RESUMO: O metil jasmonato (MeJA) é reconhecido como um hormônio vegetal que induz várias alterações bioquímicas relacionadas à qualidade dos frutos, mas é evidente que o efeito do MeJA durante a pós-colheita é muito variável quanto à concentração, espécies de plantas e até mesmo cultivares. O objetivo deste trabalho foi relacionar a aplicação deste regulador em baixa concentração (10 µmol L-1 por 24 h) às mudanças na fisiologia pós-colheita, na incidência de antracnose e na qualidade do mamão ‘Golden’ durante o armazenamento a 24 ± 1 ° C. A partir do sétimo dia de armazenamento, a incidência de antracnose foi reduzida em mais de 50% com o tratamento com MeJA. Incidência da doença também foi reduzida. Embora o MeJA tenha reduzido a acidez dos frutos, os teores de ácido ascórbico e sólidos solúveis não foram alterados durante o armazenamento com o tratamento hormonal. A cor da casca e a firmeza da polpa apresentaram ligeira retenção. A redução na produção de etileno foi acompanhada pela redução da respiração nos frutos tratados. MeJa aumentou a atividade da CAT apenas na casca, enquanto a atividade da SOD não foi induzida por MeJA na casca e na polpa. Embora o aumento da CAT a partir do terceiro dia de armazenamento possa ter contribuído para a redução da peroxidação lipídica na casca, a redução do MDA na polpa não pode ser explicada apenas pela atividade da CAT. Em resumo, a aplicação de MeJA em mamão ‘Golden’ reduziu a incidência e severidade da antracnose, diminuiu a respiração, a produção de etileno e a peroxidação lipídica. Conclui-se que a aplicação de MeJA em baixa concentração (10 µmol L-1) pode contribuir para o controle da antracnose em mamão ´Golden` e retardar o amadurecimento dos frutos.

ABSTRACT: Methyl jasmonate (MeJA) is recognized as a plant hormone that induces several biochemical changes related to improving fruit quality, but it is evident that the effect of MeJA during postharvest is very variable upon concentration, plant species, and even cultivars. The objective of this research was to relate the application of this regulator at low concentration (10 µmol L-1 for 24 h) to changes in postharvest physiology, on the incidence of anthracnose and quality of ‘Golden’ papaya fruit during storage at 24 ± 1°C. From the seventh day of storage, anthracnose incidence was reduced by more than 50% with MeJA treatment. The lesion area after infection was also reduced. Although, MeJA reduced fruit acidity, the ascorbic acid and soluble solids content were not altered during storage with the hormonal treatment. The skin color and pulp firmness showed slight retention. The reduction in ethylene production was accompanied by a reduction of respiration in treated fruits. MeJa increased CAT activity only in the skin whereas SOD activity was not induced by MeJA in both skin and pulp. Although, the increase of CAT from the third day of storage may have contributed to the reduction of lipid peroxidation in the skin, the MDA reduction in the pulp cannot be explained only by CAT activity. In summary, the application of MeJA in ‘Golden’ papaya reduced the incidence and severity of anthracnose, decreased respiration, ethylene production and lipid peroxidation. It is concluded that the application of MeJA at a low concentration (10 µmol L-1) may contribute to anthracnose control in ´Golden`papaya and slows the ripening of fruits.

ABSTRACT Heat stress can impact crop development and yield and amino acids play diverse essential roles in plants. This work aimed to study the long-term effects of foliar spray with L-arginine in antioxidant machinery, physiology, nutrition, productivity and fruit quality of tomato plants subjected to transient heat stresses. Six concentrations of L-arginine were sprayed on the plants: 0 (control), 0.10, 0.25, 0.50, 1.0 and 2.0 g·L–1. The content of hydrogen peroxide (H2O2), a reactive oxygen species, decreased concurrently to the increasing arginine concentration. The ascorbate peroxide (APX) activity had an inverse behavior to that observed for H2O2 content (r = –0.79), not only indicating that arginine is able to modulate APX, but also suggesting that this enzyme plays an important role on the mitigation of H2O2 generation under heat stress. Ascorbate peroxide and catalase (CAT) activities had a positive correlation (r = 0.82), showing that these enzymes may work in tandem. The influence of arginine on photosynthesis activity and gas exchange was generally weak and depended mainly on the plant developmental stage. Yield was increased by 19.8 and 23.1% in plants that received 1.0 and 0.5 g·L–1 of arginine, respectively, when compared to control plants. In conclusion, the use of exogenous L-arginine can protect tomato plants against oxidative imbalance under transient heat within protected environments.

ABSTRACT Spinach seeds are sensitive to high temperatures during germination and plant growth. It is known that seed priming with water or with seaweed extract (SWE) may enhance germination and seedling growth. The objective of this study was to evaluate the effects of seed priming with SWE (Ascophyllum nodosum) on the germination, seedling growth and antioxidant capacity of spinach seedlings under conditions of heat stress. Five concentrations of SWE (0.0, 0.15, 0.30, 0.60 and 1.2%) were used for priming the seeds under two temperatures (15 and 30 °C). Seeds primed with 0.3% SWE had the greatest activity of antioxidant metabolism and showed improved germination percentage, germination speed and seedling vigor under conditions of heat stress (30 °C) compared to nonprimed controls. Hydropriming and priming with 0.3% SWE resulted in lower contents of hydrogen peroxide (H2O2) and malondialdehyde (MDA) under heat stress than control (nonprimed spinach seeds). This study showed that seed priming with SWE was effective to mitigate stress due to high temperatures and to improve spinach seed germination and seedling vigor.

ABSTRACT: In general, the effects of Cadmium (Cd) on crop quality are evaluated solely by Cd accumulation in the edible plant parts; thus, the potential effects on several nutritional features are not often taken into account. This study evaluated Cd effects on the enzymatic activities of lysine (Lys) metabolism, storage protein and amino acid profile in maize. Stress parameters were also assessed. In vegetative organs, Cd was accumulated in the following decreasing order: roots > stems > leaves. Cadmium accumulation in grains decreased at grain maturity (from 0.25 to 0.07 µg g−1 DW). In leaves, neither hydrogen peroxide content nor superoxide dismutase, catalase, ascorbate peroxide and guaiacol peroxidase activities did not change in Cd-treated plants compared to control plants. Lipid peroxidation was not detected in immature grains and leaves of plants under Cd exposure, indicating that Cd accumulation mainly in the roots is a mechanism to avoid oxidative stress in aboveground parts of the plant. However, Lys metabolism in immature grains was modified, showing increases in the specific activities of aspartate kinase (AK) and dihydrodipicolinate synthase (DHDPS) after Cd exposure. AK sensitivity to Lys feedback inhibition increased, but decreased in DHDPS in Cd-treated plants, suggesting differential regulation for these enzymes. In mature grains, the Lys content did not change, while the proline content increased by 54 % in Cd-treated plants. This is the first report on Cd effects on amino acid profile, storage protein contents and enzymes from Lys metabolism in grains of a cereal plant species.

Resumo: O objetivo deste trabalho foi avaliar cultivares de feijão-caupi (Vigna unguiculata) quanto ao desenvolvimento da planta e à quantidade e à qualidade de proteínas solúveis em seus grãos, com vistas ao melhoramento. O experimento foi conduzido em casa de vegetação, em delineamento experimental inteiramente casualizado, com as cultivares Paulistinha, BRS Novaera, Epace 10 e BR 17-Gurguéia. Avaliaram-se área foliar, peso fresco e seco da parte aérea, conteúdo de proteína foliar, número de nódulos, e massa seca de nódulos e de raiz. Nos grãos maduros, também quantificaram-se as frações solúveis e os aminoácidos solúveis, e a análise eletroforética foi realizada com desnaturação das proteínas. Não houve diferenças entre as cultivares quanto às variáreis do desenvolvimento da planta. No entanto, a quantidade e a qualidade das proteínas nos grãos diferiram entre as cultivares. 'BRS Novaera' e 'BR 17-Gurguéia' apresentaram maior teor de proteína solúvel nos seus grãos. 'BRS Novaera' apresentou maior teor de dois aminoácidos sulfurados solúveis - metionina e cisteína - , não tendo diferido de 'BR 17-Gurguéia' quanto ao conteúdo de metionina. Ambas as cultivares apresentaram polimorfismo de bandas, mas BRS Novaera apresentou uma banda extra para albuminas. As cultivares BRS Novaera e BR 17-Gurguéia apresentam o maior conteúdo de proteínas solúveis nos seus grãos e o maior polimorfismo de proteínas, o que as torna adequadas para o melhoramento nutricional do feijão-caupi.

Abstract: The objective of this work was to evaluate cowpea (Vigna unguiculata) cultivars regarding plant development and the quantity and quality of soluble proteins in their grains, for breeding purposes. The experiment was conducted in a greenhouse, in a completely randomized experimental design, with the Paulistinha, BRS Novaera, Epace 10, and BR 17-Gurguéia cultivars. Leaf area, shoot fresh and dry matter, leaf protein content, number of nodules, and nodule and root dry matter were evaluated. In mature grains, soluble fractions and soluble amino acids were also quantified, and the electrophoretic analysis was performed with protein denaturation. There were no differences between cultivars for the plant development variables. However, protein quantity and quality in the grain differed between cultivars. 'BRS Novaera' and 'BR 17-Gurguéia' showed a higher soluble protein content in their grains. 'BRS Novaera' exhibited higher contents of two soluble sulfur amino acids - methionine and cysteine - , not differing from 'BR 17-Gurguéia' regarding methionine content. Both cultivars presented protein band polymorphism, but BRS Novaera had an extra band for albumins. The BRS Novaera and BR 17-Gurguéia cultivars have the highest content of soluble proteins in their grains and the greatest protein polymorphism, which makes them suitable for improving the nutritional quality of cowpea.

ABSTRACT Uptake of nutrients and cadmium (Cd) are dependent upon many factors, including plant species, ions concentration and pH. Tolerance to Cd-induced oxidative stress can be modulated by phytohormones such as abscisic acid (ABA), which induce the production of reactive oxygen species, activating proteins and enzymes involved in stress response and possibly stress tolerance. The present study aimed to evaluate the biochemical variations induced by Cd in ABA-deficient sitiens tomato mutant (sit) and its wild-type counterpart, Micro-Tom (MT), grown at different pH conditions. The plants were cultivated in nutrient solution (pH 5, 6 and 7; 20-days) and were then further grown over a 48-h period in 0 or 50 ?M CdCl2 at pH 6. Before Cd addition, the concentrations of nitrogen, sulfur, copper, iron and zinc were determined and variations in nutrients concentrations were observed. After Cd addition, sit roots grown at pH 5 and 7 did not exhibit differences in ascorbate peroxidase (APX) activity in 0 or 50 ?M CdCl2, and sit root grown at pH 6 exhibited lower glutathione reductase (GR) activity in the presence of Cd. Moreover, sit shoot grown at pH 5 showed decreased activities of superoxide dismutase (SOD), Mn-SOD II and Cu/Zn-SOD V, in 0 and 50 ?M CdCl2. The results indicated that pH modulates the plant nutrition in a complex way and may involve multiple ABA signaling pathways. Likewise, ABA status seems to be related with the Cd-translocation within the plant, suggesting that Cd, ABA and pH responses cannot be evaluated as isolated systems.

ABSTRACT: Seedling production is an important step in the lettuce production system. However, there is a tendency to apply excessive irrigation at this stage. The aim of this study was to test the use of the Simplified Irrigation Controller (SIC) under two conditions: first, with the sensor installed in the substrate (measuring the soil water tension) and second, in the atmosphere (“atmospheric” - responding to vapor demand in the atmosphere) to control the irrigation of lettuce seedlings. The performance of the SIC was evaluated by monitoring plant traits. The lettuce seeds of the Regina cultivar were sown in styrofoam trays with commercial organic substrate. Both experiments were conducted under greenhouse conditions and evaluated under different SIC activation tensions. Shoot fresh weight and dry weight, height, number of leaves, leaf length, leaf area, water use efficiency (WUE) (ratio between the dry mass of plant produced by the volume of water applied), chlorophyll content, stomatal conductance and chlorophyll a fluorescence were assessed. In the experiment with the substrate sensor, the tension of 11.5 kPa caused death in 94 % of the seedlings and was disregarded in the statistical analysis. All biometric and physiological traits evaluated decreased as the SIC tensions increased. Thus, tensions of 4.0 (substrate sensor) and 3.5 kPa (atmospheric sensor) showed greater potential for producing vigorous seedlings, with WUE average values of 1.86 and 1.37 g L−1, respectively. Cultivation of lettuce seedlings proved viable under both conditions when the SIC was used, with the emergence of a number of practical advantages of the atmospheric sensor over the substrate one.

ABSTRACT: Concerns with water crisis involve all sectors of society and irrigated agriculture remains the main water consumer. This study evaluated an agricultural production system for lettuce cultivation in greenhouse, “organic potponics”, to economize water and manure use, using a Simplified Irrigation Controller (SIC), based on soil matric potential monitoring. Five irrigation volumes were evaluated in pots with 4.8 L, fertilized with 200 g of vermicompost. One of the volumes was controlled with the SIC. The other volumes represented 130, 80, 60 and 33 % of that controlled by the SIC and all treatments received water at the same time. Shoot fresh weight, head diameter and stomatal conductance (gs) increased linearly with irrigation volumes. For shoot dry weight, number of leaves and water use efficiency (WUE), the regression was quadratic with maximum values at 126, 114 and 83 %, respectively. Leaf relative water content did not show variation among treatments and changes in some fluorescence parameters (Reo/RC, Sm, N and φR0) were much more remarkable to drought compared with the FV/ FM ratio, one of the most commonly used stress indicators. The data indicated a tradeoff between WUE and plant growth thus the economic values of water and lettuce should be taken into account to indicate the best SIC irrigation volume. Organic potponics is promising and should be further improved to save on water, labor and fertilizer use.

RESUMO: A adubação com Selênio (Se) em pastagem para a biofortificação de alimentos de origem animal tem sido realizada em solos com baixo Se. O objetivo foi avaliar o aumento no conteúdo de Se na biomassa de Brachiaria spp. com aplicação de ureia revestida com Se. O experimento foi conduzido em casa de vegetação em Latossolo Amarelo. O delineamento foi em blocos casualizados com quatro repetições em esquema fatorial com dois cortes e seis doses de Se (0, 10, 20, 40, 80 e 160gha-1). A Brachiaria brizantha demonstrou ausência de mudanças em altas e perigosas doses de Se sem alterar a atividade da enzima antioxidante glutationa peroxidase. Com isso, concluiu-se que seu enriquecimento com ureia revestida é obtida com 34,5gha-1 de Se.

ABSTRACT: Selenium (Se) fertilization in grazing to biofortification of animal products have been carried out in low Se soils. The objective of this study was to increase the Se content in the biomass of Brachiaria spp.with urea coated with Se. The experiment was performed in a typical Hapludox soil under greenhouse conditions. A completely randomized block design with four replicates in a factorial structure with two cuts and six Se doses (0, 10, 20, 40, 80, and 160gha-1) was used. The Brachiaria brizantha demonstrated the absence of changes in higher harmful doses without modifying the activity of glutathione peroxidase enzyme. We concluded that enrichment of Brachiaria brizantha with coated urea is obtained with 34.5gha-1of Se.

Studying relationships among plant and crop traits is crucial for crop scientists to understand complex biological systems that occur in plants and the field. Such knowledge constitutes the basis for more practical information on how to manage breeding and production to provide better or more suitable cultivars, higher yields, lower yield gaps, and resistance to pests etc. To acquire such knowledge, however, representative models of associations between plant and crop traits must be constructed. In path analysis - one of the major methods for analyzing multivariate relationships between quantitative traits - it is important to decide on an appropriate model for these associations, a model that is representative of the corresponding biological phenomena that are of interest to crop researchers. Adopting this "point of view", we asked various questions relating to such model building: (i) how should sequentiality in sequential path analysis be understood? (ii) how should it be interpreted? (iii) how should such sequential models be formulated? We discussed these issues in the context of crop science. Differences in simple and complex (sequential) models of path analysis are presented. Based on crop science examples, we show how important it is to correctly represent the biological relationships for a path analysis model.

Uma das principais dificuldades nos trabalhos visando a seleção de plantas tolerantes a metais pesados é a própria metodologia para avaliação eficiente de grande número de plantas, gerando poucos resíduos para o meio ambiente. Por esse motivo, propomos uma metodologia simples e eficaz que pode ser aplicada a metais ou outros elementos químicos, partindo de um estudo de caso, no qual selecionamos dois mutantes de tomateiro (cv Micro-Tom) tolerantes ao Cádmio, obtidos por mutagênese com etanosulfonato de metila (EMS). Além destes dois novos mutantes, selecionamos outros 21 com alterações potenciais quanto a respostas a este metal. Por fim, chegamos à conclusão de que o sistema proposto é ideal para trabalhos de seleção de plantas tolerantes a metais pesados e possivelmente a outros elementos, devido à facilidade de montagem da estrutura, baixo custo de implantação, minimização de geração de resíduos e possibilidade de uso em várias espécies e diferentes metais pesados.

One of the major difficulties in studies on the selection of heavy metal tolerant plants is the proper methodology that must ensure an efficient evaluation of a large number of plants, but reducing environmental contamination. For this reason, we propose a simple and effective method that can be applied to metals or other chemicals by means of a case study, in which we selected two cadmium-tolerant mutants of tomato (cv Micro-Tom) obtained by mutagenesis with methyl ethanesulfonate (MES). Aside from these two new mutants, we selected 21 others with possible alterations in the response to this metal. Finally, it was concluded that the proposed system is ideal for selection studies on plants tolerant to heavy metals and possibly to other elements, due to the ease of assembly of the structure, low installation cost, minimal waste generation and the possibility of using different species and heavy metals.

Nutrient analysis is used to estimate nutrient content of crop plants to manage fertilizer application for sustained crop production. Direct solid analysis of agricultural and environmental samples by energy dispersive X-ray fluorescence spectrometry (EDXRF) was chosen as alternative technique to evaluate the simultaneous multielemental quantification of the most important essential elements in coffee (Coffea arabica L.) plants. Inductively coupled plasma atomic emission spectrometry and certified reference materials made from leaves were used to calibrate and check the trueness of EDXRF method for the determination of the concentration of several nutrients in coffee leaves and branches. Fluorescence spectrometry proved to be advantageous and presented low cost as loose powder samples could be used. Samples collected from a field experiment where coffee plants were treated with excess of Ni and Zn were used to verify the practical application of the method. Good relationships were achieved between certified values and data obtained by EDXRF, with recoveries ranging from 82 to 117 %.

Soil contamination by heavy metals is a challenge faced by many countries, and engineering technologies to solve this problem are expensive and can cause negative impacts on the environment. One way to minimise the levels of heavy metals in the soil is to use plants that can absorb and accumulate heavy metals into harvestable parts, a process called phytoextraction. Typical plant species used in research involving phytoextraction are heavy metal hyperaccumulators, but plants from this group are not good biomass producers and grow more slowly than most species; thus, they have an important role in helping scientists understand the mechanisms involved in accumulating high amounts of heavy metals without developing symptoms or dying. However, because of their slow growth, it is not practical to use these species for phytoextraction. An alternative approach is to use non-hyperaccumulator plants assisted by chelating agents, which may improve the ability of plants to accumulate more heavy metals than they would naturally. Chelating agents can be synthetic or organic acids, and the advantages and disadvantages of their use in improving the phytoextraction potential of non-hyperaccumulator plants are discussed in this article. We hope to draw attention to ways to improve the phytoextraction potential of non-hyperaccumulator plants that produce a large amount of biomass and to stimulate more research on phytoextraction-inducing substances.

'Golden' papayas at maturity stage 1 (15% yellow skin) were chosen to study selected oxidative processes, the activity of antioxidant enzymes and lipid peroxidation in storage at 22°C, during the ripening of the fruit. An increase in ethylene production was observed on the second day of storage and it was followed by an increase in respiration. An increased activity of catalase, glutathione reductase and ascorbate peroxidase was observed concurrently or soon after this increase in ethylene production and respiration. The increased activity of these enzymes near the peaks of ethylene production and respiration is related to the production of oxidants accompanying the onset of ripening. On the fourth day of storage, there was an increased lipid peroxidation and decreased activities of catalase, glutathione reductase and superoxide dismutase. Lipid peroxidation induces the increase of antioxidant enzymes, which can be verified by further increases in the activities of catalase, glutathione reductase, superoxide dismutase and ascorbate peroxidase. Unlike the other antioxidant enzymes, the ascorbate peroxidase activity in the pulp increased continuously during ripening, suggesting its important role in combating reactive oxygen species during papaya ripening. With regard to physical-chemical characteristics, the soluble solids did not vary significantly, the acidity and ascorbic acid contents increased, and hue angle and firmness decreased during storage. The results revealed that there was variation in the activity of antioxidant enzymes, with peaks of lipid peroxidation during the ripening of 'Golden' papaya. These results provide a basis for future research, especially with regard to the relationships among the climacteric stage, the activation of antioxidant enzymes and the role of ascorbate peroxidase in papaya ripening.