. The chemistry and mode of action of plant growth substances; proceedings of a symposium held at Wye College, University of London, July 1955. Plant regulators; Auxin; Growth (Plants). Para-substitution in regulators with phenyl nuclei class, though both the initial inhibition and the final stimulation are comparatively slight. The very strong difference in the inhibiting activities of 2-naphthoxyacetic acid (2-NOA) upon flax and wheat roots {Figure 1) is paralleled by a similar shift in the anti-auxin direction for several other 2-naphthoxy deriva- tives. It seems probable that here we meet
. The chemistry and mode of action of plant growth substances; proceedings of a symposium held at Wye College, University of London, July 1955. Plant regulators; Auxin; Growth (Plants). Para-substitution in regulators with phenyl nuclei class, though both the initial inhibition and the final stimulation are comparatively slight. The very strong difference in the inhibiting activities of 2-naphthoxyacetic acid (2-NOA) upon flax and wheat roots {Figure 1) is paralleled by a similar shift in the anti-auxin direction for several other 2-naphthoxy deriva- tives. It seems probable that here we meet with a case of species difference in the auxin system. For wheat roots and Avena coleoptiles, however, the sensitivity might be of the same type, the action curves indicating at first an 'anti-auxin component' of the activity which is, at higher concentrations, superseded by the auxin effects. It is highly interesting to find that 10~^ M 2-NOA has a conspicuous restoration effect upon wheat roots inhibited by SxlO^'^M I-naphthylacetic acid (Burstrom, 1955).. Mofar concn. ââ¢â Figure 1. Theej]ectsof-\-n:ethylphenoxyaceticacid{-\-MePOA) and 2-naphthoxyacetk acid {2-NOA) upon the growth of fax roots (F), cress roots (C), wheat roots (W), and Avena coleoptile cylinders (A). Growth (G) in per cent of control, plotted against a logarithmic concentration scale. N is the number of independent experiments represented by the points. Further data, especially on the interaction of 2-NOA with other growth regulators in the growth of coleoptile cylinders, might be necessary for the final elucidation of these 'anti-auxin' effects (action II according to Burstrom, 1955). The quantitative treatment of the auxin-anti-auxin interactions can only be made in a tentative way at present, but analogies from simple model systems are certainly very useful in making more precise hypotheses as to the mechanisms vmderlying the growth results. It seems reasonable to start from the general laws governing
Size: 1744px × 1432px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookcollectionbiodiver, booksubjectgrowthplants
