Paôla de Castro Henrique

Tolerance of Sesbania virgata plants to flooding

Sesbania virgata (Cav.) Pers. is a bush, pioneer and occurs naturally in Brazil. It belongs to the Fabaceae family and it is indicated for recovery of degraded areas because of its rusticity and capacity to tolerate flooding. The present research was carried out to investigate the ability of S. virgata plants to adapt to flooding conditions. Plants containing six expanded leaves were placed in masonry tanks and were subjected to the following conditions: control (well watered), soil-waterlogging (water to the setup level of 1 cm above the soil surface – roots and parts of the stems flooded) and complete submergence (whole plant flooded). The evaluations were conducted on the day of the stress induction and after 7, 14, 21, 28, 35, 42, 49 and 56 days of the treatment. After 15 days of return to normoxic environment, plant survival was assessed. Growth (height, dry mass of shoots and roots), vigour, carbohydrate content and the activity of enzymes involved in anaerobic metabolism (lactate dehydrogenase, pyruvate decarboxylase and alcohol dehydrogenase) were also evaluated. Our results suggested that sesbania plants are tolerant to flooding, because they can survive being submerged for 56 days. The reasons for this tolerance include the accumulation and use of carbohydrates in the leaves and roots, maintenance of growth and the activation of anaerobic metabolism, particularly in steps catalysed by the enzymes pyruvate decarboxylase and alcohol dehydrogenase.

Aspectos fisiológicos do desenvolvimento de mudas de café cultivadas sob telas de diferentes colorações

Abstract – The objective of this work was to evaluate the physiological aspects of the development of coffee seedlings grown under colored screens with different spectral characteristics. Seedlings of Catucai Amarelo 2SL, in the stage known as “orelha de onca”, were arranged in a randomized block design, with five replicates, under structures individually covered with blue, white, gray, black or red screens with 50% shade. Four months after, evaluations were done for seedling growth, pigment content of the leaves, total soluble sugars and starch contents of the leaves and roots. The red screen was the most effective in promoting growth in four out of the seven studied traits: plant height, leaf area and leaf dry weight and total dry matter. For the other characteristics, there was no difference among the screens. The pigment analysis showed that, except for the gray screen, the other ones did not differ for this trait. In leaves, the red screen promoted higher levels of carbohydrates and starch. At the root, carbohydrate contents were higher under the red and black screens. Among the five screen colors, the red one was the most efficient in the production of coffee seedlings with higher vigor and quality, with outstanding carbohydrate contents and biomass.Index terms:

Stomatal behavior and components of the antioxidative system in coffee plants under water stress

Coffee (Coffea arabica) plants show a positive relationship between stomatal closure and formation and accumulation of H2O2. However, for coffee plants under water restriction such relationship has never been studied. The objective of the present study was evaluate the stomatal movement and the antioxidant capacity of coffee seedlings under different water regimes. Eight months old coffee seedlings of cv. Catuai IAC 99 were submitted to field capacity, gradual and total suspension of irrigation during a period of 21 days. Evaluations of leaf water potential (Ψw) were performed in the beginning of the morning, and stomatal resistance, transpiration rate and vapor pressure deficit were determined at 10 am and 5 pm. All biochemical and enzymatic determinations were performed in leaves collected at 5 pm. Evaluations and samplings were performed at three days intervals. There was no variation in Ψw during the evaluated period for plants in field capacity. However, an expressive decrease of Ψw following day 12, reaching values near -2.5 MPa at the end of the experiment was observed for plants submitted to gradual suspension of irrigation. For plants submitted to total suspension of irrigation, Ψw decreases after the sixth day, reaching -2.5 MPa at day 15. The decay of Ψw in plants submitted to gradual and total suspension of irrigation reflected in increased stomatal resistance and in a decreased transpiration rate leading to an increase in hydrogen peroxide formation and, on final stages, increase in lipid peroxidation. As a conclusion, an increase in the activity of antioxidant enzymes as well as in the levels of ascorbate and dehydroascorbate was observed, which act in the detoxification of free radicals formed as result of the water stress.

Características fisiológicas e anatômicas de plantas de sibipiruna submetidas à hipoxia

Plants in their natural environment are subject to adverse conditions, and the stress periods can be short or long. Some species develop mechanisms that make them bear the adverse conditions, allowing their survival. The aim of this study was to evaluate the anatomic and physiological responses in the initial development of Sibipiruna plants submitted to hypoxia. Plants with three to four leaves fully expanded were subjected to three treatments: plants without flooding, flooded on roots and totally flooded. Evaluations were carried out in the starch, total soluble sugars and reducing sugars levels in the leaves and roots collected every five days, for 30 days. Anatomical characteristics were evaluated 15 days after the beginning of each treatment. The largest reduction in starch level in leaves and in roots was observed in plants completely flooded. For total soluble sugars and reducing sugars were observed behavior similar to that achieved in starch However, the plants which had flooded roots, in some periods of assessment, had levels, mainly in the roots, higher than the plants without flooding. These plants also showed higher stomatal density than the other treatments. For the thickness of the cortex and the cylinder vascular roots, a reduction was observed for the flooded treatment, which completely flooded plants had a higher apoplastic barrier imposed by thickening in phi, which is characterized by the formation of septa in cells near the endodermis.

Isoflavone and protein content in soybeans grains submitted to flooding at different stages of development

The stress imposed on plants by soil flooding constitutes a major barrier to growth and productivity. The identification of soybean varieties that produce higher levels of isoflavones, is necessary as soybeans have been used as human food to reduce risks of chronic diseases. Thus, this study was conducted with the objective of quantifying proteins and isoflavones in soybean cultivars subjected to flooding at various stages of development. The cultivars ‘BRS267’, ‘BRS257’ and ‘BRS213’ were subjected to 15 days of flooding, starting at the stages V6 and V8 and 11 days under stress starting at the stage R4. The proteins in the grain were extracted and quantified and analyzed by SDS-PAGE electrophoresis. Isoflavones were extracted, separated and quantified on HPLC. The electrophoretic analysis of the three cultivars under study revealed the same pattern of banding relative to the total protein regardless of the treatment. However, it was noted that flooding led to an increase in the total contents of isoflavones in the BRS 267 plants flooded in stage R4, remaining constant in other cultivars.

Color, physicochemical parameters and antioxidant potential of whole grape juices subject to different UV-C radiation doses

Knowing that moderate stress such as UV radiation can activate defense mechanisms in plants, the use of UV-C radiation appears as hypothesis of a promising technique that would help to stimulate and enhance beneficial compounds for health, through a clean and healthy technology. In this study, the possible induction of secondary metabolism, the increase in the content of phytochemical compounds and physicochemical changes through the use of UV-C radiation were evaluated on whole grape juices produced with Vitis labrusca grapes, cultivar Isabel Precoce. Grapes were harvested, sanitized, exposed to UV-C radiation at doses of 0, 2, 4 and 6 KJ m-2, and then the juices were prepared and packed into amber glass bottles at room temperature. Analyses were performed at 0, 30, 60, 90 and 120 days of storage. Based on results obtained and conditions in which the experiment was performed, UV-C treatment in grapes caused abiotic stress in the fruits, affecting color, titratable acidity, soluble solids/titratable acidity ratio, vitamin C and percentage of protection against oxidation. Application of UV-C did not change levels of phenolic compounds in fruit juices or the percentage of scavenging free radicals, pH and soluble solids.

Antioxidant activity, anthocyanins and organic acids content of grape juices produced in Southwest of Minas Gerais, Brazil

O teor de compostos fenolicos e antocianinas em sucos de uva varia de acordo com a cultivar, maturidade e caracteristicas climaticas. Neste trabalho, objetivou-se a caracterizacao e a avaliacao da atividade antioxidante de sucos de uvas americanas produzidas no sudoeste de Minas Gerais. As uvas foram colhidas, sanitizadas, sendo as grainhas e demais partes dos cachos descartadas. Entao, os sucos das cultivares Bordo (Vitis labrusca), Isabel Precoce (Vitis labrusca), BRS Violeta (hibrida) e BRS Rubea (hibrida) foram produzidos em equipamento artesanal por extracao em vapor de agua, acondicionados em frascos de vidro e armazenados a 18oC±2oC por 120 dias. As seguintes analises foram realizadas ao longo do armazenamento: cor (L*), pH, solidos soluveis totais, acidez titulavel, , antocianinas, atividade antioxidante (DPPH e β-caroteno/acido linoleico), fenolicos totais, vitamina C e acidos orgânicos. Entre as cultivares avaliadas, sugere-se o consumo do suco de uva da cultivar BRS Violeta, pelos maiores valores de vitamina C, atividade antioxidante, fenolicos totais, antocianinas, alem de apresentar melhores caracteristicas fisico-quimicas quando comparada ao suco das demais cultivares.

CONSERVAÇÃO DE PERAS MINIMAMENTE PROCESSADAS SUBMETIDAS A TRATAMENTOS QUÍMICOS

O trabalho teve como objetivo testar a eficacia de tratamentos quimicos na manutencao da qualidade de peras ‘Williams’ minimamente processadas. Inicialmente, realizaram-se a lavagem, a sanitizacao e a retirada das sementes dos frutos. Em seguida, foram realizados cortes no formato de palitos, e os mesmos foram imersos nas solucoes, compondo os tratamentos: acido ascorbico a 2 % (controle); acido ascorbico a 2% + cloreto de calcio a 2%; acido ascorbico a 2% + acido citrico a 2%; acido citrico a 1%; cloridrato de L-cisteina a 1%. Os frutos foram acondicionados em bandejas de polipropileno, armazenados em câmara fria a 5oC por 12 dias e avaliados a cada tres dias. O tratamento com cloridrato de L-cisteina a 1% foi o mais eficaz na inibicao do escurecimento em peras minimamente processadas; no entanto, frutos tratados com acido ascorbico + cloreto de calcio apresentaram maior firmeza durante todo o periodo avaliado, alem de quantidades significativamente maiores de vitamina C quando comparado a formulacoes que nao continham acido ascorbico na composicao.

ANTIOXIDANT ACTIVITY DURING STORAGE OF APPLES SUBJECTED TO IRRADIATION

Nowadays, the number of studies about fruit conservation as well as the benefits of consumption of foods rich in antioxidant compounds was increased. This study aimed to quantify antioxidant compounds and their activity and to evaluate the physical and chemical changes during the post-harvest storage of Evas apple cultivars that were subjected to gamma irradiation at doses of 0; 0.5; 1.0 and 1.5 kGy. The antioxidant activity was measured by the 2.2-diphenyl-1-picrylhydrazyl (DPPH) and the β-carotene/linolenic acid methods. Levels of total phenolics, ascorbic acid, color, and soluble solids were evaluated. The results showed that, regardless of the irradiation dose, there was an increase in % SRL during post-harvest storage of Evas apples. Low irradiation doses were able to preserve the phenolic compounds, maintain the ascorbic acid levels and avoid an increase in the soluble solids content.

CRESCIMENTO E PARTIÇÃO DE CARBOIDRATOS EM PLANTAS DE Sebastiania membranifolia SUBMETIDAS AO ALAGAMENTO

Neste trabalho, avaliou-se o crescimento e a particao de carboidratos em plantas jovens de Sebastiania membranifolia em resposta ao alagamento. Sementes foram germinadas em câmara tipo BOD a 25 °C, sobre papel germitest umedecido. As plântulas foram aclimatadas durante 20 dias em sala de crescimento e, em seguida, transplantadas para sacos de polipropileno, contendo substrato constituido de areia, esterco bovino e solo (1:1:1), e transferidas para casa de vegetacao coberta com sombrite 50% de sombreamento, onde permaneceram durante 40 dias. Ao final desse periodo, foram estabelecidos tres tratamentos: plantas nao alagadas, com as raizes alagadas e totalmente alagadas. O alagamento foi realizado, colocando os sacos contendo as plantas, individualmente, em baldes com maior capacidade. As avaliacoes ocorreram com intervalo de 12 dias por um periodo total de 36 dias, sendo utilizadas quatro repeticoes para cada tratamento e periodo de avaliacao. O numero de folhas, ramificacoes, altura do caule e massa seca das partes, aumentou linearmente nas plantas nao alagadas ao longo do periodo analisado. Nas plantas com as raizes alagadas, o mesmo incremento ocorreu somente ate o 24o dia e, para as totalmente alagadas, de maneira geral, nao houve crescimento significativo. Os teores de acucares soluveis totais, redutores e amido foram significativamente inferiores nas plantas totalmente alagadas, tanto nas folhas quanto nas raizes, sendo que nas raizes tambem foi observada significativa reducao nos teores de amido para as plantas com as raizes alagadas, igualando-se, na ultima avaliacao, aos valores das plantas totalmente alagadas. Esses resultados sugerem que S. membranifolia pode ser uma especie promissora para a revegetacao de areas de deplecao sujeitas a inundacao intermitente.