Effect of Ethylene on Sucrose Uptake in Root Discs of Sugar Beet

Exogenously-added ethylene stimulated active sucrose uptake in root discs of sugar beet (Beta vulgaris L.) in a log dose-linear response manner. The ethylene precursor, 1-aminocyclopropane-1-carboxylic acid (ACC) stimulated both endogenous ethylene production and sucrose uptake. Conversely, an inhibitor of ACC synthesis, aminoethoxyvinylglycine (AVG) inhibited both endogenous ethylene production and sucrose uptake. Exogenously-added ethylene can overcome the AVG effect on sucrose uptake. Root tissue from freshly-harvested sugar beet plants contain gas-phase ethylene levels slightly below that required to stimulate active sucrose uptake. No differences were found in gas-phase ethylene levels in the root tissue of sugar beet cultivars having different concentrations of sucrose. The root tissue has an inherent capacity to synthesize ACC and ethylene at high rates. Like ethylene, propylene can stimulate active sucrose uptake in beet root discs, but it is not detected in the gas phase of the tissue. Acetylene, propane, and ethane had no effect on sucrose uptake. Exogenously-added IAA and ABA each make ethylenesensitive tissue insensitive to ethylene stimulation of sucrose uptake. Other plant hormones have no apparent effect on the ethylene response. The role that ethylene may play on sucrose uptake in root tissue of sugar beet is discussed.