Current issue: 55(3)
Under compilation: 55(4)
Seasonal fluctuations in free polyamines, spermidine, spermine, putrescine and potassium concentrations were studied for two years (1992–1993) in three needle years of Scots pine (Pinus sylvestris L.) grown on a drained mire in western Finland. Seven different fertilizer treatments involving five different sources of potassium were used.
Putrescine concentrations were high in winter and in May but low in summer. High peaks in putrescine in March and May could be found in unrefertilized or rock phosphate treatments. Spermidine and spermine concentrations were high in March and May. In December spermine concentrations were low. Biotite increased the needle potassium concentrations less than the other potassium fertilizers but the putrescine concentrations or the putrescine/spermidine ratio to about the same level. This suggests that biotite, although very slowly soluble, can reasonably satisfy potassium nutrition of young pine trees.
The potassium concentrations of needles in all the fertilization treatments were higher in winter than in summer. The response of putrescine to the potassium concentration was strongly negative in all the needle years and sampling times. In March, May and December the response of putrescine to potassium was fairly similar in both years but not in June and August. The results suggest that the potassium concentrations during the growing season cannot be used for estimating the potassium nutrition of trees, because the variation between the years may be substantial, whereas the needle putrescine concentration or putrescine/spermidine ratio indicates the suboptimum potassium status of Scots pine fairly well. Needle putrescine concentrations over 500 nmol g-1FW quite regularly coincided with a unsatisfactory potassium nutrition and concentrations over 1,000 nmol g-1FW were a reliable indication of potassium deficiency. Putrescine/spermidine ratios below 5 indicated a satisfactory potassium nutrition in all needle years throughout the year.