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Looking into a cotton cell.

Looking Into a Cotton Cell

Imagine being able to study how a plant goes about the process of living while the process is underway instead of having to examine a still life slice of plant tissue.

That's what ARS chemist Judy D. Timpa is doing with cotton by putting to work a machine more commonly seen in medicine than in agriculture.

Timpa and researcher John M. Brown at the University of Missouri Medical School have begun using magnetic resonance imaging (MRI) to look at anatomical and physiological changes that occur during cotton seed and fiber development as the changes actually occur.

To produce its living images, MRI surrounds a subject, in this case a cotton plant complete with roots, plastic pot, and soil, with a powerful magnetic field. So powerful is the field that the nuclei of certain atoms in the plant line up parallel to it.

Then the nuclei are jolted with high frequency radio waves, which causes them to resonate like microscopic tuning forks. Each atom resonates with its own specific faint radio signal, which can be read and translated into a live televised or photographed image.

But the technique does absolutely no harm to tested plants, animals, or people.

"What we finally have is a noninvasive technique that lets us see what is going on inside the cotton plant," Timpa explains. "We've been able to see seed development very clearly."

In a recently completed pilot study testing MRI, Timpa has been able to observe changes in physiology within the cotton boll, including the fiber masses at different stages of development.

A major advantage of MRI is that it doesn't require destruction of the plant.

"I can look at what is going on in the boll where fiber is formed at 8 days after flowering and go back to that same plant to see what is going on at 25 days. It's a whole lot better than relying on the expectation that sibling plants will behave exactly the same way as those sampled on the first date," Timpa says.

Another use Timpa has in mind for MRI is to reveal how cotton plants react physiologically to environmental stresses such as drought as the reaction is going on.

"We can actually track the flow of water molecules through the plant - in the leaves and the bolls - and see what else changes, instead of disturbing the tissue structures in the process of preparing a specimen for analysis or microscopic examination," Timpa says. "With MRI, we've got a whole new horizon for cotton research."
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Author:Kaplan, J. Kim
Publication:Agricultural Research
Date:Sep 1, 1991
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