Studies On The Biological And Mutagenic Effects Of Salvia Splendens And Linum Usitatissmum Irradiated By ¹²C⁶⁺ Heavy Ions

The dose and LET response were studied in Salvia splendens,Verbene hybride,and linseed irradiated by ¹²C⁶⁺ heavy ions.Moreover,the induction mechanisms of ¹²C⁶⁺ heavy ions were discussed,and a few mutants were screened out.The main findings are as follows:1.Germination rate and growth of seedling were measured on the seed of Salvia splenden and Verbene hybride radiated by ¹²C⁶⁺ heavy ions.Low dose radiation can improve germination rate which decreased with augment of dose;and a certain LET inhibited germination rate.The emergence day of the first seedling was delayed when dose or LET was heightened.The effect of dose or LET on survival,the hypocotyl and cotyledon appeared the same effect with their germination rate.In addition,survival of Salvia splendens and Verbena hybrida decreased with increasing LET values of ¹²C⁶⁺ within 100 keV/μm,while the effect at 150 keV/μm showed stimulation.Abnormal phenotype frequency increased with enhanced LET in Salvia splendens and Verbena hybrida,whereas the chromosomal aberrations of Salvia splendens reduced.Analysis of radio-sensitivity indicated that chromosome number played an important part in species.Furthermore,it was found that survival,the phenotypic and chromosomal aberrations have close relationships with different LET values of ¹²C⁶⁺ ion beam,and partly could be contributed to seed characteristics.More chromosomal damage was brought forth by lower LET values,while greater abnormal phenotype frequency for higher ones in Salvia splendens.Survival and phenotypic changes were possible affected by chromosomal aberrations.Therefore,a hypothesis was concluded that ion beams with lower LET values mainly bring forth chromosomal damages,while higher LET values for more non-chromosomal ones like proteins,cell membrane and organelles damages.Moreover,phenotypic aberrations would be decided by chromosomal and non-chromosomal damage together.It is a consequence of increasing abnormal phenotype with decreasing chromosomal aberrations as LET value enhanced in the present-generation of Salvia splendens.The optimal LET and dose were selected for radiation-induced mutation through combination of regression analysis and phenotypic aberrations frequency:Salvia splendens(50 keV/μm,50 Gy) and Verbena hybrida(150 keV/μm,100-500 Gy).Many kinds of mutant plants were selected in Salvia splendens irradiated by ¹²C⁶⁺ ion beam.Afterwards, the flower colour chimera and leaf mutants were examined the inheritance of those mutation phenotypes in their progeny.The RAPD analysis showed that the DNA changes have resulted in these mutants,and on the basis,six new DNA sequences were found and submitted to GenBank,the accession numbers were EU363530, EU363531,EU363532,EU363533,EU363534 and EU363535 respectively.In addition,it was found that those mutation phenotypes did not inherited to the progeny of Salvia splendens,which could be contributed to DNA repair.It is necessary to study the mutation mechanism in the next generations of Salvia splendens.2.The biological characters,agricultural traits,and pollens was studied in M1 and M2 generation of Linum usitatissmum irradiated by ¹²C⁶⁺ heavy ions(irradiation dose:6×10⁸ ions/cm²,1.8×10⁹ ions/cm² and 3.6×10⁹ ions/cm²).The M1 generation results showed that 6×10⁸ ions/cm² of ¹²C⁶⁺ could promote the linseed germination rate,plant height and pollen viability.The 1000-seed weight and the oil content of seed irradiated by ¹²C⁶⁺ heavy ions were increased with augment of irradiation dose.3.6×10⁹ ions/cm² was the most effective dose and increased seed weight and oil content with 16.5%and 19.9%,respectively.Cytological observation revealed that the highest dose(3.6×10⁹ ions/cm²) also induced alteration of pollen shape of linseed. Furthermore,RAPD analysis presented that 125 DNA fragments were amplificated by 18 primers and the polymorphic ratio was 52.5%.Compared to the M1 generation of linseed,some biological characters and agricultural traits of M2 generation did not maintained the same effect.The doses,which range from 6×10⁸ ions/cm² to 3.6×10⁹ ions/cm²,mostly showed the stimulation effect,and have a narrow mutation spectrum and lower mutation frequency.Hence,it is necessary to increase the dose of ¹²C⁶⁺ heavy ions for a wide mutation spectrum and higher mutation frequency.