DOES AVAILABILITY OF POTASSIUM AFFECT COLD HARDENING OF SCOTS PINE THROUGH POLYAMINE METABOLISM

The effect of different potassium availability on the polyamines and f rost resistance of Scots pine seedlings (Pinus sylvestris L.) during c old hardening was studied. Scots pine seedlings were grown applying di fferent rates of potassium by using the relative addition rate techniq ue followed by a 2- or 9-week hardening period with decreased light in tensity, day length and temperature. After 2 weeks of treatment the se edlings were not hardened (LT(50) approximate to -11 degrees C) and sh owed no differences in frost resistance, although differences in the p olyamine levels between the K levels were observed. After 9 weeks of h ardening the seedlings at the low, medium and high K levels showed a m ean frost resistance (LT(50)) of -81, -63, and -47 degrees C, respecti vely. A negative effect of K on the frost resistance of the needles wa s also found in adult trees in September. The results indicate that at the early stage of cold hardening, potassium or free polyamine levels do not affect the frost resistance of Scots pine needles. However, in hardened seedlings and adult trees potassium displays a negative and putrescine a positive correlation with frost resistance, whereas sperm idine and spermine show no correlation.