Carbohydrate Metabolism And Endogenous Hormones Changes Of Tree Peony (Paeonia Suffruticosa) Grown Under Root Restriction

This study analyzed the effect of root restriction (potted cultivated) on carbohydratemetabolism and endogenous hormones in ’Luoyang hong’ tree peony (Paeonia suffruticosa).Theresult showed that root restriction reduced the plant height, canopy size, growth and developmentlevel of bud of tree peony. The number of the rootⅠ,rootⅡ of tree peony were reduced. Freshand dry weight of the rootⅠ were significantly lower than control. Fresh and dry weight of theroot Ⅱ were not significantly different from the control. The number of root Ⅲ was increased,but their dry weight was significantly lower than the control. Water content of the rootⅠ and rootⅢ were higher than control. Water content of rootⅡ was lower than the control. So it can be seenthat dry matter of root restriction tree peony were mainly concentrated in the root Ⅱ, and thestorage ability of rootⅠwas decreased. The water absorption capacity of root Ⅲ was increasedwhich means that root were not suffered water stress when grown under root restriction. The pHvalue of peony matrix was increased when grown under root restriction.Root restriction significantly reduced the net photosynthetic rate (Pn), sucrose phosphatesynthase (SPS) activity and acid invertase (AI) activity of tree peony leaves. The declined SPSactivity and AI activity in tree peony leaves show that both source and sink strength are inhibitedby root restriction. Before anthesis, sucrose and starch levels were significantly lower in rootrestriction tree peony leaves than that in control. However, from flowering-stage to late-floweringstage, sucrose and starch were accumulated in root restriction tree peony leaves mainly because ofthe low sink strength which limited the driving force to transport sucrose to sink organ and tohydrolyze starch. Hexose content in root restriction tree peony leaves were lower than the controloverall and the chagne was smooth at anthesis. Lower level of sink strength was the main reasonfor the reduced Pn of tree peony grown under root restriction. The reduction of leaf area andaccumulation of carbohydrates in leaves can also explain the decline of Pn to a certain extent.Under root restriction, the diameter and thickness of tree peony flower were significantlyreduced. At initiating-bloom-stage, the ratio of petal dry weight to total flower dry weight wassignificantly lower than control. From round-peach stage to initiating-bloom-stage, dry matterincrease rate of petal was lower than the control, which means that root restriction inhibited drymatter increase and dry matter increase rate of petal. From round-peach stage to full-bloom stage,the ratio of stamen dry matter to total flower dry weight was higher than the control, the ratio ofpistil dry weight to total flower dry weight was lower than the control, it shows that dry matter distribution of flower organ was changed, which distributed relatively more to stamens anddistributed relatively less to petals and pistils. Sucrose content and hexose content of tree peonyflower organ were decreased. However, the reduction degrees between different flower organswere different. The reduction degree in petals and pistils were lower than the reduction degree instamens. From round-peach stage to initiating-bloom-stage, starch content in petal wassignificantly lower than the control. Starch content in stamen was significantly lower than thecontrol at round-peach stage, initiating-bloom-stage and full-bloom stage. Starch content in pistilat all the stage was significantly lower than the control. The lack of soluble content and starchcontent in pistil were the reason for the higher abortion rate of tree peony grown under rootrestriction.From round-peach stage to senescence stage, activities of AI in petals, stamens andpistils were significantly lower than that in the control. The growth and development of petals,pollen and ovary were all affected by the decreased AI activity. It can be seen that the sinkstrength of flower organ was not strong enough and have insufficient power to transport sucrose.There is less sucrose to form starch when sucrose were used. There are not enough carbohydrateand lack of motivation to mobilize carbohydrate to utilize, so the flower diameter was small,flowering badly and have higher abortion rate in tree peony when growing under root restriction.ZR, IAA and GA content in the root of tree peony was generally lower than the controlgrowing under root restriction. IAA content in the root was significantly lower than the control inall the sampling stage and its reduction was obvious. ABA content is generally higher than thecontrol. At fast-growing stageⅡand before-flowing stage, ABA content in root were significantlyhigher than the control. ZR, IAA and GA content in the stems of tree peony was generally lowerthan the control growing under root restriction. ZR content in stems at germination stage wassignificantly lower than that in the control. IAA content in stems at germination stage andfast-growing stageⅡ were significantly lower than that in the control. GA content in stems atbefore-flowing stage was significantly lower than that in the control. IAA content and GA contentin tree peony leaves were slightly lower than that in the control, but the difference were notsignificant. ZR content in tree peony leaves at fast-growing stage was significantly lower than thatin the control. ABA content in tree peony leaves at fast-growing stage and before-flowing stagewere significantly higher than that in the control. Generally root restriction reduced ZR content,IAA content and GA content in tree peony, which is more obviously in root. ABA content weregenerally increased in tree peony when grown under restriction, which is more obviously inleaves.