Rapid bioassay for kinetin & kinins using senescing leaf tissue

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Abstract
A simple and rapid bioassay for kinetin and kinins based upon the ability of these compounds to preserve chlorophyll in senescing Xanthium pensylvanicum leaves is described. Residual chlorophyll content is determined from the optical density at 665 mu of an 80% ethanol extract of leaf disks which have previously been treated with kinetin for about 2 days under standard conditions. The residual chlorophyll content is proportional to the logarithm of kinetin concentration over the range from 0.05-5.0 ug per treatment. A strong positive '' response is obtained with 6 benzylamino-purine and its riboside as well as with kinetin itself. Purines, 1,3-dimethyluria, benzimidazole and high concentrations of sugars give a weakly positive response while auxins and amino acids give a completely negative response. The assay may be used either to test materials in solution or to test directly zones from paper chromatograms.