[目的]本文旨在探究不同光照强度对琼岛杨(Populus qiongdaoensis)幼苗生长和光合特性的影响.[方法]以1.5 年生琼岛杨幼苗为试验材料,设置全光 100%(CK)、全光 70%(RI70%)、全光 40%(RI40%)和全光 10%(RI10%),处理12个月后,分析不同光强对琼岛杨幼苗生长和光合特性的影响.[结果]成活率、地径增长量、叶片数、叶长、叶宽、叶面积和单叶质量均随着光强的减弱而降低,株高增长量和叶片数增长量呈先增后减趋势,RI70%和RI40%处理的琼岛杨幼苗的成活率、株高、地径和叶片数均显著高于RI10%处理;RI70%处理的根生物量、根生物量比和根冠比显著高于RI40%和RI10%处理,而RI70%和RI40%处理的根、茎、叶生物量和总生物量均显著高于RI10%;随着光照强度的降低,叶片叶绿素a、叶绿素b和总叶绿素含量逐渐增大,类胡萝卜素含量随之减小;净光合速率(Pn)随光照强度的减小而显著下降,在RI70%光强下琼岛杨幼苗叶片的Pn最大,分别是RI40%和RI10%的1.72倍和2.16倍;叶片数增长量与株高增长量、地径增长量呈显著正相关关系,净光合速率与类胡萝卜素含量(Car)和蒸腾速率(Tr)呈显著正相关,气孔限制值(Ls)与胞间CO2浓度(Ci)和气孔导度(GS)呈显著负相关.[结论]琼岛杨幼苗能忍耐一定程度遮阴,适度遮阴可促进幼苗地上和地下部分的生长并提高其气体交换能力,但在弱光胁迫下幼苗难以成活和生长,相对光强70%下琼岛杨幼苗的适应性最强.
[Objective]This study aimed to explore the effects of different light intensities on the growth and photosynthetic char-acteristics of Populus qiongdaoensis seedlings.[Methods]One and a half-year-old P.qiongdaoensis seedlings were used as ex-perimental materials.Four light intensity treatments were set up:full light(100%,CK),70% full light(RI70%),40% full light(RI40%),and 10% full light(RI10%).After 12 months of treatment,the effects of different light intensities on the growth and photosynthetic characteristics of P.qiongdaoensis seedlings were analyzed.[Results]Survival rate,ground diame-ter growth,leaf number growth,leaf length,leaf width,leaf area,and single leaf mass all decreased with the reduction of light intensity.Stem height growth and leaf number showed an initial increase followed by a decrease trend.The survival rate,stem height,ground diameter,and leaf number of P.qiongdaoensis seedlings under RI70% and RI40% treatments were significant-ly higher than those under RI10% .The root biomass,root biomass ratio,and root-to-shoot ratio of RI70% treatment were sig-nificantly higher than those of RI40% and RI10% .RI70% and RI40% treatments resulted in significantly higher root,stem,leaf biomass,and total biomass compared to RI10% .With decreasing light intensity,leaf content of chlorophyll a,chlorophyll b,and total chlorophyll content gradually increased,while the content of carotenoids decreased.Pn significantly decreased with the decrease of light intensity.Under RI70%,P.qiongdaoensis sseedlings exhibited the highest Pn,which was 1.72 times and 2.16 times higher than those under RI40% and RI10%,respectively.Leaf number growth was significantly positively cor-related with stem height growth and ground diameter.Pn was significantly positively correlated with carotenoid(Car)and tran-spiration rate(Tr).Stomatal limitation value(Ls)was significantly negatively correlated with Ci and GS.[Conclusion]P.qiong-daoensis seedlings can tolerate a certain degree of shade,and moderate shading can promote the growth of both aboveground and underground parts of seedlings which enhancing their gas exchange capacity.However,seedlings face challenges in surviv-al and growth under weak light stress.Relative light intensity of 70% appears to be the most adaptive for P.qiongdaoensis seedlings.