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Evaluation of pollen viability by enzymatically induced fluorescence; intracellular hydrolysis of fluorescein diacetate.

Viable pollen grains immersed in a solution of fluorescein diacetate, made up in a concentration of about 10−6 M in sucrose of suitable tonicity (usually about 0.5 M), rapidly accumulate free fluorescein, which can be detected by its fluorescence. This fluorochromatic reaction (FCR) probably depends upon the entry of the nonpolar substrate into the vegetative cell where it is hydrolyzed by esterase to give the polar product, fluorescein, which is retained by the cell membrane. The test is primarily one for the integrity of the plasmalemma of the vegetative cell. Since this integrity is likely to be closely correlated with viability, the FCR provides an effective method for assessing pollen quality.