Repression of proton extrusion from intact cucumber roots and the proton transport rate of microsomal membrane vesicles of the roots due to calcium starvation

Matsumoto, H.

Plant and Cell Physiology 29(1): 79-84

1988


ISSN/ISBN: 0032-0781
Accession: 006315035

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Abstract
Proton extrusion from cucumber [Cucumis sativus] roots decreased markedly during Ca2+ starvation in the presence of KCl. Vesicles with ATP-dependent proton transport activity were prepared from the microsomal membrane fraction of control and Ca2+-starved roots. The proton transport rate of the vesicles from Ca2+-starved roots was repressed to less than half of the vesicles prepared from the control roots. K+-Mg2+-ATPase activity associated with the vesicles prepared from Ca2+ starved roots was approximately one-third of the activity associated with the vesicles prepared from Ca2+-starved roots was approximately one-third of the activity associated with those prepared from control roots. Km values of the proton transport rate and K+-ATPase for ATP were much higher in vesicles prepared from Ca2-starved roots. The repression of proton extrusion linked with K+-Mg2+ uptake in the Ca2+-starved roots could be largely caused by the reduced proton pumping activity associated with microsomal membranes in the roots.