Cork-oak reforestation – effects of preplanting root treatments and treeshelters on survival and growth seven years after plantation

Four-month old containerized cork-oak seedlings grown in nursery with different root conditioning were planted in a fenced area near Évora, southern Portugal. The effects of six precondioning root treatments and two different treeshelters on the survival and growth were evaluated seven years after plantation. Pre-planting root treatments, consisting in the combination of three different containers and two different substrates did not clearly affect survival but plants grown with a mixture of ground pine bark and vermiculite grew better than plants which received a superfosphate enriched mixture of soil and peat. Different shelters affect differently both survival and growth of the plants. The 1.20 m high, translucent light brown corrugated polypropylene shelter (Sheltatree) did not significantly affect survival, increased growth in height but trunk growth in diameter was delayed in comparison with non sheltered plants. The 0.75 cm high transparent PVC shelter (Gro-Cone) had no effects on height and significantly reduced trunk radial growth as well as plant survival but only when compared with the other shelter. The use of treeshelters appears as a promising technique which, depending on the local conditions, may conciliate the multiple use of the montado with cork-oak regeneration. The use of a seedling growth substrate like ground pine bark revealed high potential for plant growth in the usually nutrient scarce soils of cork-oak stands

Quantification of structure–property relationships for plant polyesters reveals suberin and cutin idiosyncrasies

Polyesters, as they exist in planta, are promising materials with which to begin the development of “green” replacements. Cutin and suberin, polyesters found ubiquitously in plants, are prime candidates. Samples enriched for plant polyesters, and in which their native backbones were largely preserved, were studied to identify “natural” structural features; features that influence critical physical properties. Quantitative nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), and X-ray scattering methods were used to quantify structure–property relationships in these polymeric materials. The degree of esterification, namely, the presence of acylglycerol linkages in suberin and of secondary esters in cutin, and the existence of mid-chain epoxide groups defining the packing of the aliphatic chains were observed. This packing determines polymer crystallinity, the resulting crystal structure, and the melting temperature. To evaluate the strength of this rule, tomato cutin from the same genotype, studying wild-type plants and two well-characterized mutants, was analyzed. The results show that cutin’s material properties are influenced by the amount of unbound aliphatic hydroxyl groups and by the length of the aliphatic chain. Collectively, the acquired data can be used as a tool to guide the selection of plant polyesters with precise structural features, and hence physicochemical properties

Synthesis and cycloaddition reactions of pyrrole-fused 3-sulfolenes: A new versatile route to tetrabenzoporphyrins

Pyrrole-fused 3-sulfolenes 2a,b were prepared from the corresponding α,β-unsaturated sulfone 1. These pyrroles undergo thermal extrusion of sulfur dioxide to produce highly reactive o-quinodimethanes which can be trapped in Diels-Alder reactions. The resulting pyrroles are important starting reagents in porphyrin synthesis

Estímulo do crescimento de sobreiros jovens pela utilização de abrigos individuais

Abrigos individuais (estufins) podem ser usados na protecção de sobreiros jovens após plantação, podendo as plantas instaladas no seu interior beneficiar do "efeito de estufa" criado pelos abrigos. Neste trabalho apresentam se e discutem se alguns dos resultados já obtidos com abrigos deste tipo nas condições climáticas do Sul de Portugal. Utilizaram se dois tipos de abrigo de material plástico: (A) cilíndrico com 0.75 m de altura em PVC fumado com rede incorporada, e (B) paralelipipédico, de secção quadrada com 1.22 m de altura em polipropileno canelado de cor castanha. Efectuaram se registos de temperatura e radiação (PAR) no exterior e interior dos abrigos em vários períodos do ano verificando se um aumento da temperatura média do ar no interior dos dois abrigos e um ensombramento superior no abrigo B. O desenvolvimento das plantas instaladas nos abrigos e testemunha foi avaliado com base em medições da altura, compri¬mento dos ramos, número e área foliar, comprimento radicular e produção de biomassa. Os resultados mostram que o crescimento em altura é estimulado pelos abrigos e que a ramificação é estimulada apenas pelo estufim A. O crescimento radicular não é afectado pela presença dos abrigos mas as plantas abrigadas apresentam uma maior razão biomassa aérea/biomassa radicular devida ao aumento da biomassa aérea. Mercê de uma maior produção de folhas, as plantas abrigadas no estufim A apresentam em média maior área foliar. As folhas produzidas em ambos os estufins exibem algumas características de folhas de sombra, e o "investimento" em área foliar por unidade de biomassa produzida é superior nas plantas abrigadas. Três anos após a plantação não se observam diferenças significativas na mortalidade, embora uma percentagem importante (23%) das plantas vivas do abrigo A tenham tido a parte aérea completamente seca no Verão anterior

Mechanistic insights on the site selectivity in successive 1,3-dipolar cycloadditions to meso-tetraarylporphyrins

A DFT study on site selectivity in successive 1,3-dipolar cycloadditions of meso-tetraarylporphyrins with azomethine ylide and N-methylnitrone has been carried out. The calculation of the thermodynamic stability of both ylide and nitrone-derived adducts reveals that bacteriochlorins are more stable and have stronger aromatic character than isobacteriochlorins. Calculations of whole reaction pathways show that cycloadditions of azomethine ylide on porphyrin and its derived chlorin are irreversible and hence kinetically controlled. Solvent influence on the site selectivity of this reaction has also been considered, and appears to be decisive in controlling the site selectivity. In contrast, cycloadditions of nitrone over porphyrin and chlorin are clearly reversible, pointing to a thermodynamic control of these reactions.This work was supported by the Ministerio de Ciencia y Tecnología (projects CTQ2005-08016 and Consolider Ingenio 2010 CSD2006-00), the University of Aveiro, the Fundação para a Ciência e a Tecnologia (grant SFRH/BPD/8374/2002 of A.M.G.S.) and FEDER for funding the Organic Chemistry Research Unit.Peer reviewe