1938: Botany

Hydroponics.

Dr. W. F. Gericke, of the University of California is responsible for the development of the new science of Hydroponics. This means, briefly, growing vegetables and flowers in tanks to which nutrient salts have been added. It has been known for nearly a century that such a practice is feasible. What Dr. Gericke has done is to show that it may have a commercial application.

'Four commercial growers are using the Gericke methods, under his supervision. One of these, at Montebello, Calif., has grown premium tomatoes which sold for $262 per ton at the rate of 100 tons per acre of water. Gericke does not ask for fees from these companies. 'All I want,' he says, 'is for them to set aside sufficient funds for me to carry on experiments.'

'He objects to the fact that a dozen or more small chemical companies have sprouted up to sell nutrient salts to amateurs or professionals experimenting with hydroponics. These have names like Chemi-grow, Chemi-Crop Company, Shur-Gro Fertilizer Corporation. They are legally within their rights, since hydroponics cannot be patented. The only patent which Dr. Gericke holds is for a container to diffuse the chemicals through the solution. But he argues, against the companies, that no formula works well for all plants, all climates, all conditions; and that, even if they made a great variety of formulae, there are other factors, such as temperature and acid-alkali balance, which must be thoroughly studied for successful hydroponics. Also, in his kindly if eccentric way, he accuses them of victimizing 'poor people' by selling chemicals worth a few cents at fancy prices ranging from one to three dollars.'

The chief objection, so far advanced, to these methods, is that they are expensive and difficult to control on a large scale. But that the new science has made a great stir there can be no question. Even a magazine called Hydroponics, The Magazine of Gardening without Soil was inaugurated in the spring of 1938.

As having a bearing on this subject, we should note the work of D. I. Arnon, of the University of California. Growing lettuce and asparagus plants in ordinary culture solutions, he found that a marked increase in growth was obtained by the joint addition of boron, manganese, zinc and copper, confirming results already obtained by others; also, that a further significant increase resulted from the addition of a group of seven elements — molybdenum, vanadium, titanium, tungsten, chromium, nickel, and cobalt — a fact suggesting that one or more of these last seven elements is important in the nutrition of higher plants.

Dr. E. M. Hildebrand, of Cornell University, in an admirable paper published in the Botanical Review, has brought together the various techniques for the isolation of microorganisms. To those who desire to obtain a pure culture of any particular microorganism, this paper is extremely helpful.

Colchicine.

The exact way in which colchicine affects plant tissue seems still to be more or less in doubt. According to Ruth Walker, of the Extension Division of the University of Wisconsin, colchicine 'does not seem to have any visible effect on the chromatic material.' It works rather upon the cytoplasm and the spindle in mitosis, and as a result the formation of the spindle and the new cell wall is suppressed. As a result of the first meiotic division we find, therefore, an apparently diploid nucleus (instead of a haploid), and by suppression of the walls of the next division we may have a tetraploid nucleus. This means that pollen grains formed under those conditions may be provided with double or quadruple their normal number of chromosomes.

The Fungi.

Working on the effect of light on the fruiting of myxomycetes, Dr. William S. Gray, of the University of Pennsylvania, found that, of the species studied, yellow pigmented types require light to complete their life cycles, while non-pigmented types and Didymium xanthopus fruit equally well in light or darkness.

Dr. B. O. Dodge and Bernice Seaver, of the New York Botanical Garden, in further breeding work with the fungus Neurospora tetrasperma, find that the two types of lethal factors they had already described — one causing induration and the other, deliquescence of the ascus — 'segregate independently in regular order and react without serious interference, each producing abortion of the ascus in its own way.'

Physiological Researches.

Dr. Raymond H. Wallace, of Connecticut State College, at Storrs, Conn., and Harold H. Clum, of Hunter College, New York City, in a study of leaf temperatures, conclude that transpiration (i.e., the giving off of water vapor from the leaf) is necessary at times to prevent leaves or parts of leaves from being injured by extreme heat.

It is generally known that in the chestnut blight the foliage above the attacked portion of the shoot withers and dies, and it has been assumed that in some way the supply of sap was cut off through the activity of the fungus. Now Dr. W. C. Bramble, of the Pennsylvania State College, shows that such stoppage is due to the abnormal formation of tyloses (cellular growths into the water-carrying pores) in the sapwood in the region of the fungous lesion. These tyloses, apparently the result of some kind of stimulation by the fungus, protrude into the conducting elements and thus block the passage of the sap through the wood.

Plant Hormones.

The study of the effect of growth hormones on plant tissues has continued, with some slight decrease in amount of published material. To date, seven monographs on the subject have appeared. The book 'Growth Hormones in Plants' by Drs. G. S. Avery and P. R. Burkholder, of the Connecticut College at New London, has already been reprinted; a second edition is being prepared.

Plant Diseases.

Professor Ray B. Hirt, of the New York State College of Forestry at Syracuse University, reports that infection of the needles of the White Pine in the White Pine Blister Rust, may take place through the stomata, but suggests that direct penetration of the epidermal cells is probably the commoner method of infection.

A leaf blight of Iris caused by Bacterium tardicrescens is reported by Lucia McCulloch, of the U. S. Horticultural Station at Beltsville, Md. Working at the same station, Nellie A. Brown finds that the unsightly tumors or excrescences sometimes seen on oak or hickory trees are caused by a species of fungus (Phomopsis sp.) and not by Bacterium tumefaciens as has long been supposed.

Marion E. Fowler, of the Division of Forest Pathology of the U. S. Department of Agriculture, reports that the twig blight sometimes occurring in Asiatic chestnuts, particularly in those growing on poor sites, is caused by several species of fungi.

Systematic Studies.

In the short space allotted to us it is impossible even to mention by name all the excellent work of the past year dealing with the descriptions of new plant species and of plants of particular regions. We add: Studies of American Melastomes by Dr. H. A. Gleason, of the New York Botanical Garden; of Onagraceae by Professor Philip A. Munz, of Pomona College at Claremont, Calif.; on the fern group in the Galapagos and Cocos Islands, by Dr. H. K. Svenson, of the Brooklyn Botanic Garden; on Mississippi fungi by Dr. L. O. Overholts, of the Pennsylvania State College; on Zygnemataceae (a family of the green algae) by Professor Edgar Nelson Transeau, of Ohio State University at Columbus, Ohio; but there are many other botanists that have made distinct contributions to our knowledge of plant species.

Shelter Belt.

Regarding the trees planted by the U. S. Forest Service to form a shelter belt in the Midwestern States, the Forestry News Digest reports: 'Despite unusually severe drought conditions for 1935, 1936, and 1937, the trees . . . have done well, and in many areas the owners report that they are already receiving beneficial effects. On 13,556 farms more than 83,000,000 trees have been planted, proving that shelter belts can be successfully established in areas where tree growth is scarce, and crop rotation a serious need.'