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Selenium (Se) is considered a beneficial chemical element for plants, but in high concentrations it may present symptoms of toxicity. The present study aimed to evaluate 11 concentrations of Se (0; 0.1; 0.5; 1; 5; 10; 20; 40; 80; 400; 800 mg.L-1) to determine the low and high (toxicity) critical levels to seed germination of cowpea (Vigna unguiculata). In addition, alterations in the rate of photosynthetic pigments, lipid peroxidation and sugars during the initial growth development of seedlings were analysed. Seeds exposed to 800 mg.L-1 of Se showed a decrease of 20% of seed germination index compared to the control treatment. The decrease in seedling growth reflected in the increase of total sugars and sucrose concentration in both the shoot and root in response to exposure to Se concentration. There was a decrease in the concentration of leaf chlorophyll, carotenoids

Sweet potato [Ipomoea batatas (L.) Lam.] has wide adaptability to different climatic conditions. However, its yield can be affected by prolonged periods of drought. Application of exogenous jasmonates can modulate several physiological and biochemical processes, improving plant tolerance to abiotic stress. This study sought to evaluate the role of exogenous application of methyl jasmonate (MeJA) in attenuating the adverse effects of drought stress by physiobiochemical analyses and their impact during the early initiation of tuberous roots. The experimental design was completely randomized and arranged in a 2 × 2 factorial, comprised of two concentrations of a MeJA plant regulator [without (0 µmol•L-1) and with (13 µmol•L-1) application] and two water regimes (optimum and drought conditions, corresponding to a field capacity of 100 and 40%, respectively). Plants treated with MeJA showed a reduction in total leaf area and leaf dry biomass but increased adventitious root dry biomass. In addition, MeJA application in sweet potato plants affected photosynthetic performance and increased and antioxidant phenolic compounds, carotenoids, anthocyanins, and proline. The evaluated response mechanisms showed that the severity of drought was more prominent than the positive effects of MeJA, since the increases on antioxidant pigments and secondary metabolites were not sufficient to mitigate stress caused by drought, which was reflected in the reduced tuberous root production.

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RESUMO -Este trabalho teve por objetivo analisar o efeito da perda dos cotilédones em diferentes épocas do crescimento inicial do feijoeiro. O delineamento experimental foi inteiramente casualizado em esquema fatorial de 2x5, plântulas com zero e um cotilédone, interagindo com cinco épocas de extrações: zero, um, dois, quatro e seis dias após a germinação, com cinco repetições compostas por três plântulas. Após os 15 dias foram avaliados os seguintes parâmetros: comprimento médio de raiz e parte aérea; diâmetro médio do caule; área foliar; massa seca total da parte aérea e raiz; diâmetro do fl oema e xilema; espessura da epiderme abaxial e adaxial. A remoção dos cotilédones no desenvolvimento inicial do feijoeiro infl uência todos os parâmetros avaliados neste trabalho, exceto o diâmetro médio do caule com um cotilédone. A remoção dos cotilédones nos primeiros dias de extrações difi culta o desenvolvimento inicial do feijoeiro, assim como o torna mais suscetível ao meio. Palavras-chave: estresse, morfologia vegetal, nutrientes, Phaseolus vulgaris L.ABSTRACT -Loss of cotyledons in diff erent stages in initial bean growth. The objective of this work was to analyze the eff ect of cotyledon loss at diff erent times of initial bean growth. The experimental design was completely randomized in a factorial scheme of 2x5, seedlings with zero and one cotyledon, interacting with fi ve extraction stages: zero, one, two, four, and six days after germination, with fi ve replicates composed of three seedlings. After 15 days, the following parameters were evaluated: mean root and shoot length; mean stem diameter; leaf area; total shoot and root dry mass; phloem and xylem diameter; and thickness of abaxial and adaxial epidermis. Removing cotyledons during the initial development of the bean plant infl uenced all the parameters evaluated in this work, except the mean diameter of the stem with one cotyledon. The removal of cotyledons in the fi rst days of extractions hinders the initial development of the plant, as well as making it more susceptible to the environment. Keywords: stress, nutrients, plant morphology, Phaseolus vulgaris L. INTRODUÇÃODentre as leguminosas, o feijão comum (Phaseolus vulgaris L.) destaca-se no cardápio da alimentação humana, abarcando 50% das leguminosas consumidas no mundo. O fato deste produto possuir custo baixo, torna-se uma alternativa no consumo de proteína para as populações de baixa renda na América Latina e na África (Alwathnani et al. 2012). No Brasil, esta cultura é um dos alimentos mais tradicionais, motivo pelo qual o plantio se estende por todo seu território, tornando-se o maior produtor e consumidor mundial dessa leguminosa alimentar (Barbosa & Gonzaga 2012).O feijoeiro é uma planta que possui dois cotilédones em suas sementes. Os cotilédones participam do processo fotossintético e exercem uma grande influência no desenvolvimento inicial e crescimento da plântula ao defi nir uma estratégia sincronizada na degradação de suas reservas, atuando no suprimento da demanda de energia e de nutri...

Iron (Fe) is an essential micronutrient for plants, as a cofactor in multi-heme cytochromes and within iron-sulfur clusters. However, Fe can be toxic at high concentrations. Free Fe in cells can disrupt the cell redox balance toward a pro-oxidant state, generating oxidative stress. The focuses of this review were to elucidate the Fe detoxification strategies used by plants, as well as describe the Fe excess effects on the plant body and its impact on the physiological, morphological and metabolic traits. Therefore, we highlight the importance of evaluating Fe toxicity and provide a paper compilation on Fe detoxification strategies and morpho-physiological responses to excess Fe, directing further research in this segment.

Mg, and S were observed at 90 DAT. Plants fertilized with cattle and poultry manures presented increases in the total phenol content and antioxidant activity in relation to the control plants (without fertilization), in both harvest seasons (90 and 150 DAT). In conclusion, fertilization of P. incarnata with cattle and poultry manure did not result in dry biomass gains, but promoted an increase in the quality of the raw material (higher phenolic concentration and antioxidant activity).

Nos últimos anos tem sido crescente as pesquisas científicas de inovação e tecnologia agrícola a respeito da ação do campo magnético sob a germinação e desenvolvimento de plantas. Diante do exposto, esta pesquisa teve como objetivo avaliar o desenvolvimento inicial de mudas de alface (Lactuca Sativa L.) com uso de água tratada magneticamente e não tratada (controle). O experimento foi realizado em bandejas de 120 células, sendo a parcela constituída por 12 células com 10 repetições, onde foram testados os tratamentos água tratada magneticamente e não tratada. Foram realizadas medições semanais de comprimento da parte aérea e quando as mudas atingiram 24 dias após germinadas, retirou-as das bandejas e avaliou-se os seguintes parâmetros: comprimento da parte aérea, massa seca da parte aérea, comprimento da raiz e massa seca da raiz. Nas condições de tempo de exposição e força do magnetizador, o uso da água magnetizada é benéfica para o alface e provavelmente para outras culturas. Em particular, para a alface, os resultados revelam que a irrigação com água tratada magneticamente é eficiente para obter-se mudas de alface com maior volume de biomassa na parte aérea e raiz.