Histological Reactions of Bean Plants to Certain of the Substituted Phenoxy Compounds

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Abstract
Four substituted phenoxy compounds were applied at the bases of the nearly full-sized heart-shaped leaves of the bean at 0.5% cone, using both Carbowax 1500 and lanolin as carriers. Gross responses were similar to those formerly obtained from 1% cones. Histological studies showed marked differences in responses between the 2d internode and the 1st internode and hypocotyl. The 2d internode showed little or no histological response to 2-chlorophenoxyacetic acid, but became much smaller and failed to elongate in a large % of the plants following treatment with 4 chlorophenoxyacetic, 2,4-di-, and 2,4,5-trichlorophenoxyacetic acids. With the exception of the epidermis, possibly the pericycle, and limited portions of the outer cortex, all the other tissues ot this internode responded actively, but no adventitious roots developed. The histological responses in the first internode and hypocotyl were strikingly similar from all 4 compounds, but[long dash]in contrast tc the 2d internode[long dash]only the endodermis, cambium, phloem, and ray parenchyma were activated. Roots developed in abundance.