1938: Biology

Scientists in the fields of animal and plant biology have continued to contribute outstanding discoveries throughout the past year. In a resume of contributions of the year, it becomes increasingly difficult to mention those which stand out. Contributions which now seem to play a minor part may be the stimulus or, even more, the actual beginning of a new conception in the years to follow.

Interaction of Plant and Animal Life.

One of the most interesting experiments seems to be that demonstrated by Dr. Ralph Buchsbaum, of the University of Chicago. Here we have striking evidence for the close relationship between animal and plant life. Dr. Buchsbaum used chick embryo tissues and mixed with them plant cells (chlorella) commonly found in stagnant water. He found that if this mixed culture was kept warm and under lighted conditions, the chick cells and the plant cells would continue to thrive much better than when either type of cell was cultured alone. This mutual relationship resulted in greener and healthier plant cells, while the animal cells divided more rapidly and did not become senile and die off so quickly.

Disease Viruses.

Although the virus molecules are now fairly well established as non-living things, they are nevertheless found to possess certain very lifelike characteristics. These molecules may not represent the lowest beginnings of what may turn into life; but, conversely, they may represent the last stages in the ultimate degeneration of life. Biologists throughout the country are now working on these virus units in an effort to find out how they synthesize themselves. These protein molecules can invade a cell, take parts of its living material, and then build up additional molecules like themselves. If a few of these are introduced into a plant or an animal, they multiply into millions and make the host sick.

Ever since Dr. Stanley's pioneer work on the tobacco virus and his demonstration of its protein nature, other workers have continued work on this virus with the hope that man and animals would some day be protected against the numerous virus diseases. The smallpox virus particles, hitherto unseen under the highest magnifications of the microscope, have been made visible by means of an improved electron microscope developed by Dr. Franz Krause of Germany. These viruses are very much smaller than bacteria and are rendered visible at something over 2,000 diameters. The virus of other diseases such as encephalitis, infantile paralysis, yellow fever, and parrot fever are likewise being studied in an effort to determine their physical, chemical, and biological characteristics. A new method of inactivating plant-disease viruses by ultra-violet radiation and X-rays has been reported by Dr. N. W. Pirie, of Cambridge University. Irradiation tends to enlarge the crystals that are obtained from the viruses and hinders their infectivity. This discovery may pave the way for a possible future method of vaccinating plants against certain diseases. It may also indicate a way in which safer smallpox vaccine may be prepared.

Synthetic Hormones for Large-scale Farming.

While hormones, or chemical messengers, have continued to yield new and startling results in the animal world, they have also resulted in outstanding contributions in the plant kingdom. Pioneers in plant hormone research were Drs. P. W. Zimmerman and A. E. Hitchcock, of the Boyce Thompson Institute for Plant Research, Yonkers, N. Y. As early as 1935 they demonstrated that some 16 new chemical substances would grow root hairs on plants very rapidly and on numerous parts of the plant itself. They applied these chemicals as solutions in water. At the present time these synthetic chemicals, that grow roots many days before they would otherwise sprout, are ground into a talc or other inert dusts for easier and more effective application. This year these chemicals are being used on a large scale on field trials of actual grain production in various parts of Canada. Wheat on the Western plains may be able to get its roots into the soil more quickly and securely if the seed is first dusted with hormones. This may hence mean the difference between a crop and a failure, for wheat so treated may then withstand wind and drought at an earlier time after seeding.

Roots from Flower Tissues.

Other interesting contributions have also been made in the field of plant biology. In experiments reported by Dr. La Rue, of the University of Michigan, all parts of flowers from certain plants have been induced to form roots. The secret of this feat was the technique for keeping the small and delicate pieces of plant tissue alive and in good condition. These tissues were placed on a sterile nutrient jelly after bacteria and molds had been killed by antiseptic solutions. On this nutrient substance the cells of the flower lived indefinitely and not only sprouted roots but started stems and leaves as well. These experiments show that highly organized cells which make up the flower of the plant are in reality not so fixed or determined in their organization that they cannot be induced to form the cellular components of the leaves, stems, or roots of a plant.

Plant Behavior under Chilling.

It has long been known by gardeners that certain plants have to be nearly frozen each winter so that they will grow normally the following year. Earlier experiments have shown the beneficial effects of chilling on woody plants and seeds. Now, Dr. H. Kurz, of Florida State College for Women, has added considerable new information to the above facts. He has experimented with some twenty kinds of Northern wildflowers and has demonstrated that their rootstocks must be held at temperatures near freezing for several weeks if normal growth and flowering is to take place in the spring. An interesting phase of his experiments was the peculiar behavior shown by four species of plants received from New England. These four species had to be chilled before normal growth and flowering occurred. However, identical species that normally are found in Florida required no chilling for normal growth. Here seems to be an example of physiological adaptation. While there are many Southern plants which find Northern climates too severe, there also appear to be numerous Northern plants which find that Southern climates are not severe enough for the stimulation of normal growth and reproduction.

Chlorophyll, Porphyrins and Photosynthesis.

Chlorophyll, the light-sensitive chemical which enables plants to convert light energy, water, and soil foods into bodily structure may eventually be synthesized. Drs. P. Rothmund, of Antioch College, and A. Menotti, of Ohio State University, describe the creation of chemicals, known as porphyrins, which are extremely light-sensitive. These chemicals were made synthetically by these scientists, but they may also be obtained by extraction methods from the green pigment (chlorophyll) of plants or even the red pigment of blood. When these chemicals are injected into the vascular system of animals, the animals become exceedingly sensitive to light and can carry on their normal activity only in darkness or very dim light. The derivatives of synthetic porphyrins seem to exert greater influence than do the naturally derived porphyrins. This series of studies will no doubt lead to a better understanding of the general problem of photosynthesis.

Mutual Activities among Plants.

Various phases of what may be termed plant sociology have been studied from time to time. Various American and German scientists have shown that the mere presence of odorous plant substances such as apples, turpentine, or oil of bergamot may accelerate seedling growth under light conditions but seems to hinder it under conditions of darkness. A German physician, Dr. G. Madaus, has recently shown by experimental means that corn and wheat planted in the same pot will produce a more rapid growth of the wheat. He also demonstrated that bean seeds in water first used to bathe the roots of oats sprouted more rapidly than did similar seeds in water previously used to bathe corn roots. It is probable that root secretions are responsible for these mutual activities, and this work may lead to the discovery that hormone-like substances are specifically produced and liberated through the roots of plants.

Intercellular Hormones.

A better understanding of the nature of life and cell growth may result from the discovery of substances produced from injured cells, which in turn cause the rapid multiplication and proliferation of healthy cells. These substances are at the present time called intercellular hormones. They are purified out of injured cell extracts. While they have not been completely analyzed chemically, there are indications that they are higher fractions of our well-known proteins. Practical application of these substances has already been put to use in a Cincinnati hospital for the treatment of third degree burns. Burns thus treated seem to heal in a minimum time without the wide areas of scar tissue which usually result from such burns. There are numerous kinds of injured animal and plant cells which have been shown to be capable of yielding this intercellular hormone, and they all cause a rapid growth of a wide variety of healthy cells. It seems of special interest to note that these substances induce proliferation of connective or supporting tissue cells known as fibroblasts. The fibroblasts are the cells which are characteristic of certain types of cancer. Hence a further advance in the knowledge of certain cancerous diseases may also be indirectly recorded.