Abstract: The authors have measured in situ daily changes in photosynthe-tic rate, its responses to quantum flux density, and CO2 compensation points of wheat plants (Triticum sativum L. c. v. "Fengmai 13" ) grown at both altitude localities of 840m (lowland) and 2150m (highland) during seedling, elongation, heading and early filling stages, respectiyely. The results showed that the feature of daily variation in photosynthetic rate during early growth (seedling and elongation) stages is contrary to that during later growth (head- ing and early filling) stages. During early stages, the photosynthetic rate of winter wheat grown at lowland is higher than at highland. During later stages, on the contrary, the photosynthetic rate of winter wheat grown at highland is higher than at lowland. At the same time, the light saturation point of both

Key words: Winter wheat