Effects of irradiation on Rhododendron seed germination and seedling growth under saline and alkaline stress

ObjectiveEffects of irradiation on seed germination and seedling growth of Rhododendron under saline and alkaline stress were studied in order to provide technical support for breeding saline and alkaline tolerant Rhododen-dron varieties.MethodRhododendron seeds were divided into three batches and were irradiated with different doses of 60Co-γ,the irradiation source.The effects of irradiation on seed germination and seedling growth of Rhododendron were investigated to determine suitable dose of irradiation.Irradiated seeds of R.ovatum and R.simsii were selected to be under saline and alkaline stress to study the effects of irradiation on Rhododendron seed germination and seedling growth.Re-sultInter-species differences existed in the effects of irradiation on seed germination rate of different Rhododendron spe-cies. Semi-lethal dose(LD50)of five Rhododendron species was 121-213 Gy,and the order was R.simsii>R.decorum>R. molle>R.mariesii>R.latoucheaey.The suitable irradiation dose for Rhododendron was 100-150 Gy.Although data analy-sis indicated the germination rate,seedling emergence rate and seedling rate of Rhododendron seed were negatively corre-lated with irradiation dose,100 Gy does of irradiation could promot the germination rate of R.ovatum and R.simsii seeds, 50 Gy could improve seedling growth of R.simsii,R.latoucheae,R.mariesii,and 150 Gy could promote seedling growth of R.decorum.The seed germination and seedling growth of R.ovatum and R.simsii were inhibited under saline and alka-line stress,but 100 Gy dose of irradiation promoted the seed germination rates of R.ovatum and R.simsii under saline and alkaline stress and alleviated the inhibition effects of salt stress.The seed germination of R.ovatum and R.simsii were fine in acidic environment(pH 5.0)and neutral environment(pH 6.5),and were inhibited in alkaline environment(pH 8.0).ConclusionIrradiation can be a means of improving saline and alkaline tolerance of R.ovatum and R.simsii at seed ger-mination stage,and the suitable dose of irradiation is 100-150 Gy.