Bioaccumulation of heavy metals can be affected by various crop-weed interactions in agroecosystems. An experiment was conducted to evaluate the role of below ground interaction of soybean and sunflower with purslane ( Portulaca oleracea L . ) weed plant on cadmium (Cd) uptake and its allocation to different part of crop plants specially in grains. Treatments were included two cropping systems (the crop and weed cultures were included sole planting of each species and co-planting of each crop with purslane), two salinity levels (0 and 0.5% NaCl added) and three levels of Cd in soil (Control; 3 and 6 mg/kg). In the non-saline soil decreasing uptake and grain allocation of Cd in co-planted soybean was associated with enhancing of purslane Cd uptake and the depletion of Cd in soil solution. Therefore, it can be concluded that co-planted purslane can alter the uptake of cadmium to the neighboring soybean plants. While, the growth of sunflower in the presence of purslane in comparison to mono culture of sunflower led to change of total Cd content and Cd allocated to grains only under saline conditions. Results from this experiment showed that the promoting effects of salinity on Cd uptake by soybean and Cd allocation to grains were enhanced while in sunflower these effects were alleviated in the presence of purslane comparing to absence of the neighbour plant. Keywords: Cadmium, Salinity, Sunflower, Soybean, Purslane, Co-planting
