Calibration of a desktop scanner and digital image analysis procedure for quantification of root morphology

Methodological tests with dark metal wires and barley roots showed that sel ecting proper scanner brightness adjustment is crucial when calibrating a d esktop scanner for digital image analysis of root morphology. At high brigh tness the digitization of roots was incomplete, and thus the real length an d width of the roots were underestimated. Lowering of the brightness improv ed the digitization, whereas stronger staining of the roots alone was not e ffective. Inaccurate results were produced also, if the size of the scanned sample was too large. The variation caused by the scanning and image analy sis itself was minimal. A small amount of dry matter was lost from the root s during the preservation in the ethanol solution for several months before scanning. If absolute data on root masses are required, this loss cannot b e neglected. Subsampling is strongly recommended to reduce the time require d for the procedure.