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Response of cadmium (Cd), Zn Translocation and Distribution to Organic Acids Heterogeneity in Brassica juncea L.

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Overview

This pot experiment examined how cadmium and zinc translocate from roots to shoots in Brassica juncea at different soil metal concentrations, focusing on the roles of different organic acids in xylem sap and subcellular compartmentalization in root cells. Metal concentrations are reported on a fresh weight basis.

Key numbers

Shoot and root concentrations (Table 1, mg/kg fresh weight):

Cadmium:

  • Control (0 mg/kg soil Cd): shoots 0.49 ± 0.21, roots 0.66 ± 0.15
  • 20 mg/kg soil cadmium (Cd) treatment: shoots 2.21 (approximate), roots ~15 (approximate)
  • 40 mg/kg soil Cd treatment: shoots 3.80 ± 0.62, roots 31.83 ± 6.13

Zinc:

  • Control: shoots 21.85 ± 4.49, roots ~20 (approximate)
  • 100 mg/kg soil Zn treatment: shoots 51.30 ± 9.51, roots higher

Mechanistic findings:

  • Under 20 mg/kg Cd: Cd in xylem sap occupied 64.60% of above-ground transport
  • Under 100 mg/kg Zn: Zn in xylem sap occupied 60.14%
  • Cd predominantly distributed in vacuoles (chelation-based retention)
  • Zn predominantly distributed in cell walls
  • Translocation factor (TF = shoot/root) decreased with increasing soil metal concentration
  • Cd in xylem sap at 40 mg/kg Cd treatment: 0.006 mg/L

Methods

Pot experiment; soil amended with Cd(NO3)2 and ZnSO4; harvest of shoots and roots; fresh weight basis; xylem sap collection; subcellular fractionation; organic acid analysis.

Implications

This is a mechanistic study using artificially elevated soil metal concentrations. The control-condition shoot Cd (0.49 mg/kg FW) is on a fresh weight basis and represents low background accumulation when no exogenous Cd is added. The 40 mg/kg soil Cd treatment (shoot Cd 3.80 mg/kg FW) is not a food scenario. The vacuole-dominant Cd distribution and cell-wall-dominant Zn distribution provide mechanistic insight into why TF < 1 at high concentrations and why cadmium is more mobile than zinc in xylem transport. Routes as mechanistic context for Cd translocation in mustard.

Certification: not in HMT&C threshold pools. Routes to Cadmium, Zinc, Soil-to-plant transfer of heavy metals.

App: No contamination_profile blocks are touched.

Microbiome: Not a focus of this source.

Update history

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