Table I.

Impact of temperature-stress on Chl a fluorescence

Pea plants were grown for 12 d in cool-white fluorescent light (70 μmol photons m−2 s−1) and subsequently transferred to heat stress (40°C) or chill stress (7°C) for 24 and 48 h. Leaves were dark adapted for 20 min before the measurement of their minimal fluorescence (F0) and maximum fluorescence (Fm). For recovery, after 48 h of stress treatment, plants were transferred to 25°C and kept for 24 h in light (70 μmol photons m−2 s−1). Values are mean of six measurements, and ± represents sd.

Treatment Temperature24 h48 hRecovery at 25°C
F0FmFv/FmF0FmFv/FmF0FmFv/Fm
7°C0.253 ± 0.021.08 ± 0.80.765 ± 0.020.262 ± 0.021.04 ± 0.060.748 ± 0.010.270 ± 0.021.174 ± 0.040.792 ± 0.01
25°C0.240 ± 0.011.18 ± 0.070.796 ± 0.020.280 ± 0.011.09 ± 0.060.743 ± 0.010.268 ± 0.021.136 ± 0.040.764 ± 0.01
40°C0.282 ± 0.010.805 ± 0.010.649 ± 0.010.359 ± 0.010.689 ± 0.060.478 ± 0.040.320 ± 0.020.752 ± 0.030.574 ± 0.04