Copper excess impairs mobilization of storage proteins in bean cotyledons.

Germination represents a limiting stage of plant life cycle. One of the underlying metabolic activities following imbibition of seed is the reserve mobilization. Seeds of bean (Phaseolus vulgaris L. var. soisson nain hatif) were germinated by soaking in distilled water or 200 μM CuCl(2). Storage proteins breakdown and amino acids freeing from reserve tissues were investigated. Compared to the control, Cu caused a reduction in germination rate, embryo growth, and in mobilization of cotyledonary biomass. The failure in albumin and globulin hydrolysis after the exposure to the pollutant was argued by (1) higher contents of remaining proteins than control ones, (2) persistence of some polypeptide bands resolved by polyacrylamide gel electrophoresis of albumin and globulin-rich fractions, and (3) decrease in the availability of amino acids. Nitrogen starvation in embryonic axis should be associated with the Cu-imposed delay in growth.