REGULATION OF THE RIPENING OF TOMATO PERICARP DISKS BY GA(3) AND DIVALENT-CATIONS

We have used a tomato (Lycopersicon esculentum Mill.) pericarp disc sy stem to study the inhibition of ripening caused by diazocyclopentadien e (DACP), gibberellic acid (GA(3)) and calcium (CaCl2), and to compare their modes of action. Treatment of discs with 1-aminocyclopropane ca rboxylic acid (ACC) accelerated their ripening while DACP treatment el iminated ripening in the absence or presence of a treatment with the e thylene precursor. Both GA(3) and calcium retarded color development a nd tissue softening. Calcium delayed the onset of the climacteric rise in respiration and ethylene evolution, but GA(3) had no consistent ef fect in this respect. The different modes of action of the two inhibit ors were emphasized by the synergistic effect on inhibition of ripenin g obtained when both were simultaneously applied. Inhibition of color development and softening was also achieved by applying other divalent cations such as strontium and barium. However, no such effect was obs erved with manganese or with the monovalent cations potassium and sodi um. We concluded that calcium inhibition of ripening is not specific a nd is not necessarily mediated by the calcium calmodulin complex.