FIGURE 1.

Chlorophyll a fluorescence transient of dark adapted leaves exposed to combination of cold stress and elevated CO₂ in wheat. (A) Fluorescence intensity on logarithmic time scale; (B) Variable fluorescence F_t–F_o to the amplitude F_I–F_o; (C) Ratio of variable fluorescence F_t–F_I to the amplitude F_P–F_I. Abbreviations of treatments are explained as followed: EN, elevated CO₂ + normal temperature; AN, ambient CO₂ + normal temperature; EL, elevated CO₂ + low temperature stress; AL, ambient CO₂ + low temperature stress.