In vivo measurement of cadmium ((115m)Cd) transport and accumulation in the stems of intact tomato plants (Lycopersicon esculentum, Mill.) : II. Lateral migration from the xylem and redistribution in the stem

Salt affects plant Cd-stress responses by modulating growth and Cd accumulation

Cadmium contamination is a serious environmental problem for modern agriculture and human health. Salinity affects plant growth and development, and interactions between salt and cadmium have been reported. However, the molecular mechanisms of salinity-cadmium interactions are not fully understood. Here, we show that a low concentration of salt alleviates Cd-induced growth inhibition and increases Cd accumulation in Arabidopsis thaliana. Supplementation with low concentrations of salt reduced the reactive oxygen species level in Cd-stressed roots by increasing the contents of proline and glutathione and down-regulating the expression of RCD1, thereby protecting the plasma membrane integrity of roots under cadmium stress. Salt supplementation substantially reduces the Cd-induced elevation of IAA oxidase activity, thereby maintaining auxin levels in Cd-stressed plants, as indicated by DR5::GUS expression. Salt supply increased Cd absorption in roots and increased Cd accumulation in leaves, implying that salt enhances both Cd uptake in roots and the root-to-shoot translocation of Cd. The elevated Cd accumulation in plants in response to salt was found to be correlated with the elevated levels of phytochelatin the expression of heavy metal transporters AtHMA1-4, especially AtHMA4. Salt alleviated growth inhibition caused by Cd and increased Cd accumulation also was observed in Cd accumulator Solanum nigrum.

The effects of feeding by the black bean aphidAphis fabae Scop. (Homoptera: Aphididae) on copper and cadmium accumulation in broad bean (Vicia faba L.)

Broad beans (Vicia faba L.), cultured hydroponically were supplied with 100 μg mL(-1) copper or 50 μg mL(-1) cadmium in nutrient solution. Samples of plant material from both nutrient regimes were analysed before and after infestation by the black bean aphid (Aphis fabae Scop.). Heavy aphid infestation resulted in a significant reduction in copper content of shoots in comparison with uninfested plants. A similar, but less well- defined, situation occurred in the case of cadmium.Further investigations examined the effects of different levels of aphid infestation on the above phenomena. In all cases the presence of feeding aphids reduced elemental accumulation in plant shoots. Long term infestation with population densities as low as three adult aphids showed a reduction in shoot copper and cadmium content.

In vivo measurement of cadmium ((115m)Cd) transport and accumulation in the stems of intact tomato plants (Lycopersicon esculentum, Mill.) : I. Long distance transport and local accumulation

Semiconductor radiation detectors have been used to study in vivo the long-distance transport and accumulation of cadmium ((115m)Cd) in the stems of tomato plants. Long-distance transport proceeds at a speed of 0.35-0.60 m h(-1). The shape of the accumulation curve is characterized by a shoulder after about 6 h. This corresponds to the saturation of the xylem tissue. The effects of changes in the nutritional pattern have been considered as well. The cadmium content in the stem sharply decreases after a transfer of the plant to a nonlabeled solution of high ionic strength, whereas it tends to stabilize after a shift to a low ionic strength medium. These observations are explained by exchange processes between cadmium and other divalent cations.