The aim of this study was to evaluate the effects of increasing concentrations of lead (Pb) in the nutrient solution on growth and macronutrient and organic solute contents of Helianthus annuus plants. The experimental design was completely randomized with four replications. The dry mass yield was not affected by the treatments up to a Pb concentration of 0.6 mM, indicating that H. annuus was tolerant to this Pb concentration in the growth medium. The reductions in leaf, stem and root dry masses at a Pb concentration of 0.8 mM were 74, 84 and 85%, respectively. Lead stress did not reduce the levels of nitrogen (N), phosphorus (P) and potassium (K), indicating that the growth reduction observed at 0.8 mM Pb could not be attributed to deficiencies of these nutrients. On the other hand, Pb significantly reduced calcium (Ca) and magnesium (Mg) contents in leaves, stems and roots, which might, at least in part, explain the Pb-induced growth reduction in the H. annuus plants. Pb increased soluble carbohydrate, free amino acid and proline contents in leaves, and soluble protein and proline contents in roots, showing stress-induced changes in cell metabolism. The data also suggest that Ca and Mg concentrations may be used as nutritional indicators and the proline content may be used as a biochemical indicator of Pb toxicity in H. annuus.
Physalis angulata L. has aroused the interest of the researchers, since its properties come from the great therapeutic potential attributed to the commonly called substances of physalins. However, its cultivation in the study region lacks important information on the species adaptation to local soil and climate characteristics. The aim of this study was to evaluate the growth and concentration of phenolic compounds in P. angulata L. at two different periods in the Bahia Reconcavo. The experimental design was completely randomized blocks with 10 replicates. We evaluated the stem height and diameter, number of leaves and fruits, dry mass of leaves, stems and roots, leaf area, specific leaf area, leaf area ratio, leaf mass ratio and total phenolics, total flavonoids and antioxidant activity in the different organs of the plant. The growth was favorable from April to June. However, the concentration of phenolic compounds was higher in the period from December to February. The cultivation period influenced the growth and concentration of phenolic compounds in P. angulata L. in the Bahia Reconcavo.
A hydroponic greenhouse study was carried out to evaluate the effects of increasing cadmium (Cd) concentration on plant growth, mineral nutrition and Cd distribution of H-250 sunflower genotype. Exposure to increasing Cd concentrations reduced plant biomass by 40, 34, 47 and 42% of the total, leaves, stem and roots dry weights as compared to the control. Regardless of the treatment most of Cd uptake by the genotype was allocated in the root, followed by leaf and stem. The higher bioconcentration factors values in both above ground and underground plant tissues and low transfer factor value indicated that this genotype may be an alternative for use in phytostabilization programs. The results also showed that increasing Cd concentration disrupted plant homeostasis as it increased the concentration of some nutrients and had adverse effect on others, impacting plant growth. In this context, the results suggest that the low magnesium, iron and manganese concentrations in the leaves were the main cause for plant biomass reduction and leaf chlorosis and necrosis, as each one of these elements plays a key role on the chlorophyll molecule and on photosynthesis process.
RESUMO -Alguns estudos mostram que o pré-tratamento de H2O2 em baixa concentração pode aliviar os efeitos negativos causados pelo estresse salino, aumentando a atividade do sistema antioxidante e solutos orgânicos. Assim, este estudo visou identificar as concentrações e os períodos de exposição necessários como pré-tratamento de H2O2 para reduzir os efeitos negativos do estresse salino. Este ensaio foi realizado em esquema fatorial 5 × 3 + 2, com quatro repetições. Foram testados cinco níveis de peróxido de hidrogênio (0,1; 1; 10; 100; 1000 mM H2O2) combinados com diferentes períodos de exposição de pré-tratamento (12; 24; 36 horas) juntamente com dois tratamentos adicionais: controle 1 (água deionizada); controle salino (NaCl 100 mM). Após o pré-tratamento com H2O2, as mudas foram colocadas em ambientes contendo solução nutritiva salina (100 mM NaCl, exceto o controle). No final do experimento, (35 dias) as plântulas sob tratamento controle salino apresentaram maior redução no crescimento da planta em relação ao controle. Plântulas provenientes das sementes pré-tratadas com H2O2 apresentaram maior acúmulo de massa em relação ao controle salino. Os efeitos mais representativos foram verificados com a aplicação dos níveis mais elevados e período de exposição de 12 horas e nos níveis baixos com 36 e 24 horas de exposição. required for H2O2 pretreatment to reduce the negative effects of salt stress. The assay was carried out in factorial arrangement 5 × 3 + 2, with four replications. Five levels of hydrogen peroxide as pretreatments of the seeds (0.1; 1; 10; 100; 1000 mM H2O2) were tested combined with three different exposure periods (12; 24; 36 hours) along with two additional treatments: PALAVRAS-CHAVE:control (deionized water); control salt (100 mM NaCl). After the pretreatment with H2O2, the seedlings of sunflower were placed in environments containing saline nutrient solution (100 mM NaCl, except control). At the end of the experiment (35 days) the seedlings in salt control showed stronger reduction in plant growth compared to control. Seedlings of pretreated seeds with H2O2 showed greater mass accumulation compared to the salt control treatment. The most representative effects were verified with the application of the higher levels and period of exposure of 12 hours and in the low levels with 36 and 24 hours of exposure. KEYWORD:Hydrogen peroxide, acclimatation, salinity. . Com isso, altas concentrações de Na + podem promover um aumento na absorção de Na + e consequentemente reduzir a absorção de K + (Rodrigues et al., 2013). IV INOVAGRI International Meeting, 2017 O peróxido de hidrogênio é uma molécula bem conhecida pelo seu efeito tóxico. INTRODUÇÃOEntretanto, atualmente diversas funções do H2O2 na fisiologia e bioquímica das plantas têm sido descritas nos artigos científicos (Huang et al., 2005).As plantas e os demais organismos aeróbios têm evoluído diferentes sistemas antioxidantes e as EROs são utilizados como moléculas de sinalização em processos celulares básicos. A partir deste contexto, é muito...
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