Identification of native Amazonian tree species with potential for phytoextraction and tolerance to cadmium (Cd) can be used to direct studies and phytoremediation programs for preservation of natural areas and restoration of environments contaminated by heavy metals. The study evaluated the physiological responses and the phytoextraction and tolerance capacity of young plants of Virola surinamensis to Cd. We founded that Virola surinamensis showed medium and high tolerance to Cd and low efficacy in Cd phytoextraction and suggest that Virola surinamensis may be promising for the phytostabilization of Cd.

Virola surinamensis is a forest species widely distributed in the estuaries of the Amazon. These ecosystems are susceptible to contamination by Cadmium (Cd), indicating that the plant has strategies for tolerating this metal. The aim of this study was to assess the nitrogen and carbon metabolism of young plants of Ucuúba (Virola surinamensis) in the presence of cadmium with the perspective of the phytoremediation of contaminated environments. The used experimental design was a completely randomized design with five Cd concentrations (0, 15, 30, 45, and 60 mg L− 1), for 60 days. In general, Cd did not affect nitrate concentration in the root but had a positive effect on leaves. The reduction of nitrate reductase (NR) in plants exposed to Cd was followed by a decrease in ammonia, total soluble amino acids (TSA), and total soluble proteins (TSP). Cd promoted an increase in the concentration of total soluble carbohydrates (TSC), proline, sucrose, and reducing sugars in the plants. The increase in TSC, sucrose and proline, suggests a metabolic regulatory mechanism of V. surinamensis against Cd stress.

Zinc is an essential element to plants. However, excessive zinc levels can severely damage them. Schizolobium amazonicum is an Amazon native species that presents desirable features to remediate environments contaminated with heavy metals. Silicon has the beneficial effect of reducing the toxicity of different contaminants. The aim of the current study is to investigate the effect of Si on the growth and nutritional status of S. amazonicum seedlings subjected to zinc toxicity. The study followed a completely randomized design at 4 x 2 factorial arrangement based on four zinc (1, 150, 300 and 600 μM) and two silicon (0 and 1.5 mM) concentrations with five repetitions for 30 days. Increasing Zn concentrations in the nutrient solution reduced the growth of the plant and Ca, P, Mg, Fe, Mn and Cu contents in plant tissues, increased S concentrations and led to higher toxicity in the roots than shoot of S. amazonicum plants. Si addition to the nutrient solution increased plant growth and the absorption of the evaluated macro and micronutrients. Si increased plant tolerance level from 42.8 to 41.3% at 600 µM Zn, which suggested that this element mitigated the phytotoxic effects of the excess of zinc. Based on the tolerance index, the species presented medium and high tolerance to the evaluated zinc doses. Bioconcentration and translocation factors have indicated the low Zn-phytoextraction capacity of S. amazonicum and suggested that the species may be promising for Zn phytostabilization purposes.

The aim of this study is to assess the effect of sodium nitroprusside-NPS (nitric oxide donor) on the emergence and initial growth of maize seedlings (Zea mays L.) subjected to different copper concentrations. The study followed a completely randomized design at 4 x 3 factorial arrangement, with 12 treatments and 8 repetitions, totally 96 trays with 25 seedlings per repetition. Seedlings were soaked in sodium nitroprusside (SNP) solution (0.75 and 150 µM - donor), sodium ferrocyanide (SF) (0.75 and 150 µM - compensator) and deionized water (control) on Germitest paper for 48 hours. Next, they were placed on sand saturated with CuSO4.5H2O at concentrations of 0, 100 and 200 µM. The results showed that SNP doses were not capable of mitigating copper toxicity in seedling emergence, influencing emergence speed coefficient and prolonging the mean emergence time of plants subjected to copper concentrations of 100 µM and 200 µM. Copper concentrations rose the number of abnormal seedlings and had negative influence on plant biometrics and biomass. Copper concentration of 200 µM increased proline content in the roots. NPS and sodium ferrocyanide application had effect on emergence speed index, shoot and root dry mass and on proline content in the shoot and roots. This outcome highlights that such effects were caused by treatments related to release of cyanide found in sodium nitroprusside (SNP), rather than to nitric oxide (NO)

Over time, the anthropic activity has contributed to alter biogeochemical cycle of heavy metals by releasing contaminants into water, soil and air. Due to contamination of environments with heavy metals, plants and animals consumed by population have presented some level of contamination, which has caused worries and also attempts to minimize these problem. Among heavy metals, cadmium is one of the most toxic to living creatures, occupying seventh position in toxic substances ranking, even with very low concentrations. One of measures adopted to reduce negative impact of soil contamination by heavy metals is phytoremediation. It consists of use of plants that tolerate presence of heavy metals in soil, absorbing, translocating and compartmentalizing them in aerial part, with little or no negative impact on plant growth. Among plants, trees are the most suitable for phytoremediation due to their considerable production of air biomass, which is associated with higher accumulation and consequently higher extraction of heavy metals. In this review, we address main nutritional, biochemical, physiological and molecular aspects of cadmium toxicity in plants, emphasizing role of trees in phytoremediation studies, especially recent studies on Khaya ivorensis or african mahogany and its cadmium phytoremediation potential.

The contamination of soils and water as a result of human actions has been increasingly frequent in the world, the cadmium element the as a promising contaminant of these environments. This element affects the growth and development of vegetables.The objective of the study was to evaluate the growth and concentration of macro and micronutrients in the different organs young plants of Virola surinamensis exposed to Cd. The Cd significantly affected the growth of V. surinamensis reducing the height, stem diameter and biomass production. The Cd influenced negatively Fe, Mg, Ca, N, P and K, especially in the root. The Zn increased in the roots and leaves, while Mn reduced in the root and increased in the leaves of the plants on exposure to Cd. The increase of Zn and Mn in the leaves may have been a strategy to maintain the stability and protection of the photosynthetic apparatus of the plant. the research concluded that cadmium affects the nutritional relationship of this vegetable, however, we could observe that the influence of metal depends on the species being studied, the time of exposure to the metal and the amount of this metal.

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The factors that  limit forest production the most are abiotic stresses; soon, when plants are exposed to these conditions there will be secondary metabolites production and the exogenous application of growth regulators can facilitate and accelerate some adaptive responses. Therefore, the research aimed to evaluate biochemical changes associated with nitrogen metabolism in C.fissilis seedlings submitted to water deficit with salicylic acid (SA) application. The experiment used 400 seedlings of C.fissilis and the experimental design used in the phase prior to the water deficit imposition was  completely randomized  and composed of 4 doses of SA (0; 100; 200 and 300 mg L-1) with 5 repetitions of 20 seedlings each. SA application was performed weekly for 2 months. At the end of that period, seedlings from each treatment (doses of SA) were randomly selected and submitted to water deficit for 4, 8 and 12 days. The biochemical analyzes performed consisted of relative content of water (RCW), nitrate, free ammonium, total soluble amino acids, proline and glycine-betaine. The dose of 300 mg L-1 of SA was considered extremely high because it resulted in a great alteration in seedling metabolism. On the other hand, for most parameters, the dose of 100 mg L-1 was efficient in signaling RCW as it reduced water loss and consequently kept seedlings alive longer.   Keywords: Analyzes. Nitrate. Nitrogen Metabolism. Water Deficit.  Resumo Os fatores que mais limitam a produção florestal são os estresses abióticos, logo, quando as plantas são expostas a essas condições podem sofrer muitas modificações, assim, muitos estudos têm destacado respostas pertinentes com a aplicação exógena de reguladores e alteração metabólica que pode resultar em respostas adaptativa nas plantas. Portanto, a pesquisa teve como objetivo avaliar alterações bioquímicas ligadas ao metabolismo do nitrogênio em mudas de C.fissilis submetidas a déficit hídrico e com aplicação de ácido salicílico (AS). O experimento utilizou 400 mudas de C.fissilis e o delineamento experimental utilizado na fase anterior à imposição de déficit hídrico foi o inteiramente casualizado, composto por 4 doses de AS (0, 100, 200 e 300 mg L-1), com 5 repetições de 20 mudas cada. A aplicação do AS foi realizada semanalmente por 2 meses. Ao final desse período, mudas de cada tratamento (doses de AS) foram selecionadas aleatoriamente e submetidas a déficit hídrico por 4, 8 e 12 dias. As análises bioquímicas realizadas consistiram no conteúdo relativo de água (CRA), nitrato, amônio livre, aminoácidos solúveis totais, prolina e glicina-betaína. A dose de 300 mg L-1 de AS pode ser considerada muito alta, pois resultou em uma grande alteração no metabolismo das mudas. Por outro lado, para a maioria dos parâmetros, a dose de 100 mg L-1 foi eficiente em sinalizar à condição de déficit hídrico e com isso mantendo o CRA por meio da redução da perda de água e consequentemente mantendo as mudas vivas por mais tempo.   Palavras-chave: Análises. Nitrato. Metabolismo do Nitrogênio. Déficit Hídrico