Preliminary Study On Seed Dormancy And Germination Properties Of Paeonia Lutea And Drought-resistant Characteristics Of The Seedlings

Paeonia lutea Delavay ex Franch is a wild peony species indigenous to southwest of china. Being an endanged species, it is listed as a third grade national protected species in china. P. lutea has very important germplasm resource value for new variety breeding and for medicinal purpose. The researches on P. lutea so far have been mostly concentrated in taxonomic classification, chromosome, palynology and some other limited fields. Few of studies were related to its seed physiology, whereas there was not any research report found about drought resistance of this species. So it is essential and urgent to do some researches on its reproductive biology, drought resistant physiology and ecology for this endanged species in terms of appropriate conservation and utilization.Conducting studies on seed dormancy and germination characteristics of P. lutea would be helpful to understanding better its seed physiology, exploring effective approaches for its seeding reproduction, and providing the germplasm conservation of this endanged specis with theoretical and practical references. Carrying out studies on drought resistant characteristics of P. lutea populations from different habitats would be benefitial to understanding its related physiological properties and the difference in this aspect among varied populations so as to provide germplasm resource protection and superior cultivar breeding with guidance.Two experiments were conducted: (1) Seed treatment and germination experiment: rooting and germination experiments were conducted with the seeds collected from wild P. lutea population in the Xishan Mount of Kunming City under different temperature conditions after the seed samples having been treated with different ways; (2) Simulating soil drought experiment: different soil drought statuses were simulated by irrigation control for potted P. lutea plants, and the indexes of lelf water content, chlorophyll content, the change of relative electrical conductivity, contents of proline (Pro) and melondiadehyde (MDA) were mensured together with soil water content in order to evaluate indirectly and appraise the difference in drought resistant capacity among Cangshan Mountains population in Dali, Liangwang Mount population in Yuxi and the Xishan Mount population in Kunming; the results obtained from the two experiments are as follows:(1)The following conclusions were drawn from seed treatment and germination experiment:1) Soaking the seeds in solution of 200㎎/L GA3 for 24h, contusing the testa around hilum and soaking the seeds in 50℃water could all improve the radicle growth, and the effectiveness order was 200㎎/L GA3 solution soaking >testa contusing >50℃water soaking.2) Soaking the seeds with 200㎎/L GA3 solution could break epicotyl dormancy of the rooted seeds and enhance the germination, and the effect was even better on seeds with radicles longer than 3cm.3) Only the 5℃low temperature could not effectively break epicotyl dormancy of the rooted seeds. 15℃temperature was comparatively appropriate for both radicle growth and seed germination of P. lutea.(2)The following conclusions were drawn from the simulating soil drought experiment:1) Water content of the pot planting soil dropped along with the drought process. It dropped dramatically within the 6 days, and then slowed down when the soil became very dry. Seedling leaf water content decreased obviously with the soil desiccation, and the leaf water content declining range order of the three populations was the Cangshan Mountains population in Dali﹥the Liangwang Mount population in Yuxi﹥the Xishan Mount population in Kunming.2) In the entire process of drought stress, chlorophyll content of all the three populations declined gradually. The decline became significant after the 6th day, while there was great difference in the reduction amplitude among the three populations. The biggest reduction happened to the Cangshan Mountains population in Dali , followed by Liangwang Mount population in Yuxi, and the Xishan Mount population in Kunming.3) With the aggravation of drought stress in the soil, all the relative electrical conductivity value of seedlings of the three populations increased. The increment of the value became obviousy after the 8th day, and the order of increase amplitude was the Cangshan Mountains population in Dali, the Liangwang Mount population in Yuxi, and the Xishan Mount population in Kunming. 4)Proline (Pro) content of all the seedlings inceased along with the aggravation of drought stress. Compared with the CK of each population, the proline content of the Xishan Mount population in Kunming increased by 15 times; the value of Liangwang Mount population in Yuxi increased by 14 times, and the value of Cangshan Mountains population in Dali increased by 11.5 times.5) Melondiadehyde (MDA) content of all the three populations increased along with the aggravation of drought stress in the soil. The increment became siginificant after the 8th day of drought stress, and the change amplitude order from the largest to the least was the Cangshan Mountains population in Dali, the Liangwang Mount population in Yuxi, and the Xishan Mount population in Kunming. By the 10th day of the drought stress, MDA content of the of Cangshan Mountains population in Dali increased by 47.09% compared to the CK group, the value of the Liangwang Mount population in Yuxi increased by 41.68%, and the MDA content of Xishan Mount population in Kunming increased by 37.17% versus to its own contrast.6) It was indicated by the variance analysis and the main components analysis on the inherent correlations among above physiological indices that: The proline content and the value of relative electrical conductivity indices of the Xishan Mount population in Kunming were closely related to the drought resistance characters. Indices of proline content and chlorophyll b content of both Liangwang Mount population in Yuxi and Cangshan Mountains population in Dali were closely related to their drought resistance properties. So it was proposed that these indices could be used for eualuating drought resistant capacity for P. lutea.7) The same results were obtained by the Coordinate Comprehensive Evaluation and the Affiliated Equation Evaluation on each physiological index of the three P. lutea populations, i.e., the drought-resistant capacity of the three populations was in this order: the Xishan Mount population in Kunming﹥the Liangwang Mount population in Yuxi﹥the Cangshan Mountains population in Dali.It was showed by the experiments that there was diffenrence in drought resisitant capacity among the three P. lutea populations, indicating that appropriate conservation strategies concerning of the intrinsic charactersitics should be taken for different populations. Greater efforts should be done to protect the population with weaker drought reisistance. Suitable habitats should be selected for ex situ conservation according to its drought resistant capacity. The population with stronger drought resistance should be applied in priority as parental materials in the process of P. lutea cultivar breeding, so that the new vatieties could be drought resistant beside its beauty and other superior traits.