Studies On Seed Germination And Dormancy Of Six Wild Rosa L. Species

Rosa L.is one of the famous garden ornamental plants in the world.There are totally 200 kinds of Rosa L.in the world,about 82 of them are in China,so China is one of important Rosa L. distribution centers in the world.But only small quantity kinds of Rosa L.were introduced to garden in China.Seed as an important introduction and breeding material,the biggest obstacle for it is deep seed dormancy.Moreover,only a few reports on Rosa L.seed germination could be seen.In this study,six species of wild Rosa L.were used,and they were Rosa xanthina,Rosa omeiensis,Rosa derongensis,Rosa sp.,Rosa soulieana and Rosa soulieana var.yunnanensis which were seperately collected from Ningxia Hui Autonomous Region,Beijing and Northwest Yunnan.There seeds were pretreated with different concentrations of gibberellin(GA₃),auxin(NAA),osmotic adjustment trigger reagent(PEG) at different soaking time.By measuring seed germination,respiration rate and activity changes of enzyme for different treatments during seed germination,combining of morphological and physiological factors observed,the aim of this paper was to explore the reason for its deep seed dormancy.According to all the experiment which had been finished,the key conclusions were as follows:(1) Seed germination experiments showed that the treated seeds had higer germination energy and germination rate than check seeds.Seeds of Rosa derongensis had the highgest germination rate, the germination rate increased by 61%to check.Seed germination rate of Rosa xanthina and Rosa omeiensis was very low,and the check seeds of these two species still not germinated until the last germination count.Germination rate of reated seeds of Rosa xanthina and Rosa omeiensis could be increased,respectively,to 8%and 15%.(2) Respiration rate results showed that seeds treated with low concentration longer time and high concentration had stronger respiratory metabolism.Rosa soulieana seeds treated with 20%PEG soaked 24h obviously affect seed respiratory metabolism,its biggest respiratory rate could be 7.67mgCO₂·g^-1·h^-1,increased by 41.9%to check seeds.(3) Protease and acid phosphatase measurement results showed that the change rule of these two enzymes basically had trend as respiratory rate.Most treated seeds had higher enzyme activity than check,and higher concentrations pretreatment and low concentration soaked for longer time,the material enhanced its metabolism larger.(4) Determination of high-performance liquid chromatography analysis for the seed coats of the six spices of Rosa L.when the last count,we could concluded that the of ABA content in seed coats significantly descended,except Rosa sp.,ABA of all treated seeds were lower than check seeds,most notably was Rosa xanthina.With treatment of 200 mg/L GA3 soaking 48h and 200 mg/L NAA soaking 24h,ABA content of Rosa xanthina seed coat was lower than that of the check by 71%.(5) By observing the seed morphology and the structure of the external anatomy diagram,water permeability of seed,content of seed inhibitor,as well as the existence of parts of seed vigor,we could see that Rosa L.had compact structure,but these six spices all had good water permeability. The major obstacles to seed germination may be mechanical restraints of seed coat and higher ABA content during seed germination.According to the results of this study,the main factors which lead to deep seed dormacy of Rosa L.were its hard endocarp and seed coat physical obstruction connected with its inhibitor in its seed coat.Method to break the seed dormancy was initially constructed,it could be aviability reference information for Rosa L.introduction and breeding.