. Auxins and plant growth. Auxin; Plant growth promoting substances. Extraction and Measurement Techniques 37 Reading Measure after 24 hours when approximately 90 per cent of growth has usually occurred, or at 48 hours when growth is essentially finished. Again, if growth rate is to be studied, readings will have to be made 6 hours after the test is started, for the rate begins to decline after that length of time (Christiansen and Thimann, 1950). As in the previous tests, results are expressed as the mean per treatment plus or minus the standard error. In general where serial dilutions are us
. Auxins and plant growth. Auxin; Plant growth promoting substances. Extraction and Measurement Techniques 37 Reading Measure after 24 hours when approximately 90 per cent of growth has usually occurred, or at 48 hours when growth is essentially finished. Again, if growth rate is to be studied, readings will have to be made 6 hours after the test is started, for the rate begins to decline after that length of time (Christiansen and Thimann, 1950). As in the previous tests, results are expressed as the mean per treatment plus or minus the standard error. In general where serial dilutions are used and a smooth curve is obtained repeatedly, the standard error may be considered to be 10 MG/L CONC. OF AUXIN Fig. 18. Results of an Avena straight-growth test and a pea straight-growth test showing the approximate semi-logarithmic proportionality of growth to the concen- tration of the auxin, indoleacetic acid (Thimann and Schneider, 1939). The growth obtained is approximately proportional to the log- arithm of the concentration of auxin applied. In both the Avena and the pea straight-growth tests the minimum amount of growtli regulator detectable is approximately of indoleacetic acid. Maximum growth is obtained at approximately 10 of indoleacetic acid. Sample curves for each test are shown in figure 18. Since straight-growth tests are not dependent as is the Avena test upon polar transport of auxins, they can be used to test the growth. 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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