Publications

NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.

1991

Abstract

A study on the effects of eight years application of artificial acid rain on the vegetation and soil in an old Scots pine forest is described. Artificial rain of pH 2.5 and 3.0 caused severe damage to mosses, especially Pleurozium schreberi and Dicranum polysetum. The presence of Melampyrum pratense decreased drastically in plots treated with rain of pH 2.5 and 3.0. In Vaccinium myrtillus reduced leaf production was found in plots treated with rain of pH 2.5. A considerable decrease in base saturation had taken place in plots treated with pH 2.5 and pH 3.0 rain. Exchangeable calcium and magnesium in particular had been reduced, and the content of mangnesium in tissue of Vaccinium myrtillus appeared also to be reduced in plots treated with water of pH 2.5. The study demonstrates the need for better methods in evaluating vegetation responses in field studies. The use of visual cover recording should be supplemented by frequency analysis and harvesting methods to get better estimates of changes in vegetation structure.

Abstract

Effects of various partial pressures of oxygen (5, 20 and 45 kPa) and carbon dioxide (0.03 and 6 kPa) on initiation, proliferation and maturation of somatic embryos in Picea abies were studied. The pO2 had a significant effect on the initiation of embryogenic tissue from mature zygotic embryos. However, the effect of pO2 was dependent on the strength of the basal medium.Low pO2 stimulated the formation of embryogenic tissue when the zygotic embryos were incubated on full strength medium, but was inhibitory when half-strength medium was used.Proliferation of embryogenic tissue was stimulated by higher partial pressures of both CO2 and O2. The effect of the gas phase on maturation of somatic embryos varied between different cell lines. However, there was a general tendency for 5 kPa O2 and 6 kPa CO2 to stimulate maturation.

Abstract

Seedlings of four populations from the two mentioned species were grown for 6 weeks in varying temperature, light and daylength. In accordance with earlier studies there was a strong latitudinal effect on the critical daylengths for growth. There was also a weaker, but significant effect due to altitude. Large differences were also found in growth pattern and compensation mechanisms. Fast-growing lowland populations reacted to low light levels and high temperatures by increasing their shoot/root ratios and the temperature optimum for shoot elongation. In mountain birch from Kevo, northern Finland, plants reacted to increasing temperatures by increasing their net assimilation rates. The shoot/root ratios and leaf area ratios were highest at the early stages of growth while maximum net assimilation occurred later. This illustrates the high priority in birch for leaf growth. In all populations except the northern population the plants grew better in alternating day and night temperatures than at the corresponding constant temperature.

Abstract

Selenium is determined in copper and nickel materials without any interferences. Hydrochloric acid plus hydrogen peroxide are used to dissolve the samples. The solution is then made alkaline with sodium hydroxide in order to eliminate the interference from copper and nickel by precipitation of the corresponding hydroxides. Sodium tetrahydroborate is added to the alkaline solution in order to reduce selenium(IV) to the selenide ion, and the solution is then filtered. The volatile selenium hydride is generated by acidification of the alkaline solution in a continuous flow system. The method was used successfully for the determination of selenium in three standard reference materials (SRMs) from the National Institute of Standards and Technology: SRM 398 Unalloyed Copper V, SRM 671 Nickel Oxide 1 and SRM 875 Cupro-Nickel, 10 (CDA 706) (doped). The detection limit of the method was approximately 1-mu-g g-1.