells and root
hairs, with the general
directions of auxin flow shown
in pink.
Photo by Angharad Jones |
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