3种土壤类型下红椿幼苗对铅胁迫的光合响应

采用盆栽试验,研究钙质紫色土、酸性紫色土和冲积土3种土壤类型上生长的红椿幼苗在不同浓度(0、200、450、2 000mg·kg-1)铅(Pb)胁迫下的光合生理响应,探讨红椿在不同土壤类型下Pb污染的生态适应性,为木本植物的重金属修复提供理论依据。结果表明:(1)3种土壤类型下,红椿幼苗叶片叶绿素a、叶绿素b及叶绿素总量随Pb胁迫浓度的增大呈总体降低的趋势,叶绿素含量在钙质紫色土上受Pb胁迫的影响不大,而在酸性紫色土和冲积土上降低明显。(2)不同土壤类型的红椿光合响应曲线变化趋势十分相似,红椿幼苗叶片的净光合速率均随Pb胁迫程度的加大呈先增加后降低的趋势且差异显著,并在Pb浓度为200和2 000mg·kg-1时光合速率分别达到最大值和最小值。(3)随着Pb胁迫浓度的增大,红椿的最大光合速率、表观量子利用效率、光补偿点等光合生理指标都发生了显著改变,说明Pb胁迫严重影响红椿幼苗的光合作用。研究表明,高浓度的铅抑制红椿幼苗叶片叶绿素的合成,从而抑制光合作用的强度,且铅胁迫的浓度越高,叶绿素含量越低,光合作用受到的抑制越强;较低浓度的Pb处理(200和450mg·kg-1)对酸性紫色土和冲积土上红椿的净光合速率影响很小,而对钙质紫色土上红椿的最大净光合速率的抑制最为明显。

Response of Toona ciliata Roem.Saplings Photosynthetic Characteristics to Lead Stress under Three Soil Types

In order to understand the ecological adaptability of Toona ciliata Roem.saplings under lead(Pb) pollution,we conducted a pot-culture experiment with three typical soils(alkaline purple soil,acid purple soil and alluvial soil) in Sichuan Basin.Photosynthetic characteristics and chlorophyll contents of T.ciliata Roem.saplings were studied under four levels of Pb pollution,i.e.,CK,0 mg·kg^-1;T₁,200 mg·kg^-1;T₂,450 mg·kg^-1;T₃,2 000 mg·kg^-1.The results indicated that:(1)Chlorophyll a,chlorophyll b and total chlorophyll contents of T.ciliata Roem.leaves decreased with the increase of Pb pollution regardless of soil types.However,Pb pollution had more significantly effects on chlorophyll contents in both acid purple soil and alluvial soil compared with those in alkaline purple soil;(2)The photo-response curve in three soil types showed the similar tendency.The net photosynthetic rate(P_n) significantly increased under low Pb pollution level,but significantly decreased under high levels of Pb pollution,showing the highest and lowest values under 200 and 2 000 mg·kg^-1 of Pb supply,respectively;(3)Photosynthetic indexes such as maximum photosynthetic rate(P_{n max}),apparent quantum efficiency(AQY),light compensation point (LCP) exhibited significant changes with the increase of Pb pollution,indicating Pb pollution could seriously influence the photosynthesis of T.ciliata Roem.saplings.The results here suggested that high levels of Pb could significantly limit the synthesis of leaf chlorophyll,and thus inhibit the photosynthesis capacity.The more serious Pb pollution could lead to stronger inhibition of photosynthesis.In addition,lower levels of Pb pollution(200 and 450 mg·kg^-1 supplies) had less effects on T.ciliata Roem.under the acid purple soil and alluvial soil compared with under the alkaline purple soil.