[Inhibition of flowering in Lemna gibba by ammonium ions]

Ammonium ions completely inhibit the flowering of Lemna gibba G1 and G3 without a simultaneous effect on the growth and multiplication of fronds. A concentration of 10(-4) M NH 4 (+) is effective in strain G3.The NH 4 (+) -inhibition of flowering is reversed by ATP and, more effectively, by ADP.With reference to recent literature the opinion is confirmed that ammonium ions cause a decrease of the ATP available in relation to the level of NAD(P)H and as a consequence flowering is inhibited. Possible primary actions of ammonium ions are the uncoupling of photophosphorylation, the repression of nitrate- and nitrite-reductase and the increase of NH 4 (+) -detoxication processes.