GENERAL ARTICLES

Plant Magic

Jack s Beanstalk could happen now! With colchicine man can remodel old plants or grow new ones the like of which the world has never seen

MERRILL DENISON,WILLIAM STEPHENSON February 15 1946
GENERAL ARTICLES

Plant Magic

Jack s Beanstalk could happen now! With colchicine man can remodel old plants or grow new ones the like of which the world has never seen

MERRILL DENISON,WILLIAM STEPHENSON February 15 1946

Plant Magic

GENERAL ARTICLES

MERRILL DENISON

WILLIAM STEPHENSON

Jack s Beanstalk could happen now! With colchicine man can remodel old plants or grow new ones the like of which the world has never seen

FORTY YEARS or so ago, in one of his early pseudoscientific novels, H. G. Wells explored this fascinating proposition: that there might exist a chemical with the miraculous properties of stimulating natural growth. Fed to flowers, vegetables and trees, the food produced plants such as the old earth had not known since Paleozoic times; fed to his hero and heroine it endowed them with superhuman qualities of size, beauty and intelligence.

In the curious manner in which science occasionally confirms the fantasies of such pseudoscientists, something of the sort actually took place in 1937, more than 30 years after Wells’ “The Food of the Gods” was published. Two American biologists, A. F. Blakeslee and A. G. Avery of the Carnegie Institute’s experimental botanical station at Cold Spring Harbor, New York, announced the results of plant experiments with a medicinal chemical known as “colchicine”— pronounced eoll-chi-seen.

Today, in most countries—Canada, the U. S., Great Britain, South America, China, Russia, India—at government experimental stations, in botanical laboratories and commercial greenhouses, plant.

breeders and geneticists are experimenting with the wonder chemical, colchicine, to produce bigger and better flowers, vegetables, fruits and trees.

The huge interest shown all over the world was given added impetus in Canada by the fact that only a few weeks after the Blakeslee-A very announcement, a Canadian woman and her husband at Geneva, N.Y., published reports which showed they had been experimenting widely with colchicine along lines paralleling those followed by Blakeslee and Avery— —that they really only missed being first with it by a matter of weeks. The Canadian, Mabel Rüttle Nebel, and her scientist husband since have produced—using colchicine—marigolds six inches across.

Canadian experiments with colchicine are found now almost wherever there is an experimental farm or university. In Ottawa Dr. L. V. P. Johnson, Dominion Forest Geneticist, has developed with colchicine a sugar beet double the size of its progenitors. Another Canadian. Dr. John Armstrong of the Dominion Experimental Farm, has used the chemical to produce a grain called Wheat X Agropyron—a hybrid from wheat and a type of couch grass known as Agropyron

—-which promises to lick the problem of pasture crops in the arid regions of the Canadian Prairies. One of his colleagues at the Experimental Farm, A. V. S. Hunter, has developed exceptionally fertile snapdragons.

In the U. S. a wider variety of plants has been tested in colchicine experiments. At Beltsville* Maryland, Haig Dermen and other U. S. Agricultural Research workers have used colchicine to improve existing breeds of cranberries, strawberries, tobacco, snapdragons, lilies, and other plants. Dr. A. B. Stout, Curator of Laboratories of the New York Botanical Gardens, has used colchicine successfully in flower and grape culture. In Philadelphia the Burpee Company, one of America’s largest commercial seed growers, presents as the feature of its 1946 garden catalogue a tantalizing display of “Giant Ruffled Tetraploid Snapdragons”—a colchicine development.

What is colchicine, you ask? How do you use it? Where does it come from? What does it do? And if it is miraculous, why hasn’t more been heard about it?

The Stuff Is Explosive

COLCHICINE is a poisonous alkaloid drug extracted from the seeds of the autumn crocus, a flowering plant that grows wild in Europe and as a cultured plant in this hemisphere. The drug is sold commercially in the form of a yellowish-white powder which has the weight and consistency of icing sugar. In normal times it can be bought for $15 to $25 an ounce, but at present it would cost many times that. It dissolves readily in water, gives off the odor of fine old Scotch whisky but this doesn’t make it potable. Taken internally it may kill you, and even accidental external application has been known to be harmful to the skin and eyes. »So far as is known, its uses are largely botanical. It holds no promise of producing Wellsian heroes or heroines, nor of doubling the bulk of elephants or even fruit flies.

There is no standard way of treating plants with colchicine. Seeds or cuttings can be soaked in mild solutions, it can be applied in liquid form to the growing tips of plants or to buds; it can be injected, and it has been made up in the form of a salve to rub on plants.

Unlike the better-known wartime drug sensations, colchicine is not a new discovery. Half a century ago its medicinal values were being extolled in almanacs along with other forgotten herbal remedies, and it has been hailed at various times as a cure for rheumatism, arthritis, lumbago, gout and bronchitis. In the late 1920’s it created a brief stir in medical circles as a possible aid in the treatment of cancer, but the hope quickly faded. The drug is still used in the treatment of gout, but extravagant claims are no longer made for it.

What gave it its new importance was the discovery by Blakeslee and Avery of its effect on growing plants. In an experiment at Cold Spring Harbor in 1937 they treated a specimen cutting of Jimson weed with a colchicine solution. An untreated cutting from the same plant was kept as a comparison.

As the two Jimson plants developed, researchers noted that in the treated specimen not only was the stem thicker and tougher than its untreated twin, but the leaves and flowers were larger and more numerous, and the whole plant showed signs of having received a powerful stimulus. Microscopic study of sections of the stalk and leaves showed the reason. The colchicinetreated specimen had twice as many chromosomes in each cell as the normal or untreated plant.

Chromosomes are the tiny microscopic filaments in each animal or plant cell which by their number and disposition determine what that animal or plant is like. Each species of plant or animal has its definite quota of chromosomes. Every cell in your body has 48 chromosomes—24 from your father and 24 from your mother; the Trillium has 10, the strawberry 80.

They can be watched and counted under a microscope.

All growth is the result of the cells containing the chromosomes dividing in half and redividing almost constantly. Each cell on the tip of a

bud, for instance, breaks up into two cells, and each of these new cells in turn forms two more, all to a planned pattern. Suppose we watch a Trillium, in which each cell has 10 chromosomes. During the splitting process each of the 10 chromosoma«? dividas in half, lengthwise, making 20. Under a microscope the chromosomes can be seen moving to opposite sides of the cell, 10 to each side, like rival football teams; and when they are all in place a wall grows up between them. Now, instead of one cell with 10 chromosomes, we have two cells with 10 chromosomes each.

The newborn cell possesses exactly the same component chromosomes as its parent. Inside the chromosomes are the genes, still smaller microscopic bits of matter, which carry inherited characteristics. They are responsible, for instance, for the shape of a pear, the color of a rose, or the flavor of a Niagara peach.

Now It’s a Full House

COLCHICINE does its size-doubling trick, apparently, by stopping the mechanism which causes the split chromosomes to separate into two new cells. So, after the split, the old cell finds itself with double the tenants it formerly had—in the case of the Trillium, 20 instead of 10. If the colchicine is removed or diluted at that point, so as no longer to be in effective concentration, the cells recommence splitting in the normal way, but with now double the normal number of chromosomes per cell. Thus each of the children and grandchildren cells will have double the normal number also. And when this happens the plant may be double its original size. You’d probably like to know how far this multiplication of chromosomes can go when an experiment is successful. The answer is: hundreds of times. But the huge cells thus produced are good for nothing—dropsical, pulpy, useless.

For some curious reason the drug will not make all plants double or treble in size—sometimes they stay the same. Prof. L. C. Coleman of the University of Toronto says: “We don’t know why, but sometimes when colchicine increases the size of the cells within a plant, the plant makes some kind of an adjustment to reduce its total number of cells accordingly. The finished product is a plant the same size it would have been without use of colchicine!”

Colchicine usually is applied to young germinating seeds. Then—according to Prof. Coleman—there

begins an internal struggle.

“As far as we can make out,” he says, “colchicine only affects some cells. As the plant grows, these abnormal cells engage in a struggle with the normal cells. If the normal cells win, colchicine may not change the size of the plant. If they lose, the plant may double in size—or do any number of odd things. That’s why we never know what colchicine is going to do. It may even kill the plant!”

New Plants to Order

TVTEVERTHELESS in many cases the new drug has ±X made it possible for the plant breeder to make new plants to order. More significant still it has enabled him to make sterile hybrids fertile.

Virtually all of our vegetable foods, all the roots, grains and fruits we eat, are hybrids; that is the result of crossbreeding, occurring in most cases over centuries of time. Man apparently learned very early to improve his food by keeping the seeds of his best plants for replanting; and this process was supplemented by the occasional discoveries of what technicians call “sports,” new species produced by the accidental whim of nature. But it is only comparatively recently— within the last 50 years or so—that we’ve known that the so-called sports owed their existence to the accidental doubling or trebling of the chromosomes.

Now we can do this artificially with colchicine.

And this is where the effect of colchicine on the sterility of hybrids comes in. Some hybrids are sterile because their chromosome sets don’t match up in the pairing process which should produce a new plant. By doubling the number of chromosomes colchicine makes it possible for each to find a mate in the pairing process, and fertility results.

The most dramatic development in the commercial use of colchicine is one already mentioned: The Burpee Company’s tetraploid snapdragon featured in their 1946 catalogue. (“Tetraploid” means that its cells have four sets of chromosomes instead of the usual two.) This means that a colchicine-induced variety has been developed and its characteristics well enough established for an old and reputable seed house toj begin selling its seeds under rigid guarantee.

Food for Forests

N THE U. S. the most important government research centres appear to be Department of Agriculture’s Beltsville Station and the New York Botanical Garden in the Bronx, but work with colchicine is proceeding in: many State Departments of Agri-j culture and at most universities.

Canada’s Dr. L. P. V. Johnson, previously mentioned for his work in doubling the size of the sugar beet, is in possession of about 75% of thft available Canadian supply of the drug. As Dominion Forest Geneticist he has for years been primarily interested in Canada’s greatest natural resource, her forests. Using colchicine, Johnson has produced 32 fertile hybrids, including pines, birches and other trees. All are in the nature of first experiments, which he hopes will lead to bigger and better things.

For the future he sees every farmer setting aside a portion of his farm as a timber tract, and having that lot pay off every few years. Faster-growing, disease-resistant trees, new forms of common varieties, and trees with greater commercial value, he believes to be far from remote possibilities. And he leaves this interesting speculation: “Our present-day forest trees are nearly all diploids (plants with two sets of chromosomes). When our common Canadian hard wheat was still a diploid it was little better than grass. Who can say what our forests will be like when the chromosomes of the different species of trees can be doubled?”

Canadians are at work with colchicine in other fields too. A. W. S. Hunter of the Dominion Experimental Farm in Ottawa has been applying it to flowers, and has succeeded in producing a fertile snapdragon not unlike those developed in Philadelphia and Washington. Like all workers with the new chemical, Mr. Hunter cautions against expecting too many miracles oí colchicine, but he

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BERTIE THE BEAVER

Continued from page 22

regards the power to eliminate the sterile hybrid as one of the greatest advances ever made in horticulture.

According to Dr. Armstrong, one of Mr. Hunter’s colleagues, who produced Wheat X Agropyron with colchicine, the trouble with pasture plants now growing in Saskatchewan soil is that the seeds are so small that if planted more than an inch deep the young shoots—which wholly rely on the food source in the seed itself until it reaches sunlight—exhaust this supply long before they break through to the surface. In that shallow depth of soil the amount of moisture is very small. Dr. Armstrong’s hybrid throws off seeds large enough to be sown at depths ot three inches or more where they can pick up greater quantities of moisture. About an acre of the new hybrid was cultivated in Ottawa toward the end of the war, and other areas are under cultivation in Saskatoon, Lethbridge and Swift Current. The venture promises new life to the former dust regions of the prairies.

Colchicine’s Place in Agriculture

From Chapel Hill, N. C., have come other reports that colchicine, in weak concentration, has the power of greatly speeding up plant growth. Prof. Earl H. Newcomer of the University of North Carolina placed one drop per day of a four tenths of one per cent solution on the growing points of young oaks and chestnut trees, hazel bushes and other plants. In some cases the treatment produced unfavorable results, even death, but in 16 seedlings he found that growth went on at double

the usual rate. Two Chinese researchers, T. Loo and Y. Tang, have also reported a speeding-up of seed germination in corn, rice, wheat, cabbage and mungo bean following colchicine treatment. And from Russia come persistent but so far unconfirmed rumors of spectacular success with poplar trees.

Despite the widespread interest in the new technique, the warning voiced by Mr. Hunter against expecting too much from colchicine is repeated by other experimenters. Perhaps the best summary of its present status as the “evolution chemical” is the statement given Maclean’s by Dr. S. L. Elmsweller, chief of flora culture at Beltsville:

“Colchicine is an experimental tool,” he said. “It is not for use in the direct commercial growing of crops, but is used to produce variations and to make crosses not possible by other means.

“It is still a relatively new technique, and so far not many new varieties can be attributed to it. However, it is enabling plant breeders to have better control over their genetic material, and many of us feel that we need no longer wait for the accidental hybrids of nature. By this and other plant growth regulators, science is gaining a grip on the problem of creating more useful and economic plant forms.”

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