Short communication Floating row covers affect Pb and Cd accumulation and antioxidant status in Chinese cabbage Diego A. Moreno * , Luis R. Lo Âpez-Lefebre, Gemma Võ Âllora, Juan M. Ruiz, Luis Romero Dpto. Biologõ Âa Vegetal, Facultad de Ciencias, Universidad de Granada, Fuentenueva S/N, E-18071 Granada, Spain Accepted 9 July 2000 Abstract In 1993 and 1994, crop covering treatments [perforated polyethylene PO, 500 holes/m 2 )anda polypropylene AO, Agryl-P17)] were used to produce different environmental conditions for the growth of Brassica pekinensis Lour) Rupr cv. Nagaoka 50. Plant material was sampled ®ve times fromtransplantingtoharvest,andtheamountsofchlorophylls,peroxidaseactivity,biomass,andPb and Cd accumulation in the above-ground plant material were measured. Uncovered control plants, received lower air and root temperatures as well as lower relative humidity, and showed the highest chlorophyll a, chlorophyll b, carotene and peroxidase activity values. Under ¯oating row covers PO and AO) the improved thermal conditions resulted in increased fresh and dry mass and accumulation of Pb and Cd. It is also important to consider that because of this accumulation these plants may pose a risk for human health through Pb and Cd contamination of food supplies. # 2001 Elsevier Science B.V. All rights reserved. Keywords: Brassica pekinensis; Cd; Chlorophylls; Carotene; Pb; Peroxidase 1. Introduction Plasticulture, or the use of ¯oating row covers has increased substantially in commercial vegetable production systems with bene®ts including more favourable soil and air temperature regimes, improved ef®ciency in water and fertilizer use, as well as higher and earlier crop production Lamont, 1996; Wurr Scientia Horticulturae 89 2001) 83±90 * Corresponding author. Tel.: 34-958-243-255; fax: 34-958-243-254/34-958-248-995. E-mail address: lromero@ugr.es D.A. Moreno). 0304-4238/01/$ ± see front matter # 2001 Elsevier Science B.V. All rights reserved. PII:S0304-423800)00222-3