METABOLISM OF ETIOLATED SEEDLINGS AS AFFECTED BY AMMONIUM NUTRITION

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Abstract
Seedlings were grown in complete nutrient solutions with and without (NH4)2SO4 as a source of N at pH 6.4 and in a dark room at 23-25[degree] C. for 9-22 days. Cucurbita pepo showed a very high increase in ammonia N but a considerable increase in amino, amide, and protein N. The reducing sugars decreased considerably due to utilization in the production of these forms of soluble N. The oily reserve of the seeds was little reduced after 19 days. The writer reports ammonium injury to the seedlings in 19 days. In Phaseolus vulgaris there was produced some increase in protein, amino and amide N. The ammonia N was doubled and the reducing sugars remained high for 10 days. After 22 days in the dark the ammonia N had accumulated to a very large amount, the sugar reserves had been depleted. Amides were not formed as a result of ammonia accumulation. At the 17th day the Lwpinus albus seedlings showed flaccidity of the region near the lower part of the hypocotyl although the roots were uninjured. Amide and ammonia N had increased and reducing sugars and starch showed a marked decrease. In Luvinus luteus after 9 days the ammonia N had increased greatly but there was little or no change in amino and amide N. The greatest absorption and utilization (absolute basis) of ammonia N occurred in the seedlings of C. pepo, with the least in those of P. vulgaris and L. luteus. Seedlings of Lupinus luteus practically utilized no ammonia N. The efficiency of utilization was highest in P. vulgaris. Thus the absorption and utilization were dependent upon the type and amount of non-nitrogenous reserves and varied with the stage of growth. The resistance of seedlings to ammonium injury was governed by the type and amount of non-nitrogenous reserves in the seed. Accumulation of ammonia and low concentrations of reducing sugars were associated with ammonium injury.

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