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Climatic changes are leading to an increased number of flooding year by year which impacts negatively the metabolism of roots and influences the shoot metabolism which leads to a decline in soybean productivity. This can be more drastic when it is cultivated in lowland soils. Our group hypothesized that tolerant sister-line plants have more capacity to cope with oxidative stress due to better management of energy use and dissipation on photosynthesis machinery during root-flooding and recovery conditions, while in sensitive soybean sister-line the impairment of the photosynthetic use and dissipation of energy lead to an unbalanced redox state response. For that, soybean seeds from the same parents, PELBR15- 7015C (flooding tolerant) and PELBR15-7060 (flooding sensitive) were sowed and cultivated in 500 L capacity plastic containers with lowland soil simulating the field management process. At the reproductive stage, the roots were subjected to flooding for 11 days, then drained to analyze reoxygenation (3 d) and recovery (10 d). Tolerant plants have a greater ability to manage root flooding conditions compared to sensitive ones. The ability includes efficient energy use and dissipation, which minimizes the production of reactive oxygen species (ROS) and subsequent cell damage. Conversely, in sensitive sister lines, impaired electron transport chains lead to increased ROS production and damage. Upon reoxygenation and recovery, the tolerant sister lines exhibit a faster metabolism turnover, allowing them to cope more effectively with the stress on leaves and roots. While both sister lines are capable of detoxifying ROS, the tolerant sister line's superior ability to manage energy use and dissipation allows for more stable and rapid control of oxidative stress.

Estudos com espécies florestais, em diferentes condições ambientais são essenciais para o entendimento da relação planta-ambiente. Diferentes condições de luminosidade podem interferir na produção de mudas florestais e o reflexo dessa interferência pode ser verificado pela análise da área foliar. No entanto, muitas espécies apresentam folhas compostas, sendo muitas vezes com inúmeros folíolos, o que dificulta as análises com mensuração direta da área foliar, proporcionando dúvidas durante a análise, se devem ser separados para análise ou mensurados com a folha inteira. Assim, o objetivo desse estudo foi analisar a área foliar específica em folhas inteiras e folíolos destacados de folhas compostas de seis espécies florestais submetidas à diferentes níveis de sombreamento. As espécies florestais utilizadas foram Schinus terebinthifolius Raddi (aroeira), Schinopsis brasiliensis Engl. (braúna), Dalbergia nigra (Vell.) Fr. All. ex Benth. (jacarandá-da-bahia), Chorisia speciosa A.St.-Hil (paineira), Caesalpinia peltophoroides Benth (sibipiruna) e Plathymenia reticulata Benth (vinhático), todas com folhas compostas. Cada espécie foi submetida a seis tratamentos de sombreamento: 0% (pleno sol); 20; 40; 60; 80 e 90%, com a utilização de “sombrites” para os tratamentos sombreados. A análise da área foliar específica foi realizada de duas maneiras: folíolos separados e folha inteira. Para a análise dos folíolos esses foram obtidos de três medidas (repetições) de 50 folíolos por planta, realizada em seis plantas por tratamento. Para a análise da folha inteira os dados foram obtidos de folhas inteiras de seis plantas por tratamento. Esse processo se repetiu em todas as espécies supramencionadas. Para todas as espécies, os dados indicaram um padrão de resposta semelhante em ambos os métodos de análise, variando de acordo com os níveis de sombreamento. Essa similaridade dos dados demonstra que, para essas espécies, não é necessário a utilização de métodos muito complexos para a obtenção da área foliar específica. Assim, a obtenção da área foliar específica utilizando a folha inteira fornece resultados estatisticamente iguais em relação àquela obtida utilizando somente folíolos.

The use of herbicides is a represents an efficient way to control the infesting plant population, since it is associated with low operational cost, and it does not demand large amounts of labour. An obstacle to growing cowpea (Vigna unguiculate) is the absence of herbicides registered for this crop. The objective of this work was to evaluate the tolerance of cowpea to herbicides. The experiment was carried out in a randomised block with treatment controls with and without weeding, Bentazon (720 g ha-1), Fluazifop-p-butyl (250 g ha-1), Fomesafen and a tank mix between Fluazifop-p-butyl + Fomesafen (250 + 187.5 g ha-1) with treatment replicates. The herbicides were applied on vegetative (V3 – stage) cowpea plants using a CO2-pressurised backpack sprayer with four spray tips TT 110.02 operating at a pressure of 2.5 bar and applying 240 litres of syrup per hectare. The cultivar BRS Guariba, with five planting lines per plot, was tested with the three central lines of the useful area, scoring 0.5 m of the ends. The species Oxalis latifolia was difficult to control. The Fluazifop-p-butyl + Fomesafen mixture presented better control of weeds. The herbicides caused phytotoxicity to cowpea and reduced leaf area and dry mass. The productivity of the crop was affected due to the low control of weeds. It was concluded that the cowpea presented differential tolerance to the herbicides tested doses.

This study aimed to evaluate the mechanisms of flood tolerance of the root system of Erythrina crista-galli L. plants by measuring the activity of antioxidant enzymes and oxidative stress components in the leaves and roots. Additionally, the activity of fermentation enzymes in the roots was measured. The following two treatments were used: plants with flooded roots, which were maintained at a given water level above the soil surface, and non-flooded plants, which were used as the control. The measurements were performed at 10, 20, 30, 40, and 50 days after treatment. The following parameters were evaluated at each time-point: the activities of superoxide dismutase, catalase and ascorbate peroxidase, the quantification of lipid peroxidation and hydrogen peroxide (H2O2) content in the leaves, roots, and adventitious roots, and the activities of lactate dehydrogenase, pyruvate decarboxylase and alcohol dehydrogenase in both the primary and adventitious roots. There was an increase in the activity of catalase and ascorbate peroxidase in the leaves to maintain stable H2O2 levels, which reduced lipid peroxidation. In the roots, higher activity of all antioxidant enzymes was observed at up to 30 days of flooding, which favoured both reduced H2O2 levels and lipid peroxidation. Activity of the fermentation enzymes was observed in the primary roots from the onset of the stress conditions; however, their activity was necessary only in the adventitious roots during the final periods of flooding. In conclusion, E. crista-galli L. depends on adventitious roots and particularly on the use of the fermentation pathway to tolerate flood conditions.

Waterlogging blocks the oxygen supply to the root system which inhibits respiration, and greatly reduces the energy status of cells that affect important metabolic processes. This study evaluated fermentative metabolism and carbohydrate contents in the root system of two soybean (Glycine max L. Merril) genotypes under hypoxic and post-hypoxic conditions. Nodulated plants (genotypes Fundacep 53 RR and BRS Macota) were grown in vermiculite and transferred to a hydroponic system at the reproductive stage. The root system was submitted to hypoxia by flowing N2 (nitrogen) gas in a solution for 24 and 72 h. For recovery, plants returned to normoxia condition by transfer to vermiculite for 24 and 72 h. Fermentative enzyme activity, levels of anaerobic metabolites and carbohydrate content were all quantified in roots and nodules. The activity of alcohol dehydrogenase, pyruvate decarboxylase and lactate dehydrogenase enzymes, as well as the content of ethanol and lactate, increased with hypoxia in roots and nodules, and subsequently returned to pre-hypoxic levels in the recovery phase in both genotypes. Pyruvate content increased in nodules and decreased in roots. Sugar and sucrose levels increased in roots and decreased in nodules under hypoxia in both genotypes. Fundacep RR 53 was more responsive to the metabolic effects caused by hypoxia and post-hypoxia than BRS Macota, and it is likely that these characteristics contribute positively to improving adaptation to oxygen deficiency.

The work was conducted to evaluate the effect of different Philodendron bipinnatifidum Schott. extract concentrations on the physiology and enzymatic metabolism of lettuce seeds and seedlings. The treatments extracts of mature leaves at concentrations of 0, 6, 12, 25 and 50%. Were evaluated the germination, first count germination, speed and germination speed index, length of shoot and primary root, seedling total dry mass, electrical conductivity, chlorophyll content, activity of the enzymes ?-amilase, superoxide dismutase, catalase and ascorbarto peroxidase, lipid peroxidation, hydrogen peroxide content and seedling emergence, length of shoot and total dry mass of emerged seedlings. There was a reduction of germination, germination speed index and total dry mass by increasing the concentration of the extract. While the content of hydrogen peroxide, lipid peroxidation and activity of superoxide dismutase, catalase and peroxidase ascorbarto increased with concentration. The increasing of concentration the leaf extracts of the P. bipinnatifidum negatively affects the activity of the enzyme ?-amylase and causes increase in the activity of antioxidant enzymes, affecting the physiologic performance and growth of lettuce seedlings.

This work aimed to evaluate the effect that different intensities of light have on the physiological attributes of red rice seeds and seedlings. Before and after emergence, seedlings were exposed to light levels of 35%; 65% and 100% in a greenhouse. We evaluated shoots and roots, in terms of length and dry mass, as well as leaf area and content of chlorophyll (a,b and total). In leaves and roots, we quantified the activity of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and guaiacol peroxidase (POX). We determined the leaf area ratio (F A), leaf mass ratio (F W), specific leaf area (S A), and shoot/root ratio (P W). At higher light intensities, shoot length decreased, whereas root length, dry mass and number of tillers increased. Leaf area was greatest in seedlings exposed to a 65% light level. The F A, F W, S A and P W were lowest at a light intensity of 100%. Differences in light intensity had qualitative and quantitative effects on chlorophyll contents. The activity of SOD and CAT was higher at lower light levels, whereas the inverse was true for APX and POX activity. Extremes of light availability alter the activity of antioxidant enzymes, negatively affecting the initial growth characteristics and photosynthetic pigments of red rice seedlings.

O objetivo deste trabalho foi avaliar a atividade de enzimas fermentativas em raízes e nódulos de soja (Glycine max) sob condições de hipóxia e pós-hipóxia. Os genótipos Fundacep 53 RR e BRS Macota foram cultivados em vasos de 3L contendo vermiculita como substrato em associação com Bradyrhizobium elkanii em casa de vegetação. No estádio R2, o sistema radicular das plantas foi submetido à hipóxia pelo encaixe de um segundo vaso sem perfurações e inundado com solução nutritiva diluída a 1/3 da concentração original, por 8 dias. Posteriormente, foram retirados os vasos sem perfurações para avaliação da recuperação. O material vegetal foi coletado no 2º, 4º, 6º e 8º dias após a inundação ou recuperação, juntamente com os controles para a dosagem da atividade das enzimas álcool desidrogenase (ADH), piruvato descarboxilase (PDC) e lactato desidrogenase (LDH) em raízes e nódulos. Os dados foram submetidos à ANOVA e comparados pelo teste de Tukey a 5% de probabilidade. As atividades da ADH, PDC e LDH foram fortemente estimuladas com a inundação, especialmente em nódulos, e diminuíram com a recuperação, em ambos os genótipos. Fundacep 53 RR respondeu de forma mais efetiva aos efeitos dos tratamentos.This study aimed to evaluate the activity of fermentative enzymes in soybean (Glycine max) roots and nodules under hypoxia and post-hypoxia conditions. The soybean genotypes Fundacep 53 RR and BRS Macota associated with Bradyrhizobium elkanii were grown in 3L pots containing vermiculite as substrate under greenhouse conditions. Root system of plants at the R2 stage was subjected to hypoxia by blocking drainage of the pot, by fitting a second one without holes and flooded with nutrient solution diluted one-third of the original. The flooding of the plants was carried out for eight days and after, the pot without drilling was removed for recovery assessment. Non-waterlogged plants were kept as control. Activities of the fermentation enzymes alcohol dehydrogenase (ADH), pyruvate decarboxylase (PDC) and lactate dehydrogenase (LDH) were quantified in roots and nodules collected at 2, 4, 6 and 8 days after flooding or recovery. Data were analyzed by ANOVA and compared by the Tukey test (P ≤ 0,05). Activities of ADH, PDC and LDH were hardly stimulated during flooding, especially in nodules, in both genotypes and decreased with recovery. Fundacep 53 RR responded more effectively to treatment effects.

Allelopathy effects vegetative development and is caused by chemical substances produced and released by surrounding plants. The objective of this work was to investigate the allelopathic activity of aqueous extracts of fresh and dried leaves and fruits of chinaberry (Melia azedarach L. – Meliaceae) on the germination and initial growth of tomato. The extracts were prepared at concentrations of 1, 2 and 4% and analyzed for their pH and osmotic potential. The experiment consisted of four replications of 25 tomato seeds that were distributed in Petri dishes containing two sheets of germitest paper. Each plate received 2mL of an extract. The seeds were evaluated for percentage of germination (PG), germination rate (VG) and germination speed index (IVG). The initial growth was assessed based on the length of the radicle, hypocotyl and leaf, and fresh and dry weight. All concentrations of the extracts exhibited inhibitory activity on germination and radicle growth, and the inhibitory effect increased as the concentration of the extract increased. Extracts from dried leaves had the greatest effects. The osmotic potential and pH of the extracts did not vary significantly compared to the control, indicating that the allelopathic effect was due to the allelochemicals in the extracts.

Este trabalho objetivou avaliar os efeitos alelopáticos de folhas de pariparoba sobre a germinação e o crescimento inicial do rabanete (Raphanus sativus L.). Foram utilizados extratos de folhas maduras frescas nas concentrações 2, 4 e 8% (p/v), cujo pH e potencial osmótico foram aferidos. No bioensaio de germinação foram empregadas cinco repetições de 25 sementes distribuídas em placas de petri forradas com papel Germitest, umedecido com 7 mL de extrato ou água e mantidos a 25ºC em B.O.D. por cinco dias. A porcentagem de germinação (PG), velocidade de germinação (VG), índice de velocidade de germinação (IVG) e índice de efeito alelopático (RI) foram determinados. No bioensaio de crescimento inicial, sementes germinadas até atingirem 2 mm de protusão radicular foram transferidas para caixas Gerbox contendo papel Germitest e 15 mL de extrato ou água, permanecendo sete dias a 25ºC em B.O.D. para a avaliação do comprimento da radícula e do hipocótilo, da massa fresca e seca, do conteúdo de água e do teor de clorofila (a, b e total). Todos os parâmetros de germinação (PG, VG, IVG e RI) foram afetados negativamente pelos extratos de P. mikanianum. O crescimento inicial foi influenciado pelos extratos, resultando em redução do comprimento da radícula e aumento do hipocótilo. Além disso, os extratos causaram redução da biomassa fresca e do conteúdo de água a 8% e incrementos dos teores de clorofila b e total a 2 e 4%. Assim, a espécie Piper mikanianum exerce efeito alelopático sobre o rabanete.This study evaluated the allelopathic effects of an extract from P. mikanianum leaves on the germination and early growth of radish (Raphanus sativus L.). Leaf extracts were prepared at concentrations of 2, 4 and 8%. The pH and osmotic potential of the extracts were determined. Germination bioassay consisted of five replicates of 25 radish seeds distributed in Petri dishes with germitest paper and 7 mL of extract or water, and were kept at 25ºC in B.O.D. for five days. Germination percentage (PG), germination speed (VG), germination speed index (IVG) and index of allelopathic effect (RI) were determined. For bioassay initial growth, seeds were germinated until the protrusion of the radicle was 2 mm and transferred to Gerbox boxes containing germitest paper and 15 mL of extract or water, which were kept for seven days at 25ºC in B.O.D. to evaluate the length of the radicle and hypocotyl, fresh and dry mass, water content and chlorophyll content (a, b ​​and total). Leaf extracts from P. mikanianum negatively affected all parameters examined for germination (PG, VG, IVG and RI). The extracts affected the initial growth, causing reduction of the radicle length and stimulating the growth of the hypocotyl. In addition, the extracts at 8% concentration reduced fresh weight and water content. Extracts at concentrations of 2 and 4% increased the content of chlorophyll b and total chlorophyll. Thus, Piper mikanianum exerted an allelopathic effect on radish.

A alelopatia caracteriza-se por efeitos no desenvolvimento das plantas, causados por substâncias químicas que são produzidas e liberadas por outras plantas. O objetivo deste trabalho foi investigar a atividade alelopática de extratos aquosos de folhas frescas e secas e de frutos de cinamomo (Melia azedarach L.- Meliaceae) sobre a germinação e crescimento inicial do tomate. Os extratos foram preparados nas concentrações 1, 2 e 4% e caracterizados quanto ao pH e potencial osmótico. Os bioensaios foram constituídos de quatro repetições de 25 sementes de tomate distribuídas em placas de Petri contendo duas folhas de papel germitest, sendo que cada placa recebeu 2mL do extrato correspondente ao tratamento. Para a germinação foram avaliados a porcentagem de germinação (PG), a velocidade de germinação (VG) e o índice de velocidade de germinação (IVG). O crescimento inicial foi avaliado pelo comprimento da radícula, do hipocótilo e da folha e pela massa fresca e seca. Todas as concentrações de extratos do cinamomo apresentaram atividade inibitória sobre a germinação e crescimento da radícula, sendo maior o efeito inibitório à medida que aumentava a concentração do extrato. Extratos de folhas secas apresentaram maiores efeitos sobre o tomate. O potencial osmótico e pH dos extratos utilizados apresentaram pouca variação em relação ao controle, indicando que o efeito alelopático se deve a ação dos aleloquimicos presentes nos extratos.

Neste trabalho, objetivou-se avaliar o efeito alelopático de folhas secas e pseudofrutos de Hovenia dulcis Thunb. sobre sementes de alface. Para isso, prepararam-se extratos aquosos de folhas e pseudofrutos nas concentrações 1, 2 e 4% (m/v). Realizou-se quatro repetições de 25 sementes de alface, distribuídas em placas de Petri forradas com papel Germitest e umedecidas com os extratos, mantidas em câmara de germinação à temperatura de 25°C, fotoperíodo constante e presença de luz por cinco dias, sendo o controle água destilada. Calculou-se a porcentagem, a velocidade, o índice de velocidade de germinação, o comprimento radicular e da parte aérea das plântulas, bem como o efeito das sementes na presença de diferentes soluções de pH. Observou-se que as plântulas foram significativamente afetadas na presença de extratos aquosos de folhas secas e pseudofrutos nas concentrações 2 e 4%. Os efeitos foram desvinculados do pH e potencial osmótico, indicando, portanto, interferência alelopática dos extratos obtidos de Hovenia dulcis.This paper aims to evaluate the allelopathic effect of dry leaves and pseudofruits of Hovenia dulcis Thunb. on lettuce seeds. Therefore, aqueous extracts of leaves and pseudofruits were prepared in 1%, 2% and 4% (m/v) concentrations. Four replicates were done of 25 lettuce seeds distributed in Petri dishes lined with Germitest paper and humidified with the extracts, maintained in germination chamber at 25 °C, constant photoperiod and light presence for five days, the control being distilled water. The percentage, speed, germination rate index, root length and aerial-part length of the seedlings were calculated, as well as the seeds effect in the presence of different pH solutions. It was observed that the seedlings were significantly affected in the presence of aqueous extracts of dry leaves and pseudofruits at 2% and 4% concentrations. The effects were not linked to pH and osmotic potential, indicating, therefore, allelopathic interference of Hovenia dulcis extracts.

As plantas produzem substâncias por meio do metabolismo secundário. Quando liberadas no meio ambiente são capazes de interferir na germinação e no desenvolvimento de outras plantas. Objetivou-se, nesta pesquisa investigar os efeitos alelopáticos de umbu (Phytolacca dioica L.) sobre a germinação e o crescimento inicial de alface e picão-preto, em laboratório, utilizando-se extratos aquosos de frutos de umbu nas concentrações 0, 1, 2, 4 e 8%; foi realizada análise fitoquímica dos frutos e testes de pH e potencial osmótico dos extratos de frutos. Analisaram-se, para a germinação os parâmetros: porcentagem de germinação (PG), velocidade de germinação (VG) e índice de velocidade de germinação (IVG); para o crescimento inicial analisaram-se os parâmetros: comprimento (radicular e da parte aérea) e biomassa (fresca e seca) das plântulas de alface e picão-preto. Os dados foram submetidos ao teste de Tukey, a 1% de probabilidade. Os parâmetros PG, VG e IVG foram alterados significativamente, proporcionais ao aumento da concentração dos extratos de frutos do umbu. O comprimento (radicular e da parte aérea) e a biomassa (fresca e seca) das plântulas de alface e picão-preto foram reduzidos significativamente com o aumento da concentração dos extratos aquosos de frutos de umbu. O pH e potencial osmótico dos extratos mantiveram-se dentro de padrões adequados e a análise fitoquímica revelou a presença de flavonoides. Pelos resultados os frutos de umbu apresentaram-se com efeito alelopático sobre a alface e o picão-preto.Plants produce substances through secondary metabolism. When these chemicals are released into the environment they can interfere in the germination and development of other plants. The objective of this research was to investigate the effects of allelopathic Phytolacca dioica L. on the germination and early growth of lettuce and beggartick, under laboratory conditions, using aqueous extracts of fruits of Phytolacca dioica at concentrations of 0, 1, 2, 4 and 8%. Phytochemical analysis of the fruit was performed; and pH and osmotic potential of extracts of fruit were tested. We analyzed the following germination parameters: percentage of germination (PG), speed of germination (VG) and speed of germination index (IVG), for the initial growth parameters examined are: length (root and shoot) and biomass (fresh and dry) of seedlings of lettuce and beggartick. The data were submitted to Tukey's test at 1% of probability. Parameters PG, VG and IVG were significantly affected, with increase in concentration of the extracts of fruits of Phytolacca dioica. The length (root and shoot) and biomass (fresh and dry) of seedlings of lettuce and beggartick were reduced significantly with increasing concentration of the aqueous extracts of fruits of Phytolacca dioica. The pH and osmotic potential of the extracts were maintained within appropriate standards and phytochemical analysis revealed the presence of flavonoids. The results showed that the fruits of Phytolacca dioica presented allelopathic effect on the lettuce and beggartick.

Allelopathy can be efined as any stimulatory or inhibitory effect by one plant on another through production of chemical compounds released into the environment. In this work, the effects of aqueous extracts of Duranta repens fresh, dried leaves and fruit on the germination and early growth of lettuce and tomato were investigated. Aqueous extracts at concentrations of 1%, 2% and 4% (w/v) were prepared and characterized as to pH and osmotic potential. Phytochemical analysis of leaves and fruits was also carried out. Germination parameters consisted of the percentage of germination (PG), speed of germination (VG) and speed of germination index (IVG). Initial growth was evaluated through length (root and shoot) and mass (fresh, dried and water content). Extracts of fresh and dry leaves altered the tomato PG and leaf lettuce and tomato VG and IVG. All extracts affected the root length of the lettuce and tomato, as well as the length of the shoots and mass (dry and fresh) of the lettuce. The phytochemical analysis revealed the presence of saponins and flavonoids. The action of the extracts was disassociated from any effect of osmotic potential and pH, indicating allelopathic activity.

Allelopathy can be defined as any stimulatory or inhibitory effect by one plant on another through production of chemical compounds released into the environment. In this work, the effects of aqueous extracts of Duranta repens fresh, dried leaves and fruit on the germination and early growth of lettuce and tomato were investigated. Aqueous extracts at concentrations of 1%, 2% and 4% (w/v) were prepared and characterized as to pH and osmotic potential. Phytochemical analysis of leaves and fruits was also carried out. Germination parameters consisted of the percentage of germination (PG), speed of germination (VG) and speed of germination index (IVG). Initial growth was evaluated through length (root and shoot) and mass (fresh, dried and water content). Extracts of fresh and dry leaves altered the tomato PG and lettuce and tomato VG and IVG. All extracts affected the root length of the lettuce and tomato, as well as the length of the shoots and mass (dry and fresh) of the lettuce. The phytochemical analysis revealed the presence of saponins and flavonoids. The action of the extracts was disassociated from any effect of osmotic potential and pH, indicating allelopathic activity.

Allelopathy refers to the ability that a plant has to interfere in the metabolism of another by means of chemical compounds released into the environment. The objective of this study was to determine the allelopathic effect of aqueous extracts of leaves of Phytolacca dioica L. on the germination and early growth of tomato plants and Bidens pilosa. Extracts were prepared at concentrations of 1%, 2%, 4% and 8%. We measured the pH and osmotic potential of the extracts and carried out a phytochemical analysis of the leaves. In our experiments we used four replicates of 25 seeds distributed in Petri dishes with two sheets of germitest paper dampened with 5mL extract. We evaluated the percentage of germination (PG), speed of germination (VG), speed of germination index (IVG), and length (root and shoot) and mass (fresh and dry) of seedlings of tomato and Bidens pilosa. The pH and osmotic potential were found to be within acceptable standards and the phytochemical analysis of the leaves showed the presence of flavonoids. PG, VG and IVG were affected in more concentrated treatments (4 and 8%), and the length and mass of seedlings of tomato and Bidens pilosa were affected in all treatments. Treatments at an 8% concentration completely inhibited the germination process of the plants.

Alelopatia se refere à capacidade que determinada planta tem de interferir no metabolismo de outra, por meio de compostos químicos liberados no meio. O objetivo deste trabalho foi determinar a influência alelopática de extratos aquosos de folhas de Phytolacca dioica L. na germinação e crescimento inicial de plantas de tomate e picão-preto. Extratos foram preparados nas concentrações 1%, 2%, 4% e 8%. Foram medidos o pH e o potencial osmótico dos extratos e realizada a análise fitoquímica das folhas. Nos experimentos foram utilizadas quatro repetições de 25 sementes distribuídas em placas de Petri com duas folhas de papel germitest umedecida com 5mL de extrato. Foi avaliada a porcentagem de germinação (PG), velocidade de germinação (VG), índice de velocidade de germinação (IVG), comprimento (raiz e parte aérea) e massa (fresca e seca) das plântulas de tomate e picão-preto. O pH e o potencial osmótico mantiveram-se dentro de padrões aceitáveis e a análise fitoquímica das folhas revelou a presença de flavonóides. A PG, VG e IVG foram afetados nos tratamentos mais concentrados (4 e 8%), o comprimento e a massa das plântulas de tomate e picão-preto foram afetados em todos os tratamentos. Tratamentos a 8% inibiram totalmente o processo germinativo das plantas.

Objetivou-se com este trabalho avaliar a influência da concentração do extrato de folhas maduras de Zantesdeschia aethiopica sobre atributos fisiológicos de sementes e plântulas de arroz vermelho. Os tratamentos foram extratos nas concentrações 0; 12; 25; 50 e 75%. Foram avaliados germinação, primeira contagem, comprimento de parte aérea e raiz, massa seca total de plântulas, condutividade elétrica, teores de clorofila a, b e total, atividade das enzimas superóxido-dismutase, catalase e ascorbarto peroxidase, peroxidação lipídica e teor de peróxido de hidrogênio, emergência de plântulas, comprimento de parte aérea e de raiz e massa seca total das plântulas emergidas. Os teores de clorofila foram alterados quanti-qualitativamente, a emergência de plântulas, o comprimento de raiz e a massa seca total de plântulas emergidas foram reduzidos pelo aumento da concentração do extrato. A peroxidação de lipídeos, a atividade das enzimas superóxido-dismutase, ascorbato-peroxidase e catalase aumentaram com a concentração. Os resultados encontrados no trabalho demonstraram que o extrato de folhas maduras de Z. aethiopica altera diferentes atributos fisiológicos e apresenta toxidez a sementes e a plântulas de arroz vermelho.

O trabalho objetivou avaliar o efeito alelopático de extrato aquoso de folhas de Trema micrantha sobre germinação de sementes e crescimento inicial de plântulas de rabanete. Para os extratos foram utilizadas folhas maduras e frescas nas concentrações 2, 4 e 8% (p/v), com aferição do pH e potencial osmótico. No bioensaio de germinação, foram empregadas cinco repetições de 25 sementes distribuídas em placas de petri forradas com papel Germitest, umedecido com 7 mL de extrato ou água e mantidos a 25 ºC em B.O.D., por cinco dias. Foram determinados a porcentagem de germinação (PG), velocidade de germinação (VG), índice de velocidade de germinação (IVG) e índice de efeito alelopático (RI). No bioensaio de crescimento inicial, foram avaliados o comprimento da radícula e do hipocótilo, a biomassa fresca e seca, o conteúdo de água e os teores de clorofila a, b e total. Todos os atributos de germinação, PG, VG, IVG e RI, foram afetados negativamente pelos extratos de T. micrantha. O crescimento inicial foi influenciado pelos extratos, ocorrendo redução do comprimento da radícula e aumento do hipocótilo. O extrato não alterou a biomassa fresca e seca e os teores de clorofila. Extratos aquosos de folhas de Trema micrantha exerceram ação alelopática sobre a germinação e crescimento inicial do rabanete, não influenciando na inibição da síntese de pigmentos fotossintéticos.

ABSTRACT: In this work, we compared nitrate-supplied plants (non-nodulated) with non-nitrate-supplied plants (nodulated) under oxygen privation of root system (hypoxia) and re-oxygenation (post-hypoxia; recovery) in order to verify whether N sources affect the antioxidant system during oxidative stress caused by hypoxia and post-hypoxia conditions. Antioxidant enzymatic activities, ascorbate redox state, and reactive oxygen species (ROS) levels were analyzed in roots and leaves of two soybean genotypes, Fundacep 53 RR and BRS Macota at reproductive stage R2, during hypoxia and post-hypoxia in an experiment carried out in a hydroponic system. The antioxidant system was strongly induced in roots of nitrate-supplied plants of both genotypes, with high activity of superoxide dismutase, ascorbate peroxidase, catalase, glutathione reductase and guayacol peroxidase. It also increased reduced ascorbate and ascorbate redox state and decreased ROS production under hypoxia and recovery, while in leaves of nodulated and non-nodulated plants, a slight increase on antioxidant system was observed. Nitrate may benefit soybean plants under hypoxic conditions and subsequent re-oxygenation by inducing the antioxidant system mainly in roots to cope with ROS production and reduce oxidative damage.