Studies On Photosynthetic Characteristics Of Herbaceous Peony

Paeonia lactiflora, a famous traditional flower in china, has a high ornamental and medicinal value, So far, Studies on ornamental Herbaceous peony has mainly focused on cultivar classification, seedling propagation and flowering time regulator and so on, while seldom on plant physiology and ecology. By the portable photosynthesis system (LI-6400), The effects of net photosynthetic rate (Pn) in Herbaceous peony leaves on photosynthetically active radiation and CO2 response, the relationship between Pn, transpiration rate(Tr) of Herbaceous peony leaves and physio-ecological factors, the changes of SPAD and Pn value of Herbaceous peony leaves during the development process of buds were studied. The main results were as follows:1. Pn value of three cultivars of P. lactiflora increased rapidly with the rise of PAR between 0 and 500μmol·m-2·s-1, and then slowly after that. there were differences between cultivars. Light saturation point, light compensation point and maximum net photosynthetic rate of'Huang Jin lun'were the highest, which were 1160μmol·m-2·s-1, 24μmol·m-2·s-1,and 18.96μmol·m-2·s-1, respectively. Those of'Da Fugui'took the second place and'YangFeichuyu'were the minimum. The apparent quantum efficiency (AQY) of'YangFeichuyu'was the highest, followed with'Da Fugui'the second, and'Huang Jin lun'was the minimum. The CO2 saturation point of'YangFeichuyu','huang jin lun'and'Da Fugui'ranged from 900 to 1253μmol·mol-1, the CO2 compensation point of them ranged from 50.12 to 56.8μmol·mol-1 . The carboxylation efficiency (CE) of the three cultivars ranked in the order of'Huang Jinlun'>'Da Fugui'>'Yangfeichuyu'.2. Pn value conformed to the quadratic equation curve with photosynthetically active radiation(PAR), air temperature(Ta), leaf temperature(Tl)and relative humidity (RH) , respectively.but the relationship between Tr and PAR, Ta , Tl as well as RH was linearty respectively. Multiple regression analysis showed that the most important factors effected on Pn and Tr were PAR together with RH. Quadratic equation can be fitted between Pn and stomatal conductance (Gs), Linear equation can be fitted between Pn and intercellular CO2 concentration(Ci), Tr and Gs, Tr and Ci, respectively.3.Leaf area enlarged with the development of flower bud and reached the maximum on the 30th day of squaring period, which was 3 times as those in the initial stage of squaring period. Leaf area of two cultivars ranked in the order of basal leaves > middle leaves > top leaves at the initial stage, but the middle leaves became the highest at the terminal stage. SPAD value of leaves increasd greatly within the initial 10 days, and increasd a little after that.The SPAD value of'Da Fugui'leaves in different leaf position was higher than that of'HongYanzhenghui'. In the initial stage of squaring period, the higher position of the leaves were, the lower the SPAD value were. but after 10 days of the appearance of bud, the higher position the leaves were, the higher the SPAD value were. with the development of the leaves, Pn value of leaves in different position rose all straightly, and about 3 times in 30d as in the initial stage.The Pn value in'Da Fugui'was always higher than that in'HongYanzhenghui'.