. Auxins and plant growth. Auxin; Plant growth promoting substances. Extraction and Measurement Techniques 33 Stem-reference reading If it is desired to extend the readings to the lowest ranges of auxin concen- trations, the negative curvatures may be read in addition to the conventional posi- tive curvature readings (Thimann and Schneider, 1938). To do this, place the cut stem so that the intact base is vertical on the protractor and measure the negative curvature of each arm, viz., the angle formed between (c) the vertical axis of the intact base, and (d) the tangent at the point where curva
. Auxins and plant growth. Auxin; Plant growth promoting substances. Extraction and Measurement Techniques 33 Stem-reference reading If it is desired to extend the readings to the lowest ranges of auxin concen- trations, the negative curvatures may be read in addition to the conventional posi- tive curvature readings (Thimann and Schneider, 1938). To do this, place the cut stem so that the intact base is vertical on the protractor and measure the negative curvature of each arm, viz., the angle formed between (c) the vertical axis of the intact base, and (d) the tangent at the point where curvature ceases ( the apical tip) as shown in figure 15 C. The results are expressed as the mean plus or minus the standard error. Although in the Avena test the curvature obtained is proportional to the concentration of auxin, in the slit pea test cmvature is more nearly proportional to the log of the concentration. Although the sensitivity to low concentrations of auxin is much less in the slit pea than in the Avena test the range of auxin activity which can be tested. -200 10 100 MG/L CONC. OF AUXIN Fig. 16. Sample results of slit pea tests showing the relationship between curva- ture obtained and the concentration of three auxins; lAA: indoleacetic acid; NAA: naphthaleneacetic acid; and IBA: indolebutyric acid (Thimann and Schneider, 1939).. 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
Size: 1524px × 1639px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookpublisherberkeleyuniversityofcaliforniapre
