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Effect of Light Intensity on Growth of Soy Beans and Its Relation to the Autocatalyst Theory of Growth

1926; University of Chicago Press; Volume: 82; Issue: 3 Linguagem: Inglês

10.1086/333661

1940-1205

H. W. Popp,

Soybean genetics and cultivation

The effect of different light intensities on the growth of soy beans was studied by growing four different varieties under six different light intensities, averaging 4285, 1536, 560, 390, 250, and 26 foot-candles respectively. The results were as follows: 1. The lower the light intensity, the more rapid was the rate of stem elongation during the initial period of growth. 2. The greatest general height was attained by plants under a light intensity averaging 560 foot-candles, and the lowest under an average intensity of 26 foot-candles. 3. The thickness of the stems was directly proportional to the light intensity, being greatest under 4285 foot-candles and least under 26 foot-candles. 4. In general all of the plants were unusually long stemmed. Those receiving the greatest amount of light were the most vigorous, produced the best leaves and color, and the best fruit. There was a gradual decrease in vigor, etc., with decreasing light intensity. Plants grown under 26 foot-candles were completely etiolated and died within three to four weeks. 5. Twining occurred in all plants under light intensities between 250 and 1536 foot-candles, but not under 4285 foot-candles nor under 26 foot-candles. Soy beans apparently have a latent factor for twining which is associated with stem length and thickness. Thick stems require a greater length for twining than thin ones, but in no case did twining occur in a stem less than 35 cm. high. 6. The curves of growth in length of all plants except those in the darkest compartment followed the general curve of a monomolecular autocatalytic reaction. The autokinetic phase of the curves appeared to be associated with the initiation and development of independence in the seedling brought about by the ascendency of photosynthesis, while the falling off in rate during the latter part of the autostatic phase was caused by the development of flowering and fruiting.