Morphometric Analysis of Limonium Salt Glands in Relation to Ion Efflux

Faraday, C. D. and Thomson, W. W. 1986. Morphometric analysisof Limonium salt glands in relation to ion efflux.—J exp.Bot. 37: 471–481. Surface areas and volumes of compartments within rapidly secretingand slowly secreting Limonium perezii salt glands were determinedto be similar. Molecular and volume efiluxes of secreted saltsolutions were calculated by the application of secretion ratesto plasmalemma surface areas. If ion efflux from the glandswas a transmembrane phenomenon, fluxes of 1?04?l0^–5 equivalentsm^–2 s^–1 would have been necessary to match secretionrates. These fluxes were a thousand times higher than fluxesestimated for most plant cells. Correlated with these high membranefluxes was the fact that mitochondria occupied 10% of the protoplastvolume. Thirty-two percent of the plasmalemma available forefflux was associated with wall protuberances. Wall protuberancesamplified the plasmalemma surface area by a factor of 1?6. Key words: Salt glands, ultrastructure, ion fluxes