[On the influence of kinetin and indole acetic acid on the sprouting of the buds of Pisum sativum]

Abstract

1. The experiments of WICKSON and THIMANN (1958) concerning the effect of kinetin and IAA on the sprouting of axillary buds of Pisum were repeated with slight modifications of the test with isolated nodes. 2. Kinetin, given separately had a slightly suppressive effect on bud growth at the beginning of the experiment. However, after 3-4 days a significant promotion of growth could be recognized in some cases. Suppression of bud growth induced by IAA was only partially eliminated by kinetin, about 50% elimination being recognizable after 36 h (concentrations: kinetin 20 mg/l, IAA 2 mg/l). 3. Furthermore the effect of kinetin was tested on pea stems according to GALSTON and HAND (1949). IAA increases growth of the internodes. Given separately, kinetin (0,01 mg-20 mg/l) is again either without of or slightly suppressive effect, in combination with IAA it almost totally inhibits the promotory effect of IAA (kinetin 0,2 mg/l and 20 mg/l). 4. The effect of kinetin on the growth of coleoptiles of Avena is entirely different. Given alone it operates as a strong auxin in the cylinder test (optimal concentration 0,2 mg/l), in combination with IAA it enhances the effect of IAA. 5. "Isolated nodes" of Pisum (according to the test of WICKSON and THIMANN) treated with IAA or kinetin or a combination of both for 36 h were extracted with ether, buds and stem pieces being extracted separately. The extracts were analysed by paper chromatography with isopropanol-ammonia-water 80:5:15 and then examined with the Avena cylinder test. 6. In the controls - without addition of growth substances - stem pieces contained predominantly IAA, whereas buds showed an extensive suppressor zone above Rf 0.75. 7. The chromatograms were not altered markedly by treatment of the test objects with IAA. 8. In all series with kinetin treatment buds and stems without exception contained an auxin with an Rf of 0,63. This value corresponds to that of kinetin. On addition of an optimal amount of kinetin to the buffer solution of the cylinder test this auxin disappeared totally. Therefore it must be either identical with or closely related to kinetin. This substance, which also accumulates in Pisum buds, must be at least to some extent transportable in the plant. 9. Neither the suppression of bud growth by IAA in the pea nor the elimination of this suppression by kinetin could be accounted for by appearance or disappearance of the observed auxins or suppressors. 10. As far as the experiments with isolated pea nodes are concerned, the explanation given by WICKSON and THIMANN involving an antagonism between IAA and kinetin or some substance similar to kinetin is probably correct. However, the general validity of such an explanation for correlative suppression seems questionable.