Gramine Accumulation in Leaves of Barley Grown under High-Temperature Stress

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Abstract
The indole alkaloid gramine is toxic to animals and may play a defensive role in plants. Under certain conditions, shoots of barley cultivars such as `Arimar' and CI 12020 accumulate gramine (N,N-dimethyl-3-aminomethylindole) and lesser amounts of its precursors 3-aminomethylindole (AMI) and N-methyl-3-aminomethylindole (MAMI); other cultivars such as `Proctor' do not. When grown at optimal temperatures (21°C/16°C, day/night), Arimar contained a high level of gramine in the first leaf (approximately 6 milligrams per gram dry weight), but progressively less accumulated in successive leaves so that the gramine level in the shoot as a whole fell sharply with age. In Arimar and CI 12020 plants transferred at the two- to three-leaf stage from 21°C/16°C to supra-optimal temperatures (≥30°C/25°C), there was massive gramine accumulation in leaves which developed at high temperature, so that gramine level in the whole shoot remained high (about 3-8 milligrams per gram dry weight).