© 2004 Heron Publishing—Victoria, Canada
Effects of temperature and nutrient availability on plasma membrane lipid composition in Scots pine roots during growth initiation
Sari Iivonen (1), Pekka Saranpää (2), Marja-Liisa Sutinen (3) and Elina Vapaavuori (1, 4)
1. Finnish Forest Research Institute, Suonenjoki Research Station, Juntintie 40, 77600 Suonenjoki, Finland / 2. Finnish Forest Research Institute, Vantaa Research Center, P.O. Box 18, 01301 Vantaa, Finland / 3. Finnish Forest Research Institute, Rovaniemi Research Station, P.O. Box 16, 96301 Rovaniemi, Finland / 4. Corresponding author (Elina.Vapaavuori@metla.fi) / Received March 4, 2003; accepted August 20, 2003; published online February 2, 2004
Summary
We studied the effects of root zone temperature (RZT) and nutrient availability on free sterols and phospholipids in the plasma
membrane (PM) and on PM-ATPase activity in roots of 1-year-old Scots pine (Pinus sylvestris L.) seedlings during growth initiation in the spring. Seedlings were grown for 6 weeks in hydroponic cultures with low (0.5
mM N; LN) or high (3 mM N; HN) nutrient availability. The root zone was subjected to slow warming (SW) and fast warming (FW)
treatments while maintaining similar air temperatures in both treatments. Decreases in the amount of phospholipids and in
the phospholipid/free sterol ratio, an increase in the degree of saturation of phospholipid fatty acids and changes in free
sterol composition were observed during root growth initiation. Changes in lipid composition of the PM associated with the
cold deacclimation process were detected at RZTs above 9 °C. Nutrient availability affected the lipid composition of the PM
only when RZT was increased slowly. When RZT increased from 4 to 6 °C in the SW treatment, the degree of saturation of phospholipid
fatty acids decreased, especially in HN seedlings. The sitosterol/stigmasterol ratio remained higher in HN seedlings than
in LN seedlings. After an RZT of 9 °C had been reached in the SW treatment, HN caused increases in the saturation of phospholipid
fatty acids and root PM-ATPase activity, and a decrease in the phospholipid/free sterol ratio. Possible effects of changes
in PM lipid composition on root growth and PM-ATPase activity are discussed.
Keywords:
fatty acids, free sterols, nutrient availability, phospholipids, Pinus sylvestris, root PM-ATPase activity, root zone temperature.
