Com a finalidade de determinar a disponibilidade do boro, cultivou-se o girassol em casa de vegetação, usando-se solos de cinco séries do município de Piracicaba, SP e sete doses do elemento. Durante o período experimental de 40 dias foram obtidos dados de crescimento e registrados sintomas de deficiência. No material colhido foram determinados macro e micronutrientes. Foram tiradas as seguintes conclusões principais: a altura das plantas refletiu o estado nutricional melhor do que qualquer outra característica das mesmas; o teor de B das folhas mais novas forneceu a melhor avaliação da resposta das plantas, entre as partes analisadas.
Sunflower plants were grown in the greenhpuse in five soil series of the Piracicaba Country, S. Paulo, Brazil (Terra Roxa Estruturada, TRE; Roxo Latosol, LR; Red Latosol, LV; Red Yellow Podzolic: PVA- Quartz sand, AQ), under seven rates of B (from 0 to 1 ppm). A visual assessment, based on the age of the plants when first symptoms of B deficiency showed up, disclosed that the PVA had the lowest available B concentration being followed by LV, AQ, TRE and LR. Insolar as growth data are concerned it has been found that plant heightt was the characteristic showing higher correlation with available B in the soil. The tissue concentration of P, Mg, and B consistently increased at low levels of boron in the soil. The leaf concentration of Cu, Fe, Mn, and Zn was unaffected by the B supply, the reverse being true, however, in the case of boron. The concentration of B in young leaves (upper third of the plant), among all organs (roots, stems, older leaves) analysed provided the best correlations with the availability of the micronutrient under study.