Agmatine Metabolism and Hordatine Formation in Barley Seedlings

In the shoots of dark-grown barley seedlings coumaroylagmatine concentration reaches a peak 3 d after germination; however, none could be detected 5 d after germination. Concentrations of hordatines A, B and M show maxima 6 d after germination and the concentrations decline to less than 50 per cent of the maximum by the 11th d. Putrescine, agmatine and spermidine peak respectively 3,4 and 8 d after germination. Putrescine concentration declines rapidly between the 8th and 9th d after germination. Agmatine coumaroyl transferase (ACT) activity is greatest 3–4 d after germination and activity is undetectable 5 d from germination. In the shoots of barley seedlings grown under diurnal illumination, hordatine M reached a peak 7 d after germination but no distinct peaks could be found for hordatines A and B or coumaroylagmatine.