Figure 2.
Changes of Chl fluorescence parameters during temperature treatment. Leaf discs were floated on the surface of temperature-controlled cyclic water bath with the epidermal side upward, and treated at indicated temperatures (25°C, 42°C, or 4°C) for the indicated time (1 h, 3 h, or 6 h) under illumination of about 100 μmol photons m−2 s−1. They were dark adapted at the corresponding temperatures for 10 min. Chl fluorescence was then measured at the same temperature using a PAM emitter-detector unit 101 ED as described in “Materials and Methods.” Values for Fv/Fm = (Fm − F0)/Fm (A) and ΦPSII = (Fm′ − F)/Fm′ (B) are the averages of four independent measurements. Standard errors are indicated by the vertical bars.