Floating row covers affect Ph and Cd accumulation and antioxidant status in Chinese cabbage

In 1993 and 1994, crop covering treatments [perforated polyethylene (PO, 50 0 holes/m(2)) and a polypropylene (AO, Agryl-P17)] were used to produce dif ferent environmental conditions for the growth of Brassica pekinensis (Lour ) Rupr cv. Nagaoka 50. Plant material was sampled five times from transplan ting to harvest, and the amounts of chlorophylls, peroxidase activity, biom ass, and Ph and Cd accumulation in the above-ground plant material were mea sured. Uncovered control plants, received lower air and root temperatures a s well as lower relative humidity, and showed the highest chlorophyll a, ch lorophyll b, carotene and peroxidase activity values. Under floating row co vers (PO and AO) the improved thermal conditions resulted in increased fres h and dry mass and accumulation of Pb and Cd. It is also important to consi der that because of this accumulation these plants may pose a risk for huma n health through Ph and Cd contamination of food supplies. (C) 2001 Elsevie r Science B.V. All rights reserved.