ABSTRACT
Most studies that have registered amelioration of Al toxicity due to root cation exchange capacity (CEC) decrease with B application were conducted using eudicotyledonous species (high root CEC). However, the effect of B/Al interaction on the root CEC values in species with low root CEC such as corn (Zea mays L.) has been understudied. Thus, this study aimed to: (1) verify if B decreases root CEC and if it benefits the growth and nutrient uptake in corn plants under Al toxicity; and (2) verify which method of root CEC analysis better differentiates the effects of B and Al. Corn seedlings were grown in complete nutrient solution with the following treatments: 0, 50, and 200 µM of B versus 0 and 300 µM of Al. Root attributes showed correlations with nutrient depletion from the nutrient solution, but nutrient depletion generally varied with transpiration in two depletion tests. The addition of B or Al in nutrient solution decreased root CEC; however, B failed to decrease Al toxicity in corn plants. The four methods used to determine CEC of corn roots had contrasting results, particularly with respect to the effect of B in the presence of Al.
A maioria dos estudos que registraram amenização da toxidez de Al devido ao decréscimo da capacidade de troca de cátions (CTC) radicular com a aplicação de B foram realizados com espécies eudicotiledôneas (alta CTC radicular). Contudo, o efeito da interação B/Al nos valores de CTC radicular em espécies de baixa CTC radicular, como no milho (Zea mays L.), é pouco conhecido. Assim, os objetivos desse estudo foram: (1) verificar se o B reduz a CTC radicular e se isso beneficia o crescimento e a absorção de nutrientes em plantas de milho sob toxidez por Al; (2) verificar qual método para análise de CTC radicular diferencia melhor o efeito do B e Al. Plântulas de milho foram cultivadas em solução nutritiva completa com os seguintes tratamentos: 0, 50 e 200 µM de B versus 0 e 300 µM de Al. Os atributos radiculares apresentaram correlações com a depleção de nutrientes da solução nutritiva, mas, em geral, a depleção de nutrientes variou principalmente com a transpiração em dois testes de depleção. A adição de B na solução nutritiva reduziu a CTC radicular, o que também ocorreu quando o Al foi adicionado, contudo, o B não aliviou a toxidez por Al nas plantas de milho. Os quatro métodos usados para determinar a CTC radicular do milho tiveram resultados contrastantes, particularmente com relação ao efeito do B na presença de Al.
Subject(s)
Boron , Soil Acidity , Plant Roots , Toxicity , AluminumABSTRACT
ABSTRACT Native to subtropical region of South America, yerba mate is responsive to P under some conditions, but the degree of influence of genetic and soil on the growth and composition of the leaf is unknown. The aim of study was to evaluate plant growth, nutrients and potentially toxic elements in leaves of yerba mate clones in response to P application in acid soils. In greenhouse condition, two yerba mate clone seedlings were grown (210 days) in pots, each clone in a completely randomized design in factorial scheme (with and without P; four acid soils). The elemental composition of leaves and the growth of plants were determined. Phosphorus promoted plant growth, but this was not accompanied by increased P in leaf tissue in all conditions tested. The P effect on the elemental composition varied: decrease/null (N, K, Mg, Mn, Cu, Ni, B, Mo, Al, Cd); increase/null (C/N, C, Ca, Fe, V); increase/decrease/null (Zn, Ba, Pb) and; null (Cr). The soils affect the elemental composition of the leaves, especially Mn, with accumulation greater than 1000 mg kg-1. The Ba, Pb, Al and Zn in the leaves varied among clones. Yerba mate response to P was affected by edaphic and plant factors.
Subject(s)
Phosphorus/chemistry , Soil/chemistry , Clone Cells/chemistry , Plant Leaves/chemistry , Ilex paraguariensis/growth & development , Ilex paraguariensis/chemistry , Reference Values , Seeds/growth & development , Seeds/drug effects , Time Factors , Trace Elements/analysis , Random Allocation , Plant Leaves/drug effects , Ilex paraguariensis/drug effects , Fertilizers , Plant Development/drug effectsABSTRACT
In Brazil, Zn deficiency is common in soils used for maize cultivation. However, the changes in the mineral composition in plants with Zn deficiency have been little studied. Thus, this study aimed to evaluate the relationship between Zn deficiency and the mineral composition in the parts of maize plants grown under contrasting soils. Maize was grown in greenhouse conditions with increasing of Zn rate (0, 0.125, 0.25, 0.5 and 1.0 mg kg-1) in two soils (Ferralsol and Cambisol). After 60 days of emergence, the plant were separated into roots, stalk nodes, stalk internodes, leaves and leaf sheath, and subsequently determined the dry matter and mineral composition (P, Ca, Mg, K, Zn, Fe, Mn, Cu and Al). Besides the symptoms commonly described for Zn deficiency, darkening of the stalk nodes was found (related to the preferential accumulation of Fe), and also occurred maize P deficiency in the Ferralsol. The Zn deficiency favored increasing concentrations of Fe, Mn and Al in all parts of maize plants in Cambisol, whereas in Ferralsol this did not happen for any of the elements analyzed. Relations between the elements and Zn were more correlated with maize dry matter production than Zn concentrations in leaves, leaf sheaths and stalk nodes. In conclusion, the accumulation of minerals in maize was favored by Zn deficiency, especially for maize in Cambisol.
No Brasil, a deficiência de Zn é comum em solos utilizados para o cultivo do milho. Contudo, as mudanças na composição mineral das plantas resultantes da deficiência de Zn têm sido pouco estudadas. Assim, esse estudo objetiva avaliar a relação entre a deficiência de Zn e a composição mineral nas partes de plantas de milho cultivadas em solos contrastantes. O milho foi cultivado em casa de vegetação com doses crescentes de Zn (0; 0,125; 0,25; 0,5 e 1,0 mg kg-1) em dois solos (Latossolo e Cambissolo). Após 60 dias da emergência, as plantas foram fracionadas em raízes, nós do colmo, entrenós do colmo, folhas e bainha das folhas, sendo, posteriormente, determinadas a matéria seca e a composição mineral (P, Ca, Mg, K, Zn, Fe, Mn, Cu e Al). Além dos sintomas comumente descritos para deficiência de Zn, constatou-se escurecimento dos nós do colmo (relacionado ao acúmulo preferencial de Fe), sendo que no Latossolo também ocorreu deficiência de P. A deficiência de Zn favoreceu o aumento das concentrações de Fe, Mn e Al em todas as partes das plantas de milho no Cambissolo, enquanto que no Latossolo isso não ocorreu para nenhum dos elementos analisados. As relações entre os elementos e o Zn foram mais correlacionadas com a produção de matéria seca do milho que as concentrações de Zn em folhas, bainhas das folhas e nós do colmo. Pode-se inferir que a acumulação de minerais no milho foi favorecida pela deficiência de Zn, principalmente no Cambissolo.