PROMOTION OF PETUNIA (PETUNIA-HYBRIDA L) REGENERATION INVITRO BY ETHYLENE

The influence of ethylene on shoot and root formation from petunia leaf explants was studied in cultures in test tubes placed in 51 glass jars. Reduction of the endogenously produced ethylene by inclusion of ethysorb (KMnO4), an ethylene absorbent, caused a decrease of the number of shoots. On the other hand, supplementing the cultures with ethylene (0.01-10 ppm) caused a marked increase of the number of shoots without, however, any effect on the length and fresh weight. Ethylene treatments (1 ppm) were found to be most effective when they were applied in the second week of culturing of petunia explants. Addition of Co++ to the medium resulted in a reduction of the endogenously produced ethylene and concomitantly reduced shoot formation. Similarly, inclusion of Ag+, an inhibitor of ethylene action, resulted in poor shoot formation. Ethylene also appeared to play a role on rooting of petunia microshoots in vitro in an auxin-tree medium. Ethylene at a concentration of 10 ppm induced adventitious root formation considerably, whereas at low levels (0.01-1 ppm) it had no influence on rooting.