Alteração na fotossíntese causada pela mancha de alternaria (Alternaria helianthi) em girassol.

A mancha de Alternaria (Alternaria helianthi) diminui a área fotossintética da planta, devido à formação de manchas foliares que podem coalescer, formando áreas extensas de tecido necrosado, provocando seca prematura da folha. Objetivou-se avaliar as alterações na fotossíntese causada pela mancha de Alternaria em quatro genótipos de girassol (BRS 324, BRS 321, BRS 323 e HLA 887). O delineamento experimental foi inteiramente casualizado com 4 tratamentos e 6 repetições. Plantas de girassol cultivadas em vaso foram inoculadas com o fungo, no estágio V8 (oito folhas verdadeiras). Após 32 horas, foi feita a leitura da fotossíntese líquida nas folhas 3 e 4, utilizando o analisador de fotossíntese LI-6400XT. A taxa líquida de fotossíntese foi relacionada à severidade da doença por meio do modelo Px/Po=(1-x)b, onde Px representa a taxa fotossintética líquida de folhas com severidade de doença x (em proporção), Po representa a taxa fotossintética líquida média de folhas sadias e b representa a relação entre a lesão virtual (área foliar sem sintomas mas com fotossíntese nula) e a lesão visual (área foliar coberta por sintomas). Os valores de b determinados por regressão não-linear (R2 de 0,35 a 0,52 para os diferentes materiais) variaram entre 0,77 a 2,18. Observou-se diferença na taxa de fotossíntese líquida para os genótipos BRS 324 (1,93), BRS 321 (2,15) e BRS 323 (2,17), que apresentaram b maior que 1. Esta alteração na atividade fotossintética pode ser causada por redução na interceptação da radiação (RI), resultante da perda de área foliar fotossintetizante nas áreas próximas à região necrosada

Influence of Vitis xylem fluid and xylem fluid plus cecropin on growth of Xylella fastidiosa

Colony growth of Xylella fastidiosa (UCLA PD and STL PD strains) was quantified after incubation for 48 h in xylem fluid of Vitis rotundifolia Michx. cv. Noble and Vitis vinifera L. cv. Chardonnay. Xylem fluid was collected from grapevines in the field (dormant and growing season) and from container-grown plants in a screen house (growing season). Colony forming units·ml-1 (cfu·ml-1) were counted 15 d after plating on periwinkle wilt (PW+) medium. Colony growth was promoted or inhibited compared to PW+ medium, and was dependent on X. fastidiosa strain, plant species and source of xylem fluid. The efficacy of cecropin A and B was tested against this bacterium. Colony growth of X. fastidiosa was greatly inhibited after a 1-h-exposure to cecropin A or B. The minimum inhibitory concentration (MIC) of cecropin A or B for 100 % inhibition of X. fastidiosa was < 1 μM. The activity of cecropin B in xylem fluid of V. rotundifolia cv. Noble was progressively reduced over time from 0.2 to 24 h. When 2 and 10 μM concentrations of cecropin A and cecropin B were mixed with xylem fluid for 24 h, a substantial amount of bacterial growth occurred after subsequent plating; shorter time intervals did not degrade the cecropins and did not prevent colony growth. Cecropin B (1 μM) added to xylem fluid of V. rotundifolia cv. Noble and V. vinifera cv. Chardonnay for 24, 48, 72 and 96 h did not prevent subsequent colony growth. Colony number tended to be higher for V. rotundifolia cv. Noble than V. vinifera cv. Chardonnay. Tricine-sodium dodecyl sulphate polyacrylamide gel electrophoresis (Tricine-SDS-PAGE) of cecropin B in xylem fluid showed that cecropin B degraded completely (V. vinifera cv. Chardonnay) or almost completely (V. rotundifolia cv. Noble) after 96 h

Aharonov-Bohm Effect for Bound States on the Confinement of a Relativistic Scalar Particle to a Coulomb-Type Potential in Kaluza-Klein Theory

The publication of this article was funded by SCOAP 3 . Based on the Kaluza-Klein theory, we study the Aharonov-Bohm effect for bound states for a relativistic scalar particle subject to a Coulomb-type potential. We introduce this scalar potential as a modification of the mass term of the Klein-Gordon equation, and a magnetic flux through the line element of the Minkowski spacetime in five dimensions. Then, we obtain the relativistic bound states solutions and calculate the persistent currents

Aharonov-Bohm Effect for Bound States on the Confinement of a Relativistic Scalar Particle to a Coulomb-Type Potential in Kaluza-Klein Theory

Based on the Kaluza-Klein theory, we study the Aharonov-Bohm effect for bound states for a relativistic scalar particle subject to a Coulomb-type potential. We introduce this scalar potential as a modification of the mass term of the Klein-Gordon equation, and a magnetic flux through the line element of the Minkowski spacetime in five dimensions. Then, we obtain the relativistic bound states solutions and calculate the persistent currents

Meristema apical como ferramenta de manejo da pastagem para pastos de capim Tanzânia (Panicum maximum cv. Tanzânia).

Determinar as relações entre altura do pasto e altura do meristema apical em pasto de capim-Tanzânia submetido a diferentes intensidades de manejo baseados em somas térmica

Características estruturais do capim-tanzânia (Panicum maximum cv. Tanzânia) sob diferentes somas térmicas.

Resumo: Fatores climáticos como temperatura têm grande importância no crescimento das plantas forrageiras, influenciando o acúmulo de forragem a distribuição estacional da produção. O objetivo foi quantificar características estruturais do capim-tanzânia em diferentes somas térmicas. O experimento foi conduzido em área semiárida, os tratamentos foram as somas térmicas: 250ºC, 500ºC, 750ºC e 1000ºC. As variáveis analisadas foram: altura do pasto, índice de área foliar, interceptação da radiação fotossinteticamente ativa, massa de forragem total e todos os seus componentes (folha, colmo e material senescente). As temperaturas médias foram de 27 a 29º C, sendo as máximas de 32º C a 37º C e mínimas de 21º C a 22º C O delineamento experimental foi em blocos ao acaso, com arranjo em parcelas subdivididas. Todas as variáveis, exceto relação material vivo: material morto (MV/MM) apresentaram um comportamento linear crescente, sendo as maiores produções de biomassa de 4934 kg/ha, estimadas aos 1.000o. MV/MM teve comportamento linear decrescente, sendo os maiores valores encontrados na soma térmica de 250º C. A estrutura do pasto aos 1000º C (ou 40 dias) apresentou características de altura e número de folhas compatível com pastejo para bovinos, enquanto para caprinos e ovinos as características estruturais foram mais adequadas foram aos 463º C (ou 21 dias). O acumulo total de forragem aos 1000º C foi de 4934 kg de matéria seca por hectare para condições de temperaturas estudadas. [Structural characteristics of Guinea Grass (Panicum maximum cv. Tanzânia) on different daily caloric sum]. Abstract: Climatic aspects as temperature are important to forage growth as they affect herbage accumulation as well as the seasonal distribution. These work aimed quantify structural characteristics of guinea grass on different daily caloric sum. Experiment was carried out in semi arid land conditions, Treatments were daily caloric sum: 250ºC, 500ºC, 750ºC e 1000ºC. Variables analyzed were sward height, leaf area index, interception of photosynthetically active radiation, total forage mass and their components (leaves, stem, and death material). Average temperature ranged 27 - 29º C, higher temperature ranged 32º C - 37º C and lower temperature was between 21o -22o C. Experimental design was block complete randomized in split plot. All variables presented a linear increase regression (P<0.05), except relation between live material: death material that had presented a linear decreasing regression (P<0.05). Higher forage production was estimated in 4934 kg/ha on 1000oC condition. Higher relation live material: death material was observed on 250o C. Structural characteristics of pasture on 1000oC (40 days) was more adequate to cattle grazing than small ruminants that got a better grazing condition on 463oC (21 days). Total biomass on 1000oC was estimated in 4934 dry matter kg per hectare on temperature conditions studied it

Predição de classes de enzimas usando método de agrupamento super-paramagnético.

As proteínas com atividade enzimática podem ser divididas em seis grandes classes de acordo com suas funções específicas, que são: oxirredutases, hidrolases, transferases, lyases, isomerases e ligases. Utilizando algoritmo de agrupamento não-paramétrico, este trabalho tem como objetivo predizer diferentes classes enzimáticas usando parâmetros estruturais e físico-químicos

Enhanced resistance to citrus canker in transgenic sweet orange expressing the sarcotoxin IA gene.

Citrus canker, caused by the bacterial pathogen Xanthomonas citri subp. Citri (Xcc), is a serious disease reported in most citrus-producing areas around the world. Although different levels of field resistance to citrus canker have been reported in sweet oranges, they are usually not sufficient to provide adequate control of the disease. Ectopic over-expression of antibacterial genes is one of the potential strategies to increase plant resistance to bacterial diseases. Previous in vitro results showed that sarcotoxin IA, an antimicrobial peptide isolated from the flesh fly (Sarcophaga peregrina), can be efficient to control different plant pathogenic bacteria, including Xcc. Transgenic BPera^ sweet orange (Citrus sinensis [L.] Osbeck) plants constitutively expressing the sarcotoxin IA peptide fused to the PR1a signal peptide from Nicotiana tabacum for secretion in the intercellular space were obtained by Agrobacteriummediated transformation using thin sections of mature explants. Citrus canker resistance evaluation in leaves of transgenic and non-transgenic plants was performed through inoculations with Xcc by infiltration and spraying. The Xcc population was up to 2 log unit lower in leaves of the transgenic plants compared to those of non-transgenic controls. Incidence of canker lesions was significantly higher in non-transformed controls (>10 lesions/cm2) than in the transgenic plants (<5 lesions/ cm2) after injection infiltration or spraying with Xcc inoculum. Accumulation of sarcotoxin IA peptide in sweet orange tissue did not cause any deleterious effects on the growth and development of the transgenic plants, indicating this approach is suitable to provide resistance to citrus canker

A new picture of the Lifshitz critical behavior

New field theoretic renormalization group methods are developed to describe in a unified fashion the critical exponents of an m-fold Lifshitz point at the two-loop order in the anisotropic (m not equal to d) and isotropic (m=d close to 8) situations. The general theory is illustrated for the N-vector phi^4 model describing a d-dimensional system. A new regularization and renormalization procedure is presented for both types of Lifshitz behavior. The anisotropic cases are formulated with two independent renormalization group transformations. The description of the isotropic behavior requires only one type of renormalization group transformation. We point out the conceptual advantages implicit in this picture and show how this framework is related to other previous renormalization group treatments for the Lifshitz problem. The Feynman diagrams of arbitrary loop-order can be performed analytically provided these integrals are considered to be homogeneous functions of the external momenta scales. The anisotropic universality class (N,d,m) reduces easily to the Ising-like (N,d) when m=0. We show that the isotropic universality class (N,m) when m is close to 8 cannot be obtained from the anisotropic one in the limit d --> m near 8. The exponents for the uniaxial case d=3, N=m=1 are in good agreement with recent Monte Carlo simulations for the ANNNI model.Comment: 48 pages, no figures, two typos fixe