NUKLEONIKA 2004, 49(Supplement 1):s35-s38

Croton (Codiaeum variegatum) belongs to the salinity-resistant plants. This paper presents some experimental data in order to assess usefulness of croton plants for phytoremediation of caesium-contaminated soils. The plants were grown in a greenhouse, in the soil contaminated with 0.03, 0.3, 1, 3, 5 and 10 mM CsCl solution enriched with ¹³⁷Cs as a radiotracer. The croton plant demonstrated high resistance to increasing CsCl salinity of the soil. This conclusion was based on the observation that the above-ground organ fresh-to-dry weight ratio was constant. However, this value was lower for the roots. The young-to-old leaf dry weight ratio was decreasing while the concentration of CsCl in the soil was increasing.
The increase in soil CsCl concentration was associated with the decrease in photosynthesis as well as a rise in the intra-tissue concentration of CO₂ and increase of the CO₂ stomatal conductance. Photosynthetic water utilization efficiency was constant in the range of 0.03-1 mM CsCl and it was only lower with higher CsCl concentration. This situation gives an evidence that croton plant is highly resistant to the soil CsCl salinity. The ¹³⁷Cs radiotracer experiment showed the maximal accumulation of caesium with 0.3 mM CsCl, a lower one with 0.03 mM, and poor accumulation with 3 and 5 mM CsCl solutions.
The transfer factor value for ¹³⁷Cs (plant-to-soil) was about 10, which proved a high ability of croton plants to accumulate caesium to a high extent. However, the highest accumulation took place in the roots. The intensive phytoextraction of caesium from the soil may indicate its potential capacity for bioremediation. The reported observation warrants further studies.