Abstract:

This study investigated effects of shading on the photosynthesis, and other physiological and biochemical characteristics of tree peony (luoyanghong). The result showed: Under the natural full sunshine the net photosynthesis（P_n）of tree peony had a midday depression during 10:00—14:00. F_v/F_m and Φ_PSⅡ were both decreased to the lowest point at noon. The contents of MDA and O₂ were higher, while the activity of SOD and POD, the content of total chlorophyll, relative content of chlorophyll b, total hydroxybenzene, flavonoid and glutathione were all lower than that under the condition of 30% shading. Under the condition of 30% and 50% shading the phenomenon of “midday depression” did not occur, and the F_v/F_m and Φ_PSⅡ both had a smaller decline at noon, the content of total chlorophyll and the relative content of chlorophyll b was both the higher in comparison with the full sunshine condition. P_n maintained a higher level all day under the condition of 30% shading, and the content of total hydroxybenzene, flavonoid and glutathione was all the highest among the four treatments. Under the condition of 80% shading P_n had the lowest level all day, the activity of SOD and POD was both the lowest, the content of total hydroxybenzene, flavonoid and glutathione were also the lowest, and the content of MDA was the highest. It is concluded that tree peony would grow best under the condition of 30% shading in terms of the above comparisons.

Key words: tree peony, shading, photosynthetic characteristics, antioxidative enzyme