The Uptake And Accumulation Of Fe, Mn, Cu, Zn, Ca And Mg By Water Spinach (Lpomoea Aquatica Forsk.) From Soils Under Cadmium Stress

Soil culture experiments with the highly sensitive vegetable to Cd (cadmium), water spinach, were carried out in order to investigate the effects of Cd on the uptake and transfer characteristics of Fe, Mn, Cu, Zn, Ca and Mg in the soil-plant system under Cd stress. The main results were as follows:1. The Cd concentrations of the roots and the shoots of water spinach were generally increased with increasing available soil Cd. The root-aerial part transfer factors of Cd were significantly and negatively correlated with soil available Cd and the Cd concentration of the root, showing that the transfer capacity of Cd from the roots to the shoots decreased gradually with the increase in the amount of Cd addition to the soil. The transfer factor of Cd from root to aerial part was significantly and positively correlated with the biomass of aerial part.2. The addition of Cd showed different effects on the uptake of various nutrients. The concentrations of Cd and Mg in the aerial parts had significant and positive correlation with the amount of Cd added to the soil. The concentrations of Zn, Ca and Mg in the roots also increased with the increase of the amount of Cd added to the soil while those of Fe, Mn, Cu and Zn increased first and then decreased with increasing amount of Cd added.3. The addition of Cd showed different effects on the availability of the nutrients. As the increase in the available Cd, the available Mn and Fe tended to increase while the available Cu decreased. The available Zn did not change apparently with the Cd added.4. Cd stress showed significant influences on the transfer of the nutrients. The soil-to-root transfer factors of Fe, Mn and Cu increased first and then decreased with the increase of Cd added. The root-to-aerial part transfer factors of Zn was significantly and negatively correlated with soil available Cd. The root-to-aerial part transfer factors of Fe, Mn and Cu also tended to decrease first and then increase with the increase of soil Cd. The transfer of Ca and Mg from the roots to the aerial parts was promoted by high Cd addition (≥5 mg·kg^-1). The transfer factors of Cd and those of Zn from roots to shoots were significantly and positively correlated. The transfer factors of Fe, Mn and Cu from roots to shoots tended to decrease first and then increase with increase in the transfer factors of Cd from roots to shoots.5. The fresh weights of the root and the aerial part were significantly and positively correlated with the transfer factors of Zn from root to aerial part. The transfer factors of Cu from root to aerial part decreased first and then increased with the root biomass of water spinach. No apparent effects of the biomass of the aerial part and the root on the transfer of Ca, Mg, Fe and Mn from roots to shoots were observed.