Plants Respond To Wave Lengths Like Radio Set

Hawke's Bay Herald-Tribune, Issue 55, 20 March 1937, Page 18

Plants Respond To Wave Lengths Like Radio Set

WASHIN GTON, Jan. .14.— Curious and hithexto nnsnspeeted effects of different eoloured lights on the growth of plants* are reported by the division of radiation in fhe Smithsonian Institution. Oat seedlings were exposed to light from an eleetric lamp wMch was split up into its constituent wave lengths (eolours) by passing it through a prism. The exposure was axranged in sueh a way that only a narrow band of visable light fell on eaeh plant, and from a horizontal direction. Kormally, plants which are placed in -a semi-dark xoom are bent toward the light, a phenomenon called "phototropism." This occurred when Or. Enoch Karrer, who conducted the experiments, exposed the seedlings to the blue region of the speetrum, and in addition the tips of those seedlings were bent towards each other. But while exposed to the red region of the speetrum, the seedlings bent away from each other. Br Karrer noted also a number of other specific effeets, namely: "The greatest growth in length was in the two xegions where the greatest divergenee of the tips were found. "The greenest growth was in those plants illuminated only by the orange part of the speetrum. The yellowest growth was in the blue-green region. JSoots grew longest in the extreme blue and shortest in the orangered. | "The leaf sheath, or coleoptile, was 'rnost filled out by the first leaf in the green and orange xegions and least in the blue and deepest red. • In the green,

the growth of the leaf sheath appeared to be. stunted, and the leaf broke through prematurely, but its , growth was rapid , when exposed to f ull 4white light." ' The implication of these findings is, that plants xeact to different wave lengths of light in the same manner as a radio set designed to receive broadcasts on speeial wavelength bands. Plants sedin to xeceive and make.use of speOifie wave lengths of light for specifte purposes, discarding or ignoring all others. TMs discovery renders much more complex the already complicated relationsMp between plants and their assimilation of inorganie earth-salts as food. , This basic property, called photosynthesis, by whieh plants synthesize carbohydrates, from carbon dioxide and water using sunlight in tho presenee of chlorophyll, the green pigment of leaves, is a distinguishing ehafacteristie of plants. Animals eannot do this. Plants provide all food. But apparently there is much more to plant development than synthesis of carbohydrates, Dr. Karrer finds. Carbohydrates, fats, proteins, water and minerals must be mobilized and oxidized. There are chemxcal leactiocs

with ammoida and otlier nitrogen compounds, and then further chemieal changes in the syntbcsized products. It now appears that many of these processes may be speciiically activated by specific bands of radiation.