光照条件对长苞铁杉种子萌发与幼苗生长的影响

2004-2006年研究了在不同光照下(100%,50%,25%,10%全日照)长苞铁杉(Tsuga longibracteata)种子萌发率、幼苗存活率、幼苗生物量及其分配比例和幼苗根与叶、生理特性。结果表明,50%全日照条件下,种子萌发率和幼苗存活率最高;幼苗根、茎、叶及总生物量最高;光照的增强促使生物量往地下分配以加强根部吸收水分的能力,并促使地上部分的生物量更多的分配到叶片生长上。随着光强的提高,幼苗叶片叶绿素a、叶绿素b、总叶绿素和类胡萝卜素含量均呈下降的趋势,叶绿素a与叶绿素b比值和类胡萝卜素与总叶绿素比值呈上升趋势。在光强不超过50%时,随着光强的提高,幼苗叶片和细根的MDA含量、SOD和POD活性呈升高趋势;光照强度达到全日照时,叶片MDA含量、SOD和POD活性呈下降趋势。幼苗叶片和细根Pro含量在25%全日照时最低。50%全日照附近是长苞铁杉育苗的合适光照强度。

Effect of light intensity environment on Tsuga longibracteata seed germinated, seedling survival and growth

The seed germinated rate,seedling survival rate,seedling biomass and physiological characteristics of seedlings leaves and roots were investigated after Tsuga longibracteata Cheng seeds seminated in 4 light intensity levels(100%,50%,25%,10% full sunlight) seedbeds for one growing season from 2004 to 2006.The seed germinated rate and seedlings survival rate were the highest in the 50% full sunlight environment.Full sunlight is not suitable for seedling biomass accumulation.In 50% full sunlight environment,the root,stem,leaf and total seedling biomass were all the highest.The increase of light intensity promoted more biomass distributing to roots to enhance the seedling roots′ ability of water absorbing,and promoted more overground biomass distributing to leaves.As the light intensity increasing,the contents of chlorophyll a(Chla),chlorophyll b(Chlb),chlorophyll(Chl) and carotenoid(Car) in seedling leaves declined,the rates of Chla/Chlb and Car/Chl rised.When light intensity was not more than 50% full sunlight,the MDA contents,the SOD activities and POD activities of seedling leaves and roots showed incremental trends along with light intensity increasing.When light intensity was full sunlight the MDA contents of seedling leaves,the SOD and POD activities of seedling leaves declined observably.The Pro contents of seedling leaves and roots were both lowermost in 25% full sunlight environment.The suited light intensity of T.longibracteata seeds germinating and seedlings growing should be hereabout 50% full sunlight.