Study On Seed Dormancy,germination Resistance To Adverse Stresses And Soil Seed Persistence In Genus Nitraria

The protection and utilization of plant germplasm resources has important scientific significance and potential practical value.Seed dormancy,germination resistance and soil seed persistence are of great scientific significance in plant adaptation to the environment and agricultural production.Forty eight seed samples of Nitraria genus,four of Nitraria sphaerocarpa,eleven of N.roborowskii,nineteen of N.tangutorum and fourteen of N.sibirica were collected in Gansu province and Inner Mongolia autonomous region.Dormancy and germination of forty six seed samples,germination resistance to salt stresses of thirty four seed samples,and germination resistance to drought stresses of twenty three seed samples were investigated in the laboratory.The seed viability and dormancy dynamics of seeds of the four species buried in Minqin and Yuzhong filed were monitored for one year.The results showed that:(1)Dormancy: Under 15℃-25℃,20℃-30℃ and 25℃-35℃ designed alternative temperatures,the dormancy percentages of three samples of N.sphaerocarpa was observed 0-2%.Significant differences existed between dormancy percentages of the seed samples of N.roborowskii,N.tangutorum and N.sibirica(P <0.05,N = 4).The values of dormancy percentages of nine seed samples of N.roborowskii were tested to 1%-65%,The values of nineteen samples of N.tangutorum were tested to 1%-98%,The values of fourteen samples of N.sibirica were tested to0-60%.Dormancy of one seed sample of N.roborowskii were tested higher than 20%under the three alternative temperatures,the value was 65%.Dormancy of twelve samples of N.tangutorum were tested higher than 20%,the highest value was 98%.One of that of N.sibirica was tested higher than 20%,the highest value was 60%.Among the four tested Nitraria species,the highest seed germination were observed in samples of N.sibirica,the value ranged from 19% to 98%;the second higher values of seed germination were observed in samples of N.sphaerocarpa(No.4samples excepted),the value range from 25% to 94%.The germination percentages of N.roborowskii and N.tangutorum were observed 14%-88% and 2%-83%,respectively.The dead seed percentages of N.sphaerocarpa,N.roborowskii,N.tangutorum and N.sibirica were observed 7%-75%,14%-88%,7%-73% and 2%-51%,respectively.(2)Germination resistance to salt: The highest germination percentages of four seeds of N.sphaerocarpa,seven seeds of N.roborowskii,sixteen seeds of N.tangutorum and seven seeds of N.sibirica were observed under the absence of salt stress.For N.sibirica,the highest germination percentage was observed in-0.30 MPa salt stress(P < 0.05,N = 4).The thresholds of salt stress conditions in which seeds cannot germinate for N.sphaerocarpa were-1.50 MPa to-1.80 MPa,N.roborowskii-1.20 MPa to-1.50 MPa,N.tangutorum-0.90 MPa to-1.80 MPa,and N.sibirica-0.60 MPa to-1.80 MPa,respectively.(3)Germination resistance to drought: The highest germination percentages of all of the tested Nitraria species were observed under the absence of drought stress(P< 0.05,N = 4).The thresholds of drought stress conditions in which seeds cannot germinate for N.sphaerocarpa were-1.50 MPa to-1.80 MPa,N.roborowskii-0.90 MPa to-1.50 MPa,N.tangutorum-0.90 MPa to-1.80 MPa,and N.sibirica-0.90 MPa to-1.50 MPa,respectively.(4)Persistent soil seed bank: After buried for one year in two field sites in Minqin and Yuzhong counties,the viability percentages of seeds of N.sphaerocarpa,N.roborowskii,N.tangutorum and N.sibirica were observed for 68% and 75%,52%and 71%,66% and 51%,79% and 64%,respectively.Conclution: seeds of N.sphaerocarpa showed no dormancy,the dormancy germination resistance to salt and drought stresses of seeds of N.roborowskii,N.tangutorum and N.sibirica showed significantly differences in intraspecific populations.In general,the seeds of Nitraria species have poor salt tolerance and drought resistance,Moreover,some seeds of N.tangutorum and N.sibirica showed very sensitive response to salt and drought stress.All the four species of Nitraria had the potential to form soil seed bank.The results of this study provided basic data for breeding of new high stress resistance varieties of Nitraria.