. Auxins and plant growth. Auxin; Plant growth promoting substances. OCHoCOOH MCPA The relative effectiveness of different derivatives of auxins is altered by the age of the plant. For example, it has been observed that esters and salts are essentially equally effective at the seedling stage, but as the plants become older the esters become more and more effective in comparison with the salts (Lee and Bewick, 1947). This is consonant with the generalization of Crafts (1948) that lipoidal or non-polar materials enter the plant more readily when the cuticular layers of the epidermis haye matured
. Auxins and plant growth. Auxin; Plant growth promoting substances. OCHoCOOH MCPA The relative effectiveness of different derivatives of auxins is altered by the age of the plant. For example, it has been observed that esters and salts are essentially equally effective at the seedling stage, but as the plants become older the esters become more and more effective in comparison with the salts (Lee and Bewick, 1947). This is consonant with the generalization of Crafts (1948) that lipoidal or non-polar materials enter the plant more readily when the cuticular layers of the epidermis haye matured, for these cuticular layers them- selves are primarily made up of lipoidal, non-polar materials. Comparison of different salts of auxins indicates that salts of low solubility are relatively less effective when applied to plants and con- versely that those of high solubility are more effective. Some compari- sons are shown in figure 116. Uniform quantities of the various salts. Free Ca Na NH4 Oiethanol Acid Salt Salt Salt Amine Sdt Control AUXIN DERIVATIVE Fig. 116. Relative effectiveness of various salts of 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid in inhibiting bean shoot growth. All applications were of 6 micrograms of acid equivalent per plant (Mullison, 1951).. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Leopold, A. Carl (Aldo Carl), 1919-. Berkeley, University of California Press
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