| Photosynthetic characteristics and growth indexes of Paeonia suffuticosa 'Danjing Hong 2 'and 'Hongdan Lan 1' were studied comparatively. It was aimed to clarify the growth laws of Tianpeng Tree Peony and create environmental conditions which satisfied with the development of Tree Peony. Theerfore, photosynthetic ability was improved and accumulation of photosynthetic products was increased. At the same time we expected to provide theoretical foundation for cultivating the Tree Peony scientifically and producing industrialization.The main results were as follows:1. With the increase of shading degrees, the size of tree height, crown width, area of a terminal leaf and the petiole lengths ascend. The rate of ascend was 75%>50%>25%>0.2. The diurnal variation of Tianpeng Tree Peony was inerratic. The curve of diurnal variation of net photosynthetic rate (Pn) was demonstrated single peak in spring with a peak of photosynthesis at about 10:00 o'clock, and the rate of net photosynthetic was 0>25%>50%>75%. Meanwhile, The curve of diurnal variation of Pn was demonstrated two peaks in clear days in summer, with appeared midday depression of photosynthesis and the rate of net photosynthetic was 50%>25%>0>75%. Compared with CK, the treatment of shading conquered midday depression of photosynthes. Therefore, shaded treatment in summer could prevent or abate photoinhibition and enhanced photosynthetic ability, prolonged the function period, slowered senescence, so that it favored cultivation of strong sprout and could be regarded as a routine measure of Tianpeng Tree Peony.The effect of shading PAR 50% was beter than the other treatment.3. The photosynthetic characteristics of Tianpeng Tree Peony was demonstrated seasonal variation obviously. The environmental stations in spring, duration from farming functional leaves to the earlier stage of bud inducement, such as light, temperature and air humidity, were suitable to the growth and development of Tianpeng Tree Peony. So photosynthetic ability was high and accumulated more photosynthetic products. In summer, high temperature and strong sunlight made Tianpeng Tree Peony in temporary dormancy state, only to photosynthetic ability reduced and photoinhibition occurred obviously. In autumn, photosynthetic ability rose with the improvement of the environment firstly, then decreased gradually as the senescence of the leave.4. The seasonal variation of Pn indicated that early in the growth with the increase of shading degrees, the Pn reduced gradually, and the peak point occurred in May. The value of Pn in 25% was highest. In summer, shading PAR 50% and 25% were significantly greater than 0%. The average of Pn was 50%>25%>0%>75%. In late August, the value of Pn in shading PAR 75% was highest. With the increase of shading degrees, the Chla, Chlb,total Chla and Car content increased, but Chla/Chlb decreased at the same time.5. The shading made the specific leaf mass decrease and the content of soluble sugar, soluble proline also declined. The decrease of soluble sugar content resulted in decrease of anthocyanin content, and the effect of shading PAR 25% was minimum. In summer, the moderate of shading (shading PAR 50%) resulted in the increase of soluble sugar, soluble praline content and it associated with the phenomenon which Pn maintained at high levels, because the treatment of shading conquered midday depression of photosynthes.6. The variation tendences of photosynthetic characteristics on Paeonia suffruticosa 'Hongdan Lan 1' and 'Danjing Hong 2' were similar, but the change ranges to some extent were different. They have similar seasonal and diurnal variation. However, the photoinhibition and midday depression of photosynthesis of the later under high temperature and strong sunlight in summer were lighter. So that it kept high photosynthetic ability in the anaphase of growth and development. Therefoer, we think that Paeonia suffruticosa 'Danjing Hong 2' was an eminent breed, which was worth generalizing. |
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