Most of the literature suggest use of organic solvents and acids (HCL and nitric acid) to remove the leaf epicuticular wax. Therefore it impose high stress to the tissues. But your objective is to perform ROS experiments which is in general very sensitive to stress (ROS results largely change). I assume its bit challenging. What is the motive to remove leaf epicuticular wax to Lettuce? is it tissue permiability problem?

Thank you for your answer! We suspect that the wax layer of the lettuce is inhibiting full contact of the leaf discs to the aqueous mix of buffer and pattern (we use flagellin). We are trying to eliminate this variable in hopes of more consistent results.

You can soak the leaves in 2% solution of a surface active agent ( surfactants) ,there are several types such as SDS ,cetrimid,CTAB,..or others