Does pollination induce corolla abscission of cyclamen flowers by promoting ethylene production?
Very low ethylene production rates were measured in nonpollinated Cyclamen persicum Mill flowers, and no change in production was observed during the whole life span of the flower until death. Normal senescence was accompanied by a gradual discoloration and loss of turgor followed by wilting. Pollination induced a dramatic increase in ethylene evolution, culminating in a peak 4 days after pollination, and abscission of the corolla on that day. Silver-thiosulfate, an inhibitor of ethylene action, had no effect on longevity of unpollinated flowers, but completely nullified the effect of pollination on corolla abscission. Exposing unpollinated flowers to very high ethylene concentrations (50 microliters per liter) for 48 hours did not promote corolla abscission or senescence. 1-Aminocyclopropane-1-carboxylic acid, the immediate precursor of ethylene, increased ethylene production by unpollinated flowers more than 100-fold, but did not promote corolla abscission. 1-Aminocyclopropane-1-carboxylic acid did enhance corolla abscission of pollinated flowers. It is concluded that the main effect of pollination in inducing corolla abscission of cyclamen is by rendering the tissue sensitive to ethylene, apart from the promotion of ethylene production.
Halevy
A H
AH
Department of Environmental Horticulture, University of California, Davis, California 95616.
Whitehead
C S
CS
Kofranek
A M
AM