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A botanical body builder strengthens rice.

Southern rice farmers are getting a financial boost these days from a slightly offbeat source: weight-lifting rice plants.

In lab tests, the strapping seedlings have pushed up plastic plungers loaded down with as many as four 1.2-gram metal washers, researchers report.

There's nothing magical about the plants themselves; they're ordinary semi-dwarf rice varieties used by farmers since the early 1980's. But like the cartoon character Popeye with his cans of muscle-building spinach, the germinating rice seeds get extra "oomph" from a natural product - a growth regulator called gibberellic acid (GA) that elongates emerging plant parts.

The weight-lifting plants are more than just a laboratory oddity. The extraordinary elongation and pushing power derived from the gibberellic acid ensure that after germination, the new rice plants will be able to push up through the soil on time and generally in unison - attributes of significant economic value to farmers, according to ARS geneticist Robert H. Dilday.

"In growing rice, you use emergence of the plants as a point from which to calculate when to do a lot of other things, such as applying fertilizer or herbicides," says Dilday, who works in the ARS Rice Production and Weed Control Research Unit at Stuttgart, Arkansas.

"If emergence is spread out over several weeks, it's hard for the farmer to figure out the right time to take those other actions.

"Also, timing of emergence can affect timing of harvest, which in turn affects the quality of the rice. The farmer needs to harvest rice when the moisture content of the grain is about 18 percent," says Dilday.

"If the rice is at different stages when you harvest it, you may get some rice with less moisture than that. Then you can wind up with a lot more broken kernels, and broken kernels are only worth about half as much as whole kernels."

Semi-dwarf rice varieties such as Lemont and Gulfmont have won favor with farmers because the shorter plant stems are less likely to break and dump valuable grain on the ground. In Arkansas, the nation's top-rice-producing state the Lemont variety alone has claimed about 20 percent of all rice acreage.

But farmers were also quick to discover the major drawback of semi-dwarf rice: its difficulty in emerging from the soil after planting.

When a rice seed germinates, plant parts called the mesocotyl and coleoptile are the first to push forth. Once the coleoptile has broken through the soil to sunlight, leaf growth begins.

But if seeds of semi-dwarf rice are planted even one-quarter inch too deep. the coleoptiles may not be able to reach the soil surface, leaving farmers with a spotty or nonexistent crop.

Gibberellic Acid to the Rescue!

In lab studies begun in 1988, Dilday and agronomist Ronnie S. Helms of the University of Arkansas tried treating semi-dwarf rice seed with a type of gibberellic acid called GA3. Seeds were soaked in the growth regulator at rates of 10, 50, or 100 parts per million for about 5 minutes.

When planted, the treated seeds sent shoots barreling upward to the soil surface. In some instances. Dilday says, the lengths of the mesocotyl and coleoptile were actually doubled.

Pushing power is especially important on Arkansas' Grand Prairie, heart of the state's rice-producing area. When spring rains pummel the silty clay loam soils of the prairie, tough crusts half an inch thick can form on the soil surface.

But even the treated seed needs a little help from nature - notably, soil temperatures warm enough to encourage germination.

"If you plant this treated seed when the soil temperature is about 58[degrees]F, which is fairly typical for late April and early May, you'll see an increase in germination of 2 to 30 percent with the treated seed versus untreated semi-dwarf seed," notes Helms.

"On some varieties, we've seen seven more plants per square foot emerge when treated seed was used. And there's no detrimental effect to this treatment."

The treatment is designed for rice planted into dry land, as opposed to planting on land that's already been flooded, the practice followed in California and parts of Louisiana.

Among rice farmers who use the dry-seeded method, the GA seed treatment is a hit, as evidenced by their seed purchases.

"We estimate that in 1991 in the South alone, farmers planted 500,000 acres of GA-treated rice," says Dilday. "Arkansas farmers planted about 350,000 acres of that total, and we think this year's total in Arkansas alone may be 500,000."

The GA treatment now available commercially to farmers is the result of technology transfer between ARS and Abbott Laboratories of Chicago, Illinois. Dilday and Helms worked with Abbott's Rollie Carlson and Marcus Adair on field and laboratory tests to evaluate the potential of the product, now marketed by Abbott under the brand name Release.

Part of the credit for GA's wildfire spread among farmers must go to Ronnie Helms, who passed the word on GA treatments at some three dozen growers' meeting in the winter of 1990-91.

Helms says even he was impressed by the farmers' reactions. "I know of some farmers who used this treatment on rice in one field and it came up really quick." he recalls. "Then we had a wet spell, and as soon as they could. they went back and replanted their other fields with treated seed."

David W. Hillman, who grows rice, soybeans, and wheat at Almyra, Arkansas, first used the treatment solely on an experimental basis on some of his Lemont rice fields.

"Lemont has been known to have trouble emerging when you plant too deep," Hillman says. "It's very important for maximum yields that the plants all come up at the same time. Ideally, rice should come up in a 3- to 4-day period. But with Lemont, some plants would come up in a few days, and others 2 weeks later.

"Because of this, we normally try to have an ideal seedbed, soil moisture just right, and we take a lot of time setting the depth of our seed drill when we plant Lemont.

"We'd planted part of a field under what we considered ideal conditions, with the seed down about half an inch. Then the guys came out to plant the treated seed, and they put those seed down 3 inches! But 3 days later, every single stalk came up - ours and their."

Hillman says every acre of his Lemont production this year features GA-treated seed, despite the extra expense of the treatment. And, he adds, some of his neighboring farmers wish they could go even further: "I've heard some ask, why can't we use this on wheat seed, too?"

Neighbors had a lot to do with persuading farmers Kenneth R. Maier of Stuttgart to give the treatment a try in 1990 - even though they never said a word to him about it.

"They had an experimental plot of the treated seed out the year before and I watched that plot," says Maier. "It was right by the road and as I drove by, I could see how it came up in a good even stand."

As a result of what he saw, Maier planted 200 acres of treated semi-dwarf rice in 1990, and "it did what they said it would do - came up early in a good stand.

"It's hard to get rice planted all even; you're always afraid you've got the seed too deep." Maier notes. "But with this treatment, you don't have that pressure - and you can plant down deep where the soil moisture is."

Nor are farmers the only satisfied customers for the GA treatment. At Stratton Seed Co. in Sttugart, company president Wendell Stratton says demand for the seed treatment has been impressive.

"We treated quite a bit more last year than we had anticipated, and not just the semi-dwarf varieties, " he says. "I think usage on the non-semi-dwarf rice will taper off a little bit, but I think this practice will continue to grow on the semi-dwarf rice.

"This gives the farmer a higher yield potential because the stand won't be uneven," he adds. "And as tight as things are for farmers today, we need all the production tools we can get.

"This treatment has completely lived up to its promises. It's done everything that Bob Dilday and the Extension and university people have said it would do."
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Title Annotation:rice plants treated with gibberellic acid
Author:Hays, Sandy Miller
Publication:Agricultural Research
Date:Aug 1, 1992
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