Table I.

The effect of photoperiod and temperature on freezing tolerance of birch leaves

ConditionCont1 d2 d4 d7 d14 d
LT50
SD−2.5 ± 0.21−3.4 ± 0.25−4.5 ± 0.31−5.9 ± 0.28−6.4 ± 0.35−7.1 ± 0.6
LT−2.5 ± 0.21−4.7 ± 0.28−6.8 ± 0.54−10.5 ± 0.47−11.6 ± 0.53
SD + LT−6.4 ± 0.35−9.6 ± 0.65−12.0 ± 0.73−14.8 ± 0.66−15.8 ± 0.84
  • Birch seedlings were exposed to SD length (12 h light) for 7 d; LT in LD condition (4°C, 24 h light) for 7 d and SD for 7 d followed by LT (4°C) for 7 d. The freezing tolerance (LT50) of leaves (means ± se) was measured by ion-leakage test (Sukumaran and Weiser, 1972).