LOW-MOLECULAR-WEIGHT ORGANIC ACID EXUDATION OF RAPE (BRASSICA CAMPESTRIS) ROOTS IN CESIUM-CONTAMINATED SOILS.

Cesium is an emission element from nuclear energy generation easily transferred to food chain. More evidence has been found that Brassica crops take up pollutants from soils. The objective of this study was to investigate the correlation between soil bioavailability of cesium and low-molecular-weight organic acids (LMWOAs) in rape (Brassica campestris) root exudates. Longtan (LT) red (Typic Hapladox) and Kuanshan (KS) iron-rich calcareous soils (Typic Paleudalf) were collected for this study. The pot experiments of rape were conducted with cesium-amended soils and plants grown in the soils (4 weeks). Cesium concentration in shoots and roots correlated well with Cs concentration in the amended soils. Within the amended range of 50 to 300 mg Cs kg^-1 soil, Cs did not inhibit rape growth. The bioaccumulation ratio ([Cs]root/[Cs]soil] or [Cs]shoot/[Cs]soil) for Cs in shoots of pot grown plants ranged between 9 and 31 and showed significant differences (P (less than00.05). Plant roots can exude LMWOAs, which are important components in root exudation. The total amounts of volatile and nonvolatile LMWOAs in all Cs-amended soils were higher than those in nonamended soils. Meanwhile, the LMWOA concentrations of the rape root exudates showed good correlation with Cs concentrations in the applied range of 50 to 300 mg Cs kg-1 soil.