β-Oxidation enzymes in the mitochondria of Arum and oilseed rape

-Oxidation enzymes were detected both in the mitochondria and microbodies of Arum maculatum L. spadices and Brassica napus L. seeds. It is apparent that the mitochondrial membrane barrier, which remains intact after sucrose-density-gradient centrifugation, prevents rapid access of acyl-GoA substrates to matrix oxidation tes. Thus intact mitochondria showed little -oxidation enzyme activity. Rupturing of the mitochondrial membrane allowed rapid access of acyl CoAs to matrix sites. Consequently, in ruptured mitochondria, high -oxidation enzyme activities were measured.C. Masterson thanks the Science and Engineering Research Council for the award of a postgraduate student maintenance grant. D.R. Thomas and C. Wood thank their relatives for continuing financial support. The authors also thank West Cumberland Farmers Ltd., Hexham, UK for their gift of oilseed rape seeds.     

Does DNA methylation pattern mark generative development in winter rape?

In this paper we report on changes in DNA methylation pattern in rape apices and leaves during transition from vegetative to reproductive stage due to grafting and/or vernalization. Grafted plants of winter rape (Brassica napus L., var. "Górczański") (stock from vernalized, scion from non-vernalized plants) were used together with vernalized non-grafted plants. In addition, methylation status was determined also in spring rape (var. "M?ochowski") grown under normal and low temperature. The methylation-sensitive amplification polymorphism (MSAP) method with EcoRI/MspI and EcoRII/HpaII restriction enzymes was employed. The majority (ca. 68%) of analyzed loci (566 in winter and 551 in spring rape) were monomorphic, i.e. did not undergo methylation. Both cultivars showed a similar degree of methylation. 188 loci in winter and 176 in spring cultivars expressed changes in the methylation pattern. All differentially amplified fragments resulted from either full methylation of an internal cytosine or from hemi-methylation of an external cytosine. A pair-wise comparison showed that a similar number of loci underwent development-related methylation changes in apices of the winter and spring rape. The majority (80%) of changes were demethylation events in generative (vernalized) apices of the winter cultivar. However, an increased number of demethylated loci was detected in vernalized apices in comparison with generative, non-vernalized ones. In apices of vegetative and generative grafted plants the same number of demethylation events was observed. Overall, 10 MSAP loci were detected that expressed methylation changes in vernalized apices only; among them 7 loci underwent demethylation after vernalization and remained methylated in both vegetative and generative non-vernalized stage. Only 1 locus was demethylated in generative non-vernalized apices. Thus, most of demethylation events can be ascribed to vernalization and not to the generative stage. In leaves of winter rape methylation and demethylation events occurred with similar frequency, while in the spring cultivar more demethylation events were detected. The results show that during vernalization and transition to the generative stage different sets of genes are activated.     

Does deprivation of paradoxical sleep interfere with consolidation of memory traces?

The effect of paradoxical sleep deprivation (PSD) with water tank method on memory in the passive avoidance test as well as on open field behaviour was studied in rats. The effect of combining water tank PSD with a period of normal sleep-wakefulness cycle or with PSD non-emotional awakening was investigated in a special series of experiments. It is concluded that PSD, even by the water tank procedure, does not disturb trace consolidation and formation of long-term memory in the passive avoidance test. However, change in the correlation of motor-exploratory activity and fear reaction due to stress situation intrinsic in the water tank PSD procedure, does not allow the animals to reach comparatively long temporal criteria in the passive avoidance test.     

Does handling reduce the winter body mass of the European hare?

Winter body mass of the European hare Lepus europaeus Pallas 1778 was analyzed with a special focus on changes induced by handling. Data were obtained from large scale translocation (net catchments) during 1960–1980 in Poland. The influence of handling was compared using the mass of first-time captured and repeatedly-captured hares, and, in case of repeated capture, individuals’ mass changes were investigated. The average body mass ranged from 2.1 kg to 5.0 kg. Generally, fewer factors influenced the hare’s body mass than expected. Body mass was related to age and winter precipitation, while the date of catching, sex and temperature did not have an effect. Body mass of first-captured hares were significantly higher than the re-captured ones (3.99±0.42 vs. 3.88±0.48, mean ±SD). Body mass change between captures was related to the date of the first capture, and the duration between the first capture and re-capture. Following the initial capture, a slight (2.8±2.6), but significant decrease in body weight occurred. Thus, the handling of hares should be used with caution during studies or management of the species.     

Is hypothermia necessary for the winter survival of the GoldcrestRegulus regulus?

Summary The Goldcrest is an interesting species for studies of physiological and behavioural adaptions to cold, since it is the smallest species present in Europe. Although many small birds have to lower their metabolic rate and enter hypothermia in order to make their energy reserves last throughout the night, our measurements of oxygen consumption of five Goldcrests suggest that these birds may be able to balance their nocturnal energy budget during the winter at normothermic body temperatures, provided that the available food supply is adequate. These results are in agreement with those of another small bird, the Common Bushtit, which, like the Goldcrest, reduce nocturnal heat loss by contact roosting. Since the energy saved by hypothermia decreases with decreasing ambient temperature and also decreasing body weight, this strategy might not be such an advantage for the smallest birds living at very low ambient temperatures.

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Zusammenfassung Am Wintergoldhähnchen als dem kleinsten europäischen Vogel interessieren besonders seine physiologischen und Verhaltens-Anpassungen an niedere Temperaturen. Viele Kleinvögel senken ihre Stoffwechselaktivität und verfallen in Hypothermie, um mit ihren Energie-Reserven während der langen Winternächte auszukommen. Unsere Untersuchungen über den O₂-Verbrauch von 5 Wintergoldhähnchen legen jedoch nahe, daß sich das nächtliche Energie-Budget auch im Tiefwinter auf Normalniveau bewegt und daß sie bei ausreichendem Nahrungsangebot ihre normale Körpertemperatur auch nachts beibehalten. Ähnliche Befunde liegen von den vergleichbaren kleinen amerikanischen Buschmeisen vor, die wie Goldhähnchen den nächtlichen Wärmeverlust durch Schlafen auf engem Gefiederkontakt reduzieren. Es ist anzunehmen, daß die Hypothermie als Überwinterungsstrategie für unsere kleinsten Vögel garnicht so vorteilhaft wäre: Die durch Hypothermie eingesparte Energie geht mit abnehmender Umgebungstemperatur und mit geringerer Körpergröße wieder verloren.

     

Does human scent bias the survival of bird nests?

Human-scent contamination of bird nests and the human-made trails leading to them is suspected to influence nest survival by attracting or deterring predatory mammals. This paper (1) reviews studies in which human-scent contamination was suspected to have biased the survival of real and artificial nests by influencing the behaviour of predatory mammals, (2) summarizes the procedures used in attempts to mitigate human-scent contamination in nest-survival studies, and (3) describes procedures to enhance the design and interpretation of nest-survival experiments. The behaviour of various non-domesticated mammals is confirmed or suspected to be affected by human scent, so similar effects on nest predators are plausible. However, suggestions that human scent affects nest survival by influencing the behaviour of predatory mammals are poorly supported, due to a dearth of appropriately designed experiments. Some studies failed to include measures to reduce human-scent contamination, and the effectiveness of scent-mitigation methods used in other studies has seldom been verified. In addition, volatile compounds arising from soil and vegetation disturbed underfoot by field researchers may have confounded many nest-survival studies. Investigators have routinely inferred human-scent effects from post hoc predation patterns or have simply acknowledged possible human-scent effects among other potential influences of nest fate. Studies are needed of the effects of human scent using uniform methods of scent application and verified methods of scent mitigation, where the fates of different types of nests are examined under a range of field conditions. More fundamentally, studies of naïve and experienced mammals are needed to assess their responses to human scent and clarify its salience in wildlife disturbance.     

Does the use of DM-nitrophen,nitr-5, or diazo-2 interfere with the measurement of indo-1 fluorescence?

Emission spectra of the photolabile Ca2+ chelators DM-nitrophen, nitr-5, and diazo-2 were studied alone, and in the presence of indo-1, to investigate potential interactions that would make the simultaneous manipulation and ratiometric measurement of the intracellular Ca2+ concentration difficult. Neither diazo-2 nor its photoproduct were found to be significantly fluorescent, and consequently concentrations of diazo-2 up to 20 times that of indo-1 did not distort the emission spectra of indo-1. DM-nitrophen was scarcely fluorescent, but its fluorescence did increase upon photolysis. In contrast to diazo-2 and DM-nitrophen, nitr-5 itself was found to be quite fluorescent, and this fluorescence was significantly increased upon photolysis. Thus, combined use of nitr-5 and indo-1 poses the most difficulty. The emission spectra of all the investigated compounds were used to define experimental conditions and calibration procedures that make possible simultaneous measurement and manipulation of the intracellular Ca2+ concentration.     

Does the lack of root hairs alter root system architecture of Zea mays?

Plant and Soil - Root hairs are one root trait among many which enables plants to adapt to environmental conditions. How different traits are coordinated and whether some are mutually exclusive is...     

Does maternal stress influence winter survival of offspring in root voles Microtus oeconomus? A field experiment

Maternal stress can have long‐term adverse consequences on immunocompetence and disease risk of offspring, and winter survival is a crucial demographic parameter in the life‐history of an individual that can substantially affect northern rodent population dynamics. An understanding of the effects of maternal stress on winter survival of offspring may help identify mechanisms driving population fluctuations of northern small mammals. Thus, we assessed the effects of maternal stress, resulting from high population densities, on winter survival of first generation (F₁) and second generation (F₂) in root voles Microtus oeconomus. Replicate high‐ and low‐density enclosed parental populations were established, from which we obtained F₁ generation that were used to establish new enclosed, equal‐density populations. The adults of the high‐density parental populations had higher corticosterone levels, an indication of physiological stress, than did those of the low‐density parental populations. Over‐winter survival of the F₁ generation voles from the low‐density parental populations was greater than that of those from the high‐density parental populations. Over‐winter survival of F₂ generation voles did not differ between the two treatments. Our results suggest that maternal stress affected over‐winter survival of first generations but not second generations. Reduced immunocompetence, resulting from high population density stresses, transferred to offspring may be a factor in annual (winter) population declines. Because the effect is transitory, i.e. immunocompetence of F₂ voles is not affected, reduced immunocompetence resulting from high density stresses would not contribute to lengthy periods of low population densities that are characteristic of multi‐annual population fluctuations.     

Does phylogenetic relatedness influence the strength of competition among vascular plants?

A widely assumed but largely untested hypothesis central to ecology and evolutionary biology has been Charles Darwin's suggestion that closely related species will be more ecologically similar, and thus will compete more strongly with each other than they will with more distantly related species. We provide one of the first direct tests of the “competition-relatedness hypothesis” by combining two data sets: the relative competitive ability of 50 vascular plant species competing against 92 competitor species measured in five multi-species experiments, and measures of the phylogenetic relatedness of these species. In contrast to Darwin's assertion, there were weak relationships between the strength of competition and phylogenetic relatedness. Across all species studied, the competition-relatedness relationship was weak and not significant. This overall lack of pattern masked different responses of monocot and eudicot focal (phytometer) species. When monocots served as the focal (phytometer) species, the intensity of competition increased with the phylogenetic distance separating species, while competition decreased with phylogenetic distance for eudicot phytometers. These results were driven by the monocot-eudicot evolutionary split, such that monocots were poor competitors against eudicots, while eudicots are most strongly suppressed by other eudicots. There was no relationship between relatedness and competition for eudicots competing with other eudicots, while monocots did compete more intensely with closely related monocots than with distantly related monocots. Overall, the relationships between competition intensity and relatedness were weak compared to the strong and consistent relationships between competitive ability and functional traits such as plant size that have been reported by other studies. We suggest that Darwin's assertion that competition will be strongest among closely related species is not supported by empirical data, at least for the 142 vascular plant species in this study.     

Does lack of diapause result in less insect seasonality?

Summary Unlike their temperate zone and tropical African relatives, flesh flies from the Neotropics lack the capacity for diapause. Yet, our trapping data reveal marked seasonality in flies from Panama, demonstrating that diapause is not essential for generating their seasonal patterns of abundance.     

Does lack of available suitable habitat explain the patchy distributions of rare calcicole fern species?

In Canada, as in many countries, a relatively large number of fern species occur in specialized habitats and have low numbers of known populations containing few individuals. It has been suggested that the distribution of ferns is mostly determined by factors of climate and habitat due to relatively low limitations in ferns for dispersal and establishment. Here, we attempt to explain whether the local patchy distribution of three calcicole fern species rare in Canada ( Asplenium ruta-muraria , Pellaea atropurpurea and Woodsia obtusa ) is due to a lack of available habitat. Analyses based on micro-scale differences between sites occupied by the ferns and nearby, unoccupied sites did not reveal any significant differences, thereby indicating that the rarity of these species is not entirely driven by the rarity of their microhabitat at a local scale. Our results suggest that the widely accepted premise that ferns are not limited by dispersal or establishment should be reconsidered, as such limitations are the only likely explanation for empty available and suitable habitat.     

Does climate change influence the availability and quality of reindeer forage plants?

The northward and upward movement of the tree line and gradual replacement of lichens with vascular plants associated with increasing temperatures and nutrient availability may change the reindeer pastures in Northern Fennoscandia. The productivity of reindeer forage will most probably increase, but their protein (nitrogen) concentrations may decrease because of higher temperatures and CO₂ concentration. In the long term, the nutritive value of forage will depend on the mineralization rate and nutrient uptake from the soil. Enhanced UV-B is likely to increase the concentration of phenolics, decreasing forage quality and choice, but reindeer may adapt to increased phenolics. Increased winter precipitation, the occurrence of ice layers, deeper snow cover, and the appearance of molds beneath the snow cover may reduce the availability and/or quality of reindeer forage, but prolongation of snowless periods might have the opposite effect. The net balance of negative and positive effects will vary regionally depending on the climate, bedrock, vegetation, reindeer herding systems and socio-political factors. Multidisciplinary research is needed most importantly on the effects of the changing winter climate on reindeer forage, and the effect of modified forage quality on reindeer physiology.