Enraizamento de corticeira-da-serra em função do tipo de estaca e variações sazonais

Erythrina falcata Benth. may be used as an ornamental plant, in rehabilitation of degraded land and as a component in agroforestry systems. However seedling production from seeds is difficult. The aim of this work was to evaluate vegetative propagation of E. falcata by using stem cuttings obtained from adult trees (softwood cuttings, hardwood cuttings and regrowth cuttings) and cuttings from seedlings collected in the four seasons of the year as well as the effect of indolebutyric acid on rooting of stem cuttings. After cutting preparation, the material was treated with an indolebutyric acid solution (IBA, 0, 1.5 and 3 g L-1). Cuttings were grown in 55-mL tapered plastic containers in a greenhouse at 25 to 30°C and relative humidity above 80%. The substrate for growing of cuttings was middle texture vermiculite. The highest percentage of rooted cuttings (73%) and root length of four longest roots (46 mm) and root number (6.2) were obtained in seedling cuttings collected in the summer. No rooting was observed in cuttings collected from softwood cuttings raised from adult trees. Cutting immersion in IBA solutions had no effect on rooting. Cuttings from seedlings collected in the summer are recommended because of their high percentage of rooting and survival

Can organic farming feed the world? : a contribution to the debate on the ability of organic farming systems to provide sustainable supplies of food

A recent paper Badgley et al. (2007) claimed that organic farming, if used worldwide, would provide sufficient food for a growing world population. The paper stimulated much critical response. Our paper makes a critical assessment of this claim for wheat, a major cereal crop and source of food throughout the world. We consider the problems of using experimental yields in estimating the productivity of any crop or farming system and then look at farm yields, comparing organic and conventional systems. We examine in detail the comparisons made by Badgley et al. and find many of them unsupportable: the ratio of organic : conventional wheat yields of 0.85 proposed by Badgley et al. we believe to be closer to 0.65. Nitrogen (N) fixation by legumes, the main source of N supply in organic systems, is shown to be much too small and variable to support large and consistent wheat yields of acceptable quality, and ideas that cereals could one day fix their own N found wanting. Our conclusion therefore contradicts that of Badgley et al. but agrees with that of a recent report by the University of Reading's Centre for Agricultural Strategy that organic agriculture cannot feed the world using current technologies and with the meat-rich diet that people have or aspire to. We do, though, agree with Badgley et al.'s view that there is a need to improve soil quality by adding organic material, reducing over-optimal use of fertilisers and agricultural chemicals, and optimising rotations to reduce losses to pests and diseases. There is also, perhaps, a wider societal need for people to reconsider diet in the context of their health and the ability of the world to supply the wants of its anticipated 9 billion population

cAMP acts as a second messenger in pollen tube growth and reorientation

Pollen tube growth and reorientation is a prerequisite for fertilization and seed formation. Here we report imaging of cAMP distribution in living pollen tubes microinjected with the protein kinase A-derived fluorosensor. Growing tubes revealed a uniform distribution of cAMP with a resting concentration of ≈100–150 nM. Modulators of adenylyl cyclase (AC), forskolin, and dideoxyadenosine could alter these values. Transient elevations in the apical region could be correlated with changes in the tube-growth axis, suggesting a role for cAMP in polarized growth. Changes in cAMP arise through the activity of a putative AC identified in pollen. This signaling protein shows homology to functional motifs in fungal AC. Expression of the cDNA in Escherichia coli resulted in cAMP increase and complemented a catabolic defect in the fermentation of carbohydrates caused by the absence of cAMP in a cyaA mutant. Antisense assays performed with oligodeoxynucleotide probes directed against conserved motifs perturbed tip growth, suggesting that modulation of cAMP concentration is vital for tip growth

Over-expression of LeNCED1 in tomato (Solanum lycopersicum L.) with the rbcS3C promoter allows recovery of lines that accumulate very high levels of abscisic acid and exhibit severe phenotypes

Previous work where 9-cis-epoxycarotenoid dioxygenase (NCED) was over-expressed using the constitutive Gelvin Superpromoter resulted in mild increases in abscisic acid (ABA) accumulation, accompanied by stomatal closure and increased water-use efficiency (WUE), but with apparently little impact on long-term biomass production. However, one of the negative effects of the over-expression of NCED using constitutive promoters in tomato was increased seed dormancy. Here we report the use of the rbcS3C promoter, from a gene encoding the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), to drive LeNCED1 transgene expression in tomato in a light-responsive and circadian manner. In comparison to the constitutive promoter, the rbcS3C promoter allowed the generation of transgenic plants with much higher levels of ABA accumulation in leaves and sap, but the effect on seed dormancy was diminished. These plants displayed the expected reductions in stomatal conductance and CO2 assimilation, but they also exhibited a severe set of symptoms that included perturbed cotyledon release from the testa, increased photobleaching in young seedlings, substantially reduced chlorophyll and carotenoid content, interveinal leaf flooding, and greatly reduced growth. These symptoms illustrate adverse consequences of long-term, very high ABA accumulation. Only more moderate increases in ABA biosynthesis are likely to be useful in the context of agriculture. Implications are discussed for the design of transgenic 'high ABA' plants that exhibit increased WUE but have minimal negative phenotypic effects