Metabolism of [14C]-monoethanolamine in Hordeum vulgare

The metabolism of 14C-monoethanolamine (EA) and its hydrochloride was investigated in long term experiments with intact plants of spring barley (Hordeum vlugare L.) during ontogenesis. The metabolism of EA applied as the free base (0.67 mg per plant) to an unwounded part of the fifth leaf of the main shoot proceeds relatively quickly. To a great extent, the EA taken up and translocated out of the feeding leaf was converted to volatile compounds during ontogenesis. The remaining amounts are incorporated into lipid soluble substances or metabolized via choline to glycine betaine. Wilting barley plants show a higher capacity for converting exogenous EA via the betaine pathway. However, there is no proportionality between 14C-betaine synthesis from 14C-EA and betaine accumulation. There are remarkable differences between EA and its hydrochloride with respect to metabolism. The hydrochloride is not converted to volatile compounds and glycine betaine is the main metabolite. The betaine pathway is only of minor importance for the metabolism of exogenous EA in turgid barley plants. The hydrochloride is also not completely metabolized in this way. Possible consequences are discussed. (author)