伞形科两种植物幼苗生长对光照强度的可塑性响应

Comparison of plasticity of seedling growth of two umbellaceae species in response to light intensity

将明党参（Changium smyrnioides Wolff）和峨参（Anthriscus sylvestris Hoffm．）幼苗置于按全光照百分率为100％（S100）、65％（S65）和25％（S25）的人工控制光环境下处理。结果表明，光照强度显著影响明党参和峨参幼苗的生长：明党参在S6，生长最好，株高、冠幅、叶长、叶宽、地上地下生物量等均达到最大值，且S65的明党参生物量是S100的2倍、S25的3倍左右；而峨参地上部生长随着光照强度的减弱而增强，S25生长最好，但地下部生长则在S65生长最好，表现出与明党参同样的响应规律。明党参在不同光照强度下生长速率差异显著，S65显著高于其余两个处理；峨参虽然也在S65生长速率最大，但在不同光照强度间无差异。明党参生长速率明显小于峨参，总生物量约为峨参的1／3—1／8，相对于峨参而言明党参是一个在幼苗阶段生长缓慢的物种。

Changium smyrnioides Wolff, a monotypic species in Umbellaceae, has a narrow distribution area, which can only be found in Yangtze Rive basin in China, and its seedling is rare in natural habitat. Anthriscus sylvestri （L.） Hoffm., a ruderal in Europe and China, is one of the classical clonal caespitose plants and distributed widely. A. sylvestri has been investigated in a wide ecological scope in Europe for its powful progenitive capacity and tolerance of severe environmental conditions. C. smyrnioides is an endangered plant, A. sylvestri is a ruderal, however, both species have similar lifestyle. Light is an important environmental factor for all plants, and the distribution and growth of C. smyrnioides are limited by light. Morphological plasticity plays an important role in light acquisition of plants and variations in size and placement of light-acquiring organs such as leaf,which is sensitive to light availability. In this study we investigated the influence of light on the two species seedlings growth. Three light intensity treatments, i.e. 100% relative light intensity（S100 ）, 65 % relative light intensity（S65 ）and 25 % relative light intensity（S25 ）, were established. Results showed that light was a very important factor affecting C. smyrnioides seedling growth, but not for A. sylvestri. C. smyrnioides seedling growth had a significant difference under different light indensity. Under S65 C. smyrnioides seedling grew fastest, and the height, crown amplitude, leaf length, leaf width, leaf biomass and root biomass achieved the highest valuees. The total biomass of C. smyrnioides seedling under S65 was twice than seedling under S100 and trinal times than under S25. Leaf biomass of A. sylvestri seedling was increased with the decrease of light intensity, and the leaf biomass was the highest under S25.Root biomass of A. sylvestri seedling grew fastest under S65, just as C. smyrnioides seedling.Difference of relative growth ratios （RGR） of C. smyrnioides seedling was significant under three treatments, and the RGR under S65 was significantly higher than the other treatments. The RGR of A. sylvestri had no difference among three light treatments. The RGR of C. smyrnioides seedling was significantly higher than of A. sylvestri. The total biomass of C. smyrnioides seedling was 1/3 to 1/8 of A. sylvestri, that meant it was a species with slowly growing speed during junior phase relative to A. sylvestri.