Uptake, auxin dependence

Thus, cell enlargement, for instance, depends upon auxin and involves the uptake of water, extension of the cell membrane and protein synthesis. The auxin dose-response curve consists of two peirts promotion by low concentrations and inhibition by higher concentrations via the formation of ethylene. Cytokinins and abscisic acid may possibly induce also, under special conditions, the production of ethylene. Many publications deal with effects of these plant hormones, especially of auxin, on ethylene biosynthesis in plants which occurs after a lag phase of 30 - 60 minutes and is specifically blocked by rhizobitoxin as well as by inhibitors of ENA and protein synthesis indicating that a continuous synthesis of protein is required for high rate of ethylene production (Eef. 20). 

The influence of plant hormones on endogenous levels of other hormones is indicative of the complexity of hormone interaction in the regulation of plant growth and development. When one applies auxin to plant tissue in vivo or in vitro, the interpretation of the effects should take into aceount the evidence that the uptake, metabolism, range of secondary effects and magnitude of direct effects of the hormone are dependent on the presence of other hormones. Furthermore, each of these factors may be modified by a variety of environmental... 

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