Application of bioassay techniques to herbicide investigations

Summary: Bioassay techniques used in herbicide studies are based on the response of chosen organisms, superior plants or microorganisms, to the chemical. Various means of assessment are used: germination, weight or size of plant parts, modifications in physiological activities such as photosynthesis and transpiration, and typical symptoms. Several special bioassays are described. Dose‐response relations are affected by the age of the indicator plant and environmental conditions of growth. Results can be estimated visually or by objective measurements; for correct interpretation appropriate controls and standards must be included in each experiment. Examples are given of bioassay procedures developed to investigate various aspects of herbicide behaviour: soil effects, dissipation from the soil surface, movement in soil, degradation and persistence.