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A model farm template is imagined as the central methodology. A broad range of timely science news and other topics of interest are commented on.
Friday, February 15, 2013
How Salt Halts Plant Growth
Thus gives us an actual understanding of just how the root goes
dormant and points us toward actively managing it.
As it is also plausible that biochar dressing locks up the unwanted
salt ions, it is possible that it will be possible to reclaim
irrigation wreaked soils with a combination of protocols. Ideally
one such protocol can actually collect the toxic salt. Here we are
beginning to see the road map.
As posted before, biochar allows direct sequestration but does not
remove. That may well be good enough but likely troublesome as the
ions will still alter surrounding soluble chemistry somewhat.
How salt stops
by Staff Writers
(SPX) Feb 04, 2013
is a confocal microscope image of a branching root (lateral root).
The cell boundaries are in red and the the GFP fluorescent signal
marks the endodermis. Credit: Image courtesy Jose Dinneny.
Until now it has not
been clear how salt, a scourge to agriculture, halts the growth of
the plant-root system. A team of researchers, led by the Carnegie
Institution's Jose Dinneny and Lina Duan, found that not all types of
roots are equally inhibited.
They discovered that
an inner layer of tissue in the branching roots that anchor the plant
is sensitive to salt and activates a stress hormone, which stops root
growth. The study, published in the current issue of The Plant Cell,
is a boon for understanding the stress response and for developing
Salt accumulates in
irrigated soils due to the evaporation of water, which leaves salt
behind. The United Nations estimates that salinity affects crops on
about 200 million acres (80 million hectares) of arable land and not
just in developing countries, but areas such as California as well.
As Dinneny explained:
"An important missing piece of the puzzle to understanding how
plants cope with stressful environments is knowing when and where
stressors act to affect growth."
Roots are intimately
associated with their environment and develop highly intricate
branched networks that enable them to explore the soil. The branching
roots grow horizontally off the main root and are important for water
and nutrient uptake.
The scientists grew
seedlings of a laboratory plant (Arabidopsis) that is a relative of
mustard using a custom imaging system, which enabled them to measure
the dynamic process of root growth throughout the salt response.
This ability to track
root growth in real time led the scientists to observe that branching
roots entered a dormant phase of growth as salt was introduced. To
determine how dormancy might be regulated, Lina Duan surveyed the
role of different plant hormones in this process and found that
Abscisic Acid was the key signaling molecule.
"We are familiar
with how animals use a fight or flight strategy to face external
challenges. While plants can't run for safety, they can control
how much they grow into dangerous territory," commented
Dinneny. It turns out that Abscisic Acid, a stress hormone produced
in the plant when it is exposed to drought or salty environments, is
important in controlling the plant equivalent of fight or flight."
To understand how
Abscisic Acid controls growth, the investigators devised a strategy
to inhibit the response to this hormone in different tissue layers of
the root. They developed several mutants in which the response to the
hormone was suppressed in different root layers. They found that a
significant portion of the salt response was dependent upon how a
single cell layer sensed the hormone. The live imaging allowed
them to watch what happened to root growth in these mutant plants.
the 'inner-skin' of the root, called the endodermis, was most
critical for this process. This tissue layer is particularly
important as it acts like a semipermeable barrier limiting which
substances can enter the root system from the soil environment."
remarked lead author Duan.
"Our results mean
that in addition to acting as a filter for substances in the soil,
the endodermis also acts as a guard, with Abscisic Acid, to prevent a
plant from growing in dangerous environments," said Dinneny.
agricultural land is a major contributor to soil salinity. And as sea
levels rise with climate change, understanding how plants,
particularly crops, react to salt might allow us to develop plant
varieties that can grow in the saltier soils that will likely occur
in coastal zones."