Vergleich von zwei nicht-destruktiven Methoden zur Bestimmung von Wurzeloberflächen

Comparison of two non-destructive methods for determination of root surface areas In order to study root growth and development continuously in water culture experiments, two non-destructive rapid methods of estimating root surface area were compared. In the methylene blue method roots are stained for 30 seconds in methylene blue solution (74.7 mg/l). After washing off adhering methylene blue the adsorbed cationic dye is exchanged with Ca²⁺ by incubating the stained root in 0,1 M CaCl₂ solution. The amount of exchangeable methylene blue is determined photometrically at 668 nm. In the ink method, roots are stained for 1 minute with a 1:100 diluted solution of drawing ink. Excess ink is removed by carefully rotating the plant, and adhering ink is allowed to diffuse into destilled water. The quantity of ink is determined photometrically at 500 nm. The root surface area of potato plants estimated with these two methods correlates highly significantly with the root surface area calculated from root volume and root length. In the case of the ink method the calibration curve obtained with potato roots may also be used for other plant species like maize. This is not possible with the methylene blue method. A correction factor depending on the cation exchange capacity of the roots would be needed for this method. With the ink method overestimation of root surface area may occur if abundant root hairs are present. This is due to the formation of droplets in the root hair zone. However for repeated measurements during a growth period the ink method is more suitable since with this method no negative effect on root growth and nutrient uptake can be observed.