模拟SO2湿沉降对桑树幼苗生长和光系统Ⅱ的影响

摘要

为探明SO2湿沉降对桑树(Morus alba)幼苗生长和叶片光系统Ⅱ(PSⅡ)的影响,本研究利用Na2 SO3和NaHSO3的混合液(浓度比为3∶1)模拟SO2湿沉降,连续处理两年龄的桑树幼苗28 d.结果表明,经浓度为50和100mmol·L-1的混合液处理后,桑树幼苗的叶片出现明显的灼烧伤斑,叶片光合能力显著低于对照(P＜0.05),株高、分枝数、叶片数也明显比对照低.而20 mmol·L-1模拟SO2湿沉降显著提高了桑树幼苗叶片光合能力(P＜0.05),增加了株高、分枝数和叶片数(P＜0.05),促进了桑树的生长.快速叶绿素荧光动力学参数分析表明,50和100 mmol·L-1混合液处理桑树幼苗,PSⅡ单位反应中心吸收的能量(ABS/RC)、反应中心消耗的能量(DIo/RC)和反应中心用于还原QA的能量(TRo/RC)与对照差异不显著(P＞0.05),而反应中心用于电子传递的能量(ETo/RC)、照光2 ms时有活性反应中心的开放程度(Ψo)值和吸收光能用QA-以后的电子传递的量子产额(φEo)值均较对照略有下降(P＞0.05),同时非光化学淬灭的最大量子产额(φDo)值则上升(P＜0.05),说明50和100 mmol·L-1 SO2湿沉降并未影响PSⅡ反应中心对光能的吸收,过剩的光能用于非光化学淬灭,光合性能指数PIABs显著下降(P＜0.05),是因为PSⅡ中电子传递到受到了抑制.本研究结果证明,浓度≤20 mmol·L-1 SO2湿沉降有利于PSⅡ功能和活性提高,提高了桑树光合速率,促进了桑树生长.%In order to reveal effects of SO2 wet deposition on growth and photosystem Ⅱ (PS Ⅱ)of mulberry seedlings,Na2SO3 and NaHSO3 mixture (molar concentration ratio of 3 ∶ 1) were used to simulate SO2 wet deposition for foliage spraying for 28 days.The results showed that significant burns spot appear in leaves in treatments of 50 and 100 mmol · L-1 simulation SO2 wet deposition,meanwhile,photosynthetic ability was significantly lower than control(P＜0.05),in addition,the plant height,branch number and leaf number were reduced significantly.However,the photosynthetic capacity of leaves were increased,and then,the plant height,branch number and leaf number were increased significantly,promoted the growth of mulberry.Rapid chlorophyll fluorescence kinetics parameter analysis showed that the absorbed light reaction center (ABS/RC),reaction center of dissipated energy (DIo/RC) and capture reaction center for energy reduction QA (TRo/RC) in treatments of 50 and 100 mmol · L-1 were no significant difference with CK.While,the reaction center capture of the energy for the electron transfer (ETo/RC),active reaction center of the light at 2 ms,open degree of active reaction center (Ψo) and absorb the light energy used for electron transfer quantum yield after QA-(φEo)were decreased.Meanwhile,the maximum amount quantum yield of photochemical quenching (φDo) was rised,which indicated that the light energy absorption of the reaction center were not affect in treatments of 50 and 100 mmol · L-1,while,excess light energy was used in the non-photochemical quenching,photosynthetic performance index (PIABs) were dropped significantly(P＜0.05),the reasons of the electron transport in the PS Ⅱ were suppressed.In this experiment,the PS Ⅱ function and activity of mulberry were improved under ≤20mmol · L-1 SO2 wet deposition,which could promote the mulberry growth.