Application of root growth endpoint in toxicity tests with lettuce (Lactuca sativa)

Abstract

Ecotoxicological tests are an important tool to assess the toxicity of chemical substances and even the deleterious effects of adverse environmental conditions to different species. Ecotoxicological studies with land plants and animals are relatively recent compared to those with aquatic species, with few studies reported focusing on terrestrial species. The aim of the present study was to evaluate the sensitivity of root growth (Total Part; Radicle, Hypocotyl) in lettuce (Lactuca sativa) to sodium chloride (NaCl), by means of exposing the seeds to concentrations of 0, 1.0, 2.0, 4.0, 8.0 and 16.0 g L-1 for five days in Petri dishes. The average effective concentration (EC50;120h) on germination was 5.73 ± 0.56 g L-1 (CI= 4.61 to 6.86 g L-1). The effects on root growth were detected starting at a concentration of 1.0 g L-1 of NaCl and the radicle (Rad) was the most sensitive and reliable structure. Root growth was a more sensitive endpoint than germination, since the effects were detected at concentrations some 10 times lower. Besides this, the use of the radicle as an endpoint, proposed in the present study, should be intensified in ecotoxicological studies, since it provides satisfactory results at low cost and in a relatively short time frame.