Bioassay standardization for the detection of allelopathic compounds and environmental toxicants using lettuce

Abstract

The purpose of this study was to assess different experimental conditions to determine a protocol for bioassays based on seed germination and early seedling growth using lettuce (Lactuca sativa L.) cv. Grand Rapids as indicator species. This protocol aims to provide support for the standardization of assays of various chemicals such as allelochemicals and environmental toxicants. The following tests were performed: time of germination, temperature, light, solution volume and Petri dish size. For each test (except for time of germination), the influence of the conditions investigated was determined by the endpoints germination percentage, germination speed index, root length, seedling fresh weight and total dry weight. The results showed that variations in the methods altered the results. It is recommended that bioassays using L. sativa L. cv. Grand Rapids be carried out for a minimum period of four days for assessments of both germination and initial growth and that the experimental conditions include a temperature of 20°C, 90-mm Petri dishes or larger, 0.1 mL cypsela solution, and continuous light or 12-hour photoperiod.

Keywords

• Lactuca sativa L.
• Phytotoxicity
• Plant assays
• Standardization