S. Iivonen et al., Responses of Scots pine (Pinus sylvestris) seedlings grown in different nutrient regimes to changing root zone temperature in spring, TREE PHYSL, 19(14), 1999, pp. 951-958
We examined effects of nutrient availability and changing root zone tempera
ture (RZT) on growth, gas exchange and plasma membrane H+-ATPase (PM-ATPase
) activity of roots of 1-year-old Scots pine (Pinus sylvestris L.) seedling
s during spring flushing. The 6-week growth-chamber experiment was carried
out in hydroponic cultures that supplied the seedlings with low (0.5 mM N)
or high (3 mM N) nutrient concentration and two rates of increase in RZT we
re simulated: slow warming (SW-treatment) and fast warming (FW-treatment).
Air temperature, humidity, and light conditions were similar in all treatme
nts. Growth of roots and shoots was retarded at low RZT, and fresh mass inc
rement of roots was closely correlated with RZT sum. High nutrient availabi
lity increased nitrogen concentrations of needles and stems, but only at RZ
Ts >13 degrees C, Low RZT and low availability of nutrients suppressed as e
xchange of the seedlings. Real PM-ATPase activity was highly dependent on R
ZT. At high RZTs, real PM-ATPase activity was affected by nutrient availabi
lity but this effect was related to root growth. We conclude that, under co
nditions of high nutrient availability, Scots pine seedlings can compensate
for the suppressive effects of long-term exposure to low RZT by rapidly ac
celerating growth, gas exchange and root metabolism, but only when RZT has
increased above a threshold value, which was 13 degrees C in this study.