Effects of inoculum concentration, leaf age and wetness period on the development of dark leaf and pod spot (Alternaria brassicae) on oilseed rape (Brassica napus)

Experiments were done under controlled environment and glasshouse conditions to study the effects of inoculum concentration, leaf age and wetness period on the development of dark leaf and pod spot (Alternaria brussicae) on oilseed rape (Brassica napus). On leaves of potted oilseed rape plants (cv. Bienvenu) inoculated with A. brassicae conidial suspensions, the severity (number of lesions cm^-2) of dark leaf spot increased as inoculum concentration increased from 80 to 660 spores ml^-1and as leaf age increased from 4 to 14 days. On pods on detached racemes of spring oilseed rape (cv. Starlight), the incidence of dark pod spot (% of pods diseased) increased as inoculum concentration increased from 80 to 10⁴spores ml^-1. Increasing inoculum concentration above 10⁴spores ml^-1did not increase the incidence but did increase the severity of dark pod spot. A minimum wetness period of 4 h was needed for infection of oilseed rape leaves (cv. Envol) by A. brussicue at 18°C and disease severity increased with increasing wetness period up to 12 h. The length of dry interruptions after 3–8 h of initial wetness affected the severity of dark leaf spot. A second wetness period increased the severity of dark leaf spot if the dry interruption was ≤ 6 h and if the first wetness period was ≤ 8 h. The incubation period of A. brassicae decreased from 3.5 to 2.5 days as inoculum concentration increased from 80 to 660 spores ml^-on leaves (cv. Bienvenu) at 17–25°C and from 3.8 to 1.0 day as inoculum concentration increased from 80 to ≥2 ≥ 10³spores ml^-1on pods (cv. Starlight) at 18°C.     

Regulation of monocarpic senescence of Brassica campestris by the developing pods

Senescence of Brassica campestris L. cv. B-9 was studied with regard to seed maturation and source-sink relationships. In normal control plants leaf senescence (as determined by the change in chlorophyll level) started and proceeded in a progressive manner from base to apex during the period of early pod setting. Complete yellowing of the leaves occurred well before the seed maturation and pod wall senescence. The pod wall always senesced before the attainment of final seed weight. In two different sets of acrocarpous plants containing 65 pods and 10 pods, respectively, leaf senescence was delayed during the pod filling period. It started non-sequentially after complete yellowing and senescence of the pod wall. The degree of leaf senescence at the post-pod filling stage was almost proportional to the number of pods present. When peduncles of the acrocarpous 10-podded plants were removed after the pod filling stage of the plant, leaf senescence was delayed compared to plants whose pedicels were removed, although the senescence pattern of the upper three leaves was nonsequential in both cases. Defruiting at an early stage of development delayed leaf senescence, although the pattern of such senescence remained unaltered (i.e. nonsequential). Defoliation hastened the seed-filling process and pod wall senescence. Plants containing fewer pods had higher average seed weight, although yield per plant was reduced.
These results suggest that the pod wall serves as a temporary as well as intermediary storage organ and that foliar senescence is not directly related to seed maturation. The possible cause of uncoupling between foliar senescence and seed development is discussed.     

Effect of fire on the topsoil seed banks of rehabilitated bauxite mine sites in the jarrah forest of Western Australia

Summary Germinable seed stores of 5- and 8-year-old rehabilitated bauxite mine pits in south-west Western Australia were assessed before and after burning. These seed stores were compared to those of adjacent unmined Jarrah ( Eucalyptus marginata ) forest, to identify at what age fire can be reintroduced, in order to measure restoration success and reduce fire hazard. Soils were sampled in early summer (before fire) and late autumn (after fire). Before fire, the mean topsoil seed bank of 5-year-old sites was 2121 seeds per m² while 8-year-old sites had a mean of 1520 seeds per m². Only the 5-year-old sites were significantly different from the forest mean of 1478 seeds per m² for the same season. After summer burns (and possibly due to seasonal effects) topsoil seed banks of rehabilitated areas (sampled in autumn) decreased by an average of 53 per cent. Topsoil seed banks of 5–8-year-old sites were resistant to lower intensity burns, with 362 seeds per m² of native species surviving mild burns and 108 seeds per m² of native species surviving after an intense summer fire. The topsoil seed reserve of 5–8-year-old rehabilitated areas had a high proportion of annual weed species while the forest sites had high levels of subshrubs and native annuals. Low-intensity burns did not alter the composition of life-forms in the soil seed bank, while intense burns favoured annual weed and shrub species. The results indicate that it is not appropriate to introduce fire to rehabilitated areas before 8 years, due to limited fuel reduction benefits and possible adverse effects on obligate seeding species. The large proportion of weed species in the soil seed bank of young rehabilitated areas is a concern, and remains a major consideration for future disturbance of these areas.     

CO2 enrichment of soybeans. Effects of leaf/pod ratio

The effect of varying leaf number on response of soybean ( Glycine max (L.) Merr. cv. Fiskeby V) to CO₂ enrichment was studied. Plants were trimmed at pod set to 15 pods and 1 or 3 leaves (15:1 and 5:1 pod/leaf ratio) and placed in 350 or 1000 μl/l CO₂ growth chambers. Photosynthetic rates and dry weights were measured 6 times in all plants at each CO₂ concentration over a period of 39 days. Measured at treatment CO₂ concentration, photosynthetic rates deelined rapidly in enriched plants, but remained higher than those of non-enriched plants. When all plants were measured at the same CO₂ concentration, for most sampling dates, neither growth, CO₂ concentration or pod/leaf ratio significantly affected rates of photosynthesis per unit area of comparable leaves. CO₂ enrichment significantly increased total weights and pod weights in 15:1 but not 5:1 pod/leaf ratio plants. Plants with a 5:1 pod/leaf ratio had significantly higher total and pod weights than 15:1 ratio plants. Both the photosynthesis and dry weight data suggest that plants in the 5:1 ratio enriched treatment were sink-limited, but plants in all other treatments were source limited.     

Crop Growth, Disease and Yield Components of Rusted Phaseolus Beans in Ethiopia

Crop growth and disease epidemics in sprayed and non-sprayed bean plots, artificially infected with rust (Uromyces appendiculatus) 3 weeks after emergence. were assessed weekly in two cultivars, at two locations for two seasons. Disease intensity was regulated by the application of a fungicide at 5 spray frequencies. Fungicide application influenced leaf area index (LAI) and reduced rust intensity. The fungicide had no significant effect on other diseases and dead leaf area. Fungicide application increased seed yield (SY) by increased numbers of pods per plant (PP). Rust severity was strongly correlated with pustule density but the overall relationships among rust assessment parameters depended on cultivar and location. Seed yield and pods per plant were highly correlated with LAI. The relationships between LAI and seeds per pod or seed weight depended on cultivar and location. Overall rust assessment parameters (rust severity and pustule density) showed close, negative relationships with seed yield. seed weight and pods per plant but not with seeds per pod. The relationships obtained in the partially resistant line 6-R-395 were less definite than those in the susceptible line Mexican 142. The yield parameters seed yield and pods per plant, showed strong positive relationships.     

Effects of mycorrhizal colonization on biomass production and nitrogen fixation of black locust (Robinia pseudoacacia) seedlings grown under elevated atmospheric carbon dioxide

Interactive effects of elevated atmospheric CO₂ and arbuscular mycorrhizal (AM) fungi on biomass production and N₂ fixation were investigated using black locust ( Robinia pseudoacacia ). Seedlings were grown in growth chambers maintained at either 350 μmol mol⁻¹ or 710 μmol mol⁻¹ CO₂. Seedlings were inoculated with Rhizobium spp. and were grown with or without AM fungi. The ¹⁵N isotope dilution method was used to determine N source partitioning between N₂ fixation and inorganic fertilizer uptake. Elevated atmospheric CO₂ significantly increased the percentage of fine roots that were colonized by AM fungi. Mycorrhizal seedlings grown under elevated CO₂ had the greatest overall plant biomass production, nodulation, N and P content, and root N absorption. Additionally, elevated CO₂ levels enhanced nodule and root mass production, as well as N₂ fixation rates, of non- mycorrhizal seedlings. However, the relative response of biomass production to CO₂ enrichment was greater in non-mycorrhizal seedlings than in mycorrhizal seedlings. This study provides strong evidence that arbuscular mycorrhizal fungi play an important role in the extent to which plant nutrition of symbiotic N₂-fixing tree species is affected by enriched atmospheric CO₂.     

Pathway and regulation of phosphate translocation to the pods of soybean explants

We investigated the degree to which developing fruit compete directly with leaves for mineral nutrients, e.g. phosphate coming up from the roots. When soybean ( Glycine max (L.) Merrill cv. Anoka) explants cut at mid-late podfill were given a 15-min pulse of ³²Pi via the cut stem and then transferred to distilled water, 75% of the ³²P accumulated in the leaves and 21% in stem and petiole during the first hour. The amount of ³²P entering the seeds was low (1%) initially, but thereafter increased to 30% in 48 h. An accumulation of ³²P in the seed coats preceded its entry into the embryos. Disruption (with hot steam) of the phloem between the leaf and the pods after pulse labelling indicated that more than 80% of the ³²Pi pulse moved to the leaf before redistribution to the pods. Increasing "sink" size by adjusting the pod load from 1 to 2–3 did not increase the ³²P accumulated by the pods proportionally. Conversely, excision of the seeds after pulse labelling did not prevent translocation of ³²P out of the leaves. These results suggest that the rate of transport of phosphate to the pods at mid-late podfill is controlled primarily by factors in the leaves. The results are consistent with the observation that the relative size of the sink (pod load) does not regulate leaf senescence.     

Growth, nodulation and nitrate reductase activity in the aquatic legume Neptunia plena (L.) benth. At different external nitrate concentrations

The effects of different external nitrate concentrations (0 (control), 1, 50, 100, 500, 1000 and 20 000 mmol m⁻³) on growth, nodulation and nitrate-reductase activity (NRA) of inoculated Neptunia plena (L.) Benth. were examined.

Plants given 500 and 1000 mmol m⁻³ nitrate had greater (P < 0.05) shoot length, leaf, stem and root dry mass, and carbon and nitrogen contents than the controls and plants given 20 000 mmol m⁻³ nitrate. Nodule number was not significantly affected by nitrate concentration up to 50 mmol m⁻³, but 100 mmol m⁻³ nitrate reduced nodulation by 68% and concentrations above 100 mmol m⁻³ completely inhibited nodule development. Plants given 100–20000 mmol m⁻³ nitrate had a greater nitrate content per g leaf, stem and root dry mass (DM) than controls. Nitrate per g root DM did not increase with external nitrate concentration above 500 mmol m⁻³, but levels in leaf and stem were greater at 20 000 mmol m⁻³ nitrate than at all other concentrations. NRA per g leaf, stem and root fresh mass (FM) was greater for plants given 500–20000 mmol m⁻³ than for controls, but there was no significant increase with nitrate concentration above 500 mmol m⁻³. Substantial proportions of total plant nitrate and NRA were found in both root and shoot over the entire range of external nitrate concentrations given.

Findings for N. plena are compared with data obtained previously for terrestrial legumes.     

Fruit and seed ecology of wild robusta coffee (Coffea canephora Froehner) in Kibale National Park, Uganda

Coffee fruit production, frugivorous activities and seed longevity were investigated during two seasons. The average densities of fruiting coffee trees during the first sampling period ranged from four to seven per 25 m² and during the second sampling period, four fruiting trees per 25 m² were estimated. Fruiting coffee trees were significantly less than the non-fruiting trees ( P < 0.05, t -test). Periods of maximum coffee fruit fall coincided with those of lowest rainfall. Coffee fruit yield per tree from ground collections was 7–40 m⁻² in 1992 and 16–38 m⁻² in 1993/1994. Split coffee berries ranged between 71.7% and 83.6% of all fruits collected from the forest floor in the 1993/94 sampling period. Coffee seeds collected from the forest floor were mostly undamaged. Black and white colobus and redtail monkeys were observed to feed on ripe coffee fruits but did not crush the seeds. Coffee seed viability declined rapidly during storage. Seeds left on the forest floor survived longest, those stored under laboratory conditions lost viability fastest, and those in cold storage showed intermediate longevity.     

Nitrogen fertilization affects interactions between the components of an insect–fungus–plant tripartite system

1. The chrysomelid beetle, Gastrophysa viridula and the rust fungus, Uromyces rumicis both occur on leaves of Rumex obtusifolius growing in a wide range of soil nutrient conditions. We investigated the effect of fertilizing plants with eight nitrate and four ammonium concentrations on the components of this tripartite interaction in a controlled environment.
2. Leaf weight, area and total plant weight increased as both nitrate and ammonium concentrations increased up to 15mmol l^–1. Between 15 and 50mmol l^–1 added nitrate, leaf and total plant weight decreased. Total plant weight was unaffected by increasing ammonium fertilization from 15 to 25mmol l^–1.
3. The density and percentage of U. rumicis pustules sporulating 8 days after infection decreased with increasing nitrate but were unaffected by increasing the concentration of ammonium fertilization.
4. Leaf area consumed and number of eggs laid by G. viridula decreased as the concentration of nitrate fertilization increased. Increasing the concentration of ammonium decreased leaf area eaten.
5. First instar mortality of G. viridula was increased and gregariousness and adult fecundity was decreased additively by the combination of U. rumicis infection and decreasing the nitrate concentration fed to plants from 10 to 1mmol l^–1.     

Influences of Arbuscular Mycorrhizal Fungus Glomus mosseae on Growth and Nutrition of Lentil Irrigated with Arsenic Contaminated Water

Arsenic (As) contamination of irrigation water represents a major constraint to Bangladesh agriculture. While arbuscular mycorrhizal (AM) fungi have their most significant effect on P uptake, they have also been shown to alleviate metal toxicity to the host plant. This study examined the effects of As and inoculation with an AM fungus, Glomus mosseae, on lentil (Lens culinaris L. cv. Titore). Plants were grown with and without AM inoculum for 9 weeks in a sand and terra green mixture 50:50 v/v and watered with five levels of As (0, 1, 2, 5, 10 mg As L⁻¹ arsenate). Inoculum of Rhizobium leguminosarum b.v. Viceae strain 3841 was applied to all plants. Plants were fed with modified Hoagland solution (1/10 N of a full-strength solution and without P). Plant height, leaf number, pod number, plant biomass and shoot and root P concentration/offtake increased significantly due to mycorrhizal infection. Plant height, leaf/ pod number, plant biomass, root length, shoot P concentration/offtake, root P offtake and mycorrhizal infection decreased significantly with increasing As concentration. However, mycorrhizal inoculation reduced As concentration in roots and shoots. This study shows that growing lentil with compatible AM inoculum can minimise As toxicity and increase growth and P uptake.     

Phenology of the environmental weed Achillea millefolium (Asteraceae) along altitudinal and disturbance gradients in the Snowy Mountains, Australia

This study examined the phenology of the weed Achillea millefolium over a growing season in the Snowy Mountains. Vegetative and reproductive characteristics of plants in 1 m² quadrats were compared among sites at four different altitudes (medium and high montane, low and high subalpine) and three types of infrastructure (primary road, secondary road and building, total 12 sites). Altitude, infrastructure and time of year did not affect percentage cover of vegetation. Flowering started earlier and lasted longer in the low montane sites compared to high subalpine sites. The type of infrastructure only affected the number of reproductive structures at the peak of flowering, with A. millefolium growing next to buildings having two to three times more inflorescences per m² than along primary and secondary road verges. At the peak for each reproductive stage, there was an average of 1.47 developing inflorescences, 21 inflorescences in bud, 24 inflorescences in flower, 4 inflorescences setting seed, and 3 releasing seed. Based on the maximum number of inflorescences present at any time at each site, there was an average of 36 inflorescences, giving an estimate potential seed production of 51 400 seed per one m² for A. millefolium in the Snowy Mountains. If the climate changes in the Snowy Mountains as predicted, then it is likely that yarrow will produce more inflorescences and seed in the higher altitude sites.     

Resource allocation in an annual herb: Effects of light,mycorrhizal fungi,and defoliation

Concurrent interactions and the availability of resources (e.g., light) affect the cost/benefit balance during mutualistic and antagonistic interactions, as well as plant resource allocation patterns. Mycorrhizal interactions and herbivory concur in most plants, where mycorrhizae can enhance the uptake of soil nutrients by plants as well as consuming a large fraction of the plant's carbon, and defoliation usually reduces light interception and photosynthesis, thereby causing direct losses to the hosts of mycorrhizal fungi. Both types of interactions affect the carbon budget of their host plants and thus we predict that the relative costs of herbivory and mycorrhizal colonization will increase when photosynthesis is reduced, for instance in light limited environments. We conducted a greenhouse experiment using Datura stramonium to investigate the effects of defoliation and mycorrhizal inoculation on the resource allocation patterns in two different light environments. Defoliated plants overcompensated in terms of leaf mass in both light environments, but total seed mass per fruit was negatively affected by defoliation in both light environments. Mycorrhizal inoculation had a positive effect on vegetative growth and the leaf nitrogen content, but defoliation negates the benefit of mycorrhizal interactions in terms of the leaf nitrogen content. In general, D. stramonium compensated for the relative costs of concurrent mycorrhizal interactions and defoliation; plants that lacked both interactions exhibited the same performance as plants with both types of interactions.     

Effect of plant nitrogen status on the contribution of arbuscular mycorrhizal hyphae to plant nitrogen uptake

The contribution of hyphae of Glomus mosseae (Nicol. and Gerd.) Gerd. and Trappe (BEG 107) to the acquisition of mineral nitrogen by Triticum aestivum L. cv. Hano (wheat) was tested under conditions of low P and high N (+N−P) or low N (−N−P). Mycorrhizal colonisation increased the shoot dry weight and plant tissue concentrations of P and cations. However, N tissue concentrations of mycorrhizal plants were not increased, although nitrate reductase activities were significantly higher (in vivo activity) in +N−P mycorrhizal compared to non-mycorrhizal roots. Severe plant N deficiency reduced the percentage root length colonised (but not the percentage viable colonisation), hyphal length, total 15 N uptake by hyphae and dry weight of mycorrhizal plants. Although mycorrhizal colonisation did not affect the overall plant N status, hyphae transported 1% (−N−P) and 7% (+N−P) of the 15 N-labelled NH₄NO₃ to mycorrhizal plants over 48 h. The higher rate of hyphal N uptake was apparently related to the more extensive hyphal growth at the higher level of plant N supply. However, the hyphal N supply was not sufficiently high to sustain adequate N nutrition of the plants supplied with very low amounts of N to the roots. Conversely, a sufficient N supply to the roots was important for the development of an extensive mycelium.     

Effects of artificial defoliation on reproductive allocation in the common vetch,Vicia sativa (Fabaceae: Papilionoideae)

Previous field experiments have shown that, for the annual herb Vicia sativa, leaf area lost to herbivory results in reduced number of fruit (pods) produced per plant as well as fewer seeds per pod. We conducted a controlled garden experiment to determine the precise relationship between level of defoliation and various measures of maternal fitness through fruit and seed. We employed manual clipping of individual leaflets of newly produced leaves to 25% increments of damage (from 0% to 100%) over the entire period of development and flowering of these annual herbs, harvesting pods when filled but not dehisced. We found significant reduction in number of pods, number of seeds, total seed mass, and individual seed mass with leaf area lost. Even with the highest levels of defoliation over the life of the individual, plants still produced a substantial number of pods and seeds. Seeds produced by plants in all treatment groups showed similar percentages of germination and time to germination.     

接种AM真菌对短命植物生长发育及矿质养分吸收的影响

 采用分室培养方法研究接种幼套球囊霉(Glomus etunicatum,BEG168)、摩西球囊霉(G. mosseae, BEG167)、混合菌剂(M)对两种沙漠早春短命植物小车前(Plantago minuta)和尖喙牻牛儿苗（Erodium oxyrrhynchum）生长发育及矿质养分吸收的影响。结果表明,接种AMF处理的小车前和尖喙牻牛儿苗根系形成了典型的菌根结构,侵染率为22 %～60%;接种AMF提高了小车前和尖喙牻牛儿苗两种植物的生物量、株高及N、P养分吸收量。小车前单独接种BEG167、BEG168以及混合接种都显著提高了单株种子数量,其增幅分别 为67%、50%和78%。上述结果说明,在极端贫瘠和干旱的古尔班通古特沙漠中,丛枝菌根真菌对于早春短命植物小车前和尖喙牻牛儿苗的生态适应性的贡献表现为促进营养生长、提高后代（种子）繁殖数量。     

Methanogenesis in a saltern in the Bretagne (France)

Abstract Salterns in the Bretagne (France), exhibiting different stages of salinity of 5% to 33% evolved up to 0.7 mmol methane per m² per day. Methane concentrations of up to 0.4 mM were found. High methane evolution rates and increased methane concetration were restricted to basins of up to 7% and more than 15% salinity, and to the upper 10 cm of the sediments, where high sulfate concentrations (50 to 100 mM) occurred as well. Basins of 10–15% salinity exhibited only low methane evolution rates (less than 0.05 mmol methane per m² per day) and low methane concentrations (less than 0.02 mM). Gas bubbles arising during times of increased photosynthetic activity from the microbial mats covering the sediments of the saltern basins contained up to 2% methane. Addition of methylated amines and methanol, but not of H₂/CO₂, formate or acetate, to sediments slurries from basins of up to 12% salinity resulted in a rapid enrichment of methanogenic populations. Enriched methanogenic bacteria did not grow at salinities exceeding 15% or temperatures exceeding 45°C, and showed characteristics similar to those documented for Methanococcus halophilus and strain SF1 (DSM 3243). No enrichments were obtained from basins of more than 20% salinity in spite of methane being produced and evolved from those basins.     

Seedling recruitment in semi-natural pastures: the effects of disturbance, seed size, phenology and seed bank

We examined recruitment patterns in semi-natural pastures and their relationships to disturbance and species composition at different spatial scales (0.01 m² up to 4 m²) of both the vegetation and the seed bank. Possible associations between seedling recruitment and phenology were also studied. The study was performed in four pastures with different management history. Seedling recruitment was generally enhanced by disturbance, with the greatest effect for small-seeded species that germinate in the autumn. The local species-pool contributed to a large extent to seedling recruitment; 83 % of the recruited species were found in the vegetation, whereas 44 % of the recruited species were found in the seed bank. There were a total of 88 species found in the vegetation at different spatial scales; 61 % were recorded at the smallest spatial scale (0.01 m²). The area sampled at this scale comprised 1.25% of the area examined, indicating a small scale structuring of diversity in the pastures. The species number in the vegetation varied between 7 and 14 for the smallest scale (0.01 m²), and between 23 and 42 for the largest scale (4 m²), in the four pastures. The species number in the seed bank was less variable. Like most studies of perennial grasslands, we found no close correspondence between species distribution in the vegetation and in the seed bank. Two of the pastures had a joint management history and exhibited a close similarity of species in the seed bank, despite that one of the pastures was abandoned already in the beginning of this century.     

Genetic basis of variation of yield, and yield components in mungbean (Vigna radiata (L.) Wilczek)

Additive, dominance, and epistasis genetic basis of seed yield per plant, number of pods per plant, number of seeds per pod, and 1000 seed weight in mungbean (Vigna radiata (L.) Wilczek) have been examined, using Triple Test Cross (TTC) analysis. The material for TTC test was evaluated in two seasons i.e., kharif (July-October) and spring/summer (March-June), at the research station of the Nuclear Institute for Agriculture and Biology (NIAB), Faisalabad, Pakistan. Epistasis was present significantly for number of pods per plant and number of seeds per pod when grown in the spring/summer season (March to June). Partition of epistasis showed that additive x additive ('i' type) interaction was an important component of number of pods per plant, and number of seeds per pod was found to be of both types 'i' type, and additive x dominance, and dominance x dominance ('j' and 'l' type) interactions. This indicated that epistasis might be a non-trivial factor in the inheritance of pods per plant, and seeds per pod in mungbean. The expression of epistasis was influenced differentially by particular genotypes, indicating that a limited number of genotypes may not be sufficient to detect non-allelic interactions for a trait in mungbean. Additive and dominance genetic components were significant for all four traits in kharif season (July to October) but only for seed yield and 1000 seed weight in spring/summer season. This suggests that the genes controlling seed yield per plant, and 1000 seed weight are equally sensitive to the environment. The predominance additive gene action in those traits is not significantly influenced by epistasis, suggesting that improvement of the traits can be achieved through standard selection procedures.     

Short-term thermal acclimation induces adaptive changes in the inner mitochondrial membranes of fish skeletal muscle

In the oxidative muscles (musculi laterales superficiales) of crucian carp Carassius carassius acclimated for 6 weeks to either 5 or 25° C, the volume density and the surface density of fibres per tissue did not differ significantly between the control and experimental groups. The correlation ratio (μ²) for these values was below 50, 39·3 and 43·9 respectively. After acclimation to 5° C, the surface density of outer mitochondrial membrane per fibre increased significantly from 0·93 to 1·23m² cm⁻³ in the summer population but dropped from 0·94 to 0·67 m² cm⁻³ in the winter population. The surface density of outer mitochondrial membrane per mitochondrion increased from 3·24 to 4·52 m² cm⁻³ in summer fish. After acclimation to 25° C, the surface density of inner mitochondrial membranes per muscle fibre decreased from 4·04 to 1·79 m² cm⁻³ in summer fish and from 3·86 to 1·07 m² cm⁻³ in winter fish. The surface density of inner mitochondrial membranes per mitochondrion increased from 14·17 to 15·60 m²cm⁻³ in summer fish but dropped from 13·91 to 10·67 m² cm⁻³ in winter fish. Correlation matrices demonstrate a negative correlation of the surface density of outer mitochondrial membrane per mitochondrion with the volume density of mitochondria per fibre and temperature, suggesting cold-induced proliferation of small mitochondria. It was concluded that short-term cold acclimation increased surface area of the inner mitochondrial membranes in summer fish.