Abstract: Root architecture is closely associated with plant nutrient uptake，and can influence the
nutrient competition among different plants. Root architectures of Stylosanthes‘Graham’and‘CIAT 184’
were compared，and their effects on plant growth and nutrient uptake of Citrus limonia in inter-cropping
condition were investigated. Results indicated that，the biomass，total root length，tap root length and root
tip number were comparable for‘Graham’and‘CIAT 184’in mono-cropping condition，however，the
basal root angle，root surface area and average root diameter of‘CIAT 184’were lower than those of
‘Graham’. In inter-cropping condition，41.4% roots of‘CIAT 184’grew into the root zone of citrus while
only 0.8% roots of‘Graham’grew into the root zone of citrus. Therefore，the biomass and phosphorus
uptake of citrus seedlings inter-cropped with‘CIAT 184’were significantly lower than those with
‘Graham’. This study suggests that Stylosanthes‘CIAT 184’with horizontal root growth are not suitable
for sod culture in orchard when compared with Stylosanthes‘Graham’with vertical root growth，and that
root architecture can be regarded as critical indicator for the screening of grass species.

Key words: citrus, Stylosanthes, root architecture, nutrient competition