Abstract
Three series of plants, including sunflower, tomato, cucumber, soy beans, nasturtium, and corn, were grown entirely with artificial radiation under 3 ranges of wave lengths,[long dash]2650-7200 A, 2900-7200 A, and 3130-7200 A. The results indicate that wave lengths 2900-3100 A increase the dry weight and the calcium content, and have little effect on the P content; and that wave lengths shorter than 2900 A are injurious and have little effect on Ca and P content. Spectrograms show that the upper epidermis transmits radiations shorter than 2900 A but that these rays are absorbed by the remainder of the leaf.
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