Phytotoxicity of lead on Lactuca sativa: effects on growth, mineral nutrition, photosynthetic activity and oxidant metabolism

Abstract

Pb (lead) contamination in water and soils is increasing and its accumulation in plants may have serious deleterious consequences for environment and human health. Lead effects on plants still remain unclear and, therefore, a selection of Pb sensitive parameters used as biomarkers is required for improvement within the scope of Ecological Risk Assessment. In this study Lactuca sativa L. plants were exposed to Pb to contaminated irrigation solutions (12.5 mg l-1 and 125 mg l-1) for 15 days. Orthogonal analyses (time vs. Pb concentration vs. organ) were carried out after one, seven and fifteen days to elucidate about the effects of this element in plants. During exposure, plant growth, nutritional imbalance, water content, soluble protein content, lipid peroxidation (malondyaldehyde accumulation) and photosynthesis (chlorophyll contents and PSII fluorescence) were assessed in order to find the most adequated parameters for further studies in under realistic environmental conditions. Morphological and growth parameters showed decreases of root and shoot growth and alterations in root branching pattern. Biochemical parameters showed nutritional imbalance mostly concerning Pb, K (potassium) and Fe (iron) contents, changes in chlorophyll content and chlorophyll a:b ratio and malondyaldehyde accumulation. Therefore, such biochemical parameters may be used/ recommended as assessment parameters complementary to morphologic ones (e.g. shoot and root lengths) both in toxicological tests and further studies under realistic environmental conditions.