A COLOR COMPOSITE TECHNIQUE FOR DETECTING ROOT DYNAMICS OF BARLEY (HORDEUM-VULGARE L) FROM MINIRHIZOTRON IMAGES

Quantification of root dynamics by destructive methods is confounded b y high coefficients of variation and loss of fine roots. The minirhizo tron technique is non-destructive and allows for sequential root obser vations to be made at the same depth in situ. Observations can be stor ed on video tape which facilitates data handling and computer-aided im age processing. A color composite technique using digital image analys es was adapted in this study to detect barley root dynamics from seque ntial minirhizotron images. Plants were grown in the greenhouse in box es (80 X 80 X 75 cm) containing soil from a surface horizon of a Typic Cryoboroll. A minirhizotron was installed at a 45-degrees-C angle in each box. Roots intersecting the minirhizotron were observed and video -recorded at tillering, stem extension, heading, dough and ripening gr owth stages. The images from a particular depth were digitized from th e analog video then registered to each other. Discrimination of roots from the soil matrix gave quantitative estimates of root appearance an d disappearance. Changes in root appearance and disappearance were det ected by assigning a separate primary color (red, green, blue) to sele cted growth stages, then overlaying the images to create red-green and red-green-blue color composites. The resulting composites allowed for a visual interpretation and quantification of barley root dynamics in situ.