Abstract
A localized supply of phosphorus may affect root morphology and architecture, and thereby affect phosphorus
uptake by rice plants. In the present study, we attempted to test this hypothesis using two rice cultivars representing
upland and lowland ecotypes grown in specially designed split and stratified soil cultures with a low-phosphorus
red soil. Our data indicate that a localized supply of phosphorus increased both total root length and root fineness,
particularly in the high-phosphorus zone. In split culture, plants roots tended to preferentially grow on the highphosphorus
zone, with about 70–75% of the total root length allocated to the high-phosphorus compartment. The
total root length on the high-phosphorus side in the split-phosphorus treatment was significantly longer than that
in the homogenously high-phosphorus treatment, implying that a phosphorus-deficiency signal from the lowphosphorus
side may stimulate the growth of the roots located in the high-phosphorus zone. In stratified soil
culture, changes in root morphology and architecture were also observed as indicated by increased total root length,
root fineness and relative root allocation in the high-phosphorus layers, again suggesting altered root morphology
and preferential root proliferation in the high-phosphorus regions. The induced changes in root morphology and
architecture by localized phosphorus supply may have both physiological significance and practical implications
in that plants can meet the demand for phosphorus with parts of the roots reaching the high-phosphorus zone,
hence localized fertilization methods such as side dressing or banded application of phosphorus fertilizers may
both minimize phosphorus fixation by the soil and increase phosphorus uptake efficiency from the fertilizers.