A comparative analysis of the effects of in-vivo and in-vitro abscisic-acid treatment on the surface electrical properties of barley chloroplast membranes.

The effects of in-vivo and in-vitro abscisic acid (ABA) treatments on the surface charge density (σ) of barley (Hordeum vulgare L.) thylakoids were compared using 9-aminoacridine fluorescence. The estimated surface charge density of isolated thylakoid membranes from control (non-treated) barley leaves was-0.065 C · m(-2). The net negative surface charge density decreased after application of various concentrations of ABA (10(-6), 10(-5) M) for 7 d in-vivo, the more pronounced effect being observed at 10(-5) M ABA. When ABA was added to the suspension of isolated thylakoids the opposite effect was observed. The average charge density increased in in-vitro-treated thylakoids at 10(-5) M ABA to -0.081 C · m(-2). The results are discussed in terms of a specific ABA-induced influence of the composition and-or stoicheometry of charged protein complexes within the thylakoid membranes.