Long distance pollen transport cause problems for determining the timing of birch pollen season in Fennoscandia by using phenological observations

The male flowering and leaf bud burst of birch take place almost simultaneously, suggesting that the observations of leaf bud burst could be used to determine the timing of birch pollen release. However, long‐distance transport of birch pollen before the onset of local flowering may complicate the utilization of phenological observations in pollen forecasting.

We compared the timing of leaf bud burst of silver birch with the timing of the stages of birch pollen season during an eight year period (1997–2004) at five sites in Finland. The stages of the birch pollen season were defined using four different thresholds: 1) the first date of the earliest three‐day period with airborne birch pollen counts exceeding 10 grains m^?3 air; and the dates when the accumulated pollen sum reaches 2) 5%; 3) 50% and 4) 95% of the annual total. Atmospheric modelling was used to determine the source areas for the observed long‐distance transported pollen, and the exploitability of phenological observations in pollen forecasting was evaluated.

Pair‐wise comparisons of means indicate that the timing of leaf bud burst fell closest to the date when the accumulated pollen sum reached 5% of the annual total, and did not differ significantly from it at any site (p<0.05; Student‐Newman‐Keuls test). It was found that the timing of leaf bud burst of silver birch overlaps with the first half of the main birch pollen season. However, phenological observations alone do not suffice to determine the timing of the main birch pollen season because of long‐distance transport of birch pollen.     

Dark inactivation of ferredoxin-NADP reductase and cyclic electron flow under far-red light in sunflower leaves

The oxidation kinetics under far-red light (FRL) of photosystem I (PSI) high potential donors P700, plastocyanin (PC), and cytochrome f (Cyt f) were investigated in sunflower leaves with the help of a new high-sensitivity photometer at 810 nm. The slopes of the 810 nm signal were measured immediately before and after FRL was turned on or off. The same derivatives (slopes) were calculated from a mathematical model based on redox equilibrium between P700, PC and Cyt f and the parameters of the model were varied to fit the model to the measurements. Typical best-fit pool sizes were 1.0–1.5 μmol m⁻² of P700, 3 PC/P700 and 1 Cyt f/P700, apparent equilibrium constants were 15 between P700 and PC and 3 between PC and Cyt f. Cyclic electron flow (CET) was calculated from the slope of the signal after FRL was turned off. CET activated as soon as electrons accumulated on the PSI acceptor side. The quantum yield of CET was close to unity. Consequently, all PSI in the leaf were able to perform in cycle, questioning the model of compartmentation of photosynthetic functions between the stroma and grana thylakoids. The induction of CET was very fast, showing that it was directly redox-controlled. After longer dark exposures CET dominated, because linear e⁻ transport was temporarily hindered by the dark inactivation of ferredoxin-NADP reductase.     

Empowering her guardians to nurture our Ocean’s future

Reviews in Fish Biology and Fisheries - Coastal Indigenous and Traditional communities are starting to see changes to their lives from climate change, whether this is from species range changes or...     

Basin‐scale phenology and effects of climate variability on global timing of initial seaward migration of Atlantic salmon (Salmo salar)

Migrations between different habitats are key events in the lives of many organisms. Such movements involve annually recurring travel over long distances usually triggered by seasonal changes in the environment. Often, the migration is associated with travel to or from reproduction areas to regions of growth. Young anadromous Atlantic salmon (Salmo salar) emigrate from freshwater nursery areas during spring and early summer to feed and grow in the North Atlantic Ocean. The transition from the freshwater (‘parr’) stage to the migratory stage where they descend streams and enter salt water (‘smolt’) is characterized by morphological, physiological and behavioural changes where the timing of this parr‐smolt transition is cued by photoperiod and water temperature. Environmental conditions in the freshwater habitat control the downstream migration and contribute to within‐ and among‐river variation in migratory timing. Moreover, the timing of the freshwater emigration has likely evolved to meet environmental conditions in the ocean as these affect growth and survival of the post‐smolts. Using generalized additive mixed‐effects modelling, we analysed spatio‐temporal variations in the dates of downstream smolt migration in 67 rivers throughout the North Atlantic during the last five decades and found that migrations were earlier in populations in the east than the west. After accounting for this spatial effect, the initiation of the downstream migration among rivers was positively associated with freshwater temperatures, up to about 10 °C and levelling off at higher values, and with sea‐surface temperatures. Earlier migration occurred when river discharge levels were low but increasing. On average, the initiation of the smolt seaward migration has occurred 2.5 days earlier per decade throughout the basin of the North Atlantic. This shift in phenology matches changes in air, river, and ocean temperatures, suggesting that Atlantic salmon emigration is responding to the current global climate changes.     

Genome‐wide SNP analysis reveals a genetic basis for sea‐age variation in a wild population of Atlantic salmon (Salmo salar)

Delaying sexual maturation can lead to larger body size and higher reproductive success, but carries an increased risk of death before reproducing. Classical life history theory predicts that trade‐offs between reproductive success and survival should lead to the evolution of an optimal strategy in a given population. However, variation in mating strategies generally persists, and in general, there remains a poor understanding of genetic and physiological mechanisms underlying this variation. One extreme case of this is in the Atlantic salmon (Salmo salar), which can show variation in the age at which they return from their marine migration to spawn (i.e. their ‘sea age’). This results in large size differences between strategies, with direct implications for individual fitness. Here, we used an Illumina Infinium SNP array to identify regions of the genome associated with variation in sea age in a large population of Atlantic salmon in Northern Europe, implementing individual‐based genome‐wide association studies (GWAS) and population‐based F_ST outlier analyses. We identified several regions of the genome which vary in association with phenotype and/or selection between sea ages, with nearby genes having functions related to muscle development, metabolism, immune response and mate choice. In addition, we found that individuals of different sea ages belong to different, yet sympatric populations in this system, indicating that reproductive isolation may be driven by divergence between stable strategies. Overall, this study demonstrates how genome‐wide methodologies can be integrated with samples collected from wild, structured populations to understand their ecology and evolution in a natural context.     

Prenatal and Childhood Growth,and Hospitalization for Alcohol Use Disorders in Adulthood: The Helsinki Birth Cohort Study

Background

Small birth size - an indicator of a sub-optimal prenatal environment - and variation in growth after birth have been associated with non-communicable diseases in later life. We tested whether birth size or growth in childhood associated with the risk of hospital admission for alcohol use disorders (AUDs) from early to late adulthood.

Methods

The sample comprised 6544 men and 6050 women born between 1934 and 1944 in Helsinki, Finland. Data on anthropometric measures were extracted from medical records and diagnoses of AUD from the Finnish Hospital Discharge Register and Causes of Death Register covering a 40-year period from 1969 to 2008.

Results

Altogether 171 women (2.8%) and 657 men (10.0%) were diagnosed at a hospital with AUD. After adjusting for major confounders, shorter length at birth, shorter height up to two years of age, and lower weight at two years associated with hospitalization for AUD in women. In men, slower growth in height, particularly from 2 to 7 years, and slower weight gain from 7 to 11 years as well as shorter height and lower weight at 7 and 11 years associated with a diagnosis of AUD in men.

Conclusions

Pre- and postnatal growth associates with the risk for AUD later in life differently in women than in men: the fetal period and infancy seem to be the sensitive periods for women, whereas those for men the occur from toddlerhood onwards.     

Fatty acid mobilization in voles--model species for rapid fasting response and fatty liver

Factors regulating fatty acid (FA) composition of small herbivores are poorly known. Because of the fast response to food deprivation, the tissue FA profiles of voles could be rapidly modified. The selectivity of incorporating dietary FA into tissue total lipids and mobilizing tissue FA was examined in two Microtus vole species either fed or fasted for 12-18 h. The FA composition of the tissues reflected the dietary lipids, but FA were selectively incorporated depending on their structure. The FA profiles of white and brown adipose tissues were different and contained more saturated and monounsaturated FA and less polyunsaturated FA (PUFA) than the diet. The essential PUFA precursors with smaller tissue percentages were likely converted into longer-chain derivatives for structural lipids. The FA composition of the vole tissues was selectively modified by food deprivation. The preferences for retention or loss were tissue-specific and related to the FA structure. Livers displayed steatosis with characteristic accumulation of triacylglycerols, while FA prevalent in membrane phospholipids decreased in proportion. Hepatic FA could be partly derived from lipids hydrolyzed in fat depots. The FA profiles of the vole tissues reflect the dietary lipids and are rapidly and selectively modified by food deprivation.     

The responsiveness of TrkB to BDNF and antidepressant drugs is differentially regulated during mouse development

Background

Previous studies suggest that the responsiveness of TrkB receptor to BDNF is developmentally regulated in rats. Antidepressant drugs (AD) have been shown to increase TrkB signalling in the adult rodent brain, and recent findings implicate a BDNF-independent mechanism behind this phenomenon. When administered during early postnatal life, ADs produce long-lasting biochemical and behavioural alterations that are observed in adult animals.

Methodology

We have here examined the responsiveness of brain TrkB receptors to BDNF and ADs during early postnatal life of mouse, measured as autophosphorylation of TrkB (pTrkB).

Principal Findings

We found that ADs fail to induce TrkB signalling before postnatal day 12 (P12) after which an adult response of TrkB to ADs was observed. Interestingly, there was a temporally inverse correlation between the appearance of the responsiveness of TrkB to systemic ADs and the marked developmental reduction of BDNF-induced TrkB in brain microslices ex vivo. Basal p-TrkB status in the brain of BDNF deficient mice was significantly reduced only during early postnatal period. Enhancing cAMP (cyclic adenosine monophosphate) signalling failed to facilitate TrkB responsiveness to BDNF. Reduced responsiveness of TrkB to BDNF was not produced by the developmental increase in the expression of dominant-negative truncated TrkB.T1 because this reduction was similarly observed in the brain microslices of trkB.T1 ^−/− mice. Moreover, postnatal AD administration produced long-lasting behavioural alterations observable in adult mice, but the responses were different when mice were treated during the time when ADs did not (P4-9) or did (P16-21) activate TrkB.

Conclusions

We have found that ADs induce the activation of TrkB only in mice older than 2 weeks and that responsiveness of brain microslices to BDNF is reduced during the same time period. Exposure to ADs before and after the age when ADs activate TrkB produces differential long-term behavioural responses in adult mice.