An assay was conducted under growth chamber condition to study the hairy beggar-ticks (Bidens pilosa) tolerance to different pH levels of the substrate. Three seedlings were transplanted into recipients containing Hoaglands & Anion's nourfishing solution with pH ajusted to 3.5, 4.0, 5.0, 6.0, 7.0 and 8.0 . The experimental design used was the completely randomized with three replications. At the end of the experimental period (42 days after transplantation) the development of the plants at pHs 3.5 and 8.0 appeared to be smaller in the following aspects: radicular system in length and volume, number of living leaves, and dry matter of the leaves, stem and roots. The N and S contents in the roots diminished as the substrate pH increased, while the Ca and Mg contents increased and K and P diminished at pH 5.0 to 6.0. Mg was the only element to be affected in the stem, showing a positive response. The highest contents of P, S, Ca and Mg were obtained on the leaves when the plant developed at pH 6,0. No significant difference was observed among the pHs 5.0, 6.0 and 7.0 on the evaluated parameters; however, at pH 6.0 a better development of the begga r-tick was evaluated through a regression analysis. It was concluded that the beggar-tick shows its better development at pHs close to neutral, although it presents certain tolerance to extreme pHs (3.5 and 8.0).
mineral nutrition; weed biology; plant growth; weed; Bidens pilosa