Relationships of Certain Nutrients, Metabolites, and Inhibitors to Growth in the Avena Coleoptile

Abstract

The effects of various Na and K salts upon growth of Avena coleoptile sections were investigated. In media at pH 6. 5 K salts of organic or inorganic acids resulted in increased growth. Na salts of the same acids produced little or no growth response at this reaction. Responses to K salts were accentuated in the presence of Mn. In the presence of inhibitory concns. of iodoacetate at pH 6. 5, K salts of malate, malonate or phosphate resulted in increased growth. Smaller responses to the corresponding Na salts in the presence of iodoacetate were attributed to decreased penetration of inhibitor when the media were buffered. At pH 5. 0 in media containing K and Mn, iodoacetate inhibition was alleviated or prevented by the Na salt of any of a number of intermediates. Growth was increased by. 005 [image] succinate at pH 4. 5-5. 0, but not at pH 6. 0-6. 5. Severe inhibition was caused by. 003 [image] malonate at pH 4. 5-5. 0, but not at higher pH values. When supplied concurrently with malonate, each of the following prevented or lessened inhibition: fructose, fructose-6-phosphate, phosphoglycerate, pyruvate, succinate, l-malate, citrate and fumarate. Sections placed in malonate until growth had nearly ceased were induced to resume growth by subsequent addition of succinate or fumarate, but little or no reversal resulted from fructose or pyruvate. Where fructose and succinate were both added to malonate-inhibited sections, growth resumed and exceeded growth of sections in which inhibition had been reversed by succinate alone.