. Auxins and plant growth. Auxin; Plant growth promoting substances. Physiological and Anatomical Effects 121 longiflorum var. eximium Nichols) responds chiefly by proliferation of the epidermis (Beal, 1938). Leaf Effects The most common immediately observable response to auxins applied to foliage of plants is the development of epinasty; that is, the downward curling and bending of leaves occasioned by swelling of cells, particularly those on the dorsal sides of veins. In some cases the leaves bend upward, which is known as hyponasty. Figure 51. Fig. 54. Epiiiastic responses of tomato induced
. Auxins and plant growth. Auxin; Plant growth promoting substances. Physiological and Anatomical Effects 121 longiflorum var. eximium Nichols) responds chiefly by proliferation of the epidermis (Beal, 1938). Leaf Effects The most common immediately observable response to auxins applied to foliage of plants is the development of epinasty; that is, the downward curling and bending of leaves occasioned by swelling of cells, particularly those on the dorsal sides of veins. In some cases the leaves bend upward, which is known as hyponasty. Figure 51. Fig. 54. Epiiiastic responses of tomato induced by naphthaleneacetic acid; left, untreated control, center, NAA sprayed upon the foliage, and right, NAA solution injected in stem (Zimmerman and Wilcoxon, 1935). shows some typical epinastic cinling and epinastic distorticjn of leaf outline in tomatoes sprayed with 2,4-D. Epinasty is not strictly an auxin function, for many poisons which inhibit cell enlargement can also cause epinastic responses. These are discussed in more detail in chapter VII. As in the case of stems, leaves too will differ in their responses from species to species and will also differ with the growth regulator used. For example, 4-chlorophenoxyacetic acid produces extensive epinasty in tobacco and Kalanchoe leaves, whereas 2-chlorophenoxya- cetic acid produces relatively little or none. Yet these two auxins. 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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