Changes in Photosynthetic Pigments Content in Non-Transformed and AtCKX Transgenic Centaury (Centaurium erythraea Rafn) Shoots Grown under Salt Stress In Vitro

Abstract

The effects of graded sodium chloride (NaCl) concentrations (0-, 50-, 100-, 150-, and 200-mM) on photosynthetic pigment contents in in vitro grown shoots of important medicinal plant species (Centaurium erythraea Rafn) were investigated. Non-transformed, one AtCKX1 and two AtCKX2 transgenic centaury lines, with altered cytokinin profiles, were used in this study. The chlorophyll (Chl) and carotenoid contents differed in the non-transformed and transgenic lines. In general, salinity significantly reduced the Chl a and Chl b contents in comparison to the NaCl-free medium. The lowest Chl content was observed in AtCKX2 transgenic shoots grown on all the culture media. The total carotenoid content was increased in shoots of non-transformed and both AtCKX2 transgenic lines grown in 50-mM NaCl. On the other hand, in concentrations >50-mM NaCl, the total carotenoid content was decreased in all analysed centaury shoots. The Chl a/Chl b ratio in all the shoots increased progressively in the graded NaCl concentrations. Contrarily, the addition of NaCl in the culture medium reduced the Chl/carotenoid ratio in centaury shoots. Taken together, the results of this study partly explained the mode of centaury plant adaptations to salt stress in vitro. Thus, the results on centaury shoots confirmed that the determination of the photosynthetic pigment contents can be a very useful non-destructive screening method in order to discriminate susceptible and resistant plant species/lines to salt stress conditions.