Studies on the Growth Hormone of Plants. II. The Entry of Growth Substance into the Plant

Abstract

In the course of experiments to elucidate the relationship between growth substance and growth in the plant, it was necessary to determine whether all of the growth substance applied to the plant actually entered, or, if not, what proportion remained in the agar. The experiments of Went (1928) seemed to show that the curvature is proportional to the amount of growth substance in the agar block. Thus, he found that if its concentration was reduced by some factor, and the size of the block increased by the same factor, the resulting curvatures appeared to be the same. However, van der Wey (1932) found that the curvature was proportional to the concentration of the growth substance in the agar and nearly independent of the size of the blocks. In general, we have confirmed the finding that the curvature is proportional to the concentration of growth substance and not to the amount of it present in the block. It will be shown, however, that if it be assumed, as seems justified, that the rate of entry of the substance into the plant is proportional to its concentration in the block at each moment, then the variation of curvature with size of block is a necessar3y consequence, and that hence an explanation of the divergent results of different investigators is found.

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