The permeability of ammonia methylamine and ethylamine in the charophyte chara corallina chara australis

Ritchie, R.J.

Journal of Experimental Botany 38(186): 67-76


ISSN/ISBN: 0022-0957
Accession: 006733301

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The permeabilities of the amines, ammonia (NH3), methylamine (CH3NH2) and ethylamine (CH3CH2NH2) in the giant-celled charophyte Chara corallina (C. australis) R.Br. have been measured and compared. The permeabilities were corrected for uptake fluxes of the amine cations. Based on net uptake rates, the permeability of ammonia was 6.4 .+-. 0.93 .mu.m s-1 (n = 38). The permeabilities of methylamine and ethylamine were measured in net and exchange flux experiments. The permeabilities of methylamine were not significantly different in net and exchange experiments, nor to that of ammonia (Pmethylamine = 6.0 .+-. 0.49 .mu.m s-1 (n = 44). In net flux experiments the apparent permeability of ethylamine was slightly greater than that of ammonia and methylamine (Pethylamine, net = 8.4 .+-. 1.2 .mu.m s-1 (n = 40)) but the permeabiity of ethylamine based on exchange flux data was significantly higher (Pethylamine, exchange = 14 .+-. 1.2 .mu.m s-1 (n = 20)). Methylamine can be validly used as an ammonium analogue in permeability studies in Chara. The plasmalemma of Chara has acid and alkaline bands; little diffusion of uncharged amines would occur across the acid bands. The actual permeability of amines across the alkaline bands is probably about twice the values quoted above on a whole cell basis i.e. the permeability of ammonia across the permeable part of the plasmalemma is probably about 12 .mu.m s-1.