VARIETAL RESPONSE TO LEAD BY LETTUCE

Nine lettuce varieties [6 of Lactuca sativa var. copitata, 2 of L. sativa var. crispa, and L. sativa var. logifolia] were hydroponically-grown at 6 substrate Pb concentrations to 50 ppm in substrate. Top and root tissue Pb concentration, amounts assimilated, and translocation to edible tissue were dependent on the variety as well as substrate lead and exposure duration. Even though Pb in substrate was in a precipitated form, lettuce plants could assimilate and translocate Pb. Differential response of varieties with similar morphology indicated genetical regulated physiological mechanisms of Pb assimilation and translocation. This evidence suggests varietal selection could minimize human and animal dietary intake of Pb via food plants. While early growth of some varieties was stimulated by low concentrations of Pb, and high solution concentrations suppressed growth of several varieties, genetic variation also included non-significant response of growth.