Response of Olea europaea ssp. maderensis in vitro shoots exposed to osmotic stress

Abstract

Olea europaea ssp. maderensis shoots (2.5 cm) were grown for 2 months on Driver and Kuniyuki medium (DKW) supplemented with 4.4 μM benzyladenine (BA) and 0.4 μM indole-3-butyric acid (IBA). Osmotic stress was induced for 1 month in shoots by the addition of sorbitol (0.1 and 0.2 M) to DKW. Moderate stress (0.1 M) did not affect shoot growth, and induced osmotic adjustment by increasing K content without water lost. Also no decrease in chlorophyll fluorescence was detected although chlorophyll content decreased. However, at 0.2 M sorbitol (a more severe stress) growth was reduced. This sorbitol concentration increased tissue osmolality and lipid peroxidation, but decreased water and soluble protein contents. It also decreased chlorophyll content and chlorophyll fluorescence, by increasing basal fluorescence ( F o) and decreasing maximal fluorescence ( F m) values. Both sorbitol concentrations decreased Mg and Zn contents while 0.2 M decreased K and Cu contents in shoots. Rooting was reduced by moderate stress (0.1 M) and completely inhibited by 0.2 M sorbitol.