Concentrações de fenóis totais nas folhas do cafeeiro durante desenvolvimento dos frutos

Vegetables have a natural defense against external factors synthesizing phenolic compounds, which depends on the maturity stage and on the climate. Total phenol grades were extracted from mature and young coffee leaves and were analyzed in relation to yield, phenology and climate. The climatic conditions were described by air temperature, global radiation and daily insolation. Evaluations were made on height, diameter and length of reproductive branches to determine the respective vegetative growth rates of the plants. The amounts of total phenols in the plants at the production stage was 174.0 mg g-1 and 138.9 mg g-1 for young and mature leaves, respectively, and for plants without fruit formation 186.5 mg g-1 and 127.6 mg g-1 for young and mature leaves, respectively. The total phenol concentrations in young leaves with and without fruit formation were 25% and 46% greater compared to mature leaves. The secondary phenol synthesis in seed (146.8 mg g-1) was 31% lower than during grain maturation (212.4 mg g-1). The total phenol metabolization depends indirectly on the temperature and on the global radiation, presenting an inverse trend in relation to these climatic variables. Crop protection management should take into consideration periods of endanger of this natural defense of the plant.Os vegetais apresentam defesa natural contra fatores externos, por meio da síntese de fenóis, as quais variam com as fases fenológicas e com o clima. Os teores de fenóis totais foram extraídos das folhas fonte e dreno e analisados em relação à produção de café, fenologia e clima. As variáveis climáticas consideradas foram: temperatura, radiação e insolação. Realizaram-se avaliações de altura, diâmetro e comprimento de ramos para determinar as taxas de crescimento. As quantidades de fenóis determinadas nas plantas com produção (174,0 mg g-1 e 138,9 mg g-1 - nova e madura) e sem produção (186,5 mg g-1 e 127,6 mg g-1 - nova e madura) não variaram. No entanto, a concentração de fenóis nas folhas nova das plantas com e sem produção foi maior que a quantidade determinada nas folhas madura, da ordem de 25% e 46%, respectivamente. A síntese de fenóis na granação (146,8 mg g-1) foi 31% inferior em relação às quantidades determinadas na maturação (212,4 mg g-1). A metabolização de fenóis depende, indiretamente, da temperatura e da radiação global. A orientação do manejo deve levar em consideração as épocas de comprometimento da defesa natural, em relação à produção de fenóis

Influência de estresses nutricionais no teor e produção de esteviosídeo durante o desenvolvimento da estévia

This paper presents the results of two experiments about stevioside in Stevia rebaudiana (Bert.) Bertoni. In the first one the effects of the deficiencies of N, P, K, Ca, Mg, S, B and Zn as well as the B and Zn toxicity on the stevioside concentration in nutrient solution grown plants were evaluated. In the second trial the objetive was to estimate the content of the stevioside produced during the first cycle of growth under field conditions. Only severe Ca deficiency caused reduction in the glycoside concentration. The content of stevioside under field conditions reached a maximum value 30 days after transplanting (dat), namely 8.2% which dropped to 6.0% at 90 dat. The highest production rate of the glycoside, taking into account either the preexisting total dry weight or leaf area, took place before transplanting and between 15 and 30 dat. During the interval of 30 to 45 dat, a period of vigorous growth of the inflorescences, there was a decrease in the stevioside production rate.O trabalho apresenta os resultados referentes a dois experimentos: o primeiro em solução nutritiva, com o objetivo de avaliar a influência da deficiência de N, P, K, Ca, Mg, S, B e Zn, e da toxidez de B e Zn sobre o teor de esteviosídeo nas folhas de estévia (Stevia rebaudiana (Bert.) Bertoni). O objetivo do segundo experimento foi analisar a concentração e a quantidade de esteviosídeo ao longo do primeiro ciclo de crescimento da planta em condições de campo. Os ajustes matemáticos realizados visando determinar as correlações significativas permitem afirmar que apenas a deficiência severa de Ca provoca diminuição no teor do esteviosídeo. O teor de esteviosídeo, no campo, alcançou o valor máximo 30 dias após o transplante, com 8,2%. Daí em diante, houve queda na concentração, chegando a 6,0% 90 dias após o transplante. A maior taxa de produção de esteviosídeo, considerando-se a massa ou a área foliar preexistente, ocorreu antes do transplante, e entre 15 e 30 dias após o transplante. Ocorreu taxa de produção negativa de esteviosídeo nas folhas entre 30 e 45 dias após o transplante, período de crescimento vigoroso das inflorescências

Occurrence of powdery mildew disease in wheat fertilized with increasing silicon doses: a chemometric analysis of antioxidant response

Blumeria graminis (Bgt) is a pathogenic fungus that affects severally wheat plants provoking high losses in wheat production. Biochemical parameters like enzyme activity of catalase, superoxide dismutase, or peroxidases can be used to detect changes of metabolism in response to pathogen infection. We evaluated different biochemical and biometrics parameters to assess the effect of silicon, a widely recognized beneficial nutrient, in wheat infected naturally with Bgt. Integral study and interpretation of results obtained by multivariate analysis is the challenge of present work. Wheat plants growing in hydroponic solution were fertilized with increasing concentration of silicon. Responses of wheat plants to silicon treatments were assessed through the analysis of lipid peroxidation and antioxidant enzymes activity (catalase, ascorbate peroxidase and superoxide dismutase). Furthermore, biometric measures such as Pathogen Index, dry weight of shoot and roots, tiller height, spike length, spike mass, grain number and grain mass production were assessed. Pathogen Index decreased while mass and number of grain, dry weight of shoots were significantly increased, proportionally to silicon concentration increasing in culture media; biochemical parameters were also influenced by the concentration of silicon. Multivariate analysis indicated correspondence between increase of silicon treatments and decrease of antioxidant activities of APX, CAT and SOD. Relationships between the applied doses of silicon and decreasing Bgt expansion in foliar surfaces were also observed. Chemometrics proved to be an optimal tool for integrating data about metabolic status and demonstrate, in present case, that increasing concentration of silicon and the reduction of antioxidant enzyme activity are closely related to decreasing of powdery mildew disease.EEA AnguilFil: Moldes, Carlos Alberto. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; ArgentinaFil: Lima Filho, Oscar Fontão de. Empresa Brasileira de Pesquisa Agropecuária Oeste; BrasilFil: Merini, Luciano J. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Anguil. Laboratorio de Malezas y Herbicidas; ArgentinaFil: Tsai, Siu M. Universidade de Sao Paulo. Centro de Energia Nuclear na Agricultura; BrasilFil: Camiña, José Manuel. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentin

Assessment of the effect of silicon on antioxidant enzymes in cotton plants by multivariate analysis

Silicon has been extensively researched in relation to the response of plants to biotic and abiotic stress, as an element triggering defense mechanisms which activate the antioxidant system. Furthermore, in some species, adding silicon to unstressed plants modifies the activity of certain antioxidant enzymes participating in detoxifying processes. Thus, in this study, we analyzed the activity of antioxidant enzymes in leaves and roots of unstressed cotton plants fertilized with silicon (Si). Cotton plants were grown in hydroponic culture and added with increasing doses of potassium silicate; then, the enzymatic activity of catalase (CAT), guaiacol peroxidase (GPOX), ascorbate peroxidase (APX), and lipid peroxidation were determined. Using multivariate analysis, we found that silicon altered the activity of GPOX, APX, and CAT in roots and leaves of unstressed cotton plants, whereas lipid peroxidation was not affected. The analysis of these four variables in concert showed a clear differentiation among Si treatments. We observed that enzymatic activities in leaves and roots changed as silicon concentration increased, to stabilize at 100 and 200 mg Si L–1 treatments in leaves and roots, respectively. Those alterations would allow a new biochemical status that could be partially responsible for the beneficial effects of silicon. This study might contribute to adjust the silicon application doses for optimal fertilization, preventing potential toxic effects and unnecessary cost.Fil: Moldes, Carlos Alberto. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Lima Filho, Oscar Fontão de. Embrapa Agroindustrial Tropical - CNPAT; BrasilFil: Camiña, José Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Kiriachek, Soraya Gabriela. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Molas, María Lía. Universidad Nacional de La Pampa. Facultad de Agronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Tsai, Siu Mui. Universidade de Sao Paulo; Brasi