Comparação de métodos para a observação de fungos micorrízicos arbusculares e endofíticos do tipo dark septate em espécies nativas de Cerrado

As espécies vegetais de Cerrado sensu stricto apresentam estratégias adaptativas às condições edáficas e climáticas de altos investimentos em fotoassimilados, nutrientes e água para sua estruturação. A simbiose entre fungos e raízes de plantas é uma importante adaptação radicular que auxilia as plantas na absorção de nutrientes e água do solo, sendo determinantes para a sobrevivência no Cerrado. Com o objetivo de estudar fungos micorrízicos arbusculares (FMAs) e fungos endofíticos do tipo dark septate (DSEFs) nas raízes de algumas espécies arbóreas e herbáceas, nativas do Cerrado sensu stricto, foram testados diferentes métodos para melhor observação das estruturas fúngicas em simbiose. O melhor método de clarificação foi observado quando as raízes foram autoclavadas a 121 °C em KOH 2 %, por 20 min, e com a subseqüente transferência para solução nova de KOH 2 %, por 24 h, em temperatura ambiente. Este procedimento foi repetido e, em seguida, essas amostras foram imersas em H2O2 2 % por 2 h. Os arbúsculos foram observados com maiores detalhes após a inclusão em resina, seccionamento e coloração com azul-de-toluidina. Todas as espécies avaliadas encontravam-se colonizadas por FMAs, e apenas em Xylopia aromatica não se observaram os DSEFs. As espécies herbáceas apresentaram maiores freqüências de colonização micorrízica do que as arbóreas. O caráter generalista dos FMAs e DSEFs observado nas espécies vegetais do Cerrado sensu stricto sugere a importância dessas simbioses como mecanismo adaptativo às condições de Cerrado.

Soil organic matter and fertility of anthropogenic dark earths (Terra Preta de Índio) in the Brazilian Amazon basin

Fertility properties, total C (Ctot), and chemical soil organic matter fractions (fulvic acid fraction - FA, humic acid fraction - HA, humin fraction - H) of anthropogenic dark earths (Terra Preta de Índio) of the Amazon basin were compared with those of Ferralsols with no anthropogenic A horizon. Terra Preta soils had a higher fertility (pH: 5.1-5.4; Sum of bases, SB: 8.93-10.33 cmol c kg-1 , CEC: 17.2-17.5 cmol c kg-1 , V: 51-59 %, P: 116-291 mg kg-1) and Ctot (44.6-44.7 g kg-1) than adjacent Ferralsols (pH: 4.4; SB: 2.04 cmol c kg-1, CEC: 9.5 cmol c kg-1, V: 21 %, P 5 mg kg-1, C: 37.9 g kg-1). The C distribution among humic substance fractions (FA, HA, H) in Terra Preta soils was also different, as shown by the ratios HA:FA and EA/H (EA=HA+FA) (2.1-3.0 and 1.06-1.08 for Terra Preta and 1.2 and 0.72 for Ferralsols, respectively). While the cation exchange capacity (CEC), of Ferralsols correlated with FA (r = 0.97), the CEC of Terra Preta correlated with H (r = 0.82). The correlation of the fertility of Terra Preta with the highly stable soil organic matter fraction (H) is highly significant for the development of sustainable soil fertility management models in tropical ecosystems.

Interaction of prechilling, temperature, osmotic stress, and light in Picea abies seed germination

Summary

Dark energy equation of state and anthropic selection

We explore the possibility that the dark energy is due to a potential of a scalar field and that the magnitude and the slope of this potential in our part of the Universe are largely determined by anthropic selection effects. We find that, in some models, the most probable values of the slope are very small, implying that the dark energy density stays constant to very high accuracy throughout cosmological evolution. In other models, however, the most probable values of the slope are such that the slow roll condition is only marginally satisfied, leading to a recollapse of the local universe on a time scale comparable to the lifetime of the Sun. In the latter case, the effective equation of state varies appreciably with the redshift, leading to a number of testable predictions.

Seed production characters and germination performance of reed canary grass in Finland

Selostus: Ruokohelven siementuotanto-ominaisuudet ja itävyys Suomessa

Looking for factors involved in the light-dependent degradation of phytochrome A

SUMMARY : Phytochromes constitute a family of red/far-red photoreceptors regulating all the major transitions during the life cycle of plants. In Arabidopsis, five members: phyA,_ B, C, D and E, were identified. Phytochromes are synthesized in their inactive red-light absorbing form called Pr. Upon light absorbance they convert to the far-red light absorbing Pfr form. The Pfr form is the active conformer which converts back to the Pr form either rapidly upon far-red perception or in a slower process called dark reversion. ph~A represents an exception, in that it does not significantly dark-revert and two specific processes have been developed by the plants to decrease the amount of biologically active phyA. The first one is alight-dependent repression of the PHYA gene expression and the second one is alight-dependent degradation of the phyA protein. The latter is the most efficient process to rapidly decrease the level of active phyA. The ability of plants to regulate the amount of active phyA is critical in a far-red rich environment, a situation observed under a canopy. In these conditions, phyA is essential to induce the germination and the deetiolation of the young seedling. Later in the development the ability of phyA to repress growth counteracts the shade avoidance response. Therefore decreasing the amount of phyA allows stem growth and to compete with neighbours for the light. In this thesis, I investigate the light-dependent degradation of phyA. I developed a reverse genetic approach based on the systematic analysis of the light-dependent accumulation of phyA in the different cullin mutant cull, cul3a; cul3b and cul4. This analysis allowed me to show that CUL1 and CUL3A-based E3 ligase complexes are involved in the regulation of phyA degradation. Surprisingly, our results also demonstrate that cu14 is not affected in the degradation of phyA whereas constitutive Photomorphogenic 1 (COP1) a subunit of one CUL4based E3 complex was reported to be involved. Further investigations showed that the phenotype of cop1 is conditional, the mutant being defective in phyA degradation only in the presence of metabolisable sugars. I also showed that phyA is degraded by a proteasome-dependent mechanism both in the cytoplasm and in the nucleus using mutants and transgenic lines affected in the localization of phyA. Interestingly, I observed that phyA degradation was faster in the nucleus than in the cytosol and that rapid degradation of Pr also occurred in the nucleus suggesting that cytosolic accumulation of phyA in the dark is a way to regulate its proteolysis. Finally, we identify a short region similar to a PEST sequence required for phyA stability and we developed a unbiased genetic screen to identify new components involved in the regulation of the light-dependent degradation of phyA. The significance of these results are discussed. RESUME : Les phytochromes (phy) constituent une famille de photorécepteurs absorbant la lumière rouge et rouge lointaine et régulant toutes les étapes de transitions majeures dans la vie des plantes. Chez Arabidopsis, cinq membres : phyA, B, C, D et E ont été identifiés. Les phytochromes sont synthétisés sous une forme inactive appelée Pr absorbant la lumière rouge. Après perception de lumière ils passent sous une forme active Pfr absorbant dans le rouge lointain. La forme Pfr peut retourner sous la forme Pr après absorption de lumiëre rouge lointaine ou dans un processus lent appelé «réversion à l'obscurité ». phyA représente une exception à cette règle car il ne retoune pas significativement sous sa forme inactive dans le noir. Deux processus spécifiques ont donc été développés pour diminuer le taux de phyA actif. Le premier consiste en la répression du gène PHYA en condition de lumière et le second en une dégradation induite par la lumière de la protéine phyA. Ce dernier processus est le plus efficace pour diminuer rapidement le niveau de phyA. La capacité des plantes à réguler le taux de phyA actifs est critique dans un environnement riche en lumière rouge lointaine, une situation observée sous une canopée. Sous une canopée, phyA est essentiel pour induire la germination et la dé-étiolation de la jeune pousse. Plus tard dans le développement la capacité de phyA de réprimer la croissance freine la «réponse à l'évitement de l'ombre ». Par conséquent diminuer le taux de phyA permet la croissance de la tige et donc de rentrer en compétition pour la lumière avec les plantes avoisinantes. Dans cette thèse, j'ai étudié la dégradation de phyA. J'ai développé une approche génétique inverse basée sur l'analyse systématique de l'accumulation de phyA en condition de lumière dans les différents mutants cullin, cul1, cul3a, cul3b et cul4. Ces analyses nous ont permis d'identifier qu'un complexe E3 ligase CUL1 et un complexe E3 ligase CUL3A sont impliqués dans la régulation de la dégradation de phyA. Mes résultats démontrent aussi que le mutant cul4 n'est pas affecté dans la dégradation de phyA alors que Çonstitutive Photomorphogenic 1 (COPI) une sous unité d'un complexe CUL4 à été identifier dans la régulation de cette dégradation. Des analyses supplémentaires suggèrent que l'effet de la mutation cop1 est dépendante dë la présence de sucres métabolisables. J'ai aussi montré que phyA est dégradé dans le noyau et dans le cytoplasme par un mécanisme dépendant du protéasome et que la dégradation dans le.noyau est non seulement aspécifique de la forme Pr ou Pfr mais aussi est plus rapide que dans le cytoplasme. Ceci suggère que l'accumulation de phyA dans le cytoplasme permet son accumulation à des niveaux élevés à l'obscurité. Enfin j'ai identifié une région similaire à un motif PEST requise pour la stabilité de phyA et j'ai aussi développé un criblage génétique non biaisé pour identifier de nouveaux composants impliqués dans la régulation de la dégradation de phyA. L'importance de ces résultats est discutée dans le dernier chapitre de cette thèse.

Spore germination and development of young mycelia in some Rhizopogon species

Spore germination in Rhizopogon abietis, R. luteolus, R. roseolus and R. villosulus was induced in the presence of Rhodotorula glutinis and activated charcoal, in agar medium (N6:5). In one R. roseolus sample, 51% of spores germinated within 35 days, allowing observation of the course of spore germination and the different developmental patterns of homokaryotic mycelia. In these plates, spores showed two times of germination. The spores that germinated early produced an apical germ tube. Later other spores germinated in proximity to young mycelium, by forming a germ vesicle. One of the hyphal growth patterns obtained (interruption-swelling-ramification) is similar to that reported for other fungi. With this technique for inducing spore germination, it is possible to obtain enough monosporic cultures to perform mating tests. Key words: Basidiomycotina, Hypogeous, Monosporic Cultures.

Matriconditioning integrated with gibberellic acid to hasten seed germination and improve stand establishment of pepper and tomato

Emergence and stand establishment of tomato (Lycopersicon lycopersicum (L.) (Karsten ex Farw) and pepper (Capsicum annus L.) seeds are often slow and erratic, particularly under stress conditions. Field emergence trials sometimes have not responded to priming in pepper. This study examined the combined effects of matriconditioning and gibberellin application on the germination and stand establishment of pepper and tomato seeds. Pepper and tomato seeds were conditioned with a solid carrier, Micro Cel E, in the presence of gibberellic acid (GA) for 1, 2 , 3 and 4 days at 15 and 25ºC. The results showed that, in all cases, even under stress conditions, the combination of matriconditioning with GA was effective in improving germination and emergence of pepper and tomato. The germination time was, in average, reduced by 2 to 3 days by primed seeds. Thus, matriconditioning, during which germination is suspended, provides an unique means to rapidly and efficiently digest the endosperm by GA-induced enzymes and reduce the mechanical restraints of endosperm thus providing energy to start and sustain embryo growth.

Effect of dark chocolate on renal tissue oxygenation as measured by BOLD-MRI in healthy volunteers.

Background: Cocoa is rich in flavonoids, has anti-oxidative properties and increases the bioavailability of nitric oxide (NO). Adequate renal tissue oxygenation is crucial for the maintenance of renal function. The goal of this study was to investigate the effect of cocoa-rich dark chocolate (DC) on renal tissue oxygenation in humans, as compared to flavonoid-poor white chocolate (WC). Methods: Ten healthy volunteers with preserved kidney function (mean age ± SD 35 ± 12 years, 70% women, BMI 21 ± 3 kg/m2) underwent blood oxygenation level-dependent magnetic resonance imaging (BOLD-MRI) before and 2 hours after the ingestion of 1 g/kg of DC (70% cocoa). Renal tissue oxygenation was determined by the measurement of R2* maps on 4 coronal slices covering both kidneys. The mean R2* (= 1/T2*) values in the medulla and cortex were calculated, a low R2* indicating high tissue oxygenation. Eight participants also underwent BOLD-MRI at least 1 week later, before and 2 hours after the intake of 1 g/kg WC. Results: The mean medullary R2* was lower after DC intake compared to baseline (28.2 ± 1.3 s-1 vs. 29.6 ± 1.3 s-1, p = 0.04), whereas cortical and medullary R2* values did not change after WC intake. The change in medullary R2* correlated with the level of circulating (epi)catechines, metabolites of flavonoids (r = 0.74, p = 0.037), and was independent of plasma renin activity. Conclusion: This study suggests for the first time an increase of renal medullary oxygenation after intake of dark chocolate. Whether this is linked to flavonoid-induced changes in renal perfusion or oxygen consumption, and whether cocoa has potentially renoprotective properties, merits further study.

The cave (La caverna -1952-1969) by Josep Palau i Fabre: theatre versus philosophical allegory in order both to perform and stop the tragic and dark end of the bright art of thinking

What is the use of representing in performance the image of the cave from book VII of Plato’s Republic? Josep Palau i Fabre considers that in Plato’s dialogues the speakers are mere instruments at the service of his dialectical purpose. The aim of this article is to show how, by turning the myth into a tragedy and relying on Heraclitus’s conflict or war of opposites, the playwright succeeds in favouring a sort of thought which is not one-sided or univocal. On the contrary, in Palau i Fabre’s La Caverna, the tragic hero, the released prisoner transformed by the light of Reality and finally killed by his “cavemates” –after having been imprisoned again and having tried to rescue them from their ignorance or shadows– still leaves them his powerful experience of the agonistikós thought, which might bear fruit in their life to come.

Influence of label information on dark chocolate acceptability

The aim of the present work was to study how the information on product labels influences consumer expectations and their acceptance and purchase intention of dark chocolate. Six samples of dark choco- late, varying in brand (premium and store brand) and in type of product (regular dark chocolate, single cocoa origin dark chocolate and high percentage of cocoa dark chocolate), were evaluated by 109 con- sumers who scored their liking and purchase intention under three conditions: blind (only tasting the products), expected (observing product label information) and informed (tasting the products together with provision of the label information). In the expected condition, consumer liking was mainly affected by the brand. In the blind condition, differences in liking were due to the type of product; the samples with a high percentage of cocoa were those less preferred by consumers. Under the informed condition, liking of dark chocolates varied depending on both brand and type of product. Premium brand chocolates generated high consumer expectations of chocolate acceptability, which were fulfilled by the sensory characteristics of the products. Store brand chocolates created lower expectations, but when they were tasted they were as acceptable as premium chocolates. Claims of a high percentage of cocoa and single cocoa origin on labels did not generate higher expectations than regular dark chocolates.

The IBO germination quantitative trait locus encodes a phosphatase 2C-related variant with a nonsynonymous amino acid change that interferes with abscisic acid signaling.

Natural genetic variation is crucial for adaptability of plants to different environments. Seed dormancy prevents precocious germination in unsuitable conditions and is an adaptation to a major macro-environmental parameter, the seasonal variation in temperature and day length. Here we report the isolation of IBO, a quantitative trait locus (QTL) that governs c. 30% of germination rate variance in an Arabidopsis recombinant inbred line (RIL) population derived from the parental accessions Eilenburg-0 (Eil-0) and Loch Ness-0 (Lc-0). IBO encodes an uncharacterized phosphatase 2C-related protein, but neither the Eil-0 nor the Lc-0 variant, which differ in a single amino acid, have any appreciable phosphatase activity in in vitro assays. However, we found that the amino acid change in the Lc-0 variant of the IBO protein confers reduced germination rate. Moreover, unlike the Eil-0 variant of the protein, the Lc-0 variant can interfere with the activity of the phosphatase 2C ABSCISIC ACID INSENSITIVE 1 in vitro. This suggests that the Lc-0 variant possibly interferes with abscisic acid signaling, a notion that is supported by physiological assays. Thus, we isolated an example of a QTL allele with a nonsynonymous amino acid change that might mediate local adaptation of seed germination timing.