光照强度对六种草地植物种子萌发和幼苗生长的影响

Effects of light intensity on seed germination and seedling growth of six species in grassland

光是影响种子萌发和幼苗生长的环境因素之一,光照强度具有日动态和季节动态,对植物出土和光合物质积累有重要影响。通过室内控制实验,研究松嫩草地六种植物种子萌发及幼苗生长对光照强度的响应,对深入理解松嫩草地植物生活史早期阶段的适应策略具有重要意义。研究结果表明:防风(Saposhnikovia divaricate)、角蒿(Incarvillea sinensis)和黄金菊(Hypochaeris grandiflora)种子萌发率不受光照强度影响,反枝苋(Amaranthus retroflexus)、大果琉璃草(Cynoglossum divaricatum)和紫菀(Aster tataricus)在弱光或中等光照下种子萌发率最高。六种种子的萌发指数在中等光强下最大,且与无光处理间差异显著。除大果琉璃草和反枝苋在中等光强或弱光下胚根生物量最大外,角蒿、防风、黄金菊、紫菀均在较强光下胚根生物量最大,无光下最小;大果琉璃草、黄金菊、防风、反枝苋的地上生物量不受光照强度影响,而角蒿、紫菀在较强光下地上生物量最大;角蒿和大果琉璃草在弱光或中等光强下根冠比最大,防风、黄金菊、紫菀、反枝苋均在较强光下根冠比最大;萌发率和萌发指数与种子大小之间没有显著相关性,幼苗地上和胚根生物量与种子重量成显著正相关关系。光照强度对萌发率和种子大小之间的关系无显著影响,但胚根生物量与种子大小之间关系的斜率受到光照强度影响,中等光强下斜率最大。因此,中等光照条件有利于松嫩草地植物种子萌发和幼苗建植。

Light is one of the environmental factors that affect seed germination and seedling growth.Light intensity has diurnal and seasonal dynamics,which influences plant emergence and accumulation of the photosynthetic products.The responses of seed germination and seedling growth of six species in Songnen grassland to light intensity were investigated in this study through indoor control experiment.The results are important for understanding adaptation strategies at early stage of plant history for Songnen grassland species.Results showed that light intensity had no effect on seed germination percentage of Saposhnikovia divaricata,Incarvillea sinensis and Hypochaeris grandiflora.Germination percentage was the highest at low light or medium light intensity for the other three species Amaranthus retroflexus,Cynoglossum divaricatum,and Aster tataricus.The germination index was the largest at medium light intensity for the six species,which was significantly higher than that in dark.The radicle biomass of C.divaricatum and A.retroflexus were the highest at medium light or low light intensity,but those of the other four species were the highest at strong light and were the lowest in dark.Light intensity had no effect on aboveground biomass of C.divaricatum,S.divaricata,H.grandiflora and A.retroflexus,while aboveground biomass of I.sinensis and A.tataricus were the highest at strong light.The root shoot ratios of I.sinensis and C.divaricatum were the largest at low light or medium light intensity,but those of the other four species were the largest at strong light.There was no significant relationship between seed mass and germination percentage and index,while a positive relationship between seed mass and aboveground/radicle biomass was observed.Light intensity had no significant effect on the relationship between seed mass and germination percentage,but light intensity significantly influenced the slope of linear relationship between seed mass and radicle biomass.The value of slope was the largest at medium light.Therefore,medium light condition favors seed germination and seedling establishment of plants in Songnen grassland.