Senna pendula seeds dormancy is caused by impermeability of the seed coat to water. In order to determine the best methodology to overcome dormancy and to perform a morphological characterization, two batches of seeds were submitted to the following treatments: a) mechanical scarification of the seed coat; b) immersion in hot water at 70 °C for 5, 10, 15 and 20 minutes; c) immersion in hot water at 90 °C for 5, 10, 15 and 20 minutes; d) sulfuric acid concentrate for 5, 10, 15 and 20 minutes; e) no treatment. The experiment was conducted in laboratory using a completely randomized design, with four replications of 25 seeds each, with daily verification for 7 days. The results showed that the use of water does not overcome the dormancy, however mechanical and chemical scarifications were the most effective treatments, with germination percentage of up to 94%.

O ferro (Fe) é um nutriente essencial para as plantas, sendo insubstituível ao metabolismo. Todavia, o aumento em sua concentração leva ao acúmulo de espécies reativas de oxigênio e estresse oxidativo que resultará em prejuízos aos vegetais. O objetivo deste trabalho foi verificar o efeito de elevadas concentrações de Fe na germinação e desenvolvimento de Cecropia hololeuca Miq. A espécie foi submetida às concentrações de 0,045, 4 e 8mM aplicados na forma de sulfato ferroso e Fe-EDTA. Foram analisadas a porcentagem de germinação, índice de velocidade de germinação, comprimento da parte aérea, radicular, massa fresca e seca. Para a análise de desenvolvimento foi analisado a área folhar o comprimento do caule, comprimento radicular, massa fresca e seca, os pigmentos cloroplastídeos, fluorescência da clorofila, e análise dos teores de elementos via EDS. Foi verificado a atividade enzimática (SOD, CAT, POX). Ambas as fontes de Fe resultaram em danos à germinação e desenvolvimento. O tratamento com Fe-EDTA mostrou efeitos mais significativos na germinação, crescimento aéreo e radicular e biomassa das sementes. O mesmo tratamento se mostrou mais prejudicial nas plântulas jovens com quedas na clorofila a, crescimento radicular, aéreo, área folhar e biomassa. As plântulas expostas ao Fe apresentaram queda no desempenho fotossintético e no teor de cálcio (Ca) folhar. Não foi observado aumento na atividade da CAT e SOD. A POX apresentou elevação quando submetida ao Fe-EDTA 8mM. Tais resultados evidenciam que a espécie C. hololeuca se mostra sensível a toxidez por ferro, acarretando danos ao metabolismo e crescimento inicial.    Palavras-chave: Embaúba. Estresse. Metal Pesado. Toxidez.  Abstract Iron (Fe) is as an essential nutrient for plants and is irreplaceable in many metabolic processes. However, the increase in its concentration leads to the accumulation of reactive oxygen species and oxidative stress that will result in damage to plant. The objective of this work was to verify the effect of high Fe concentrations on germination and initial development of Cecropia hololeuca Miq. They were submitted to concentrations of 0.045, 4 and 8mM applied as ferrous sulfate and Fe-EDTA. Germination percentage, germination speed index, shoot length and root, fresh and dry mass were analyzed. For the initial developmental the following variables were analyzed: Leaf area, stem length, root length, fresh and dry mass, chloroplast pigments, chlorophyll fluorescence analysis, analysis of element contents via EDS. The activity of enzymes (SOD, CAT, POX) was verified. Both sources of Fe resulted in damage to germination and development. Fe-EDTA treatment showed the most significant negative effects on germination, root and air growth and seed biomass accumulation. The same treatment was more detrimental in the establishment of young seedlings with decreases in chlorophyll a, root growth, aerial growth, leaf area and biomass accumulation. Seedlings exposed to Fe showed a decrease in photosynthetic performance and a decrease in leaf calcium (Ca) content. No increase in CAT and SOD enzymes activity was observed. POX increased its activity when submitted to 8mM Fe-EDTA. These results show that the species C. hololeuca is sensitive when exposed to toxic levels of Fe, causing damage to metabolism and initial growth.   Keywords: Embauba. Stress. Heavy Metal. Toxicity.

Plant's essential oils have a wide range of allelopathic effects with potential uses as bioherbicides. In addition, the application of oils through nanoemulsions represents a promising alternative for agriculture, as it offers better performance and lowers toxic waste generation. Therefore, this study aimed to evaluate the chemical constitution of Rosmarinus officinalis (rosemary) essential oil, as well as its effects on germination, initial growth, Catalase (CAT), Peroxidase (POX), and Superoxide-Dismutase (SOD) enzymes activity of Lactuca sativa seeds. Nanoemulsions were produced at 5% concentration and then diluted with distilled water to 5.0, 7.0, and 10.0 mg/mL. We compared data obtained using variance (ANOVA) analysis, followed by Tukey's test at 5% probability. Rosemary oil showed a wide variety of terpenoid compounds, mainly the 1,8-cineol monoterpene, which accounted for 46% of the sample. The oil showed a dose-dependent negative allelopathic influence on all variables analyzed, causing a drop in germination percentage (%G), germination speed index (GVI), mean germination time (MTG), and leaf and root length. There was no change in CAT and SOD activity. The POX activity showed a reduction starting at the concentration of 7.0 mg/mL. The results showed allelopathic effects of rosemary oil, with potential use as a natural bioherbicide.

Effects of iron toxicity on germination and initial growth ofCarica papaya L.Efeitos da toxicidade por ferro na germinação e crescimento inicial de Carica papaya L.

Alelopatia é a interferência causada por substâncias químicas produzidas por plantas em organismos da comunidade, acarretando tanto efeitos benéficos quanto prejudiciais. Devido ao grande potencial alelopático do gênero Solanum, o objetivo do presente trabalho foi avaliar o efeito alelopático dos extratos hexânico, metanólico e de acetato de etila de folhas de Solanum pimpinellifolium L. sobre a germinação de Lactuca sativa e Bidens pilosa. Os extratos foram obtidos por maceração à temperatura ambiente por 7 dias. Depois foram secos e diluídos para as concentrações 1,0; 2,0 e 5,0 mg/mL. Em seguida, 100 sementes de cada espécie foram distribuídas em placas de Petri umedecidas com as diferentes concentrações de cada extrato e colocadas para germinar sob luz constante em câmara de germinação tipo BOD. Os bioensaios foram monitorados diariamente, obtendo-se ao final de 7 dias a porcentagem de germinação e o índice de velocidade de germinação (IVG). Dos três extratos analisados, o obtido pela extração com acetato de etila apresentou melhor desempenho, diminuindo a velocidade e a porcentagem de germinação em todas as concentrações e na concentração 5,0 mg/mL apresentou apenas 7% de germinação para L. sativa. O extrato hexânico diminuiu a velocidade e a porcentagem de germinação de B. pilosa em todas as concentrações. As análises fitoquímicas realizadas por meio de técnica de cromatografia em camada delgada (CCD) nos extratos de folha de Solanum pimpinellifolium identificaram quatro grupos químicos: flavonoides, saponinas, alcaloides e mono e diterpenos, sendo apenas esta última classe presente em todos os extratos analisados.

The increased demand for food promotes greater use of agricultural inputs and pesticides used in pest control. Many of these products have negative environmental and public health impacts. Thus, there is a need for alternative products, with allelopathic capacity that reduce such impacts. The objective of this work was to verify the allelopathic potential of Piper nigrum L. extracts on the germination and initial growth of Panicum maximum Jacq. and Lactuca sativa seeds. The experimental design used was completely randomized, using two plant organs (leaf and seed), three extractors (hexane, ethyl acetate and methanol) and five concentrations (0 mg/L, 200 mg/L, 400 mg/L, 600 mg/L and 800 mg/L). It was verified the influence of these extracts on germination speed index (IVG), germination percentage (G), mean germination time (TMG), allelopathy index (IA), shoot growth (CPA) and in the root growth (CR) of seeds and seedlings. The leaf and seed extracts, at all concentrations and extractors tested, did not show phytotoxicity or had a very small inhibitory effect on germination and initial growth of Lactuca sativa. For Panicum maximum, ethyl acetate and methanol seed extracts, at the highest concentrations tested, had the most significant negative effects on the weed. Thus, it was possible to infer that extracts from Piper nigrum seeds have potential use in the control of the weed Panicum maximum.

Iron is essential to plant development. However, its excess can provoke an increase in reactive oxygen species and oxidative stress in plants. The objective of this work was to verify the effects of high concentrations of iron on the oxidative stress of seeds and young plants of Cecropia hololeuca and Carica papaya. The species were submitted to concentrations of 0.045, 4 and 8mM of iron in the form of ferrous sulfate and FeEDTA.The experiments of germination and initial growth took place in a growth chamber, with temperature of 25ºC and 12h photoperiod. We performed the lipid peroxidation test by extraction and quantification of malonaldehyde and hydrogen peroxide. The application of iron did not cause a significant elevation in the contents of malonaldehyde and hydrogen peroxide in the germination of C. hololeuca and C. papaya. In the young plants, the hydrogen peroxide did not change in any of the treatments. However, it was possible to observe an expressive increase in malonaldehyde concentration in both species when exposed to FeEDTA 4 to 8mM. The results indicate a sensibility of C. hololeuca and C. papaya to high iron levels, amplifying the oxidative stress process that can harm their growth and initial development.