Development of a tunable diode laser absorption spectrometer for measurement of the 13C/12C ratio in methane

A tunable diode laser absorption spectrometer (TDLAS) for measuring the ratio in methane has been developed. Using a triple path arrangement the spectra of the CH4 sample, a isotope standard and pure 13CH4 are recorded simultaneously and compared to evaluate the ratio of the sample, using a 13CH4---12CH4 absorption line pair near 3007 cm−1. Systematic effects due to variations in temperature, pressure, and optical density were measured for this rotational-vibrational transition pair. Optical interference effects are effectively suppressed by linearly polarizing the laser beam and using Brewster windows for gas cells and detectors. The overall δ13C accuracy vs. the PDB scale is about ± 1 ‰ for a CH4 concentration of 2.5 % (sample size: 5 μmoles = 0.11 STP cm3 CH4) using 36 cm long absorption cells. The future application of a multipass cell should allow measurement concentrations of CH4 down to about 50 ppm. The main advantages of the new method are the short measurement time of 10–15 min for one sample and the direct measurement on the CH4 molecule without the need to chemically convert it to CO2. With the present accuracy the new method should be useful for the measurement of CH4 sources, allowing a greater sample throughput compared to the conventional mass spectrometry technique

Interspecific transmission and recovery of TCBS-induced disease between Acanthaster planci and Linckia guildingi

The susceptibility of the coral-feeding crown-of-thorns starfish Acanthaster planci to disease may provide an avenue with which to effectively control population outbreaks that have caused severe and widespread coral loss in the Indo-Pacific. Injecting thiosulfate-citrate-bile-sucrose (TCBS) agar into A. planci tissues induced a disease characterized by dermal lesions, loss of skin turgor, collapsed spines, and accumulation of mucus on spine tips. Moreover, the symptoms (and presumably the agent) of this disease would spread rapidly intraspecifically, but interspecific transmission (to other species of echinoderms) is yet to be examined. Vibrio rotiferianus, which was previously reported as a pathogen isolated from lesions of experimentally infected A. planci, was also recovered from Linckia guildingi lesions after several days of direct contact with diseased A. planci, demonstrating disease transmission. However, all L. guildingi fully recovered after 31 ± 16 d. Further studies are in progress to understand the ecology of Vibrio infection in A. planci and the potential transmission risk to corals, fishes, and other echinoderms to evaluate whether injections of TCBS could be a viable tool for controlling A. planci outbreaks

Longevidade de inflorescências de Epidendrum ibaguense tratadas com aminoetoxivinilglicina Extending vase life of cut Epidendrum ibaguense inflorescences with aminoethoxyvinylglycine

O objetivo deste trabalho foi avaliar a influência do inibidor da síntese de etileno aminoetoxivinilglicina (AVG) aplicado na forma de solução de condicionamento e pulverização sobre a abscisão e longevidade de inflorescências de Epidendrum ibaguense Kunth. As hastes foram colhidas e imediatamente condicionadas em solução com 0, 0,5, 1, 1,5 e 2 mM de AVG por 6, 12, 18 e 24 horas. Os mesmos tratamentos foram aplicados na forma de pulverização até o molhamento completo da inflorescência. O experimento foi conduzido em um esquema fatorial entre tempo de aplicação e doses de AVG, mais doses de AVG aplicadas em pulverização nas flores, e o delineamento foi em blocos ao acaso, com cinco repetições, com três hastes por unidade experimental. Independentemente do modo de aplicação do AVG, as concentrações utilizadas promoveram aumento da longevidade das flores em aproximadamente 70% em comparação ao controle, com resposta máxima nas concentrações de 1,5 e 2 mM. Apercentagem de abscisão de flores foi reduzida em todos os tratamentos com AVG, principalmente quando se utilizou pulverização, com decréscimo na abscisão acumulada superior a 80% nas concentrações entre 1 e 2 mM de AVG.A aplicação de AVG prolongaa longevidadee reduz a abscisãode flores de Epidendrum ibaguense.<br>This work evaluated the influence of the aminoethoxyvinylglycine (AVG), an inhibitor of ethylene synthesis, when applied in pulsing solution or sprayed, on the abscission and longevity of cut star orchid (Epidendrum ibaguense Kunth) inflorescences. The cut stems were placed in solutions with 0, 0.5, 1, 1.5 and 2 mM AVG concentrations immediately after the harvest for periods of 6, 12, 18 and 24 hours. The same treatment concentrations were sprayed on the inflorescences until runoff. The experiment had a randomized complete block design with factorial treatments of rate and duration plus rate of application to the flowers, with five replicates, with three stems per experimental unit. Regardless of the way the AVG was applied, the inhibitor extended the flowers'longevity in approximately 70% compared to the control treatment, reaching maximum effect at 1.5 and 2 mM AVG. The percentage of abscissed flowers diminished in all treatments containing AVG, with higher efficiency when sprayed over the inflorescence, decreasing the abscission by 80% at concentrations between 1 and 2 mM AVG

Plants reward seed dispersers in proportion to their effort: the relationship between pulp mass and seed mass in vertebrate dispersed plants

In this paper I develop a null model for the expected relationship between seed mass and the mass of dispersal structure (reward) for vertebrate-dispersed plant species. The model is based on the simple assumption that the reward associated with a given seed mass is commensurate with work required to move it, and predicts that reward mass should scale relative to seed mass with an exponent of 4/3 (1.3). I tested this relationship between- and within-species of vertebrate-dispersed plants from four families from tropical rain forest in north Queensland, Australia. At a community-level there was a significant isometric relationship between log mean pulp mass and log mean seed mass across species. When family membership was considered, the estimate for the common slope between families was 1.32, surprisingly similar to the exponent predicted from commensurate reward. In addition, the 95% CI of the common slope did not include unity, providing no support for isometry. There was also no evidence that the relationships between mean log pulp mass and mean log seed mass were significantly different between families. This simple null model may be a common “rule” governing mean allocation to reward in all plant–animal dispersal mutualisms and its confirmation is the first evidence that animal dispersers have shaped the evolution of seed traits. However, I found no evidence that the scaling relationships within-species were consistently predicted by commensurate reward – a “taxon-level effect”. I suggest that the taxon-level effect arises because mean seed and mean reward mass within each species arises due to community-wide, disperser-mediated selection to produce equally attractive fruits, whereas within-species allometries may be determined by selection for fruit traits that enhance either dispersal probabilities, offspring survival or both, and these will be contingent on the environmental context into which seeds are released