Photosynthetic Physiology Of Peony Under Different Light Conditions

Photosynthesis is the physiological function of green plant and the basis of the plant growth. Studying the photosynthetic characters of peony in natural field can not only supplement the physiological research of peony, but also provide theoretical basis for cultivation. Five varieties in natural field were used as materials to study the diurnal variations and seasonal variations of photosynthetic parameters. Then the effects of different light conditions on the photosynthetic parameters and chlorophyll fluorescence parameters were examined. We expected to comprehensively analysis the photosynthesis of peony and find out the optimal way of cultivation. The main results were as the followings:1. The diurnal variations of peony was inerratic, it indicated higher at AM and lower at PM. The highest Pn occurred at 9:00 to 10:00 AM. The Pn of five varieties was different:(1)It indicated a double peak curve and had ‘midday depression' phenomenon of ‘Hongyan Zhenghui', ‘Zhushapan' and ‘Zifengyu'; the highest Pn was 10.1?9.1 and 10.9 ?mol·m-2·s-1;(2)‘Fenyunu' and ‘Qiaoling' showed a single peak curve and the highest Pn was 8.4 and 10.9?mol·m-2·s-1.2. The seasonal variations of peony was also inerratic, it indicated “climb up and then decline”. In April and May, the Pn increased quickly and in June, it was maximized. In July and August, it decreased and in September, it bottom out. However, the decline of five varieties was different:(1)The Pn of ‘Hongyan Zhenghui', ‘Zhushapan' and ‘Zifengyu' were higher in July and August;(2)The Pn of ‘Fenyunu' and ‘Qiaoling' decreased very serious and the above ground part was presenile.3. The LCP of peony was between 25 and 53 ?mol·m-2·s-1 and the LSP was between 700 and 1100 ?mol·m-2·s-1 which indicated peony belongs to heliophyte. The LCP and LSP were different among five varieties:(1)The LSP of ‘Hongyan Zhenghui', ‘Zhushapan' and‘Zifengyu' was between 900 and 1100 ?mol·m-2·s-1;(2)The LSP of ‘Fenyunu' and ‘Qiaoling'was 700 ?mol·m-2·s-1. Under nature condition, the PAR was easy higher than the LSP of‘Fenyunu' and ‘Qiaoling', so the Pn was decreased.4. The Fv/Fm was between 0.675 and 0.742 at noon, it was inferior to 0.832. That said photoinhibition happened. The PS ? of the leaf which suffered from photoinhibition was irreversible destroyed and the photosynthetic apparatus would be destroyed too.5. Shading treatment made the Pn and the content of soluble sugar decreased in May and it made them increased in June. In autumn, shading could make the ground part remained. So,shading treatment should process in summer and autumn and under the condition of 30 %shading, the Pn and the content of soluble sugar were highest.6. Shading treatment made the amplitude decreases of Fv/Fm reducing. Under the condition of full sunlight, Fv/Fm was between 0.675 and 0.742, under the condition of 30%shading, Fv/Fm was between 0.697 and 0.765, under the condition of 60%shading, Fv/Fm was between 0.745 and 0.811. Shading treatment effectively slow down the photoinhibitionh.