Study On The Characteristics Of The Propagation Of The Rhizome Segment Of Herbaceous Peony

Herbaceous peony（Paeonia lactiflora）,belonging to the Paeoniaceae and the Paeonia,is traditional Chinese perennial flower and popular all over the world.The rhizome of herbaceous peony is the key of crown division.After cutting,the regeneration ability of rhizome is strong.Rhizome propagation can be used as an effective supplement to the vegetative propagation method of herbaceous peony,which has a broad prospect of application.In this study,the rhizome of herbaceous peony were cut into segments and cultivated.Through the measurement of morphological indexs and rhizome histological and cytological observation,combined with the determination of physiological and biochemical indexes such as nutrients,enzymes and endogenous hormones,the effects of peony variety,segment type,low temperature treatment time,type and concentration of hormones on rhizome propagation were studied.The reproductive characteristics of rhizome of herbaceous peony were explored preliminarily.The main results obtained are as follows:（1）Study on the difference of rhizome reproductive ability of different cultivars of peony’s variety groups:The effect of rhizome propagation in some varieties is well,such as‘Tuan Ye Hong’and‘Fen Yu Nu’of lactiflora group,‘Going Banana’of Itoh group,‘Carina’of hybrid group.The seedling emergence rates reach 97.22%,95.67%,90.48%,84.92%respectively.The seedling emergence rates are relatively low in‘Roselette’（hybrid group）and‘Border Charm’（Itoh group）,reach 60.32%and 50%respectively.The average plant height of two varieties of lactiflora group are more than 200 mm,while others are between 120～190 mm.（2）Study on the effect of growth years of segments on rhizome propagation:Rhizome segments（3～6 cm）of the first,second and third segments from top to bottom all can root and shoot.There is no significant difference in their growth.The young rhizome segments of’Fen Yu Nu’are more likely to root.（3）Study on chilling requirement for rhizome segment:Rhizome segment needs to accumulate low temperature to break dormancy before germination and seedling emergence.Treatment time varies by varieties.‘Fen Yu Nu’,an early-flowering variety,needs 28～42 d under the low temperature treatment of 4℃,while the mid-flowering variety’Tuan Ye Hong’needs 42～56 d.（4）Study on physiological metabolism of rhizome removed from dormancy by low temperature:During the dormancy releasing,the contents of soluble sugar,reducing sugar and sucrose increase with the increased refrigeration time.They decrease after the complete release of dormancy.Starch content decreases with the accumulation of low temperature and decreases or increases after dormancy release.The content of soluble protein in the rhizome is low and the overall change is small during the dormancy releasing.The activity of SOD is stable or slightly decreased in the initial stage of low temperature treatment,and then increased.The activity of CAT increases first and then decreases during dormancy release.The activity of POD increases briefly before dormancy release,and remains stable at a low level at the rest of the time.IAA/ABA,ZR/ABA and GA₃/ABA increase first and then decreased during the cold storage period in the first rhizome segment of‘Fen Yu Nu’,which show‘decreasing-increasing-decreasing’of‘Tuan Ye Hong’.（5）Study on the effects of hormone treatment on the rooting of rhizome segments:IBA,NAA and ABT could significantly increase the number of roots in the rhizome of‘Fen Yu Nu’.The rooting rate of all treatment groups reach 100%.Rhizomes begin to take root at 7 d after treatment and adventitious roots are abundant at 14 d after treatment.In the experimental treatment concentration range,soaking for 30 min in the higher concentration(400～800 mg.L^-1)of various hormones could induce the rhizomes to produce more adventitious roots.NAA and ABT have better effect than IBA.After hormone treatment,the germination rate of rhizomes decreases,and the inhibition of perennial rhizomes is stronger than that of the young.（6）Study on the effects of hormone treatment on physiological metabolism of rhizome segments:The contents of carbohydrate and soluble protein in rhizomes treated with ABT decrease or remain stable at low levels after planting.The activity of POD increases at the beginning of rooting and then increases or remains high activity.The activity of PPO increases significantly at the period of extensive rooting and continues to increase or decreases at the later stage.