Wintertime changes in the ultrastructure and metabolism of the microsporangiate strobili of the Scotch pine

Terminal buds of Pinus silvestris L. containing microsporangiate strobilus primordia were collected once a month throughout the winter. The electron microscopic studies indicated that in October and December, the cells of the strobili contained a large number of vacuoles, a portion of which was supposedly autophagic, and stacked rough endoplasmic reticulum. By February, the amount of these had decreased, and instead, a large population of dense bodies was visible. Additional phenomena, characteristic at this state, were the occurrences of highly uneven contours of the plasmalemma and of inclusions of various kinds between the plasmalemma and the cell wall. In March, autolysis was visible in a portion of cells outside the sporangia. In the sporangia the ground cytoplasm was thin but the number of organelles was increasing. In the April collections, cell divisions were visible. The amount of protein per dry weight increased during the winter reaching a peak in February. The activity of RNases, having optima of pH 5.0 and pH 7.5, was measured in two successive years. Both series showed a period of high activity during the middle of the winter. The exact timing of this period depended on the year in question. On the basis of these observations, the dormant period of the microsporangiate strobili of the Seotch pine is divided into three sub-periods. It is also suggested that the definition of dormancy of these structures should include a mentioning of alterations in the metabolical machinery of the cells.Abbreviations CH chromosome - CW cell wall - D dictyosome - ER endoplasmic reticulum - L lipid spherule - M mitochondrion - N nucleus - NE nuclear envelope - P plasma membrane - Pp proplastid - RER rough ER - V vacuole     

Organogenesis and fine structure in megagametophyte callus lines of Picea abies

Differentiation and fine structure were studied in 63 callus lines originating from the haploid megagametophyte of Picea abies (L.) Karst. Developing cones were collected from 27 trees growing in 13 localities in Finland. Vernalization of cones for 12–42 days at 4°C was optimal for callus initiation from the immature megagametophyte (primary endosperm). Five combinations of media based on the macronutrient elements of Chu et al. (1975; Sci. Sin. 18: 659–668) and the micronutrient elements and vitamins of Murashige and Skoog were tested for callus induction, growth and differentiation. Only about 1.5% of the megagametophytes produced subculturable callus (which may be partly due to the high frequency of lethal genes), although in certain mother trees callus production was as high as 20%. In most of the trees sampled, polyamines could not replace casein hydrolysate and glutamine in induction of megagametophyte callus. About half of the originally haploid, diploid and mixoploid callus lines were able to differentiate. A combination of three polyamines (putrescine 0.25, spermidine 0.1 and spermine 0.025 m M ) favoured development of roots. In five callus lines shoots and roots developed in the same piece of callus, but these organs usually had no connection with each other. The fine structure of the callus cells was normal, but their starch stores were rather abundant. Mesophyll cells of needles differentiated from originally haploid callus had chloroplasts with fairly well-developed grana. Secondary metabolites were observed in the vacuoles of some callus cells and in organ initials. Plasmodesmata were very rare in callus cells but they were characteristic of those of the needles. The electron microscope observations showed that the poor capacity for differentiation of P. abies callus cultures was not due to cytological instability.     

Home ranges and densities of medium-sized carnivores in south-east Finland, with special reference to rabies spread

Home ranges and densities of medium-sized carnivores were studied in south-east Finland by radio tracking. The species studied included potential vectors of rabies: the raccoon dogNyctereutes procyonoides (Gray, 1834), red foxVulpes vulpes (Linnaeus, 1758), European badgerMeles meles (Linnaeus, 1758) and domestic catFelis silvestris catus (Schreber, 1777). Home ranges of badgers were largest (mean 14.7 km²) and those of cats smallest (1.5 km²). Home ranges overlapped largely, both within and between species. Most home ranges were larger and population densities lower in south-east Finland compared with those in Western Europe. The pooled density of medium-sized carnivores with overlapping home ranges was, however, high, which may indicate a high risk of a rabies epizootic in this multi-host community. Rabies might also spread rapidly to new areas, because of the large home ranges and, consequently, long dispersal distances.     

Habitat impact on raccoon dogNyctereutes procyonoides home range size in southern Finland

Monogamous canid home range size is often negatively correlated with population density. Home range size, in turn, may be affected by the habitat. Here we examined landscape features that may affect home range size of the invasive raccoon dogNyctereutes procyonoides (Gray, 1834), an important vector of diseases and parasites in Europe. The aim was thus to reveal the habitats where population density and the risk for epizootics is highest. We radio tracked 42 raccoon dogs in three areas in southern Finland between 2001 and 2007. There was an inverse relationship between home range size and the proportions of meadows and gardens, as well as habitat richness. Also mixed forests were more common in areas where home ranges were small. The risk for epizootics, such as rabies, is thus highest in areas which constitute of a mosaic of small patches of meadows, gardens and mixed forests. The preventive measures, such as bait vaccinations, against epizootics should therefore be concentrated in these areas which are mainly in and around villages.     

The chemical character and burial of phosphorus in shallow coastal sediments in the northeastern Baltic Sea

The chemical composition and vertical distribution of sediment phosphorus (P) in shallow coastal sediments of the northeastern Baltic Sea (BS) were characterized by sequential extraction. Different P forms were related to chemical and physical properties of the sediments and the chemistry of pore water and near-bottom water. Sediment P composition varied among the sampling sites located in the Archipelago Sea (AS) and along the northern coast of the Gulf of Finland (GoF): the organic rich sites were high in organic P (OP), while apatite-P dominated in the area affected by sediment transportation. Although the near-bottom water was oxic, the sediments released P. Release of P was most pronounced at the site with high sediment OP and reduced conditions in the sediment-water interface, indicating that P had its origins in organic sources as well as in reducible iron (Fe) oxyhydroxides. The results suggest that even though these coastal areas are shallow enough to lack salinity stratification typical for the brackish BS, they are vulnerable to seasonal oxygen (O₂) depletion and P release because of their patchy bottom topography, which restricts mixing of water. Furthermore, coastal basins accumulate organic matter (OM) and OP, degradation of which further diminishes O₂ and creates the potential for P release from the sediment. In these conditions, an abundance of labile OP may cause marked efflux of P from sediment reserves in the long-term.     

Habitat preferences of the native badger and the invasive raccoon dog in southern Finland

We compared the habitat preferences of the alien raccoon dog Nyctereutes procyonoides (Gray, 1834) and the native badger Meles meles (Linnaeus, 1758) in two areas (Ruissalo and Tuulos) in southern Finland by radio-tracking the animals during summer from 2005 to 2008. We assumed that the habitat preferences of these two medium-sized carnivores differ to some extent (ie they are able to share the resources), because they have been sympatric for more than 50 years in southern Finland and populations of both species have increased during that period. The results indicated that the habitat preferences of these species are indeed different: raccoon dogs favoured meadows, gardens and open woodlands with tall and abundant undergrowth, whereas badgers favoured both pine forests and deciduous and mixed forests with thick canopy but sparse undergrowth. However, fields were favoured by both species in one study area (Tuulos). The results show that although both species are flexible in their habitat use and share some habitat preferences, the most favoured habitats differ between the species.     

Electron microscope observations on the differentiation of protocorm cells of Dactylorhiza maculata

The fine structure of aseptically cultivated protocorm cells of Dactylorhiza maculata (L.) Sod was studied with special reference to differentiation of leaf cells. In the young protocorm the characteristic structures are compound amyloplasts and smooth ER. In the older, the green shoot pole contains many proplastids storing starch, some membrane–bound protein crystalloids and lipid droplets attached to the nuclear membrane and plasmalemma. In the leaves of the young seedling, two types of chloroplasts are found. One contains little or no starch but many osmiophilic plasto–globuli; the other has only a few plastoglobuli but a large starch grain.