Mast cells/eosinophilic granule cells of salmonids: staining properties and responses to noxious agents

Observations were made on mast cells/eosinophilic granule cells in swimbladder tissue spreads and sections of gills and intestinal tissues from species of the generaSalmoOncorhynchusSalvelinusCoregonusThymallus. Some individuals had been reared in captivity and others were caught in rivers or lakes, and both apparently healthy fish and fish with persistent inflammation, due to helminths or unknown causative agents, were included in the study. Acute responses to noxious agents were studied in swimbladder tissue spreads after intraperitoneal injections of inactivatedAeromonas salmonicida, compound 48/80 and hydrocortisone. The tissue spreads were fixed in ethanol and stained with thionin. Other tissues were fixed in a solution containing 4% formaldehyde and 5% acetic acid in methanol, and stained with May-Grünwald Giemsa combination dye, haematoxylin and eosin, or Alcian blue. Intestinal tissue histamine was assayed fluorometrically, and vascular responses to histamine and compound 48/80 were studied in perfused gill preparations. The staining properties of salmonid mast cells/eosinophilic granule cells resembled those of mammalian mucosal mast cells and globule leucocytes, with both acidophilic and basophilic components in their granules. May-Grünwald Giemsa staining revealed that in cells found in connective tissues the basophilic character was dominant, whereas the acidophilic character was most marked in those present in epithelia. The granule cells in swimbladder tissue spreads stained metachromatically with alcoholic thionin. Intraperitoneal injections of inactivatedA. salmonicidaproduced acute inflammatory reactions, with degranulation of mast cells/eosinophilic granule cells, in tissues of the swimbladder. Degranulation of the granule cells was also noticed after injection of compound 48/80. Massive degranulation of mast cells/eosinophilic granule cells in the swimbladder wall, followed by an acute inflammatory reaction, was induced by intraperitoneal injections of hydrocortisone. Persistent inflammation, e.g. in tissues infected with helminths, was accompanied by recruitment of mast cells/eosinophilic granule cells. Presence of many or few mast cells/eosinophilic granule cells in tissues of the intestine seemed to have no influence on the content of histamine, which was always low. Compound 48/80 produced increased resistance in the perfused branchial vascular bed, but effects of histamine were slight or completely absent. The responses of mast cells/eosinophilic granule cells of salmonids in acute and persistent inflammation, as revealed in the present investigation, are similar to the known responses of mammalian mast cells. Since their staining properties are also similar, the term ‘mast cell’ should be adequate.     

Growth and Dormancy in Norway Spruce Ecotypes (Picea abies) I. Interaction of Photoperiod and Temperature

Growth and dormancy as affected by photoperiod and temperature have been studied in Norway spruce ecotypes of different latitudinal and altitudinal origin. First-year seedlings were used. In all ecotypes apical growth cessation and terminal bud formation occurred within 2 weeks after exposure to SD at temperatures of 18 to 24°C. At lower temperatures or at near-critical photoperiods the response was delayed. The critical photoperiod for apical growth cessation varied from 21 hours in ecotype Steinkjer, Norway (64°N) to about 15 hours in ecotype Lankowitz, Austria (47°04′N). High-elevation ecotypes also had longer critical pholoperiods than low-elevation ecotypes from the same latitude. A detectable growth depression resulted from as little as 1 or 2 SDs of 10 hours, and with 4 or more SDs apical growth cessation took place. In contrast to the situation in the shoot, root growth was not affected by photoperiod. Accordingly, the top:root ratio is drastically affected by photoperiod. The critical photoperiod for cambial growth was shorter than that for apical growth in all ecotypes and cambial growth cessation was delayed for several weeks compared with cessation of apical growth. A transition to formation of late-wood tracheids with thick walls and narrow lumens took place upon exposure to SD. The photoperiodic effects were significantly modified by temperature, but the critical photoperiods were only slightly changed by temperature in the range of 12 to 24°C. However, a 10-hour “night” at 4°C caused growth cessation in continuous light in four ecotypes tested. Temperature optimum for apical growth under non-limiting photoperiods (24 hours) was 21°C in all ecotypes, but with little difference among 18,21 and 24°C. The Q₁₀ for apical growth was 3.5 in the temperature range 12 to 18°C. The growth potential as determined in 24-hour photoperiods was not significantly different among the various ecotypes except for one northern eco-type which was clearly inferior to the others. However, the growth of ecotype Steinkjer (64°N) was greatly suppressed even by the long midsummer days at 59°40′N, thus demonstrating the misleading impression one gets of the growth potential of northern ecotypes when they are moved southwards.     

Growth and Dormancy in Norway Spruce Ecotypes

Height and radial growth of spruce in years n+ 1, n+ 2, and n+ 3 as affected by photoperiod and temperature in year n have been studied in controlled environments and in the field. In agreement with common opinion apical shoot growth in year n+ 1 was strongly dependent on the temperature conditions prevailing in the period following budset in year n. This was found mainly to be a direct effect upon the differentiation of the shoot and needle primordia for next year's growth. A similar, although less pronounced effect, was found also on radial growth, possibly an indirect effect elicited through the effect on apical growth. A rather wide temperature optimum of 18 to 24°C was found in three Norwegian ecotypes and a somewhat lower optimum (15 to 18 C) in an Austrian high altitude ecotype. The shorter the bud differentiation period, the higher was the temperature optimum in all ecotypes (heat sum effect). Photoperiod which is the main factor controlling the time of budset, thus had a great after-effect. The after-effect was strongly modified by photoperiod and to a lesser extent also by temperature in the current growing season. It is concluded that in second-year or older spruce plants the important effect of photoperiod in the current growing season is to control quantitatively and qualitatively the amount of secondary (lammas) shoot formation, and to modify shoot extension in the main growth flush. Longer photoperiods were needed for continuation or resumption of growth in second-year plants than for maintenance of uninterrupted growth in first-year seedlings. Delayed flushing was observed in plants maturing at high temperatures, indicating that these plants had entered a deeper state of dormancy than those maturing at lower temperatures. Also in years n+ 2 and n+ 3 apical and radical growth was significantly related to photoperiod and temperature conditions in year n. This effect gradually became an indirect one through the effects on general plant size (leaf and root area). The results are discussed in the light of previous work in the field.     

Storms can cause Europe-wide reduction in forest carbon sink

Disturbance of ecosystems is a major factor in regional carbon budgets, and it is believed to be partly responsible for the large inter-annual variability of the terrestrial part of the carbon balance. Forest fires have so far been considered as the most important disturbance but also other forms of disturbance such as insect outbreaks or wind-throw might contribute significantly to the largely unexplained inter-annual variability, at least in specific regions. The effect of wind-throw has not yet been estimated because of lack of data on how carbon fluxes are affected. The Gudrun storm, which hit Sweden in January 2005, resulted in ca. 66 million m³ of wind-thrown stem wood on an area of ca. 272 000 ha. Using a model (BIOME-BGC) calibrated to CO₂ flux measurements at two sites, the annual net ecosystem productivity during the first year after the storm was estimated to be in the range −897 to −1259 g C m⁻² yr⁻¹. This is a much higher loss compared with harvested (clear-cut) forests in Europe, which ranged between ca. −420 and −100 g m⁻² yr⁻¹. The reduction in the carbon sink scaled to the whole wind-thrown area was estimated at ca. 3 million tons C during the first year. By historical data on wind-throw in Europe combined with modelling, we estimated that the large Lothar storm in 1999 reduced the European carbon balance by ca. 16 million tons C, this is ca. 30% of the net biome production in Europe. We conclude that the impact of increased forest damage by more frequent storms in future climate change scenarios must be considered and that intermittent large wind-throw events may explain a part of the large inter-annual variability in the terrestrial carbon sink.     

Photoperiod and Temperature Interactions in Growth and Flowering of Strawberry

Growth and flowering of strawberry cultivars were studied in controlled environments. Early cultivars adapted to marginal growing areas in Scandinavia initiated flower buds in all photoperiods including continuous light at temperatures of 12 and 18°C. At 24°C they remained vegetative in photoperiods above 14 or 16 h. The later cultivars ‘Senga Sengana’ and ‘Abundance’ did not initiate flower buds in 24-h photoperiods at any of these temperatures. Their critical photoperiod changed from above 16 h at 12°C to about 14 and 13 h at 18 and 24°C, respectively. It is concluded that at high latitudes temperature is as important as photoperiod in controlling flowering in the strawberry. Stolon formation, petiole elongation, and leaf area growth were stimulated by high temperature and long days, usually with optima at 16 h and 18°C for petiole elongation and 16 h and 24°C for stolon formation. Although growth and flowering responses in general were opposite, the results indicate that they are to some extent independent. The photoperiodic growth responses were mainly of morphogenetic nature. Dry weight of stem and leaves was little influenced by photoperiod when the irradiance was kept constant.     

Production of juvenile salmonids in small Norwegian streams is affected by agricultural land use

1. We estimated the biomass and production of juvenile anadromous brown trout (Salmo trutta) and Atlantic salmon (Salmo salar) (parr) in 12 streams in the Skagerrak area of Norway to identify controlling environmental factors, such as land‐use and water chemistry. 2. Production estimates correlated positively with fish density in early summer, but not with the size of the catchment. The summer biomass of age‐0 brown trout and Atlantic salmon was smaller than that of age‐1 and constituted 27.4 and 25.7%, respectively, of the total biomass of the two groups. 3. Mean production of brown trout from July to September varied between streams, but in most cases it was below 2 g 100 m^?2 day^?1. Yearly cohort production from age‐0 in July to age‐1 in July was 10 g m^?2 or less, with mean annual production of 1.32 g 100 m^?2 day^?1, equivalent to 4.8 g m^?2 year^?1. The corresponding annual cohort production of Atlantic salmon was 0.38 g 100 m^?2 day^?1 or 1.4 g m^?2 year^?1. Annual production to biomass ratio (P/B) for brown trout of the same cohort in the various streams was between 1.47 and 4.37; the overall mean (±SD) for all streams was 2.25 ± 0.94. Mean turnover rate of Atlantic salmon was 2.73 ± 0.24. 4. Production of 0+ brown trout during the summer correlated significantly with the percentage of agricultural land and forest/bogs in the catchment, with maxima at 20 and 75%, respectively. Age‐0 brown trout production also correlated with concentration of nitrogen and calcium in the water, with maxima at 2.4 and 14 mg L^?1, respectively. 5. The results support the hypothesis that brown trout parr production reflects the quality of their habitat, as indicated by the dome‐shaped relationship between percentage of agricultural land and the concentration of nitrogen and calcium in the water.     

Use of stable isotopes to assess the intraspecific foraging niche of males and female colour morphs of the damselfly Enallagma hageni

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Annual and seasonal reproductive trends in the Lesser Spotted Woodpecker Dendrocopos minor

Annual and seasonal variation in reproductive timing and performance were studied in a population of the Lesser Spotted Woodpecker Dendrocopos minor over 10 years in southern Sweden. The median laying date of the first egg varied by up to 17 days between years, being generally larger than the variation of laying dates within years. Neither clutch size, brood size in successful nests, fledging success in successful nests nor mean nestling weight differed significantly between years. There was no trend for mean clutch size to vary between early and late years. In spite of a more than threefold variation in population size, no reproductive variable demonstrated an apparent density-dependence. Within the season, clutch size declined steeply with increasing clutch initiation date, whereas fledging success and nesting success did not, leading to a trend in brood size almost identical to the trend in clutch size. The survival prospects of fledged young declined with increasing clutch initiation date, and it is argued that the clutch size laid is a strategic adjustment to laying date. Out of 124 breeding attempts, 34% did not produce fledged young. In 9% of the breeding attempts, pairs laid no eggs. At least 20% of the breeding attempts failed after egg-laying. The most common cause of breeding failure was loss of the breeding partner followed by nest abandonment (40% of the failures). Only 16–28% of the failures were due to predation on the nest. Most complete failures, and also partial losses from nests, occurred at the early breeding stages. It is argued that the early nestling phase may be a critical stage, which the woodpeckers adjust to coincide with the seasonal food peak, explaining the strikingly late breeding season compared with other non-migrant species.     

Activity of Various Growth Substances in the Avena First Internode Test

The elongation growth of the Avena first internode segments was studied in the presence of one or several of the following growth substances: indoleacetic acid (IAA), 6-fur-furylamino purine (FAP, kinetin), 6-benzylamino purine (BAP), gibberellin A₃ (GA₃) and A₄₊₇ (GA₄₊₇), and abscisic acid (ABA). The cytokinins at concentrations of 10^?7 to 10^?6M stimulated growth with 4 to 6 per cent but this effect was not statistically significant. Concentrations higher than 5 × 10^?6M inhibited growth. FAP and BAP (from 10^?8M to 10^?6M) had no significant interaction with any other growth substance used. The two-factor interactions of IAA × ABA, IAA × GA₃, and GA₃× ABA, as well as the three-factor interaction IAA × ABA × GA₃ were significant. However, the IAA × ABA interaction was significant only when high concentration (10^?6M) of ABA was used. The growth inhibition produced by 10^?7 and 10^?6M ABA was overcome by about equimolar concentrations of IAA. The stimulation of growth by GA₃ and GA₄₊₇ (10^?9 to 10^?7M) was prevented by simultaneous application of ABA, and it was reduced significantly by application of IAA (10^?7 to 10^?8M). GA3 at 10^?8M combined with different concentrations of IAA gave slightly higher elongation than IAA alone but the observed values were significantly lower than expected assuming independent additive action.