Mechanical stress during dormancy stimulates stem growth of Scots pine seedlings

Abstract

The effects of mechanical stress imposed during dormancy on stem growth were examined in 5-year-old Scots pine ( Pinus sylvestris L.) seedlings. The treatments were different degrees of manual bending, which were executed in freezing-storage (−6°C). After thawing, seedlings were reactivated and grown in a climate chamber for 8 weeks. Bending promoted a statistically significant increase in xylem width at the point of bending, but had no effect on tracheid width, indicating that the increase in xylem width was caused by a faster rate of tracheid production. The results show that Scots pine seedlings record mechanical stress during their dormant period, and respond to this during the following growth period. The ecological and silvicultural significance of this response is breifly discussed.