Absorption and subcellular distribution of cadmium in tea plant (Camellia sinensis cv. Shuchazao)

A hydroponic experiment was performed to investigate the Cd absorption and subcellular distribution in tea plant, Camellia sinensis. Increased Cd accumulation potential was observed in the tea plant in a Cd-enriched environment, but most of the Cd was absorbed by the roots of C. sinensis. The Cd in all the root fractions was mostly distributed in the soluble fraction, followed by the cell wall fraction. By contrast, the Cd was least distributed in the organelle fraction. The adsorption of Cd onto the C. sinensis roots was described well by the Langmuir isotherm model than the Freundlich isotherm. Most of the Cd (38.6 to 59.4%) was integrated with pectates and proteins in the roots and leaves. Fourier transform infrared spectroscopy (FTIR) analysis showed that small molecular organic substances, such as amino acids, organic acids, and carbohydrates with N-H, C=O, C-N, and O-H functional groups in the roots, bonded with Cd(II). The Cd accumulation in the C. sinensis leaves occurred in the cell wall and organelle fractions. C. sinensis has great capability to transport Cd, thereby indicating pollution risk. The metal homeostasis of Fe, Mn, Ca, and Mg in C. sinensis was affected when the Cd concentration was 1.0-15.0 mg/L.