Abstract
The mechanism of growth amelioration of NaCl-stressed rice (Oryza sativa L. cv. Nipponbare) by δ-aminolevulinic acid (ALA) was investigated. Rice growth recovered when plants were pretreated with 0.1 or 1 μM ALA before treatment with 50 mM NaCl. There was no increase in chlorophyll content by ALA treatment, indicating that the growth recovery was not due to increased chlorophyll content although ALA is a precursor of chlorophyll biosynthesis. The activities of antioxidative enzymes, including catalase (CAT), glutathione reductase (GR), ascorbate peroxidase (APx), and superoxide dismutase (SOD), increased with ALA treatment. In particular, stimulation of CAT, GR, and APx activities by ALA was significant. The hydrogen peroxide (H2O2) content decreased after ALA treatment under NaCl-stress conditions. Peroxidation of membrane lipids, as measured by ethane evolution, also decreased after ALA treatment. These results suggest that ALA induces growth amelioration in NaCl-stressed rice by stimulating antioxidative enzyme activity, which resulted in decreased reactive oxygen generation and lipid peroxidation.
