1988 Volume 57 Issue 4 Pages 671-677
Paddy rice ( Oryza sativa L.) root mass was analyzed from the viewpoint of developmental changes in quantitative characters and growth correlation with leaf mass. The total root length was expressed as (primary root number)×(average primary root length)×("coefficient of branching"), or (total primary root length)×("coefficient of branching"), where the "coefficient of branching" is the ratio of the total root length to the total primary root length. The average primary root length and the "coefficient of branching" increased linearly, while the primary root number, the total primary root length and the total root length increased exponentially with plant age in leaf number. To the increase in the total root mass, the increase in the primary root mass contributed much more than in the degree of primary root branching. The allometric formula : log (root mass) = k·log (leaf area) + b was calculated in earlier and Later growth periods separately. The coefficient of allometry, k, was smaller than l during the earlier period when the main stem leaves emerged quickly, while the value of k exceeded l after the leaf emergence speed became slower. This showed there might be two developmental stages before heading in rice plants, probably corresponding to the conversion of growth phase. Such a switching was presumably regulated by the changes in the primary root mass rather than in the degree of primary root branching.
