Scots pine seedlings were exposed to three different potassium availability levels under steady-state nutrition in three computer controlled growth units. The relative addition rates of K were 2, 4 and 6 %. The daily temperature was 22/20°C (day/night) and the daily light period 20/4 hours with photon flux density of 400 mol/m2/s. The relative growth rate per day, K and N concentrations and polyamines were determined from the seedlings at certain intervals during a ten-week growth period.
Needles and roots were collected for light and electron microscopical studies. Morphometric measurement will be made with the image analyser and the cell structure will be studied at the ultrastructural level.
The growth rates of the seedlings at the end of the experiment were 4.7 %, 5.4 % and 5.8 % at 2, 4 and 6 % K levels, respectively. Potassium concentrations in the needles at different K levels were 2.0, 3.8 and 6.8 mg/gDW and in the roots 1.6, 2.5 and 8.2 mg/gDW. Putrescine concentrations were higher at the lower K levels being 710.6, 502.3 and 176.5 nmol/gFW in the needles at 2, 4 and 6 % K levels. Spermidine and spermine concentrations were higher at the higher K levels.
Earlier results show that it is possible to separate structural characteristics of the needles at different K levels from Scots pines growing on drained peatland. Now we are comparing the results from adult trees in the field with those from the seedlings grown under controlled conditions.
The interactions between the growth rate, K concentrations, polyamines and structural characteristics will be discussed.
Key words: Scots pine, potassium deficiency, relative growth rate, needle structure, polyamines.
Correspondence: Anne Jokela, University of Oulu, Department of Botany, FIN-90570 Oulu, Finland
Telefax: +358-81-5531500
E-mail: anne.jokela@oulu.fi