The bioassay methods which may be employed for the estimation of cytokinin in a plant tissue may be summarized as follows:

Cell Division Test:

The most satisfactory method of cytokinin bioassay is based on the induction of cell division in tissue cultures. Best tissues used for this bioassay are tobacco pith tissue and soybean callus tissue. Tissues are generally grown for 2-4 weeks on media in which cytokinins have been added, after which fresh and dry weights are determined and compared with suitable controls.

Chlorophyll Preservation Test:

This bioassay is based on the Richmond-Lang effect which suggests that cytokinins are involved in the retardation of senescence through the preservation of chlorophyll. In this bioassay, leaf DISCS are placed in test solutions in dark, then after a definite period chlorophyll is extracted and measured. A linear relationship is found between the amount of chlorophyll retained and LOG of cytokinin concentration.

Cell Enlargement Test:

Leaf discs of Raphanus sp. are floated on cytokinin solutions in light for a definite period of time and then weighed after blotting off the excess liquid. It is also suggested to MEASURE the increase in diameter of the leaf discs caused by cell enlargement which is proportional to cytokinin CONCENTRATIONS.

Differentiation Test:

Generally, moss Protonema RESPOND to cytokinin by an increase in bud formation and a bioassay seems to be possible by using this cytokinin effect.

The bioassay methods which may be employed for the estimation of cytokinin in a plant tissue may be summarized as follows:

Cell Division Test:

The most satisfactory method of cytokinin bioassay is based on the induction of cell division in tissue cultures. Best tissues used for this bioassay are tobacco pith tissue and soybean callus tissue. Tissues are generally grown for 2-4 weeks on media in which cytokinins have been added, after which fresh and dry weights are determined and compared with suitable controls.

Chlorophyll Preservation Test:

This bioassay is based on the Richmond-Lang effect which suggests that cytokinins are involved in the retardation of senescence through the preservation of chlorophyll. In this bioassay, leaf discs are placed in test solutions in dark, then after a definite period chlorophyll is extracted and measured. A linear relationship is found between the amount of chlorophyll retained and log of cytokinin concentration.

Cell Enlargement Test:

Leaf discs of Raphanus sp. are floated on cytokinin solutions in light for a definite period of time and then weighed after blotting off the excess liquid. It is also suggested to measure the increase in diameter of the leaf discs caused by cell enlargement which is proportional to cytokinin concentrations.

Differentiation Test:

Generally, moss Protonema respond to cytokinin by an increase in bud formation and a bioassay seems to be possible by using this cytokinin effect.