Variation of delta C-13 in Aegiceras corniculatum seedling induced by cadmium application

Abstract

To test whether the values of delta C-13 in mangrove plants are affected by Cd application, the seedlings of Aegiceras corniculatum, a dominant mangrove species, were cultured in soil supplied with CdCl2 solution at the concentration of 0, 0.5, 2.5, 5, 20, 30 and 50 CdCl2 mg/kg wet soils. Plants were grown in 10 replicate pots with 5 propagules each. After 5 months of Cd exposure, three pots contained 15 seedlings with average shoot heights were selected for each treatment. Leaves and roots of seedling were sampled respectively and analyzed for delta C-13. Growth traits (fresh weight, shoot height and root length), total chlorophyll content, and Cd concentrations in leaf, root and dry soil were determined. After 5 months of the seedling growth, the concentrations of Cd in dry soil were 0.47, 0.83, 2.77, 4.54, 18.89, 29.79 and 47.35 mg/ kg respectively. The values of delta C-13 in roots and leaves were affected to some extent by Cd application. Although root delta C-13 showed more sensitive to Cd compared with leaves, the values of delta C-13 in roots were not significantly affected by Cd until Cd level higher than 29.78 mg/kg which was not expected to exist in natural environments. Minor variation in delta C-13 values observed in roots and leaves was likely due to limited Cd uptake by seedlings and subsequent lack of negative impacts on photosynthesis.