Effect of plant age on PCB accumulation by Cucurbita pepo ssp. pepo.

A greenhouse experiment was conducted to investigate polychlorinated biphenyl (PCB) uptake and translocation from soil over time in pumpkin plants (Cucurbita pepo ssp. pepo cv. Howden). Plants were grown in weathered soil collected from a former industrial site contaminated with Aroclor 1248 (mean [PCB](soil) = 6.5 mg kg(-1)). Plants were harvested five times over 42 d and analyzed for total PCB concentration in the root and shoot tissues. The concentration of PCBs in the root was not significantly different between harvests (mean [PCB](root) = 21.5 mg kg(-1)). The concentration of PCBs in the shoots was also relatively stable over time (mean [PCB](shoot) = 3.5 mg kg(-1)) despite increases in shoot biomass (fresh weight of 4.3 g at Day 12 to 59 g at Day 42). This suggests that PCBs were continuously accumulated throughout the growth period. The trends found in this study indicate the optimal time to harvest C. pepo ssp pepo plants to maximize PCB phytoextraction is when the plant shoot has reached its maximum biomass.