Study On The Dormancy Characteristics Of Seed Needles

Seed dormancy,refers to the phenomenon that seeds are unable to germinate in a specified period of time under a combination of optimum environment fators.In this research,Zanthoxylum nitidum(Z.nitidum)seeds were studied on seed coat structure,germination inhibiting ingredients,seed metabolism and seed proteomics,to explore the mechanism of seed dormancy,and to provide technical base for seed testing,breeding and propagation.1.Viability and germination testing of Z.nitidum seedsIn accordance with the rules for agricultural seed testing,the viability testing of Z.nitidum seeds were detected by soaking seeds with 0.1%TTC solution for 24 hours.The viability of Z.nitidum seeds was high,while its germination rate was low.From the perspective of that the seeds undergo dormancy,the seed samples were stratificated in fridge and soaked with gibberellin,to increase the germination rate and shorten the germination duration.2.The mechanical restriction of germinationExperiment of water absorption of Z.nitidum seeds showed easy permeability of seed coat to water.Z.nitidum testa was scanned for its microstructure using scanning electron microscope.The exotesta was shown contained a layer of thin,dense wax and a layer of palisade cells;while the mesotesta,which formed the main part of the seed testa,was hard and dense that may mechanically restrict the elongation of embryo and constraine the germination of seeds.Stratification can soften seed testa and weaken the factor of mechanical restraintion,thereby increased the seed germination rate.3.Germination inhibiting ingredients of Z.nitidum seedsGermination testing of Chinese cabbage was conducted by soaking with different extract of Z.nitidum seeds to compare the inhibition effects.It was shown that germination was inhibited significantly by water extract.GC-MS analysis on four different extracts tested showed long-chain aliphatic acids and their esters,may be responsible for the inhibition of germination.4.Seed metabolism During the period of cold stratification,the content of primary metabolites and related enzyme activities of Z.nitidum seeds was dynamically determined monthly.With the stratification time increasing,the soluble sugar content decreased;at the same time,the starch content reduced firstly,then gradually increased,along with the amylase activity increased firstly,and then slightly reduced,indicating the process of starch accumulation.Determination of fat content showed that during stratification,the fat content of seeds gradually reduced;the trend of acid phosphatase activity showed accordant with the reducing process of fat,indicating the transformation between lipids,carbohydrates,and protein;the late stage tended stable to make reserves for seed germination.5.Seed proteomicsUsing two-dimensional electrophoresis technology,31 different proteins of Z.nitidum seed were obtained,followed with identification of 14 proteins;of which 4 proteins were identified as manganese superoxide dismutase,4 proteins were annotated to seed metabolism enzymes,and the rest proteins needed further annotation.In conclsion,Z.nitidum seeds are dormant seeds which are due to combination of hard seed testa,endogenous germination inhibiting ingredients,and physiological after-ripening.Cold stratification and gibberellin treatment can significantly increase seed germination rate.Further research on the mechanism of seed dormancy and techniques of seed germination for Z.nitidum is needed to provide technical support for application of seed testing,breeding and propagation of Z.nitidum.