The objective of this work was to evaluate the effects of boron rates on dry matter yield and root morphologic parameters of two varieties of upland rice. The experiment was carried out from April to July of 2004, in a greenhouse, in Botucatu, São Paulo State, with two varieties of rice, Caiapó and BRS Talento. The seeds were germinated in a controlled chamber, and five days later, the plants were transplanted in plastic pots of 8 L, being supported by cleaned sand, being kept four plants per pot. The boron rates were 0.0; 0.5; 1.0; 2.0; 4.0 and 8.0 mg of B L-1, applied via nutrient solution. The harvest was accomplished 70 days after planting, being collected separately the shoot and root, and being determined their dry matter and N and B concentrations, as length, surface area and medium diameter of the roots. It was not able to get to the positive effects of boron application, evidencing that, for the rice cropping the optimum rate was lower than 0.5 ml L-1 of B. The application of 3.4 and 3.8 mg L-1 of B caused toxic effects to the Caiapó and Talento cvs., respectively. The toxic limit for the two cvs. roots is the 2.7 mg L-1 of B concentration. Under several boron toxic, the plants of rice reduced drastically the length and increased the radicular diameter, resulting in a smaller absorption nutrients area.
Oryza sativa L.; boron rates; plant nutrition; dry matter yield
