Induction and growth curve of calli from leaf and nodal explants of genipap.

The aim of this study was to determine the effect of the auxin 2,4-D (2,4-dichlorophenoxyacetic) in calli formation from leaf and nodal segments of genipap and to characterize its growth curve. Explants obtained from shoots previously established from in vitro seedlings were used for calli induction. The experimental design was completely randomized in a 3x5x2 factorial with three accessions (NB, SA, SAL), five concentrations of 2,4-D (0.0; 2.0; 4.0, 6.0 or 8.0 mg L-1) and two times of measurement for calli fresh weight (30 and 60 days). There was callus formation in all treatments tested. It was observed that the best response for callus induction from leaf segments was with 2.0 mg L-1 of 2,4-D. For the nodal segment, the response among the accessions was different due to 2,4-D concentrations. The growth curve was plotted according to the fresh weight of callus obtained at intervals of 10 days up to 60 days. Through the established growth curve, the nodal-derived calli from accession SA should be transferred to a new medium, after 40 days of culture

Qualidade físico-química e sensorial de frutos de abacaxizeiro cultivados em diferentes densidades de plantio no sistema orgânico de produção.

A produção orgânica vem crescendo de forma sustentada ao redor do mundo, devido principalmente à tomada de consciência da população dos riscos dos resíduos químicos presentes nos alimentos à saúde humana e ao apelo à conservação do meio ambiente

Avaliação da longevidade de grãos de pólen de de Manihot esculenta spp. flabellifolia por teste colorimétrico e fluorescência.

O conhecimento sobre a longevidade e viabilidade polínica é crucial para o melhoramento genético de uma espécie. Este trabalho teve como objetivo avaliar a longevidade do pólen de Manihot esculenta spp flabellifolia por meio de teste colorimétrico e pelo método de reação fluorocromática. Como material vegetal foram utilizados grãos de pólen do acesso FLA 029V-01. Para avaliação da longevidade polínica foram utilizadas flores estaminadas em quatro estádios distintos: 1 ? pré-antese; 2 ? antese; 3 ? 24 horas após antese e 4 ? período superior a 24 horas da antese. Para avaliação da viabilidade polínica foram utilizados os métodos de fluorescência e colorimétrico com o uso do corante carmim acético 1%. A viabilidade nos testes colorimétricos variou de 90% no pólen em antese a 75% nos grãos após um período superior a 24 horas à antese. Já nos testes por reação fluocromática a porcentagem de pólen viável foi de 81% para o pólen avaliado na antese e 50% no pólen na pré-antese, não ocorrendo germinação quando se utilizou de grãos de pólen 24 horas após a antese. Os resultados indicam que a perda de viabilidade em Manihot esculenta parece ser bem marcante 24 horas após a antese e o teste colorimétrico superestimou a viabilidade polínica não sendo recomendado para este tipo de avaliação

Magnetic Instabilities and Phase Diagram of the Double-Exchange Model in Infinite Dimensions

Dynamical mean-field theory is used to study the magnetic instabilities and phase diagram of the double-exchange (DE) model with Hund's coupling J_H >0 in infinite dimensions. In addition to ferromagnetic (FM) and antiferromagnetic (AF) phases, the DE model supports a broad class of short-range ordered (SRO) states with extensive entropy and short-range magnetic order. For any site on the Bethe lattice, the correlation parameter q of a SRO state is given by the average q=, where theta_i is the angle between any spin and its neighbors. Unlike the FM (q=0) and AF (q=1) transitions, the transition temperature of a SRO state (T_{SRO}) with 0<q<1 cannot be obtained from the magnetic susceptibility. But a solution of the coupled Green's functions in the weak-coupling limit indicates that a SRO state always has a higher transition temperature than the AF for all fillings p<1 and even than the FM for 0.26\le p \le 0.39. For 0.39<p<0.73, where both the FM and AF phases are unstable for small J_H, a SRO phase has a non-zero T_{SRO} except close to p=0.5. As J_H increases, T_{SRO} eventually vanishes and the FM dominates. For small J_H, the T=0 phase diagram is greatly simplified by the presence of the SRO phase. A SRO phase is found to have lower energy than either the FM or AF phases for 0.26\le p0 but appears for J_H\neq 0. For p near 1, PS occurs between an AF with p=1 and either a SRO or a FM phase. The stability of a SRO state at T=0 can be understood by examining the interacting DOS,which is gapped for any nonzero J_H in an AF but only when J_H exceeds a critical value in a SRO state.Comment: 38 pages, 11 figures, submitted to New Journal of Physic

Induction, growth kinetics and morpho-histological characterization of Neem callus.

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