Exogenous indoleacetic acid induces cadmium accumulation and growth in Cinnamomum camphora

The application of plant hormones such as indoleacetic acid (IAA) has attracted increasing attention for enhancing the potential of phytoremediation. Research suggests that Cinnamomum camphora is resistant to heavy metals and suitable for soil remediation. However, the mechanism of how IAA would alleviate the cadmium (Cd) stress in C. camphora remains unclear. This study evaluated the effects of IAA application on the Cd uptake by C. camphora seedlings in Cd contaminated soils, with growth, physiological, and biochemical characteristics explored. Results showed that the Cd accumulation in C. camphora increased with the rising soil Cd concentrations. Under the Cd stress, especially for the high-level stress, the growth and photosynthesis of C. camphora declined, while the peroxidase activity, the contents of malondialdehyde (MDA) and osmotic regulators (including soluble sugars, soluble proteins, proline) increased on contrary. The IAA application in general alleviated the negative influences of Cd stress on C. camphora by enhancing the Cd accumulation in plants, promoting biomass and the photosynthetic efficiency, improving the superoxide dismutase activity, but reducing the contents of MDA and osmotic regulators. Overall, C. camphora has a good defense system with high capabilities in Cd tolerance and accumulation, which are conducive to its normal growth and metabolism under the Cd stress, and therefore is suitable for remediating Cd contaminated soils.