Primary dormancy of seeds of Korean pine(Pinus koraiensis Sieb.et Zucc.)after dispersal in the autumn and the induction of secondary dormancy the fi rst summer following seed dispersal limit the regeneration of mixed ...Primary dormancy of seeds of Korean pine(Pinus koraiensis Sieb.et Zucc.)after dispersal in the autumn and the induction of secondary dormancy the fi rst summer following seed dispersal limit the regeneration of mixed broadleaved Korean pine forests in Northeast China.This study was to determine how changes in the levels of abscisic acid(ABA)and gibberellic acid(GA)maintain primary and secondary dormancy of Korean pine seeds under germination conditions.We transferred seeds with one of fi ve primary dormancy states or three secondary dormancy states to germination conditions and measured changes in the levels of ABA,GA 1+3(GA 1 and GA 3)and GA 4+7(GA 4 and GA 7)in the seed coat,megagametophyte and embryo during incubation.Seed coat ABA levels in primary dormant seeds(PDS)and ABA levels in various parts of secondary dormant seeds(SDS)gradually declined during incubation but were still higher than in seeds for which dormancy was progressively released.GA 4+7 and GA 1+3 levels in embryos greatly decreased 35%and 24%,respectively,during incubation of SDS,and thus,the ratio of ABA to GA 4+7 in embryos and megagametophytes signifi cantly increased.The ratio of ABA to GA 1+3 in various parts of SDS increased slightly during incubation.In contrast,in seeds for which secondary dormancy was already released,GA 4+7 and GA 1+3 levels in the embryo,GA 4+7/ABA ratio in the embryo and seed coat,and the GA 1+3/ABA in the embryo and megagametophyte signifi cantly increased during incubation.There was no trend in the changes in the levels of ABA,GA 4+7 or GA 1+3 in embryos and megagametophytes of PDS or the levels of GA 4+7 or GA 1+3 in megagametophytes of SDS during incubation.The results suggest that high ABA levels in the seed coat maintain primary dormancy of Korean pine seeds.Maintenance of secondary dormancy involves a reduction of GA 4+7,GA 1+3,GA 4+7/ABA,and GA 1+3/ABA and the retention of high ABA levels.展开更多
Aims In species with morphophysiological seed dormancy(MPD),little is known about the effects of desiccation of imbibed seeds on embryo growth and germination.We studied seed responses to dehydration in nine species w...Aims In species with morphophysiological seed dormancy(MPD),little is known about the effects of desiccation of imbibed seeds on embryo growth and germination.We studied seed responses to dehydration in nine species with different levels of MPD.Methods For each species,a control test was conducted by keeping seeds permanently hydrated and exposed to the optimal stratification-incubation sequenee to promote embryo growth.Simultaneously,tests were run in which seed stratification was interrupted for 1 month by desiccation at room temperature.Important Findings In Clematis vitalba and Ribes alpinum,with non deep simple MPD,desiccation affected neither embryo growth nor seed viability,but the desiccation led to a decrease of germinative ability in R.alpinum by 16%.The seeds of Narcissus pseudonarcissus subsp.munozii-garmendiae,with deep simple epicotyl MPD,tolerated desiccation in different embryo growth stages,but their germinative ability decreased slightly.The response of species with complex levels of MPD to desiccation was more variable:Delphinium fissum subsp.sordidum,with intermediate complex MPD,and Anthriscus sylvestris and Meum athamanticum,both with deep complex MPD,tolerated desiccation.In contrast,Ribes uva-crispa with nondeep complex MPD,Lonicera pyrenaica with intermediate complex MPD and Chaerophyllum aureum with deep complex MPD,had diminished germination ability by desiccation.Although seeds of the species with simple levels of MPD tolerated desiccation,those of some species with complex levels were also highly tolerant.Thus,desiccation did not induce secondary dormancy in late embryo growth stages.The desiccation tolerance of imbibed seeds of most of the nine species may show their adaptability to climate change in the Mediterranean region.展开更多
基金We thank Kai Yang and Lizhong Yu and Xiao Zheng and Tao Sun for valuable discussion and suggestions about this study.We also thank Hongjun Xu,Jingpu Zhang,Weiwei Zhang and Shuang Xu for fi eld support and technical assistance.
文摘Primary dormancy of seeds of Korean pine(Pinus koraiensis Sieb.et Zucc.)after dispersal in the autumn and the induction of secondary dormancy the fi rst summer following seed dispersal limit the regeneration of mixed broadleaved Korean pine forests in Northeast China.This study was to determine how changes in the levels of abscisic acid(ABA)and gibberellic acid(GA)maintain primary and secondary dormancy of Korean pine seeds under germination conditions.We transferred seeds with one of fi ve primary dormancy states or three secondary dormancy states to germination conditions and measured changes in the levels of ABA,GA 1+3(GA 1 and GA 3)and GA 4+7(GA 4 and GA 7)in the seed coat,megagametophyte and embryo during incubation.Seed coat ABA levels in primary dormant seeds(PDS)and ABA levels in various parts of secondary dormant seeds(SDS)gradually declined during incubation but were still higher than in seeds for which dormancy was progressively released.GA 4+7 and GA 1+3 levels in embryos greatly decreased 35%and 24%,respectively,during incubation of SDS,and thus,the ratio of ABA to GA 4+7 in embryos and megagametophytes signifi cantly increased.The ratio of ABA to GA 1+3 in various parts of SDS increased slightly during incubation.In contrast,in seeds for which secondary dormancy was already released,GA 4+7 and GA 1+3 levels in the embryo,GA 4+7/ABA ratio in the embryo and seed coat,and the GA 1+3/ABA in the embryo and megagametophyte signifi cantly increased during incubation.There was no trend in the changes in the levels of ABA,GA 4+7 or GA 1+3 in embryos and megagametophytes of PDS or the levels of GA 4+7 or GA 1+3 in megagametophytes of SDS during incubation.The results suggest that high ABA levels in the seed coat maintain primary dormancy of Korean pine seeds.Maintenance of secondary dormancy involves a reduction of GA 4+7,GA 1+3,GA 4+7/ABA,and GA 1+3/ABA and the retention of high ABA levels.
基金supported by the local Government of Castilla-La Mancha(Regional Plan for Research and Technological Development,Regional Ministry of Education and ScienceProject:Germination ecology of 12 singular or threatened plant species with morphophysiological dormancy,PEII10-0170-1830).
文摘Aims In species with morphophysiological seed dormancy(MPD),little is known about the effects of desiccation of imbibed seeds on embryo growth and germination.We studied seed responses to dehydration in nine species with different levels of MPD.Methods For each species,a control test was conducted by keeping seeds permanently hydrated and exposed to the optimal stratification-incubation sequenee to promote embryo growth.Simultaneously,tests were run in which seed stratification was interrupted for 1 month by desiccation at room temperature.Important Findings In Clematis vitalba and Ribes alpinum,with non deep simple MPD,desiccation affected neither embryo growth nor seed viability,but the desiccation led to a decrease of germinative ability in R.alpinum by 16%.The seeds of Narcissus pseudonarcissus subsp.munozii-garmendiae,with deep simple epicotyl MPD,tolerated desiccation in different embryo growth stages,but their germinative ability decreased slightly.The response of species with complex levels of MPD to desiccation was more variable:Delphinium fissum subsp.sordidum,with intermediate complex MPD,and Anthriscus sylvestris and Meum athamanticum,both with deep complex MPD,tolerated desiccation.In contrast,Ribes uva-crispa with nondeep complex MPD,Lonicera pyrenaica with intermediate complex MPD and Chaerophyllum aureum with deep complex MPD,had diminished germination ability by desiccation.Although seeds of the species with simple levels of MPD tolerated desiccation,those of some species with complex levels were also highly tolerant.Thus,desiccation did not induce secondary dormancy in late embryo growth stages.The desiccation tolerance of imbibed seeds of most of the nine species may show their adaptability to climate change in the Mediterranean region.
