Smoke-water preparation. A smoke-water solution was prepared by igniting dry rice straw (Oryza sativa)
material (1 kg) in a 3-L metal drum. Using compressed air, the smoke was continuously bubbled through a 500 ml
graduated cylinder of distilled water for 45 min. Solutions of this smoke extract (500 ml) were filtered through
Whatman No.1 filter paper and was used as the stock solution.