Nitric oxide can induce tolerance to oxidative stress of peanut seedlings under cadmium toxicity

To study the role of sodium nitroprusside (SNP, a donor of NO) in alleviating cadmium (Cd) toxicity in peanut (Arachis hypogaea L.), peanut seedlings exposed to 50, 100, or 200 mu M Cd as CdCl2 were treated with 250 mu M SNP. Cd exposure depressed plant growth, inhibited the photosynthesis, and resulted in oxidative stress. In roots, Cd was mostly trapped in the cell wall under low Cd stress, but most Cd was accumulated in the soluble fraction under high Cd concentrations. In leaves, a majority of Cd was accumulated in the cell wall regardless of Cd treatment level. Addition of SNP at 250 mu M significantly alleviated Cd toxicity in peanut seedlings, including improved photosynthesis, up-regulated antioxidant system, and reduced Cd translocation from roots to shoots as evidenced by decreased Cd accumulation in stems and leaves. SNP application also changed the subcellular distribution of Cd in leaf and root tissues, by increasing Cd retention in root and leaf cell wall while reducing Cd accumulation in the soluble fractions and cell organelles. These results indicate that SNP has great application potential for improving the growth of plants under heavy metal stress such as Cd toxicity.