Study On The Dormancy Causes And Dormancy Breaking Technique Of Paeonia Rockii Seeds From 11 Provenances

Low rooting and germination rates have always been important factors restricting the development of Paeonia rockii.The purpose of this study was to discover the dormancy reasons,and to find the efficient way to promote seed rooting and sprouting.We investigated the wild resources in some areas,collected P.rockii seeds from 11 provenances(6 native provenances and 5 secondary provenances)in 4 provinces,determined 7 morphological indexes(length,width,thickness,length-width ratio,length-thickness ratio,width-thickness ratio,long-width-thickness product)and 8 quality indicators(thousand seed weight,water content,viability,water absorption,respiratory rate,embryo ratio,endosperm ratio,seed coat ratio)of the seeds,and observed the seed coat structure of different provenances under scanning electron microscope.Based on the above researches,we divided 11 provenances into different districts preliminary.This research studied the cause of the seed dormancy by Pisum sativum seed germination test and embryo culture methods.researched the effects of temperature and GA3 concentration on seed rooting and the effects of root length,low temperature time and GA3 concentration on seed germination.The main research results were as follows:1.Provenance investigation showed that P.rockii in Yaowang Valley,Taibai County and Red River Valley,Mei County in Shanxi Province are in a stable growth period.Resources in Songping forestry experience base,Taibai Mountain in Shanxi Province and Baiyun Mountain,Song County in Henan Province have almost extinct.Although,there are still some wild resources in Kang County,Gansu Province,The community is in a recession period for there are few seedlings in it.2.Scanning electron microscope showed that the seed coat is made up of hard cuticle composed of bone cells covered with a thin waxy layer,palisade layer composed of column cells and wavy transversely arranged spongy layer from the outside to the inside.Seed coat of Hubei provenances is the thinnest.Coat of Henan provenances is in the middle,and coat of Shaanxi and Gansu are thickest.Outer surface of coat is irregular polygon(Hubei,Henan)or irregular convex lines(Gansu,Shaanxi);The inner surface of coat is scaly;The palisade layer of Hubei provenance is oblique with seed coat surface,while others are perpendicular.3.Correlation analysis between seed shape and quality index showed that there is a significant positive correlation between viability and length,width and thickness product,1000 grain weight,water content and respiration rate.Besides rooting percentage is significantly or extremely significantly positively correlated with viability,width and thickness product,1000 grain weight,water content and respiration rate.4.In accordance with the biological characteristics of morphological indexes and quality indicators,using Squared Euclidean distance method,11 provenances were divided into 4 large provenance,namely,southeast provenance(Hubei).northeast cultivated provenance(Luanchuan,Lushi in Henan).northeast wild provenance(Song County in Henan)and western provenance(Gansu and Shanxi).5.The seed coat permeability,the inhibitory substances in seed coat and endosperm are the reason for hypocotyl dormancy.Embryo is the reason for epicotyl dormancy.Removing seed coat,endosperm or cotyledon can not release the epicotyl dormancy,only low temperature can make it release.The dormancy reasons that include exogenous dormancy caused by seed coats,endosperm and embryo dormancy,belongs to comprehensive dormancy.6.The suitable temperature for seed rooting is 15?20?,and the adaptability for primary provenance seed rooting to 25? temperature decreases with increasing latitude;The optimum concentration of GA3 for primary provenance seed rooting is higher than that of secondary provenances,which are 400?450mg/L and 300?350mg/L respectively.7.Interaction of root length,GA3 concentration and chilling treatment has a significant effect on the first sprouting time,germination energy and germination rate;GA3 and chilling treatment promote the seeds with longer than 40 mm radicle roots to germinate more effectively.The best treatment combination for germination is zonal differently,chilling treatment for 20 days,combined with 300 mg/L GA3 is optimum for seed germination of southeast provenance;chilling treatment for 20 days,combined with 200 mg/L GA3 is optimum for seed germination of northeast wild and cultivated provenances,while the best treatment for western provenance seeds is 40 day's chilling treatment combined with 300mg/L GA3.