以3个来源于广东茂名的土沉香〔Aquilaria sinensis(Lour.)Spreng.〕种源(大白、小白和大黄)和1个来源于云南的土沉香种源的1年生幼苗为研究对象,对不同遮光条件下〔相对光强100%(对照,自然光强)、50%、25%和5%〕4个种源幼苗叶片的净光合速率(Pn)的光响应和CO₂响应曲线、光合和气体交换参数、叶绿素含量和叶绿素a/b(Chla/b)值进行了分析,并比较了4个种源幼苗的相对生长速率(RGR)。结果表明:4个种源的Pn均随光合光量子通量密度的增加而上升,且对照组各种源的Pn值均明显高于各处理组;4个种源的Pn值均随胞间CO₂浓度的升高或相对光强的增大逐渐提高。随相对光强的降低,4个种源的最大光合速率、光补偿点、光饱和点、暗呼吸速率、最大电子传递速率、最大羧化速率和磷酸丙糖利用速率均下降或显著下降(P<0.05),而表观量子效率则略有升高。在相对光强100%～25%条件下,随相对光强降低,4个种源的叶绿素含量显著提高、Chla/b值显著减小;大白和小白种源的RGR逐渐增大,大黄种源的RGR差异不显著,而云南种源的RGR显著减小。而在相对光强5%条件下,大黄和云南种源的叶绿素含量显著降低,Chla/b值显著增大,RGR显著减小;大白和小白种源幼苗全部死亡。由种源间的比较可见:4个种源的各项光合参数以及叶绿素含量、相对生长速率均有一定的差异,其中云南种源的各项指标总体上均最低。综合来看,土沉香为半阳生植物,对不同的光环境表现出相对较强的适应性。

Taking one-year-old seedlings of three provenances ( Dabai， Xiaobai and Dahuang ) of Aquilaria sinensis ( Lour．) Spreng． from Maoming of Guangdong Province and one provenance of A．sinensis from Yunnan Province as research objects， light and CO₂ response curves of net photosynthetic rate ( Pn ) ， photosynthetic and gas exchange parameters， chlorophyll content and Chla /b value of seedling leaf of four provenances under different shading conditions〔relative irradiance 100% ( control，natural light intensity) ， 50% ， 25% and 5% 〕were analyzed， and seedling’s relative growth rate ( RGR) was also compared． The results show that Pn value of four provenances all increase with increasing of photosynthetic photon flux density， and Pn value of four provenances in the control all are higher than that in the treatment groups． And Pn value of four provenances gradually increase with rising of intercellular CO ₂ concentration or increasing of relative irradiance． With reducing of relative irradiance， the maximum photosynthetic rate， light compensation point， light saturation point， dark respiration rate， maximum electron transport rate， maximum carboxylation rate and triose phosphate utilization rate of four provenances all decrease or significantly decrease ( P＜0． 05) ， while the apparent quantum yield slightly increases． Under relative irradiance 100% －25% conditions， with reducing of relative irradiance， chlorophyll content of four provenances significantly increase but their Chla /b value significantly decrease， RGR of Dabai and Xiaobai provenances increase gradually and that of Dahuang provenance has an un-significant difference， but that of Yunnan provenance significantly decreases．Under relative irradiance 5% condition， chlorophyll content of Dahuang and Yunnan provenances significantly decrease and their Chla /b value significantly increase， and their RGR significantly decrease，while all seedlings of Dabai and Xiaobai provenances die． According to comparison result among provenances， it is suggested that there is a certain difference in photosynthetic parameters， chlorophyll content and relative growth rate among four provenances， in which， all indexes of Yunnan provenance generally are the lowest． In general， A． sinensis is a semi-sun plant， and has relatively strong adaptability to different light environments．