EVALUATION OF SORGHUM ROOT BRANCHING USING FRACTALS

Root branching and architecture play a significant role in water and n utrient uptake, but description of these parameters has not been easy due to the difficulty of observing roots in their natural arrangement. Fractal geometry offers a novel method for studying the branching pat terns of roots. Piano of ten diverse sorghum (Sorghum bicolor (L.) Moe nch) genotypes (five of African origin, three of US origin and two hyb rids composed of African x US lines) were grown in root boxes containi ng 80% sand and 20% fine-textured Sharpsburg silty clay loam topsoil. The poor fractal dimension (D) and abundance (log K) were determined a t nine regions within the profile. Roots were washed free of growth me dia and photographic slides were taken of each region. Values of D and log K were determined by projecting photographs onto grids of progres sively increasing sizes. The number of intersects was regressed on log grid size. Differences in D were found among genotypes (1.44 less tha n or equal to D less than or equal to 1.89) suggesting that these sorg hum genotypes may be associated with greater root branching patterns. Greater fractal dimension (branching) and abundance values occurred in the 0-35 and 35-70 cm depths of the soil profile within the root box, indicating a greater root distribution in that part of the profile. S ignificant differences were also noted in branching patterns for sorgh um genotypes derived from different sources. In general, the African s orghums were more branched and deeper rooted than the US-derived genot ypes. Results indicated that fractal dimension can be used for the des cription of sorghum root system morphology and provides a good measure of branching patterns which can be distinguished.