Studies On Seed Dormancy And Germination Characteristics Of Fritillaria Przewalskii Maxim.

Fritillaria przewalskii Maxim.is a perennial medicinal herb of the angiosperm Fritillary and belong to Liliaceae,which is one of the basic plants of the rare medicinal herbs in China Fritillaria cirrhose D.Don.It is known as the“Min Bei”,and the wild resources of the drug have become endangered.Wild tending and domestication cultivation is the key to the protec-tion of wild resources.However,F.przewalskii is the proto-embryonic seed with deep dor-mancy,which has low effectiveness in artificial cultivation.In this study,we studied the dy-namic changes of endogenous hormones and physiological indexes during the development process of the embryo in F.przewalskii seeds,and the regulation on seeds of exogenous hor-mones.The aim of this study was to investigate the dormancy mechanism,dormancy-release characteristics and pathways of breaking dormancy in F.przewalskii,and provide scientific and technical basis for the wild tending and domestication cultivation of F.przewalskii,pro-moting the sustainable application of F.przewalskii resources.The main results are summa-rized as follows:1.Investigating the characters of 500 F.przewalskii fruits and seeds showed that the fruits are dried fruits.The indicators were 13.221 mm in carpopodium length,0.972 mm in car-popodium thickness,13.574 mm310.952 mm in fruit length and width.The single fruit fresh weight is 0.1127 g,the number of single fruit pieces was 90.940,the single fruit grain weight was 0.0746 g,and the fresh weight of the peel was 0.0381 g.The seeds were oval or obovate,with a length of 4.130 mm,a width of 2.982 mm,and a thickness of 0.263 mm.There was no significant correlation between the traits of the capsules and the seed size.Microscopic ex-amination showed that there was no wireless embryos of F.przewalskii when they naturally fell off,and belonged to the typical postembryonic type.The seeds were in a deep dormant state,but the seed coats were barrier-free and did not affect the water and air permeability of seeds,speculating that the difference in endogenous germination inhibitors of F.przewalskii may be the source of embryonic development and deep dormancy.2.The seed stratification of different conditions showed that the mature seed embryo rate of F.przewalskii was more than 70%after the warm-stratification treatment,and the original embryo gradually developed into a punctate shape,which was followed by a globular shape.During the different warm-temperature stratification process,The activities of SOD,POD and CAT increased gradually,the starch content gradually increased,while the RCt and MDA content showed a decreasing trend.The soluble sugar content decreased first and then in-creased and the soluble protein content fluctuated.The amylase activity is decreasing during the stratification process,while the protease activity decreases at the beginning and remains higher levels in the later stage.The activity of MDH showed a downward trend,and G-6-PDH activity maintained at a certain level of change.The above description shows that the suitable sand reservoir stratification conditions are beneficial to the embryo morphology after-ripening of F.przewalskii seeds.The uncomfortable temperature can significantly delay the morphology after-ripening process of seed embryos,and the high temperature can cause the seeds to soften and rot.3.The morphology matured F.przewalskii seeds,which were treated with different low-temperature stratification treatments at-15°C to 5°C,showed that the release of physio-logical dormancy was related to the activity of related enzymes and the metabolism of sub-stances.With the stratification time of low temperature,the activity of SOD and CAT re-mained at a high level,while the activity of POD increased gradually,and the changes in the stratification treatment at-10°C and-15°C were different.The RCt rised in the later stage,and the content of MDA remained at a certain level after 135 d.The soluble sugar content de-creased in the early stage and increased later,and the soluble protein content continued to de-cline before the low temperature stratification for 135 d.The starch content decreased obvi-ously during the whole stratification process.The activity of amylase and protease increased first and then decreased,and finally increased.At 135 d,the activity of MDH decreased and the activity of G-6-PDH increased.After 135 d,the physiological maturity of seeds was basi-cally completed and entered the germination state.It is indicated that the suitable temperature and conditions can promote the physiological after-ripening of the embryo.4.Exogenous GA₃ seed soaking treatment with different concentrations(50⁴50 mg·L^-1)showed that exogenous GA₃ soaking requires a certain low temperature to break the physio-logical dormancy of F.przewalskii seeds,and the promotion of germination increased with the decrease of concentration.The treatment effect is more significant of using the concentration of 50 mg·L^-1 GA₃ to soaking seeds.5.The study on the stratification treatment of moisturizing sand at different temperatures showed that the suitable temperature and conditions were conducive to the completion of em-bryo morphology after-ripening.Endogenous GA₃,IAA and ABA were involved in the regu-lation of morphology dormancy and release process of F.przewalskii seeds,and the gradual increase of its content and GA₃/ABA is to the benefit of the completion of the seeds af-ter-ripening,IAA can assist GA₃ to accelerate the completion of the embryonic morphology after-ripening,but the IAA/ABA is too high to inhibit the development of the embryo.The elevation GA₃/ABA and IAA/ABA promotes the completion of physiological after-ripening and then germination,but directly sensing the low temperature will destroy the internal struc-ture of the seed and affect the seed germination.