Root branching and architecture play a significant role in water
and nutrient 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
patterns of roots.
Plants of ten diverse sorghum (Sorghum bicolor (L.) Moench) genotypes
(five of African origin, three
of US origin and two hybrids composed of African×US lines) were grown
in root boxes containing
80% sand and 20% fine-textured Sharpsburg silty clay loam topsoil. The
root fractal dimension (D)
and abundance (log K) were determined at nine regions within the
profile. Roots were washed free
of growth media and photographic slides were taken of each region. Values
of D and log K were
determined by projecting photographs onto grids of progressively increasing
sizes. The number of
intersects was regressed on log grid size. Differences in D were
found among genotypes
(1·44[les ]D[les ]1·89) suggesting that these sorghum
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. Significant differences were also noted in branching
patterns for sorghum
genotypes derived from different sources. In general, the African sorghums
were more branched and
deeper rooted than the US-derived genotypes. Results indicated that fractal
dimension can be used
for the description of sorghum root system morphology and provides a good
measure of branching
patterns which can be distinguished.