A new method for seedling assay of phytotoxic substances: liquid shaking culture

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Abstract
A new method for seedling assay of phytotoxic substances is described. When the seeds were germinated in continuously shaken Erlenmeyer flasks containing distilled water, growth of the seedlings was more rapid and more uniform than the growth under a conventional petri dish-filter paper system. Uniformity of the growth in the liquid shaking culture was improved by selecting seedlings with similar length at day 1 or 2 of the culture. When using 100 ml flasks, the most suitable conditions for seedling assay were as follows: Culture temperature, 30°C; shaking rate, 80rpm; volume of test solution, 20 ml; seedling density, lOplants/ flask; duration of exposure to a test substance, day 1–3 (for rape and turnip), day 1.5–3.5 (for sesame), and day 2–4 (for cucumber and rice). The method could be applied to more than 20 plant species. Cadmium inhibited both shoot and root elongation in rape, turnip, sesame, cucumber, and rice. The dose-response patterns were similar in all cases, whereas critical concentrations for which the growth begins to decrease varied with plant species, plant parts, and especially, nutrient conditions.