Abstract:

Cucumber（Cucumis sativus L.）was used to understand the effects of ethylene（ETH）and nitric oxide（NO）on rooting of plant explants. The results showed that the effects of ETH on adventitious rooting in cucumber explants were dose-dependent，and 0.5 μmol · L^-1 ethrel treatment was the most effective concentration to promote the adventitious rooting. The root number and root length of explants treated with ETH and NO was significantly higher than that of explants treated with ETH or NO alone. But the positive effect of ETH could be reversed by NO scavenger 2-（4-carboxy-2-phenyl）-4,4,5,5- tetramethylimidazoline-1-oxyl-3-oxide（c-PTIO），nitric oxide synthase（NOS）inhibitor N-nitro- L-arginine methyl ester（L-NAME）or nitrate reductase（NR）inhibitor NaN₃，indicating that there might exist synergistic action between ETH and NO on mediating cucumber adventitious rooting. ETH treatments enhanced endogenous NO levels in explants. Meanwhile，the exposure of cucumber explants to ETH up-regulated NOS and NR activity and their gene relative expression. Together，these results indicate that NO may play crucial roles in the adventitious root development induced by ETH.

Key words: cucumber, ethylene, nitric oxide, adventitious root