Thus gives us an actual understanding of just how the root goesdormant and points us toward actively managing it.
As it is also plausible that biochar dressing locks up the unwantedsalt ions, it is possible that it will be possible to reclaimirrigation wreaked soils with a combination of protocols. Ideallyone such protocol can actually collect the toxic salt. Here we arebeginning to see the road map.
As posted before, biochar allows direct sequestration but does notremove. That may well be good enough but likely troublesome as theions will still alter surrounding soluble chemistry somewhat.
How salt stopsplant growth
by Staff Writers
Washington DC(SPX) Feb 04, 2013
Thisis a confocal microscope image of a branching root (lateral root).The cell boundaries are in red and the the GFP fluorescent signalmarks the endodermis. Credit: Image courtesy Jose Dinneny.
http://www.seeddaily.com/reports/How_salt_stops_plant_growth_999.html
Until now it has notbeen clear how salt, a scourge to agriculture, halts the growth ofthe plant-root system. A team of researchers, led by the CarnegieInstitution's Jose Dinneny and Lina Duan, found that not all types ofroots are equally inhibited.
They discovered thatan inner layer of tissue in the branching roots that anchor the plantis sensitive to salt and activates a stress hormone, which stops rootgrowth. The study, published in the current issue of The Plant Cell,is a boon for understanding the stress response and for developingsalt-resistant crops.
Salt accumulates inirrigated soils due to the evaporation of water, which leaves saltbehind. The United Nations estimates that salinity affects crops onabout 200 million acres (80 million hectares) of arable land and notjust in developing countries, but areas such as California as well.
As Dinneny explained:"An important missing piece of the puzzle to understanding howplants cope with stressful environments is knowing when and wherestressors act to affect growth."
Roots are intimatelyassociated with their environment and develop highly intricatebranched networks that enable them to explore the soil. The branchingroots grow horizontally off the main root and are important for waterand nutrient uptake.
The scientists grewseedlings of a laboratory plant (Arabidopsis) that is a relative ofmustard using a custom imaging system, which enabled them to measurethe dynamic process of root growth throughout the salt response.
This ability to trackroot growth in real time led the scientists to observe that branchingroots entered a dormant phase of growth as salt was introduced. Todetermine how dormancy might be regulated, Lina Duan surveyed therole of different plant hormones in this process and found thatAbscisic Acid was the key signaling molecule.
"We are familiarwith how animals use a fight or flight strategy to face externalchallenges. While plants can't run for safety, they can controlhow much they grow into dangerous territory," commentedDinneny. It turns out that Abscisic Acid, a stress hormone producedin the plant when it is exposed to drought or salty environments, isimportant in controlling the plant equivalent of fight or flight."
To understand howAbscisic Acid controls growth, the investigators devised a strategyto inhibit the response to this hormone in different tissue layers ofthe root. They developed several mutants in which the response to thehormone was suppressed in different root layers. They found that asignificant portion of the salt response was dependent upon how asingle cell layer sensed the hormone. The live imaging allowedthem to watch what happened to root growth in these mutant plants.
"Interestingly,the 'inner-skin' of the root, called the endodermis, was mostcritical for this process. This tissue layer is particularlyimportant as it acts like a semipermeable barrier limiting whichsubstances can enter the root system from the soil environment."remarked lead author Duan.
"Our results meanthat in addition to acting as a filter for substances in the soil,the endodermis also acts as a guard, with Abscisic Acid, to prevent aplant from growing in dangerous environments," said Dinneny.
"Irrigation ofagricultural land is a major contributor to soil salinity. And as sealevels rise with climate change, understanding how plants,particularly crops, react to salt might allow us to develop plantvarieties that can grow in the saltier soils that will likely occurin coastal zones."
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