INTERACTION BETWEEN METHYL ESTER OF JASMONIC ACID AND BENZYLADENINE DURING THE GROWTH OF EXCISED GREENING COTYLEDONS OF Cucurbita pepo L. (zucchini)

Treatment of excised marrow cotyledons (Cucurbita pepo L. (zucchini) growing under photoperiod with methyl ester of jasmonic acid (MeJA) resulted in a decrease of their fresh weight. This effect did not depend on the exogenously applied MeJA concentrations. Furthermore, in vivo labelling experiments showed an inhibition of the total protein synthesis. On the other hand, specific quantitative changes were observed in the spectrum of soluble proteins resulting in the formation of abundant jasmonate-induced proteins (JIPs). Benzyladenine (BA) applied together with MeJA neutralized the jasmonate action on the growth of the excised cotyledons, as well as on the in vivo protein synthesis. Similar antagonistic interaction between BA and MeJA was observed on the formation of JIPs both when the substances were applied together and in the case of subsequent treatment of cotyledons. The antagonism observed between the two plant growth regulators during the growth and development of excised greening cotyledons can be considered as one possible mechanism in the maintenance of plant cell homeostasis under stress conditions in the earlier stages of germination.