THE EFFECT OF OIL INDUSTRY HIGH-DENSITY BRINES ON DUCKWEED LEMNA-MINOR-L

Duckweed Lemna minor L. is a suitable plant model for toxicity evaluat ion of many substances due to its small size, rapid growth and ease of culture. Saturated water solutions of calcium chloride and calcium br omide and their 1:1 mixture are commonly used as ''high density brines '' for pressure control in oil wells. These solutions were added in Ho agland's nutrient medium in amounts appropriate to achieve 0.5%, 1.0%, 1.5% and 2.0% (v/v) dilutions and after two weeks of exposure the eff ect of tested chemicals on growth was estimated by counting fronds, me asuring fresh and dry weights and determining total surface area of pl ants. Chlorophyll and carotenoid content in Lemna minor was also measu red. Additionally, anthocyanin content in Spirodela polyrrhiza (L.) Sc hieiden was determined. During 14 days of exposure tested chemicals in lower concentrations (0.5%, 1.0% and 1.5% v/v) promoted the growth of Lemna minor, but they inhibited it in the highest (2.0% v/v). With in creased concentration of tested solutions the concentrations of chloro phyll a and chlorophyll b were correspondingly higher in comparison wi th the control. Total carotenoid content and chi a/chl b ratio were al so increased. The highest anthocyanin content in lower epidermis of Sp irodela polyrrhiza was noticed after the treatment with media containi ng 2.0% (v/v) CaCl2 and 1:1 mixture of CaCl2 and CaBr2, but lower conc entrations of all three tested solutions also resulted in anthocyanin content increase. (C) 1998 Elsevier Science Ltd. AII rights reserved.