Regulation of nitrate reductase in cultured tobacco cells

The Components of Plant Tissue Culture Media I: Macro- and Micro-Nutrients

Summary
Twenty-one L-amino acids and the amides L-glutamine and L-asparagine have been tested for their effects on the growth of excised tomato roots, by adding them singly to a medium of pH 4.8 containing the standard amount of nitrate. L- and D-cystine were growth-stimulatory. The amides, L-aspartic acid and L-arginine, did not significantly affect growth in concentrations up to 25 mg/1. The other amino acids were, to very differing extents, inhibitory to growth. The inhibitory activity of certain amino acids was greater at pH 6.8 than at 4.8. At this pH low concentrations of L-arginine enhanced growth. The L- and D- forms of the amino acids differed in their inhibitory activity.

With the exception of L-glutamine and, to a lesser extent, of L-asparagine and the natural forms of the dicarboxylic amino acids, all the amino acids tested as sole nitrogen sources for root growth were completely ineffective at both pH 4.8 and 6.8. This applied also to the ‘balanced’ mixtures of amino acids which had only low inhibitory activity when added to a nitrate-containing medium.

“Bacto’ casamino acids (an acid-hydrolysed casein) was more effective than ammonium as a nitrogen source over the range pH 4.8 to 7.0, but was only as effective as nitrate at pH values close to neutrality.

At pH values of 5.3 or above, the growth of excised tomato roots on ammonium was markedly stimulated by the addition of amino-acid mixtures whose composition was based upon amino-acid analyses of hydrolysed casein. A mixture of the basic amino acids only was almost as effective as more complex mixtures. At pH 6.8 ammonium plus a suitable amino-acid mixture supported growth equal to that with the casamino acids. The very poor growth of excised tomato roots supplied with ammonium at pH 4.8 was, however, not significantly enhanced by the amino-acid additions which were markedly stimulatory at higher pH values, and was inferior to growth with casamino acids at this pH. A high level of root growth cannot yet be achieved at pH 4.8 in the absence of nitrate.

https://nph.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-8137.1959.tb05345.x

Studies on the growth of excised roots

https://mmbr.asm.org/content/mmbr/43/1/42.full.pdf

Growth inhibition as a consequence of antagonism between related amino acids: effect of valine in Escherichia coli K-12.

Introduction .................................................................................................................................................................. 513 Developments in Excised Root Culture Technique ...................................................... 514Inorganic Nutrition ............................................................................................................................................. 518 Nitrogen Metabolism .......................................................................................................................................... 521 Carbohydrate Uptake and Metabolism ....................................................................................... 528 The B Vitamins ...................................................................................................................................................... 533 Release of Metabolites .................................................................................................................................... 533 Growth-Regulating Substances ............................................................................................................... 536 Differentiation ............................................................................................................................................................ 542 General Discussion ............................................................................................................................................. 547 Literature Cited ........................................................................ : ............................................................................ 574

Excised root culture

Brown (I906) has described the results of an early investigation on the ability of mature, isolated cereal embryos to utilize organic forms of nitrogen. He reported that ammonium sulphate, aspartic acid, glutamic acid, potassium nitrate and asparagine, at concentrations supplying equivalent quantities of nitrogen, showed progressive increases in their capacity to increase the dry weight and nitrogen content of barley embryos cultured for a period of one week. Out of these nitrogen sources only asparagine produced an increase in the growth in length of the roots, while all, with the possible exception of ammonium sulphate, produced an increase in the length attained by the shoot system. Phenylalanine, tyrosine and leucine were distinctly inhibitory to growth. So far as the author is aware, there have been no other recent reports of comparable studies on the ability of isolated cereal embryos to utilize organic forms of nitrogen for growth. The purpose of the present investigation was to assess the value of amino acids as sources of nitrogen for the growth of mature oat embryos isolated from their endosperm. Particular attention has been given to interactions occurring between amino acids in their effects on the growth of the embryos. A note on some of the experiments described has appeared elsewhere (Harris, I953a).

https://nph.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-8137.1956.tb05284.x

G. P. Harris

Papers

Amino acids as sources of nitrogen for the growth of isolated oat embryos