| Aralia continentalis Kitagwa belongs to family Araliaceae which is a renowned perennial wild edible herbs in Northeast of China due to its exceptional nutritional and medicinal value. However, the quantity and quality of Aralia continentalis Kitagwa is dramatically reduced by over-exploitation. Artificial cultivation of Aralia continentalis Kitagwa is gradually increased in recent years to effectively protect and exploit the resource. A large number of Aralia continentalis Kitagwa seedlings are needed for artificial cultivation, whereas high quality seedlings of Aralia continentalis become a key factor limiting the development of Aralia continentalis Kitagwa industry due to seed dormancy. In this study, we focus on the factors that affect seed quality and seed dormancy. In addition, metabolism changes in seed dormancy and environmental stimulation are conducted by physiological andl biochemical reactions. Our results will lay a solid foundation for gaining better seeds, removing seed dormancy and developing seedlings with high quality for Aralia continentalis.The results are as follows:1. Effective accumulated temperature was the main factor affecting seed development of Aralia continentalis Kitag through correlation analysis of the factors influencing seed quality in different ecological areas(Liaoning,Jilin,Heilongjiang). An effective accumulated; temperature of 553.7-1147℃ was defined as flowering; an effective accumulated temperature of 1029-1586℃ was defined as fruiting period; an effective accumulated temperature of 1438-1810℃ was defined as seed harvest period. The region with high accumulated temperature, adequate light and low rainfall was beneficial to obtain the seeds with high level of embryo quality, low seed dormancy, rapid seed ripening and high rate of seed germination. August 30th to September 10th was suitable for Shenyang city and seeds in top inflorescence were with high quality compared with other parts of the whole plant.2. NaCl solution is effective for seed selection. The rate of seed sedimentation could be up to 50% by 10% NaCl solution treated 6h. These seeds were with good quality and high uniformity of germination and the rate of germination was up to 91.8%. These data provided an important information for the breeding of Aralia continentalis seedling.3. The embryo of Aralia continentalis was not fully developed and phenolic compounds in seeds inhibited the germination of embryos. In addition, high concentrations of ABA and low concentration of GA3 were also responsible for the dormancy of the new seeds of Aralia continentalis, which resulted in the deep dormancy of Aralia continentalis Kitag seeds. Anatomical observation of new mature seeds revealed that embryo was small, vesicular, transparent, oval and liquid and the endosperm was gelatinous and elastic. Therefore, the seed mature and embryo post-maturation were not totally finished. The bacca, seed coat and embryo included phenols which inhibited seed germination, especially in embryo. Seed coat had certain obstacles on water uptake, whilst this did not affect the effects of water uptake. So, Aralia continentalis seed was morphophysiological dormancy.4. Storage was helpful for the development of Aralia continentalis embryo. The metabolism and transformation of Aralia continentalis Kitag seeds were enhanced. Total phenolic content decreased, the activity of amylase and peroxidase (POD) and G-6-PDH were activated with increased storage time, which accelerated the remove of seed dormancy.12 months natural storage could remove seed dormancy.Phenolic compounds significantly decreased after 12 months storage. The activity of a-amylase and a+(3 amylase was improved which promoted material metabolism and accumulated energy for seed germination. The content of GA3 was rapidly increased, while the content of ABA was quickly decreased and the content of IAA was slowly decreased. Moreover, the ratio of GA3/ABA was dramatically enhanced, whilst the change trend of ZR/ABA and IAA/ABA was consistent. Seed anatomy observation also confirmed that the embryo developed completely and the seed dormancy was relieved.5. Alternating stratification contributed to seed dormancy release through accelerating the development of the embryo, increasing the activity of nutrients decomposing enzymes and respiratory metabolism pathway key enzymes, regulating hormone content and balance in seeds. The seed dormancy was relieved at 5/25℃ alternating stratification for 30d, which accelerated embryo developmental process of Aralia continentalis Kitagwa. The change of embryo was significantly after 10d treatment at 5/25℃ alternating stratification and the differentiation and growth of cotyledon and radicle were earlier 10-20d than 5℃ and 10℃ stratification.6. Effect of Exogenous GA3 on the seed dormancy of Aralia continentalis Kitagwa was remarkable. Exogenous GA3 could accelerate seed metabolism speed, reduce germination inhibitory substance concentration, regulate related enzyme activity of seed respiration EMP-TCA and PPP pathway and maintain seed endogenous hormones balance. The total phenolic content of Aralia continentalis Kitag seeds decreased with increased GA3 concentration and the prolonged treatment time.50 mg·L-1 and 150 mg·L-1 GA3 treatment could greatly decreased total phenols contents. In this study, the highest germination rate was 51.83% and the higher germination potential was 15-19 d with the treatment of 150 mg·L-1GA3.7. Seed dormancy of Aralia continentalis released rapidly with alternating stratification and 150mg·L-1 GA3 treatment. Treated 20d, GA3 content sharply increased; ABA content greatly decreased; IAA and ZR content changed very little; GA3/ABA increased quickly and IAA/ABA, ZR/ABA decreased slowly with the prolongation of treatment time. Compared with seed embryo development, the dormancy period (30 days) was a rapid growth period for embryo. Therefore, the application of exogenous GA3 treatment could stimulate the accumulation of GA3 and significantly decrease the content of ABA, both of them released seed dormancy for embryo germination.8. The establishment of Aralia continentalis breeding system.The effective accumulated temperature for the breeding base should be more than 1670℃. Top flower branches should be obtained and get rid of the early flowering and late flowering branches based on phenological phase of Aralia continentalis. Harvest time is around September. The dry seeds should be selected before germinating and treated with 10% NaCl solution for 6h. The treated by10% NaCl and located in lower layer seeds were treated by 150 mg.L-1GA3 for 2h, then these seeds were placed on 5/25℃ alternating stratification for 30d. seedings will be got after 10 days germinating and the seedlings are uniform and with good quality. Excellent seedlings can be obtained about 30 d. |
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