Abstract
In the previous paper on the growth of etiolated pea epicotyl, section it has been shown that the effect of gibberellin (GIB) is markedly dependent on the endogenous growth of the section. Since GIB is inactive in Avena curvature test, it is felt desirable to obtain the evidence as to whether or not GIB promotes the growth of coleoptile sections. This paper, therefore, reports the experiments with influence of GIB, comparing with that of indoleacetic acid (IAA), on the coleoptile sections isolated from wheat and oat.
GIB had no effect in promoting the growth of wheat coleoptile sections under any experi-mental conditions as in Tables 1_??_3 and Fig. 1.
GIB was, however, found to be slightly active in increasing the growth of the upper sec-tions of oat coleoptile, when these were cut from about 2.5cm. long plants of age 60 hours or less, but inactive in the other parts of the coleoptile as well as in the sections from the older plants (Table 4, Fig. 2). The effect of the optimal concentration of GIB is of the same order of magnitude as that of the lower concentration of IAA (0.02γ_??_0.05γ/cc.).
In Avena curvature test GIB is inactive, because the upper part of the coleoptile, GIB is effective, has been removed in carrying out this test.
Wheat coleoptiles are about ten times lower than oat in sensitivity to IAA, as measured by straight growth. This will be a tentative explanation for the reason why GIB has no effect on the straight growth of wheat coleoptile sections.
