Abstract

Pea seeds were treated with 5 mM CdCl₂ for 5 days. Experiments carried out in cotyledons and embryonic axes were performed to evaluate the redox and oxidative properties. Germination rate and embryonic axis growth were determined. After five days, Cd treatment caused 60% decrease in germination success, and 50% inhibition in embryo length. The reduction level [NADPH/ (NADP⁺ + NADPH)] was used to define the redox status. The reduction level in Cd-treated mitochondrial and peroxisomal fractions was ~20 to 70% lower than that of the control (water-treated) from 120 h of exposure. Under normal conditions, the intracellular milieu is predominately reducing, but stress conditions can shift the redox balance toward an oxidizing milieu. NADPH oxidase is considered to be oxidative stress-related enzymes. NAD(P)H oxidase activities were strongly stimulated after Cd exposure. We suggest that alteration of redox and oxidative properties in both tissues of pea seeds due to treatment with CdCl₂ is highly responsible for decrease of germination success and inhibition of embryonic axes growth.

Key words: Cadmium, germination, oxidative stress, Pisum sativum, redox.