Regulation of sucrose efflux from soybean leaf discs.
Plant Physiol
; 83(1): 143-8, 1987 Jan.
Article
en En
| MEDLINE
| ID: mdl-16665190
ABSTRACT
Net sucrose efflux from discs of fully expanded leaves of soybean (Glycine max [L.] Merr.) plants was studied to characterize sucrose efflux into the apoplast. Net sucrose efflux had a Q(10) of 2.3, was linear for at least 3.5 hours, and was selective for sucrose over glucose. Sulfhydryl group inhibitors reduced sucrose efflux by up to 80%. There was a biphasic promotion of sucrose efflux by KCl with an apparent saturable component up to about 20 millimolar, above which the effect was linear. Sucrose efflux was promoted by NaCl as a linear function of concentration. Monovalent cation ionophores did not affect sucrose efflux, regardless of external KCl concentration. Light in the absence of added HCO(3)-increased sucrose efflux by about 20%. Sucrose efflux was promoted by increasing pH from 4 to about 8, above which no additional effect was observed. When leaf discs were bathed at pH 6.0, the protonophore carbonyl cyanide m-chlorophenylhydrazone (CCCP) increased sucrose efflux by about 25%. CCCP in the presence of valinomycin had the same effect as CCCP alone. Inhibition of plasmalemma ATPase activity with N,N'-dicyclohexylcarbodiimide, diethylstilbestrol, or orthovanadate increased sucrose efflux. These data indicate that sucrose efflux from soybean leaf discs is not a result of simple leakage but is a regulated process.
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MEDLINE
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En
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Plant Physiol
Año:
1987
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Article