明党参幼苗存活与生长对光照强度的响应

以濒危植物明党参低温催芽形成的幼苗和常温正常萌发的幼苗为对象，对其存活及形态、结构、生物量及其分配、生长速率等指标进行测定和分析.结果表明,明党参幼苗在较高光强（65％全光照）存活率最高，有利于幼苗建成，低光强存活率最低.低温催芽形成的幼苗和常温正常萌发的幼苗对光照强度的响应规律类似，明党参幼苗的生长参数（株高除外）叶生物量、根生物量、总生物量、生长速率和总叶面积均在65％全光照条件下达到最大值，表现出最佳生长状况，表明适宜明党参幼苗生长的光照条件是65％全光照；利用低温催芽形成的幼苗生物量约是常温正常萌发幼苗的5倍，能提高其经受不利环境的能力，为明党参的栽培和保护提供一种新的途径.

Responses of Changium smyrnioides seedlings survival and growth to light intensity

Changium smyrnioides,a monotypic species in Umbellaceae,can only be found in Yangtze Rive basin in China,and its seedlings are rare in natural habitats.The study on the effects of light intensity on C.smyrnioides seedlings survival and growth showed that the seedlings had the highest survival rate under higher light intensity (65% of direct sun light) but the lowest one under 25% of direct sun light,indicating that medium light intensity was propitious to seedlings establishment.The seedlings growth of C.smyrnioides was also the best under 65% of direct sun light,showing the maximum values of growth rate,total leaf area,leaf biomass,root biomass,and total biomass.Low temperature pregermination gave five times higher seedlings biomass than normal germination,and helped the seedlings enduring disadvantageous environment,which provided a new approach to planting and protecting C.Smyrnioides.