BIOASSAYS

FOR THE DETECTION OF AUXIN AND CYTOKININ ACTIVITY IN PRODUCTS FOR AGRICULTURAL USE

A bioassay is the process used to determine the potential of a substance based on the responses produced in biological organisms.

At Intra Radice we carry out bioassays to obtain information on auxin or cytokinin-like activity of certain products, e.g. seaweed extracts, humic substances, etc.

It is important to determine the auxin and cytokinin content present in each product, as well as the auxin/cytokinin ratio.

A product where auxins are dominant should produce more of an auxin-type response in a treated plant. Similarly, a product would be expected to generate more of a cytokinin-type reaction when cytokinin predominates, almost independently of the total amount of both.

The hormone ratios will determine the responses in the plants, so it is important to know these data for products with agricultural uses.

STUDY METHOD 1

Auxin activity

The capacity of the products under study to develop auxin-like activity is detected using the oat coleoptile elongation test.

This test compares the activity of the products on coleoptiles with that resulting when using a substance with known auxinic capacity.

STUDY METHOD 2

Cytokinin activity

The method used consists of following the principles proposed by Letham (1971) in his “Radish cotyledon bioassay for cytokinins”.

This study demonstrates the capacity of cytokinins (6-furfurylaminopurine or Kinetin) to promote the expansion of excised radish cotyledons.

The cotyledon mass weight results obtained with the products tested are then compared with those corresponding to known concentrations of cytokinin.