HARDENING BY ABSCISIC-ACID OF TOBACCO PLANTLETS GROWN IN-VITRO

Tobacco plantlets were grown in vitro on Murashige and Skoog's medium with 2 % of saccharose. Addition of 0.01 mM abscisic acid (ABA) into t he medium decreased stomatal conductance of the adaxial epidermis and especially the abaxial epidermis without negative effects on growth pa rameters. As a result the rate of water loss from ABA-treated plantlet s taken out of cultivation vessels was slower than that of control pla ntlets. This could help their acclimation after transplantation to ex vitro conditions.