Resumen
This study investigated the comparative phytotoxcity effect of heavy metal contamination on Jatropha curcas, Jatropha gossypifolia and Jatropha multifida in contaminated soil from a dump site in Ibadan Nigeria. Seeds of J. curcas, J. gossypifolia and J. multifida were planted in a germination tray and later transplanted into polythene pots filled with 2kg of either control soil or heavy metal contaminated soil, a 3 × 2 factorial experiment laid out in complete randomized design (CRD) replicated four times was adopted; treatments imposed include T1 ? J. curcas/Control Soil, T2 ? J. gossypifolia/Control Soil, T3 ? J. multifida/Control Soil, T4 ? J. curcas/Contaminated soil, T5 ? J. gossypifolia/Contaminated Soil, and T6 ? J. multifida/Contaminated Soil. Weekly variation in growth parameters: the plant height, leave production and stem diameter were measured over the course of 12 weeks. The growth parameters were dependent on a combination of both specie type and level of heavy metal contamination of soil. J. multifida (T3) (36.93cm) performed best, comparable with J. gossypifolia (T2) (34.1cm) after 12 weeks while J. multifida (T6) had the lowest mean plant height (7.23cm) which is not significantly (p<0.05) different from other species on the contaminated soil; for leave production, J. gossypifolia (T2) produced the highest mean number of leaves (9.67) which is comparable with J. multifida (T3) (9.00) and less so with J. curcas (T1) (6.67) with significant leave losses on the contaminated soils after 12 weeks; variation in stem diameter shows that J. curcas (T1) had the highest stem girth (1.96 mm) which is comparable to the value obtained for J. curcas (T4) (1.95mm), while J. multifida (T6) had the lowest stem girth (1.09 mm). J. gossypifolia (T2) and J. multifida (T3) had comparable stem girth of 1.57mm and 1.47mm respectively. Toxicity of heavy metals in the contaminated soil greatly affect the growth parameters of the Jatropha.