Effects Of Different Shading Treatments On Photosynthetic Characteristics And Flower Quality Of Paeonia Suffruticosa

The effects of different shading treatments (100%,65%,45% and 15% of full sunlight) on the photosynthetic characteristics (net photosynthetic rate-light response curves, Tr, Gs, Pn, Ci, pigment content, soluble proteins content, leaf areas, stomata density)and flower quality (the amount of flowers, the number of petals, the flower color, diameter and weight, the length of flowering shoots) were examined for six cultivars of Paeonia suffruticosa. The following results were achieved.The light-saturation point (LSP) and the light-compensation point (LCP) of the six cultivars of Paeonia suffruticosa under the full sunlight were quite high. The LSP were 1000～1200μmol/m2s and the LCP were 73～112μmol/m2s. With the reducing light intensity, the LSP and LCP of all cultivars decreased gradually. The net photosynthetic rate (Pn) of 'Fen Zhong Guan','Lan Bao Shi'and 'Zhu Guang Mo Run'under 65% sunlight were significantly higher than those under full sunlight, while the Pn of other three cultivars had no remarkable change. Under 45% sunlight the Pn of 'Ao Yang'and 'Zhu Guang Mo Run'were significantly higher than those under full sunlight, while the Pn of other four cultivars had no remarkable change. The Pn of all the cultivars under 15% sunlight were significantly lower than those under full sunlight. The content of total chlorophyll, chlorophyll a (Chla), chlorophyll b (Chlb) and carotenoid increased with light intensity decreased, while Chla/Chlb had no remarkable change.The contents of soluble proteins in leaves of 'Fen Zhong Guan', "Lan Bao Shi'and 'Ying Ri Hong' under 65% sunlight were higher than those under full sunlight, while the others lower. Under 45% sunlight it was higher for 'Fen Zhong Guan'than those under full sunlight but the others were lower. Except'Fen Zhong Guan', the contents of soluble proteins in leaves of other five cultivars under 15% sunlight were significantly lower than those under full sunlight.The leaf areas of all cultivars under 65% and 45% sunlight were much bigger than those under full sunlight. Under 15% sunlight the leaf areas of 'Ao Yang' and 'Zhu Guang Mo Run' were smaller than those under full sunlight, while the others were significantly bigger than those under full sunlight but lower than those under 45% sunlight. With the reducing light intensity, the stomata density of all cultivars decreased gradually.The flower diameter, weight and the amount of flowers of 'Ming Xing'under 65% and 45% sunlight were decreased, while the others were increased with more flowers. Except'Ming Xing', the flower quality of the others was improved. Under 15% sunlight, the flower diameter and weight, the amount of flowers and the number of petals of all cultivars were decreased. The color of petals of'Fen Zhong Guan'under 15% sunlight was changed from pink to light pink but it had no remarkable change for other cultivars under different shading treatments. The color of the spot at the base of the petals of 'Lan Bao Shi','Ming Xing' and'Ying Ri Hong' was light and more colorful.The evaluation results showed that'Ying Ri Hong'and'Zhu Guang Mo Run' got grade A,'Ming Xing' got grade D, the others got B under 65% sunlight. Under 45% sunlight,'Zhu Guang Mo Run'got grade A,'Fen Zhong Guan'and'Ming Xing'got grade C, the others got B. Under 15% sunlight, Ying Ri Hong'and'Lan Bao Shi'got grade E and the others got F.Summarizing all the results above, Paeonia suffruticosa was a sun plant with shade tolerance. Except 'Ming Xing', the net photosynthetic rate and the flower quality of the other five cultivars were improved under 65% and 45% sunlight, but both were worsened under 15% sunlight.