Polyphenol oxidase activity and ortho‐diphenolic content in sunflower leaves in relation to boron nutrition.

Homogenates were prepared from the leaves of hydroponically cultivated sunflowers (Helianthus annuus, L.) under deficient, normal and toxic B conditions and the polyphenol oxidase activity together with the ortho‐diphenolic and micronutrient content was measured every week from one month to flowering.

B deficiency slightly depressed polyphenol oxidase activity and B toxicity decreased it significantly at all times, the response fitting a line versus the logarithm of the B concentration in solution. We found a positive correlation between polyphenol oxidase activity and the B content in leaves.

B action on enzymatic activity seemed not to be caused by direct interaction with substrates as the infiltration of B into deficient leaves did not restore the normal activity

According to our results we suggest that polyphenol oxidase activity may be a valid functional parameter to indicate the nutritional status of B in sunflower plants, if its specificity for B can be demonstrated.

The ortho‐diphenolic content did not change with the B levels used in our experiments. Neither did we find any correlation between enzymatic activity and the o‐diphenolic content of the leaves.     

Effect of phosphorus,copper, and zinc addition on the phosphorus/copper and phosphorus/zinc interaction in lettuce

The effect of phosphorus (P), copper (Cu), and zinc (Zn) addition on the P‐Cu and P‐Zn interaction in lettuce (Lactuca sativa L.) was analyzed following a factorial design. The experiment was conducted in a greenhouse. Two levels of P (62 and 224 ppm), three levels of Zn (0, 0.17, and 0.34 ppm), and three levels of Cu (0, 0.03, and 0.06 ppm) were applied in all combinations to lettuce grown in perlite. The influence of the different treatments on the leaf P concentration suggests that the P‐Cu interaction was positive, whereas P‐Zn was negative. An increase in root absorption and retention and a decrease in translocation to leaves were observed for Zn and Cu when the nutrient solution was supplied at a luxurious consumption level of P.     

Electron paramagnetic resonance studies of manganese toxicity,tolerance, and amelioration with silicon in snapbean

Plant genotypes within species differ widely in tolerance to excess manganese (Mn) that may occur in acid soils, or in neutral or alkaline soils having poor aeration caused by imperfect drainage or compaction. However, Mn tolerance mechanisms in plants are largely unknown. Silicon (Si) is reported to detoxify Mn within plants, presumably by preventing localized accumulations of Mn associated with lesions on leaves. Because Mn is paramagnetic, electron paramagnetic resonance (EPR) spectroscopy, shows promise as a tool for characterizing toxic and non‐toxic forms of Mn in tolerant and sensitive plants. The objective of our study was to use EPR to: i) determine the chemical/ physical state of Mn in Mn‐tolerant and ‐sensitive snapbean cultivars; and ii) characterize the protective effects of Si against Mn toxicity. Manganese‐sensitive Wonder Crop 2 (WC) and Mn‐tolerant Green Lord (GL) cultivars of snapbean were grown at pH 5.0, in a greenhouse, in a modified Steinberg solution containing: Mn=0.05mg.L^‐1 (optimal); Mn=1.0mgL^‐1 (toxic); Mn=1.0 mg L^‐1 plus Si=4 mg L^‐1; and Mn=0.05 mg L^‐1 plus 4 mg Si L^‐1. All trifoliate leaf samples exhibited a 6‐line EPR signal that is characteristic of hexaaquo Mn²⁺. In both cultivars, a higher EPR Mn²⁺ signal‐intensity generally correlated with lower total leaf mass, higher total Mn concentrations and more pronounced symptoms of toxicity. Tolerance to excess Mn coincided with lower Mn²⁺ signal intensity. Silicon treatments ameliorated Mn toxicity symptoms in both genotypes, decreased total leaf Mn concentrations, and decreased EPR Mn²⁺ signal intensity. Results suggest that Mn toxicity is associated with reduced electron transport and accumulation of oxidation products in leaves. Amelioration of Mn toxicity by Si is regarded as connected with a reduction in this Mn‐induced process. Results indicated that EPR spectroscopy can be useful in investigating the biochemical basis for differential Mn tolerance in plants. The EPR observations might also help plant breeders in developing Mn‐tolerant cultivars.     

Whither the future of controlling quantum phenomena?

This review puts into perspective the present state and prospects for controlling quantum phenomena in atoms and molecules. The topics considered include the nature of physical and chemical control objectives, the development of possible quantum control rules of thumb, the theoretical design of controls and their laboratory realization, quantum learning and feedback control in the laboratory, bulk media influences, and the ability to utilize coherent quantum manipulation as a means for extracting microscopic information. The preview of the field presented here suggests that important advances in the control of molecules and the capability of learning about molecular interactions may be reached through the application of emerging theoretical concepts and laboratory technologies.     

Screening brassicaceous plants as biofumigants for management of Phytophthora cinnamomi oak disease

Brassicaceous plants rich in glucosinolates have been used as biofumigants for the management of soilborne pathogens. Efficacy of Brassica plant tissue has mainly been attributed to toxic isothiocyanates released upon the hydrolysis of glucosinolates. Management of Phytophthora cinnamomi, the causal agent of oak root rot in rangeland ecosystems using biofumigation, is promising, but requires further validation. The biofumigation activity of 14 brassicaceous plants was evaluated under experimental conditions. All evaluated plants rich in sinigrin suppressed (100%) the mycelial growth of P. cinnamomi, while plants rich in aromatic or other aliphatic glucosinolates had little or no suppressive effect. Simulating soil amendment in field conditions, the effects on natural soil artificially infested with P. cinnamomi chlamydospores were examined with Brassica juncea, Eruca vesicaria and Lepidium sativum, three species with different glucosinolate profiles. Only B. juncea decreased the viability of chlamydospores significantly in comparison with untreated soil only 1 day after biofumigation, whereas E. vesicaria needed 8 days to reach significance and L. sativum had no effect at all. Despite the decreases in soil inoculum, biofumigation with B. juncea did not prevent the root infections in a highly susceptible host (Lupinus luteus). However, biofumigation with plants rich in sinigrin, such as B. juncea, decreased P. cinnamomi soil inoculum under the experimental minimum threshold for oak disease expression. Although biofumigation should be considered as an effective measure to be incorporated in integrated control of the oak disease, biofumigation by itself would not be effective enough for the substantial suppression of P. cinnamomi inoculum.     

Quantitative aspects of solid-state C-NMR spectra of humic substances from soils of volcanic systems

Cross-Polarisation Magic Angle Spinning Carbon-13 Nuclear Magnetic Resonance spectroscopy (CPMAS ¹³C-NMR) represents one of the most powerful tools to investigate soil organic matter (SOM) mainly because of its inherent capacity to provide a semi-quantitative evaluation of carbon distribution. A critical parameter during acquisition of CPMAS ¹³C-NMR spectra is the contact time required to obtain the cross-polarisation between proton and carbon nuclei. The procedure to evaluate the best contact time for the acquisition of a quantitative CPMAS ¹³C-NMR spectrum is to perform Variable Contact Time (VCT) experiments. In this work the structural features of a number of purified humic substances from Italian and Costarican volcanic soils were investigated by CPMAS ¹³C-NMR spectroscopy after having performed preliminary VCT experiments. The VCT experiments showed that the average contact times vary according to the origin and chemical structure of the humic material. The optimal contact times (OCT) for nine humic samples were between 250 and 800 μs These values were different from the time of 1000 μs that is commonly applied as the best average contact time for humic materials. Moreover, by comparing the NMR data to those obtained by elemental analysis (C/H ratio), it appeared that the efficiency of the cross-polarisation between protons and carbons, and hence the contact time, is affected not only by the number of protons, but also by their distribution over the molecules. The evaluation of errors in quantitative estimation of the different carbons revealed that the use of OCT generally reduced by half the loss of signals occurring when the average contact time of 1000 μs is used in CPMAS ¹³C-NMR spectra of humic substances.     

A regional scale model for the calculation of episodic concentrations and depositions of acidifying components

An eulerian long-range transport model for the calculation of concentrations of SO₂, SO₄, NO _x , and NO₃ and wet and dry depositions of SO _x (sum of SO₂ and SO₄) and NO _y (sum of NO, NO₂ and NO₃) over Europe is presented. The model is developed in such a way that only routinely available, analyzed or prognostic meteorological fields are required as input data. In this way it is possible to obtain a forecast of the air quality during smog episodes. For evaluation of smog episodes the model provides a way to estimate the contributions of different sources and the effect of emission scenarios. The model has been evaluated for four winter and three summer episodes. The modeled concentrations of SO₂ and SO, are in agreement with the available measurements. A less good agreement is found for NO₂ and NO _x (sum of NO and NO₂) concentrations. For these components the model tends to underpredict the measured values.     

Genetic correlates of musical pitch recognition in humans

We used a twin study to investigate the genetic and environmental contributions to differences in musical pitch perception abilities in humans. We administered a Distorted Tunes Test (DTT), which requires subjects to judge whether simple popular melodies contain notes with incorrect pitch, to 136 monozygotic twin pairs and 148 dizygotic twin pairs. The correlation of DTT scores between twins was estimated at 0.67 for monozygotic pairs and 0.44 for dizygotic pairs. Genetic model-fitting techniques supported an additive genetic model, with heritability estimated at 0.71 to 0.80, depending on how subjects were categorized, and with no effect of shared environment. DTT scores were only weakly correlated with measures of peripheral hearing. This suggests that variation in musical pitch recognition is primarily due to highly heritable differences in auditory functions not tested by conventional audiologic methods.     

Characterization of exopolysaccharides produced by Bifidobacterium longum NB667 and its cholate-resistant derivative strain IPLA B667dCo

Bifidobacteria are natural members of the human intestinal microbiota and some strains are being used as probiotics. Adaptation to bile can allow them to increase survival in gastrointestinal conditions, thus improving their viability. Bifidobacterium longum NB667 and the cholate-resistant strain B. longum IPLA B667dCo produced exopolysaccharides (EPS) that were partially characterized. Analysis by size exclusion chromatography-multiangle laser light scattering indicated that the EPS crude fractions of both strains contained two polymer peaks of different molar mass. On the basis of chromatographic techniques both peaks appeared to be heteropolysaccharides. The smaller peak was mainly composed of glucose, galactose and rhamnose whose molar ratios and linkage types showed slight variations between the EPS fractions of both strains. The bigger peak consisted of glucose and galactose; the monosaccharide composition was identical in the EPS fractions of the two microorganisms, but their infrared spectra presented some differences regarding compounds other than carbohydrates that seem to be associated to the polymer. Differences in the composition of EPS fractions did not affect the capability of crude EPS from B. longum to be fermented by the human intestinal microbiota in fecal batch cultures.     

Local population structure of a naturally occurring metapopulation of the quokka (Setonix brachyurus Macropodidae: Marsupialia)

We investigated the population structure of the quokka (Setonix brachyurus) on the mainland of Western Australia using mark–recapture techniques. Seven previously known local populations and one unconfirmed site supporting the preferred, patchy and discrete, swampy habitat of the quokka were trapped. The quokka is now considered as locally extinct at three sites. The five remaining sites had extremely low numbers, ranging from 1 to 36 individuals. Population density at these sites ranged from 0.07 to 4.3 individuals per hectare. There has been no response to the on-going, 6 year fox control programme occurring in the region despite the quokkas’ high fecundity and this is due to low recruitment levels. The remaining quokka populations in the northern jarrah forest appear to be the terminal remnants of a collapsing metapopulation.