Subspecies-Level Variation in the Phytoextraction of Weathered p,p‘-DDE by Cucurbita pepo

Previous studies indicate that Cucurbita pepo can phytoextract highly weathered persistent organic pollutants (POPs) from soil and translocate large quantities to aerial tissues. To investigate intraspecific variability in uptake potential, a field study was conducted to quantify the phytoextraction of weathered p,p‘-DDE by 21 cultivar varieties of summer squash from two distinct subspecies, C. pepo ssp texana and C. pepo ssp pepo. Significant differences exist between the two subspecies, with average root and stem to soil bioconcentration factors (BCF, dry weight ratio of contaminant concentration in the vegetation to that in the soil) of 7.22 and 5.40 for ssp pepo and of 2.37 and 0.454 for spp texana, respectively. The amounts of weathered p,p-DDE extracted from the soil by ssp pepo and ssp texana were 0.301 and 0.065%, respectively, with maximum values within each subspecies of 0.780 and 0.182%, respectively. The quantities of 14 inorganic elements were determined in both the soil and tissues (roots, stems, leaves, and fruit) of all 21 cultivar varieties. Phosphorus concentrations in the tissues of ssp pepo were 14 (fruit)-73% (stems) greater than those of ssp texana. These data support our hypothesis that the unique ability of certain cultivars of C. pepo to phytoextract highly weathered POPs from soil is the result of low molecular weight organic acid exudation as a unique phosphorus acquisition mechanism.