首页|PHYTO-EXTRACTION OF FIELD-WEATHERED DDE BY SUBSPECIES OF CUCURBITA AND EXUDATION OF CITRIC ACID FROM ROOTS
PHYTO-EXTRACTION OF FIELD-WEATHERED DDE BY SUBSPECIES OF CUCURBITA AND EXUDATION OF CITRIC ACID FROM ROOTS
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Two subspecies of Cucurbita pepo L. (summer squash) differ in phyto -extraction of weathered DDE when grown in the field. Three cu ltivars were selected from each of the two subspecies; Cucurbita pepo ssp pepo (zucchini) with a greater ability to take up DDE, and Cucurbita pepo ssp ovifera (summer squash) with a lesser ability to take up DDE. When grown in the field, ssp pepo extracted 0.4 to 1.0 milligrams of DDE per plant, while ssp ovifera removed from the soil only 0.02 to 0.1 milligram per plant. These cultivars were grown in hydroponics to evaluate whether exudation of organic acids from the roots was involved in uptake of weathered DDE. Phosphorus nutrition played a significant role in exudation of organic acids into the hydroponics solution. For both subspecies, the bette r the phosphorus nutrition, the more tartaric and less citric acid was exuded. Subspecies pepo showed a greater increase in citric acid exuded under phosphorus depletion than ovifera. However, when solutions of root exudates w ere used to batch extract DDE from soil, effect of subspecies was opposite to that seen in the field. This suggests there are factors other than disruption of the soil matrix that play a role in phyto-extraction by plants. Nevertheless, among subspecies of Cucurbita pepo, the exudation of citric acid was related to phyto -extraction of more weathered organic contaminants in soil.
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