Comparison of seed germination of four Artemisia species (Asteraceae) in northeastern Inner Mongolia,China

摘要

Two psammophile-dominated Artemisia semi-shrubs (A.wudanica and A.halodendron) and two annual Artemisia forbs (A.sieversiana and A.scoparia) bear significant ecological functions in Horqin Sandy Land,but systematical information on their achenes' germination is very limited.A set of studies were conducted to evaluate seed germination responses to storage periods and methods,different temperatures,lights conditions and sand burial depths,in order to determine inter-specific germination variation in the same genus and to explain how the species adapt to its microhabitat.Fresh achenes of A.wudanica,A.halodendron and A.sieversiana showed high germination capacities,but those of A.scoparia had obvious innate dormancy,which could be broken by chilling and dry storage,especially long-term dry storage.Achene germination of the two semi-shrubs preferred lower temperature fluctuation (10 to 22oC) and was not sensitive to light.But the two annuals preferred higher temperature fluctuation (34 to 22oC) and strong light for their achene germination.These four Artemisia species showed similar responses to sand burial,i.e.soil surface was most favorable for seedling emergence,and the deeper the sand burial,the fewer the seedling emergence.For the two semi-shrubs,their microhabitats are sand dunes with high temperature and intense light,which are not favorable for germination and seedling survival.Only rainfall contributes to temporary decrease of temperature and then triggers germination.We deduced that germination is not the main but a supplementary reproductive mode for the two semi-shrubs in sand dunes.For the two annuals,achene germination is the only reproductive mode,but different responses have been developed for microhabitat adaptation.For A.sieversiana,high germination capacities in wide temperature ranges and all light conditions could improve its competition and advancement in the wettest microhabitats.For A.scoparia,obvious innate dormancy of fresh achenes and germination inhabitation under unfavorable conditions are important adaptation to environmental disturbances.