温带半干旱地区一年生植物种子的萌发特性

在实验室条件下研究了中国温带半干旱地区科尔沁沙地的23种1年生植物的种子萌发特性（新采集种子、冷藏和干藏种子）.大籽蒿、虎尾草、冠芒草、沙蓬和地锦的新种子萌发率达90%左右,11种植物新种子萌发率均低于70%,说明这些植物的新种子具有或多或少的休眠属性.经过150d的冷干藏后,大籽蒿、虎尾草萌发率保持在90%以上,说明这两种植物完全没有休眠机制;冠芒草、沙蓬和地锦的种子萌发率下降较多,可能是储藏的环境条件导致的2次休眠现象;冷藏和干藏处理均能使绿珠藜、毛马唐、细叶益母草、雾冰藜、金狗尾草、苋菜、马齿苋、碱地肤和水稗草的种子在生长季开始时完成生理后熟,萌发率达到80%以上;干藏有利于促进毛马唐、细叶益母草、马齿苋和鹤虱的种子成熟,冷藏有利于促进绿珠藜和金狗尾草的种子成熟;黄蒿、灰绿藜、画眉草和烛台虫实在不同处理下的萌发率都比较低,说明种子内在生理休眠作用较强,具有减少种子一次性萌发数量的风险分摊策略.大多数1年生植物均能在较短时间内达到最终萌发率的90%,表现出迅速萌发的特性;黄蒿、灰绿藜、碱地肤和沙蓬种子则在不同处理中表现出延长萌发时间的策略来适应半干旱地区不确定的环境条件.最后,探讨了几种主要1年生植物的种子萌发对策与其对环境适应机制之间的关系.

Seed germination characteristics of annual species in temperate semi-arid region

Annual species is an important part of vegetation of Horqin sandy land, which locates in temperate semi-arid zone of northern China. Seed germination behavior plays a key role in the persistence and dynamics of annual desert plants, but germination data in this region is not available. Accordingly, using a standardized procedure, a laboratory experiment was made on the seed germination for 23 annual species collected from a wide range of habitats in the western regions of Horqin sandy land. Measurements were conducted on freshly collected seeds and on samples subjected to chilling in natural filed soil and dry storage in laboratory for about 150 days. The germination characteristics observed in this study leads us to the conclusion that certain regenerative mechanisms of some species in the field and is favor of conservation, restoration and management of plant communities or species.Significant differences were observed in the capacity of freshly collected seeds for immediate germination. Five species attained germination values above or near 90%, but 11 species failed to exceed 70%, which indicated that these freshly collected seeds have more or less dormancy mechanism. After chilling and dry storage for 150 days, two of five species with high germination values of freshly collected seeds, still maintained high germination values greater than 90%, and other three species decreased, which seems to be the secondary dormancy after storage. Most species that germination percentage of freshly collected seeds was under 80%, germination percentage increased to exceed 80%, some even attain 100%, which showed that freshly collected seeds of most annual species have post-maturation mechanism and they can germinate under favorable environmental conditions in the beginning of a growth season. For three species (A. scoparia, C. glaucum, E. pilosa), their seed germination values were under 70% in different treatments, which means that seeds of these species had stronger innate dormancy; Chilling and dry storage to break dormancy were not significant for seeds of E. pilosa and A. scoparia (P>0.05), but chilling was more significant than dry storage to break seed dormancy for C. glaucum; the trait that the fraction of viable seeds did not germinate even in favorable conditions is a benefit strategy to avoid risks in severe desert. Under the experimental conditions, germination time required for 50% and 90% of the final germination percentage to be attained is very short, which indicates that most of the annual species showed the potential for rapid germination, but Artemisia scoparia, Chenopodium Glaucum, Kochia sieversiana and Agriophyllum squarrosun had longer germination duration in different treatments, which may be another favorable strategy. The relationships of germination mechanisms and adaptability to uncertain desert environments of some mainly annual species were discussed.