Effects of different treatment durations on leaf photosynthesis in Populus yunnanensis plantlets under different stresses.

(A) F_v/F_m images (bottom). The pseudocolor code depicted at the bottom of the image ranges from 0 (red) to 1.0 (purple). The experiment was replicated three times with similar results. One representative result is shown. (B) Average F_v/F_m values. F_v/F_m was determined for whole leaves exposed to different treatments. Data represent the means of five replicate experiments (± SE). Means labeled with different letters were significantly different according to Tukey's test (P<0.05). (C) Electron transport rates determined after different durations of exposure to heat and drought stress. The data represent the means of five replicate experiments (± SE).