Research On Biological Characteristics Of Paeonia Lactiflora Seed's Germination And Dormancy Breaking Technique

Paeonia lactiflora, perennial herbaceous flowers of the genus Paeonia Paeoniaceae, are good material in plantscaping as well as cut flower and it has with high ornamental value. Because both high and low hypocotyl of Paeonia lactiflora seed all have dormancy characteristics, the time duration from sowing to emerging for Paeonia lactiflora seeds needs approximately for 6⁷ months under the natural condition, the vegetative cycle is long. At present, domestic and foreign research on dormancy and germination of Paeonia lactiflora seed was found only in few literature, and most of them focued on Paeonia lactiflora's radicle dormancy, research on embryo dormancy are few and don't go deep into it, yet lack the system research that takes the radicle dormancy and the embryo dormancy as a whole. Therefore, research on dormancy and germination of Paeonia lactiflora seed has the broad prospects.This article researches the Paeonia lactiflora seed's biological characteristics and dynamic changes of nutrients content as well as the enzyme activity in the process of germination to explore its internal relationship with the seed germination, and adopts simultaneously 28 kinds of dormancy breaking method to process the Paeonia lactiflora seed. The results showed that 12 dormancy breaking methods relieve the radicle dormancy significantly and 10 methods relieve the embryo dormancy significantly, which caused the seedling emergence ahead of time for 3 months compared with the natural growth cycle. The results are as follows:1. The relationship of Paeonia lactiflora seed's biological characteristics with its germination: The seed coat of Paeonia lactiflora is thick and hard, weight accouns for 20.78%, full of oil and the water permeability is bad, which inhibit Paeonia lactiflora seed's germination, but not the main reason for its dormancy. Endosperm of seed is abundant and its weight accounts for 78.54%, which provide sufficient energy for seed's germination. Embryo is extremely small, the weight accounts for only 0.68%, must complete the afterripening to be able to germinate. The main nutrients of seed are soluble protein, soluble sugar, starch, crude fat and free amino acids, those provide nutrition assurance for germination. Among them, the soluble protein content is 3.45mg/g, soluble sugar content accouns for 43.93%, starch content accouns for 9.79% and free amino acid content is 12μg/g.2. The 28 kinds of treatment methods used in rooting and emergence test all break Paeonia lactiflora seed's dormancy in varying degree. For rooting seed after 25℃high temperature stratification treatment, use GA₃ 300mg/l to soak seed for 24h when their root length reaches 4-5cm, seeding begin to emerge after 98 days, germination cycle advance 3 months compared with cycle under natural conditions, and the germination rate is highest, reaching 79%. In addition, compare with using 100mg/l GA₃ alone, dormancy breaking effect enhanced 3～5 times when using mix of concentrated sulfuric acid (1min) and 1 mg/l hydrochloric acid (1h) with 100mg/l GA₃.3. Stratification temperature also has an impact on Paeonia lactiflora seed's dormancy breaking. 5℃low temperature delays seed's rooting but has a catalytic role on germination emerging. 25℃high temperature has good effect on rooting than 15℃constant temperature and processing of temperature change has most significant effect on dormancy breaking.4.There are correlation between dynamic changes of nutrients content as well as enzyme activity and Paeonia lactiflora seed's germination. The soluble protein content has been in a relative stable state during the period of seed germination and has a slight increase after seed germination. The change trend of soluble sugar content first increase and then decrease. The starch content reduces continuously. Free amino acids content is few and has been in a relatively stable state, a slight increase after seed germination. Peroxidase (POD) activity is in a downward trend, catalase (CAT) activity was in a slowly upward trend. And nutrients content and the CAT activity except for free amino acids and POD all displayed the obvious density effect to the GA3 and 6-BA, namely the density of GA3 and 6-BA is bigger, the germination rate is higher, the soluble sugar content and the CAT activeness are higher, but the soluble protein content and the starch content are lower.