Effects of silicon on the distribution of cadmium compartmentation in root tips of Kandelia obovata (S., L.) Yong

The Effects of silicon (Si) on the distribution of cadmium (Cd) compartmentation in root tips of Kandelia obovata (S., L.) Yong were investigated by pot experiments. Cd concentrations in the apoplastic saps and symplastic fractions of the root tips of K. obovata seedlings were decreased at both Si-supplied treatments. Si addition reduced the concentrations of BaCl2-extractable cell-wall-Cd in root tips, but increased the concentrations of Na3citrate-extractable cell-wall-Cd and HCl-extractable cell-wall-Cd in root tips. The total root-tip contents of Cd were mainly distributed in the apoplast and most of the Cd in the apoplast was bound to the cell wall. Our experiment found that Si increased the ratio of apoplast Cd (>87.08%) and reduced the ratio of Cd in the symplast (<12.92%). This suggested that Si enhanced binding of Cd to the cell walls and restricted the apoplastic transport of Cd. - Graphical abstract: Si addition reduced the concentrations of BaCl2-extractable cell-wall-Cd in root tips, but increased the concentrations of Na3citrate-extractable cell-wall-Cd and HCl-extractable cell-wall-Cd in root tips. Highlights: ► Filtration of centrifugal forces to extract apoplastic saps from root segments. ► Si addition reduced the concentrations of BaCl2-extractable cell-wall-Cd. ► Si addition increased the concentrations of Na3citrate-extractable cell-wall-Cd. ► Si addition increased the concentrations of HCl-extractable cell-wall-Cd. ► Si increased the ratio of apoplast Cd and reduced the ratio of Cd in the symplast. - The present study indicates that Si plays an important role in alleviating the toxicity of Cd in K. obovata seedlings.