. Auxins and plant growth. Auxin; Plant growth promoting substances. Physiological and Anatomical Effects 1 15 per cent and this stimulation continued for at least 5 successive inter- nodes. Tests of auxin activity of these extracts were not made with any standard assay procedures. There appears the inviting possibility that the hormones extracted were stabilized against normal auxin- destroying systems in the plant and hence could continue their stimu- lative effects over a long period of time. Another overall stimulation of growth by auxin applications to intact plants has been achieved by m
. Auxins and plant growth. Auxin; Plant growth promoting substances. Physiological and Anatomical Effects 1 15 per cent and this stimulation continued for at least 5 successive inter- nodes. Tests of auxin activity of these extracts were not made with any standard assay procedures. There appears the inviting possibility that the hormones extracted were stabilized against normal auxin- destroying systems in the plant and hence could continue their stimu- lative effects over a long period of time. Another overall stimulation of growth by auxin applications to intact plants has been achieved by means of the short-time application of auxins to seeds. Experiments in which seeds are germinated in auxin solutions and permitted to remain in them nearly always re-. 100 mg/l CONC. OF AUXIN Fig. 52. Effects of the soaking of oat seeds with various concentrations of indole- acetic acid on later growth. The data on root length taken after six days; the dry weight and height after maturity (from Thimann and Lane, ). suit in gross inhibitions of growth and development. However, short- time treatments of seeds in auxin solution have frequently given very considerable gains in subsequent growth rate of both shoots and roots. A graphic case is the report of Thimann and Lane (1938). They soaked oat seeds for 24 hours in indoleacetic acid solutions, and ob- tained 30 to 60 per cent increases in subsequent root length, plant height and final plant weight (figure 52). The auxin treatments of seeds yielded earlier and more abundant flowering. The possibility of using this type of treatment to obtain greater growth in crop plants has led to many attempts of this sort. However, it seems that gains in. 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 Califor
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