Influência de doses crescentes de chumbo sobre o teor e o conteúdo de nutrientes e Pb em mudas de ipê-roxo (Tabebuia impetiginosa (Mart.) Standl.)

Abstract

O efeito da aplicação de chumbo sobre o teor e o conteúdo de nutrientes e Pb na raiz, no caule e nas folhas de mudas de ipê-roxo (Tabebuia impetiginosa (Mart.) Standl.) foi estudado em um experimento realizado em casa de vegetação do Departamento de Ciência do Solo da Universidade Federal de Lavras. As mudas foram cultivadas em solução nutritiva de Clark e submetidas a doses crescentes de Pb: 0, 48, 96, 192 e 288 mimol/l. O experimento foi conduzido em delineamento estatístico de blocos ao acaso, e após 60 dias de exposição ao metal pesado foram feitas avaliações do teor e do conteúdo de macro, micronutrientes e chumbo na matéria seca de raiz, caule e folha. Os resultados mostraram que a aplicação de chumbo aumentou o teor de P e praticamente não afetou os teores de S, Ca e Mg nas mudas. De modo geral os teores de Cu, Fe e Mn sofreram redução, o teor de Zn não foi afetado, enquanto o conteúdo de macro e de micronutrientes sofreu redução. O teor de Pb na matéria seca de raiz, caule e folha aumentou com as doses aplicadas, principalmente na raiz, e se mostrou pouco móvel nas plantas analisadas.

Growth and Micronutrient Concentration in Maize Plants Under Nickel and Lime Applications

“…Paiva et al (2002) observed that in stems and leaves of cedar seedlings, the iron content had a positive quadratic response, falling to doses of 128.4 and 98.0 mmol of nickel, respectively, and increasing with higher doses, indicating that, up to a certain dose of nickel, there is restricted iron transport from the root to the shoot. This effect has been observed in many plant species (YANG et al, 1996), although in tomato plants a reduction in iron absorption occurred when the nickel dose of the nutrient solution ranged from 0 to 510 mmol (PALACIOS et al, 1998).…”

“…A decrease in manganese concentration in barley shoots was observed by Rahman et al (2005) in response to nickel application.In tomato plants, manganese was the divalent cation that suffered the most restriction in terms of absorption when nickel was present (PALACIOS et al, 1998).As in the case of manganese, he application of nickel and liming significantly reduced (P <0.01) zinc concentrations in leaves and roots ( Figures 3A and 3C), but not in stems ( Figure 3B). The greatest differences in zinc concentrations in leaves and roots under liming were observed at lower doses, and consequently there was a reduction of this difference as nickel doses increased.…”

“…Paiva et al (2002) demonstrated that nickel applications led to a positive quadratic response in the root zinc content of Cedrela fissilis Vell, suggesting an antagonistic response up to a dose of 200.2 mmol. Likewise, Palacios et al (1998) observed a reduction in root zinc content in tomato plants exposed to nickel doses.…”

“…Yang et al (1996) found that there was a reduction in copper absorption in the presence of nickel in Trifolium repens and Brassica oleracea plants, while copper absorption was not affected by nickel in Lolium perenne plants. In tomato plants, Palacios et al (1998) found that the presence of nickel significantly decreased copper absorption. In the case of iron, there were significant differences in iron concentration in leaves at various nickel doses, with iron increasing linearly with increasing nickel dose ( Figure 5A).…”

“…In addition to causing toxicity in plants when present at high concentrations in the soil, nickel can also interfere with the absorption of other nutrients. Nickel is absorbed in the form of Ni +2 , so its absorption at high concentrations can significantly decrease the absorption of other divalent cations, such as Mg, Fe, Mn, Cu and Zn, with Mn the element that is most restricted (PALACIOS et al, 1998). In soils with high levels of nickel, liming can promote a significant reduction in the absorption and accumulation of this element by plants, thus reducing its toxic effects.…”