Changes in wheat plastid membrane properties induced by cadmium and selenium in presence/absence of 2,4-dichlorophenoxyacetic acid

The aim of the work was to recognize the effect of cadmium (Cd) and selenium (Se) onto properties of plastid lipid membranes. Plastids were isolated from wheat calli cultured during 2 weeks on Murashige-Skoog media with presence/absence of 2,4-dichlorophenoxyacetic acid. Plastids obtained in presence of 2,4-D represented an earlier developmental stage in comparison to those, got in absence of 2,4-D, which reached a pre-chloroplast stage. The studied metals were introduced to culture media separately (2 mu M Na2SeO4 or 800 mu M CdCl2) or together (Se + Cd). The changes of following properties of plastid envelope membrane caused by both metals were measured: composition of main lipid fractions, their fatty acid saturation, membrane fluidity, lipid peroxidation and membrane zeta potential. Results of experiments led to the conclusion that galactolipid component plays a predominant role in modification of plastid membrane properties responding to Cd and Se addition. It was shown that galactolipid protecting reaction to Cd toxic action can consists in increased plastid envelope membrane stiffness. The presence of hormone (2,4-D) and Se did not counterbalance Cd toxic effects (at least under concentration level applied in the experiments). Se applied separately can probably stimulate plastid/chloroplast transformation in wheat cells by increasing a galactolipid unsaturation degree. The zeta potentials seem to be important physicochemical parameter in determination of properties of membranes exposed to metal stress conditions.