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

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.

Abstract

The Eurasian sprucc bark beetle, Ips typogaphus carries spores of several fungi induding Ophiostoma bicolor, O. pellicillatum and O. polonicum. However, after attack on Norway spruce trees O. polonicum is the pioneer invader of the sapwood while other species follow. To determine the causes behind this distinct succession experiments were performed comparing growth rate, tolerance to oxygen-deficient conditions and to spruce resin between these early invaders. In sealed tubes with limited oxygen. O. polonicum grew for a longer time than three other species regularly associated with I. typagraphus in Norway. The non-volatile components of lesion resin induced by fungal attack, as opposed to preformed resin, inhihited the growth of all species, but partirularly O. polonicum. O. polonicum grew rapidly on malt agar, but not faster than some of the other species associated with I. typographus. It is concluded that rapid growth and the abilily lo tolerate low oxygen pressure are important attributes for primary invaders, allowing tree resistance mechanisms to be overcome following mass inoculation.