| Abstract: | Bean plants (Phaseolus vulgaris L. cv. Fardenlosa Shiny) werelabelled with carbon-11 via their first trifoliate leaves when3-weeks-old and the transient inhibitions of translocation causedby the application of ammonium chloride solutions (10 mol m–3)to a peeled region of stem were studied. At pH 6·5 theammonium was without effect. At pH 11·0 even a briefapplication inhibited translocation for many minutes, whilelonger applications inhibited translocation for considerablylonger. Solutions of 10 mol m–3 sodium chloride were withouteffect at either pH. At pH 6·5 ammonium chloride solution contains predominantlyammonium ions (NH4+) and at pH 11·0 predominantly dissolvedammonia gas (NH3). Hence we conclude that phloem transport withinbean stems is inhibited by dissolved ammonia gas but not ammoniumions. Key words: Phloem translocation, transient inhibition, ammonia, ammonium ion |
