Nitrogenous compounds and nitrogen metabolism in the Liliaceae. 6. Changes in nitrogenous composition during the growth of Convallaria and Polygonatum

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Abstract
Variations occurring in the nitrogenous composition during the growth of Convallaria majalis and Polygonatum multiflorum plants were investigated. At 4 stages of growth the concentrations of total N, 75% (v/v) ethanol-soluble N and certain amino and imino acids were determined separately for roots, rhizome and shoots. The soluble-N content of both plants, but particularly that of Polygonatum, was high when expressed as a percentage of the total N. This observation is in agreement with those recorded previously for typical storage organs. The 2 plants contained very large amounts of the imino acid, azetidine-2-carboxylic acid. N present in azetidine-2-carboxylic acid represented more than 50% of the total N of Polygonatum rhizome. The imino acid was also present in high concentrations in the young shoots of both plants, but its concentration in the mature shoots was much lower. The analytical data indicate that the root may form a major site of synthesis of azetidine-2-carboxylic acid in Convallaria. It is more difficult to draw conclusions for Polygonatum since the very high concentrations present in its rhizome at all stages of growth tended to overshadow smaller changes of concentration elsewhere in the plant.