EVALUATION OF VIDEO IMAGE-ANALYSIS AND LINE-INTERCEPT METHODS FOR MEASURING ROOT SYSTEMS OF ALFALFA AND RYEGRASS

Improved quantification of plant root systems is essential for determi ning the functional efficiencies of plant roots. The objective of this study was to evaluate the video image analysis procedure of quantifyi ng roots of different species and compare it with more traditional mea surements. Three methods were used to quantify roots of alfalfa (Medic ago sativa L.) and perennial ryegrass (Lolium perenne L.) from a green house experiment: (i) root length by video image analysis, (ii) root l ength by the line-intercept method, and (iii) dry root weight. Estimat es of root length by image analysis and line-intercept methods were co mparable for alfalfa acid were positively correlated with root weight. In contrast, the correlation between image analysis and line-intercep t estimates of ryegrass root length was poor (r(2) = 0.090), and no si gnificant relationship was found between ryegrass root length and root weight. Difficulty in the quantification of ryegrass roots was relate d to the large numbers of very fine roots, which resulted in extremely large root lengths and excessive error, Root data of ryegrass (and sp ecies with similar Foot morphology) obtained by the line-intercept met hod may provide only relative values to be compared among these specie s. The image analysis method of root measurement is bound to improve r oot data with increased magnification and resolution of the video imag es when the root density in the image (cm cm(-2)) is sufficiently low.