Physiological and anatomical features of Cd-tolerance in Pfaffia glomerata were examined by exposing plantlets to nutrient solutions with increasing Cd concentrations (0, 15, 45, and 90 µmol Cd L-1), and possible Cd-tolerance markers were established. Cd contents were found to be higher in roots than in shoots. According to the bio-concentration factor data, this species is effectively a Cd-hyperaccumulator, as previously attested. Cd induced the appearance of xeromorphic characteristics in leaves (decreased water potential, increased numbers and decreased stomata size) and increased root endodermis thickness. The enzymatic antioxidant systems of roots and leaves were differently affected by Cd. The coordinated activities of antioxidant enzymes were effective in reducing Cd-induced reactive oxygen species in plants, mainly in leaves. Root endodermis thickness, stomatal size and numbers, root superoxide dismutase, and guaiacol peroxidase, as well as leaf guaiacol peroxidase and catalase activities can all be considered Cd-tolerance markers in Pfaffia glomerata. Due to its high root Cd accumulation, Pfaffia glomerata may be useful in Cd-phytoextraction programs, however the pharmacological use of plants grown in the presence of Cd must be avoided.

The growth and developmental characteristics of grasses and their high biodiversity make such plants suitable for remediation of areas contaminated by heavy metals. Nevertheless, heavy metal toxic effect on the plants may cause alteration in their metabolic pathways, such as photosynthesis, respiration, and growth, modifying plant anatomy. This work aimed to evaluate the effect of levels of soil contamination (0, 7.5 % and 15 % m³ m-3) on biomass production, on photosynthetic characteristics and on anatomical changes in roots and leaves of brachiaria (Brachiaria decumbens Stapf.). After seeds were planted, seedlings were uprooted and replanted in vases containing soil at different contamination levels, being left to rest for 120 days. At the end of that time, plants presented reduced yield of root and shoot dry matter, contents of chlorophyll a, chlorophyll b, total chlorophyll and potential photosynthesis with increased of soil contamination. The cell layers of endodermis and exodermis in the root tissues and the cell walls of the xylem and cortical parenchyma all thickened as contamination increased. In the leaf tissues, the adaxial and abaxial epidermis presented increased thickness while the leaf blade presented reduced thickness as contamination increased with consequent change in the root growth rate. In general, the effects of heavy metal increased with the metal concentration. Some results indicate that B. decumbens seems to have some degree of heavy metal tolerance.

A poluição por metais pesados, particularmente pelo cádmio (Cd), é gerada principalmente pelas atividades de mineração e industrial, uso de adubos fosfatados e lodo de esgotos. Com o objetivo de avaliar o efeito do Cd em características fisiológicas e anatômicas, mudas de eucalipto foram plantadas em concentrações crescentes de Cd em solução nutritiva. As mudas de Eucalyptus camaldulensis permaneceram durante 20 dias em vasos de 1 L contendo solução nutritiva de Clark, sendo os tratamentos de 0, 15, 25, 45 e 90 mmol Cd L-1 fornecido como CdSO4. Durante o período experimental, foram realizadas avaliações de estado hídrico e de teores de pigmentos nas datas 1, 3, 6, 12 e 20 dias após indução dos tratamentos (DAT). As avaliações de produção de fitomassa, teores de Cd e características anatômicas foram feitas com material vegetal coletado no final do período experimental. Houve redução na produção de matéria seca, mesmo nas menores concentrações do elemento. Os teores de clorofila diminuíram com o aumento da concentração de Cd aos 20 DAT, enquanto os teores dos carotenoides foram maiores nas concentrações de 45 e 90 mmol Cd L-1. A peroxidação de lipídeos nas folhas foi crescente com o aumento da concentração do metal aos 20 DAT, enquanto nas raízes o efeito do Cd foi pouco acentuado. O potencial hídrico aumentou em todas as concentrações de Cd aos 12 e 20 DAT. As espessuras dos tecidos radiculares também aumentaram com o aumento das doses de Cd, porém as do mesofilo e do limbo foliar diminuíram. Portanto, os resultados obtidos evidenciam que o tempo de exposição e maiores doses de Cd acentuam os danos ocorridos em E. camaldulensis para a maioria das características avaliadas. Algumas alterações observadas revelam o potencial de tolerância de plantas de E. camaldulensis à exposição ao Cd.

Pollution caused by heavy metals, mainly by cadmium (Cd), is generated by mining and industrial activities, and by the use of phosphated fertilizers and sewage sludge in agriculture. Aiming to investigate the Cd effects on physiological and anatomical features, eucalyptus seedlings in Cd-increasing concentrations in nutrient solution. Seedlings of Eucalyptus camaldulensis remained for 20 days in 1L vases with Clark solutions, and the treatments with 0, 15, 25, 45 and 90 mmol Cd L-1 supplied as CdSO4. Water potential, water potential and pigment content evaluations were carried out on dates 1, 3, 6, 12 and 20 days after treatments induction (DAE). Evaluations of mass production, Cd contents and anatomical characteristics were made with vegetal matter collected in the end of the experimental period. There was a decrease on dry matter production, even in the lowest Cd concentration. Total chlorophyll content decreased with the increase of Cd content in nutrient solution at 20 days after exposure (DAE) whereas carotenoid contents were the highest at 45 and 90 mmol Cd L-1. Lipid peroxidation in leaves increased with increasing Cd levels at 20 DAE, whereas in root, the effect of Cd was less pronunciated. Water potential increased at all Cd concentration at 12 and 20 DAE. Root tissues thickness also increased increased as Cd levels increased, but mesophyll and leave blade thickness decreased. Thus, the results indicate that the exposure time and higher doses of Cd accentuate damages in E. camaldulensis for most of the evaluated traits. Some changes observed reveal the tolerance potential of E. camaldulenses to Cd-exposition.

Toxic levels of Cd can cause protein denaturation and oxidative stress, which result in membrane damage, enzimatic activity changes and other metabolic damage. Some plants may show alteration in the activity of their antioxidant enzymes as a heavy metal tolerance mechanism. This study aims at evaluating the role of enzymes of the antioxidant system in adaptive responses of the accumulator P. glomerata species to levels of cadmium (Cd). Plants were cultivated in nutrient solutions containing concentrations of Cd in the form of CdSO4 (0, 45 and 90 µmol L-1), for 20 d. Cd concentrations and yields of root and shoot dry matter were determined at the end of the experiment. Malondialdehyde (MDA) production and the activities of antioxidant enzymes were determined after days 1, 12 and 20. Higher Cd concentrations in tissues of P. glomerata were found to reduce biomass production in both roots and shoots. The lipid peroxidation rates in leaves and roots were smaller at the start of the experiment for all Cd levels. Superoxide dismutase (SOD) activity increased in leaves on day 1 and in roots on day 20 as Cd levels increased. Cd stress induced an increase in the activity of APX in leaves, whereas in roots ascorbate peroxidase (APX) activity was reduced at high concentration of Cd. At the end of the experiment, catalase (CAT) activity in leaves was reduced as Cd concentration increased. Nevertheless, the glutathione reductase (GR) and guaiacol peroxidase (GPX) activities increased. In roots, GR activity was reduced on days 1 and 20.

A poluição por metais pesados, gerada principalmente pelas atividades de mineração e industrial, exige estudos que possibilitem a recuperação de áreas contaminadas. Foram estudadas respostas de crescimento e características anatômicas de plantas jovens de salgueiro cultivadas em solo multicontaminado por metais pesados. As plantas foram cultivadas em três níveis de misturas de solo contaminado: 0%; 15% e 30% (v/v), durante 60 dias. No maior nível de contaminação foi observado menor produção de matéria seca das raízes e da parte aérea e menor crescimento das raízes. Nesta condição, as raízes apresentaram maior espessura da epiderme, exoderme e endoderme e menor número de elementos condutores de xilema. As folhas apresentaram modificações no número de elementos condutores de xilema, na densidade e diâmetro dos estômatos, e na espessura da epiderme, endoderme, colênquima e do mesofilo.

The heavy metal pollution caused mainly by mining and industrial activities requires studies for the recovery of contaminated areas. Thus, we studied growth and anatomical characteristics responses of young willow plants grown in heavy metal multicontaminated soil. Plants were grown in three mixture levels of contaminated soil: 0%, 15% and 30% (v/v) for 60 days. At the highest level of contamination was noted a less dry matter production of roots and shoots and reduced root growth. Accordingly, the roots exhibited epidermis, exodermis and endodermis thicker, and a smaller number of conducting elements of xylem. Leaves showed changes in the number of conducting elements of xylem diameter and density of stomata, and epidermis, endodermis, collenchyma and mesophyll cell thickness.

Avaliaram-se em casa-de-vegetação o acúmulo e a distribuição de metais pesados nas raízes, caule e folhas de mudas de vinte espécies arbóreas tropicais crescendo em solo contaminado com metais pesados. As mudas com tamanho ideal para plantio foram transferidas para vasos contendo 3,3 kg de solo sem contaminação ou contaminado com Zn, Cd, Cu e Pb, onde permaneceram por 90 dias. As espécies que cresceram em solo contaminado apresentaram teores foliares elevados, variando de (mg kg-1): Zn = 154 a 1177; Cd = 0,6 a 54,6; e Cu = 2,8 a 134. Essas concentrações foram, em muitos casos, superiores aos níveis críticos de toxidez, ao passo que os teores foliares de Pb variaram de 0,1 a 4,3 mg kg-1, não atingindo níveis considerados fitotóxicos. Em algumas espécies como Machaerium nictidans, Myroxylon peruiferum, Piptadenia gonoacantha, Senna macranthera e Trema micrantha, que tiveram o crescimento muito inibido pela contaminação, houve elevada translocação de Zn e/ou Cd para parte aérea. Dendropanax cuneatum, que foi pouco afetada pelos metais, também apresentou índice elevado de translocação de Zn e Cd, mas reteve esses elementos no caule. Acacia mangium, Copaifera langsdorffi e Cedrella fissilis também apresentaram baixa sensibilidade à contaminação e apresentaram elevado acúmulo de Zn e Cd nas raízes, indicando que a baixa translocação desses elementos para a parte aérea está envolvida na tolerância dessas espécies ao excesso de metais pesados no solo. O padrão de distribuição proporcional de Zn e Cd nas raízes e parte aérea das plantas se relaciona com o comportamento dessas ao excesso de metais pesados no solo.

An experiment was carried out in greenhouse to evaluate total content and distribution of heavy metals in seedlings of twenty different tree species growing in a soil contaminated by Zn, Cd, Cu and Pb. Plantable size seedlings were transfered to 3.3 kg pots containing a contaminated soil mixture and to a control soil without contamination where they were allowed to grow for ninety days. Metal foliar concentrations for plants grown in the contaminated soil were high, ranged from (mg kg-1): Zn= 154 to 1177; Cd = 0.6 to 54.6 and Cu= 2.8 to 134. In most cases, these concentrations were superior to what has been considered as critical toxic levels, whereas foliar Pb concentrations ranged from 0.1 to 4.3 mg kg-1, below the critical toxic level. In some species that were highly affected by contamination such as Machaerium nictidans, Myroxylon peruiferum, Piptadenia gonoacantha, Senna macranthera and Trema micrantha it was found high translocation index for Zn and/or Cd. However, Dendropanax cuneatum that was only slightly affected by contamination, exhibited high translocation of Zn and Cd to shoots. In contrast to others species, Dendropanax cuneatum retained these elements in the stems. Other group of plants that were only slightly affected by soil contamination such as Acacia mangium, Copaifera langsdorffi and Cedrella fissilis accumulated more Zn and Cd in the roots than in the shoots, therefore indicating that reduced translocation is involved in their tolerance to the excess of heavy metal in soil. The proportional distribution pattern of Zn and Cd in the roots and shoots of the studied plant species is related to their behavior to the excess of heavy metals in soil.

Este trabalho foi elaborado com o objetivo de verificar o efeito das palhas de milho e lab-lab, dos tipos de manejos do solo e da presença de uma fonte externa de N, no evolvimento de CO2 e na mineralização de N. Usou-se um Latossolo Vermelho-Escuro distrófico textura argilosa fase cerrado, da região de Sete Lagoas (MG), com histórico de uso envolvendo cinco anos sob plantio direto e plantio convencional com arado de disco e arado de aiveca. Amostras de solo (0-20 cm) foram incubadas a 25ºC durante 55 dias, na presença e na ausência de palhada residual e de fonte externa de N aplicada no início e 25 dias após. De modo geral, a palhada de milho apresentou maior taxa de CO2 evolvido do que o lab-lab (935 e 764 mig CO2 g-1 solo, respectivamente). O tipo de palhada residual influenciou mais o evolvimento de CO2 do que os manejos de solo. A adição de N aumenta a taxa de CO2 evolvida, apenas quando N é aplicado no início do período de incubação. A disponibilidade de N e o tempo de imobilização são alterados pela relação C/N da palhada incorporada e pelo preparo do solo.

The objective of this work was to verify the influence of different types of straw (maize and lablab) and soil management on evolving CO2 and N mineralization. A dystrophic clayey Dark-Red Latosol under Cerrado from the region of Sete Lagoas, MG, Brazil, was cultivated during five years with no-tillage, disc-plow and moldboard-plow. Soil samples (0-20 cm) were incubated at 25ºC during 55 days, with and without N fertilizer applied at the beginning and 25 days afterwards. As a general rule, the maize straw had higher rates of evolved CO2 than the lablab (935 e 764 mug CO2 g-1 soil, respectively). The type of straw influenced the amount of CO2 evolved more than the type of soil management did. Nitrogen addition increases the rate of CO2 evolved only when applied at the beginning of the incubation period. The N availability and the duration of the immobilization are modified by the C/N ratio and by the type of soil management.

O objetivo do trabalho foi avaliar o teor de metais pesados e o crescimento de mudas de 20 espécies arbóreas tropicais em solo com elevado grau de contaminação com metais pesados. Em casa de vegetação, as mudas foram transplantadas para vasos contendo 3,3 kg de misturas com diferentes proporções (0, 20, 40 e 60% v/v) de solo contaminado. Verificou-se comportamento diferenciado das espécies quanto à inibição de crescimento e aos teores de metais na raiz e na parte aérea em decorrência da contaminação. Com base na produção de matéria seca da parte aérea, concluiu-se que apenas Myrsine umbellata, Cedrella fissilis, Tabebuia impetiginosa e Copaifera langsdorffii não foram afetadas pela contaminação, enquanto Hymenaea courbaril, Mimosa caesalpiniaefolia, Acacia mangium e Platypodium gonoacantha sofreram pequeno impacto. As demais espécies foram muito inibidas pela contaminação do solo, o que é causado pela absorção, na maioria dos casos, de Zn e Cd. Várias espécies apresentaram elevada capacidade de reter esses metais nas raízes, evitando sua translocação para a parte aérea.

The objective of the paper was to evaluate metal content and ability to grow in soil with excess of heavy metals of seedlings of 20 woody species. In the greenhouse, seedlings were transplanted to pots with 3.3 kg of soil-mixes with different proportions (0, 20, 40, 60% v/v) of a heavy metal contaminated soil. It was found that plant species behaved differently in terms of growth inhibition and metal content in the shoots and roots. Based upon the dry matter yield, only Myrsine umbellata, Cedrella fissilis, Tabebuia impetiginosa and Copaifera langsdorffii were not affected by increasing contamination, whereas Hymenaea courbaril, Mimosa caesalpiniaefolia, Acacia mangium and Platypodium gonoacantha were only slightly affected by it. All the other species were highly inhibited by the excess of metals in the soil, being such effects related, in most cases, to high uptake of Zn and Cd. Several species were able to retain large quantities of these metals in the roots, therefore avoiding their translocation to shoots.