Indirect assessment of callus fresh weight by non-destructive methods.

The size of callus of Nicotiana plumbaginifolia was measured by determinations of fresh weight (FW), area (electronic planimeter and a point-counting method) and width (standard width and greatest width). All these methods, with the exception of the standard width measurements, were found to produce adequate substitutes for fresh weight.Particular advantages apply to the use of the point-counting method, but the relationship between callus area and point interval was found to be critically important in determining the accuracy of measurements. The use of surface dimensions rather than FW permits continuous measurement of callus size without disturbance of the callus or its environment within the containers.