. The cell and protoplasm ... Cells; Protoplasm; Cytology; Cytoplasm. 154 THE CELL AND PROTOPLASM finable in chemical terms. Still, the rela- tionship between applied auxin and the re- sulting growth shows that auxin is involved in a reaction with a very high rate of com- bination between auxin and substrate, or carrier, the latter being present in a very small quantity only. This same type of reaction we encounter in enzymatic reac- tions. The substrate, or carrier, seems to be the factor which is transported under the influence of the diffusible auxin. The combination between auxin and its c
. The cell and protoplasm ... Cells; Protoplasm; Cytology; Cytoplasm. 154 THE CELL AND PROTOPLASM finable in chemical terms. Still, the rela- tionship between applied auxin and the re- sulting growth shows that auxin is involved in a reaction with a very high rate of com- bination between auxin and substrate, or carrier, the latter being present in a very small quantity only. This same type of reaction we encounter in enzymatic reac- tions. The substrate, or carrier, seems to be the factor which is transported under the influence of the diffusible auxin. The combination between auxin and its carrier is probably the process which is pH de- counterpart of the enzymatic processes, and which is able to account for all available facts. Among these I can mention the fact that although auxin application does not result in an appreciable increase in respira- tion, aerobic respiration is nevertheless es- sential for the action of auxin; and that HCN can inhibit its effect (Bonner 1933). This is understandable if the electron transfer and final oxygen disposal are part of the reaction chain in which auxin takes part; this would be expected if auxin acts as a hydrogen acceptor, and the auxin Phenomenon Cell elongation (with effect on tro germination, etc.) Bud inhibition Parthenocarpy Root initiation Eeaction involved ^ Growth reaction -. Preparatory reaction ^ > Root forming reaction' Substances active *^ ^uxin a and b Indole acetic acid Indole butyric acid ^aphthalene acetic acid Ciscinnamic acid \ Phenyl acetic acid 7 phenyl butyric acid *^ Ethylene ? TABLE I Relation between the Various Growth Phenomena, the Reactions Involved in Each Phenome- non, AND SOME of THE SUBSTANCES ABLE TO TAKE PART IN THESE REACTIONS pendent, so that at low pH a greater amount of auxin is combined. This implies that the auxin is fastened to its carrier by means of its carboxyl group. This picture is in agreement with the fact that neither the carboxyl group, nor nitriles, nor esters of growth
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