GROWTH, POTASSIUM AND POLYAMINE CONCENTRATIONS OF SCOTS PINE-SEEDLINGS IN RELATION TO POTASSIUM AVAILABILITY UNDER CONTROLLED GROWTH-CONDITIONS

Scots pine (Pinus sylvestris L.) seedlings were grown under controlled growth conditions with three relative addition rates (2, 4 and 6% RAR per day) of potassium. The relative growth rate (R(G)) of the seedlin gs, and the potassium, nitrogen, phosphorus and free polyamine concent rations of the needles and roots were measured during the growth perio d. Visible symptoms of potassium deficiency developed in the needles a t the lowest potassium level after 6 weeks. Although the needle potass ium concentrations and the relative growth rate correlated positively, the decrease in potassium from the highest K level (6% RAR) to the me dium one (4% RAR) affected only slightly the relative growth rate per day, which decreased from R(G) 5.8% to 5.5%. At the same time putresci ne accumulated in needle and root tissues. A clear decrease in the rel ative growth rate from R(G) 5.5 % at the 4% RAR level to R(G) 4.7% at the lowest 2% RAR level coincided with the high putrescine concentrati ons and low spermidine and spermine concentrations of the needles at t he 2% RAR level. The spermidine and spermine concentrations of the roo ts were lower than in the needles and at about the same level in all t he treatments. These results show that the putrescine concentrations i ndicate the potassium status of the seedlings and that spermidine and spermine may be involved in changes of the growth rate of the Scots pi ne seedlings under varying potassium nutrition.