Avena curvature test is a bioassay for examining the activity of

• auxins

• cytokinins

• gibberellins

• ethylene.

A.

auxins

Bioassay is a testing of biological activity like growth response of a substance by employing plant part. Avena curvature test is a bioassay for examining the activity of auxins. It is based upon experiments of Went. 10° curvature is produced by auxin concentration of150 g/lit at 25⁰C and 90% relative humidity. It can measure auxin upto 300g/litre. Auxin from shoot tip or any other plant organ is allowed to diffuse in a standard size agar block. 15- 30 mm long oat coleoptile grown in dark is held vertically over water. 1 mm tip of colcoptile is removed without injuring the primary leaf. After 3 hours a second decapitation is carried out for 4mm distance. Primary leaf is now pulled loose and agar block supported against it at the tip of decapitated coleoptile. After 90- 100 mm the coleoptile is found to have bent. The curvature is measured