Lanthanum content and effects on growth, gas exchanges, and chlorophyll index in maize plants / Teor de lantânio e efeitos no crescimento, trocas gasosas e teor de clorofila em plantas de milho

Rare earth elements, such as lanthanum (La), have been applied to agriculture via fertilizers, aiming to increase the productivity and crop quality, such results observed mainly in China. However, the knowledge about the effect of La on maize growth, as well as for other species, despite the growing interest it is still limited. The aim of this study was to evaluate the effects of La on maize growth, La content,photosynthetic rate and chlorophyll content in maize plants in response to La treatment (0, 25, 50, 100, 150, 300 and 600 μM) in nutrient solution for three weeks. The plants were placed in geminated pots using a split-root technique. One of the pots in the geminated set was filled with a complete nutrient solution without La, while another was filled with a nutrient solution without phosphorus but containing different concentrations of La. It was verified that roots of maize plants can accumulate approximately sixty percent more La than shoots. Moreover, low La concentrations stimulated an increase in chlorophyll index,resulting in a slight increase in shoot biomass. At higher levels, La didn’t reduce growth but caused adecrease in both photosynthetic rate and chlorophyll index.

Elementos terra rara, como lantânio (La), são aplicados à agricultura via fertilizantes, com oobjetivo de aumentar a produtividade e a qualidade das culturas agrícolas, fato observado principalmente naChina. Entretanto, o conhecimento sobre o efeito de La no crescimento do milho, bem como para outrasculturas agrícolas, ainda é limitado apesar do interesse crescente. O presente estudo objetivou avaliar oefeito da aplicação de La sobre o crescimento, teor de La, fotossíntese e teor de clorofila em plantas demilho, expostas a concentrações crescentes de La (0, 25, 50, 100, 150, 300 e 600 μM) em solução nutritivapor três semanas. As plantas foram colocadas em vasos geminados usando uma técnica de raiz divisória.Um dos potes no conjunto geminado foi preenchido com solução nutritiva completa que não continha La,enquanto outra foi preenchida com solução nutritiva sem fósforo, mas contendo diferentes concentraçõesde La. Foi verificado que as raízes das plantas de milho podem acumular sessenta por cento mais La quandocomparado à parte aérea. Além disso, as baixas concentrações de La estimularam o aumento do teor declorofila, resultando em um aumento na biomassa da parte aérea. Em concentrações mais elevadas, aaplicação de La não reduziu o crescimento das plantas de milho, mas causou diminuição na taxafotossintética e no índice de clorofila.

Selective spectrophotometric determination of thorium, uranium and lanthanum using arsenazo I

Several techniques are used for the determination of Th, U and La in different media. But these techniques are limited considering the performance, including UV/VIS Spectrophotometer, X-ray fluorescence spectrometry, atomic absorption and emission spectrometry [1,2]. The atomic absorption spectrometry isn't applicable for the determination of Th and U because of the non-availability of the hollow cathode lamps[3]. Strong claims are made for the specificity and sensitivity of NAA, ICP-AES and ICP-MS, inspite of the fact that interference is a problem using these techniques. Hence the application of organic reagents for the spectrophotometric determination of these elements is well-known and continues to be applied[4]. Several organic and inorganic reagent have been reported for the spectrophotometric determination of Th, U, and La[5,6]. Arsenazo I is considered to be suitable for the spectrophotometric determination for many elements because it is commercially available and is water-soluble. The reagent has ability to form stable complexes in strong acidic and basic media. Th, U and La often coexist in ores like monazite and other minerals and their selective determination is a problem in analytical chemistry[4] therefore the aim of the present investigation is to establish a procedure for the selective determination of Th, U, and La depending on pH adjustment