Cr胁迫对‘中山杉406’幼苗生长和生理生化特性的影响

Effects of Cr stress on growth and physiological and biochemical characteristics of‘Zhongshanshan 406’seedlings

采用水培法模拟实验,以亲本落羽杉〔Taxodium distichum(Linn.)Rich.〕为对照,比较了不同浓度和处理时间Cr胁迫对‘中山杉406’(‘Zhongshanshan 406’)幼苗生长、抗氧化系统和光合系统的影响。结果显示:在中浓度(5.00μmol·L^(-1))和高浓度(20.00μmol·L^(-1))Cr处理28 d时,‘中山杉406’幼苗的相对生长速率和相对含水率以及叶片的相对电导率、叶绿素含量和丙二醛(MDA)含量的变幅均小于落羽杉。随着Cr浓度的增加和处理时间的延长,‘中山杉406’幼苗叶片的超氧化物歧化酶(SOD)和过氧化物酶(POD)活性总体呈升高的趋势,而落羽杉幼苗叶片的SOD和POD活性总体呈先升高后降低的趋势,‘中山杉406’在处理后期(28 d)能维持较高的抗氧化酶活性。与对照(0.00μmol·L^(-1)Cr)相比,在1.25和5.00μmol·L^(-1)Cr处理下,‘中山杉406’幼苗叶片的PSⅡ最大光化学效率(F_(v)/F_(m))、PSⅡ有效光化学效率(F_(v)′/F_(m)′)和PSⅡ实际光化学效率(Φ_(PSⅡ))总体变化不大,而落羽杉的这3个叶绿素荧光参数在5.00μmol·L^(-1)Cr处理下显著降低,且在20.00μmol·L^(-1)Cr处理28 d时的降幅明显大于‘中山杉406’;随着处理时间的延长,‘中山杉406’幼苗叶片非光化学猝灭系数(NPQ)总体呈升高的趋势,而落羽杉从处理14 d开始变化不大。Cr胁迫下2种植物相对生长速率与叶片的光合系统指标(叶绿素含量、F_(v)/F_(m)值、F_(v)′/F_(m)′值、Φ_(PSⅡ)值)以及抗氧化系统指标(SOD活性、POD活性和MDA含量)有较高关联度,Φ_(PSⅡ)值和叶绿素含量与抗氧化系统指标间有较强关联性。综上所述,‘中山杉406’和落羽杉对低浓度(1.25μmol·L^(-1))Cr胁迫有一定的生长适应性,‘中山杉406’对中、高浓度Cr胁迫的抗性更强。Cr胁迫下较强的PSⅡ光化学性能、抗氧化能力和PSⅡ热耗散能力是‘中山杉406’维持较高生长速率以及防御光抑制和光破坏的重要机制。

Taking the parent Taxodium distichum(Linn.)Rich.as the control,the effects of different concentrations and treatment times of Cr stress on growth,antioxidant system,and photosynthetic system of‘Zhongshanshan 406’seedlings were compared by using hydroponic simulation experiments.The results show that the variation degrees of relative growth rate and relative water content,and relative conductivity,leaf chlorophyll content and malondiadehyde(MDA)content in leaves of‘Zhongshanshan 406’seedings are smaller than those of T.distichum under medium concentration(5.00μmol·L^(-1))and high concentration(20.00μmol·L^(-1))of Cr treatment for 28 d.With the increase of Cr concentration and the extension of treatment time,the activities of superoxide dismutase(SOD)and peroxidase(POD)of leaves of‘Zhongshanshan 406’seedlings show a tendency to increase in general,while the SOD and POD activities of leaves of T.distichum seedlings show a tendency to first increase and then decrease,and‘Zhongshanshan 406’can maintain relatively high antioxidant enzyme activities in the later stage of treatment(28 d).Compared with the control(0.00μmol·L^(-1)Cr),the variations of maximum photochemical efficiency of PSⅡ(F_(v)/F_(m)),effective photochemical efficiency of PSⅡ(F_(v)′/F_(m)′),and actual photochemical efficiency of PSⅡ(Φ_(PSⅡ))of leaves of‘Zhongshanshan 406’seedlings are not great in general under the treatment of 1.25 and 5.00μmol·L^(-1)Cr,while these three chlorophyll fluorescence parameters of T.distichum significantly decrease under 5.00μmol·L^(-1)Cr treatment,and the decrease degree under 20.00μmol·L^(-1)Cr treatment for 28 d is obviously greater than that of‘Zhongshanshan 406’;with the extension of treatment time,the nonphotochemical quenching coefficient(NPQ)of leaves of‘Zhongshanshan 406’seedlings shows a tendency to increase in general,while that of T.distichum remains relatively unchanged since treatment for 14 d.The relative growth rate of the two plants under Cr stress has relatively high correlation degrees with both photosynthetic system indexes(chlorophyll content,F_(v)/F_(m)value,F_(v)′/F_(m)′value,andΦ_(PSⅡ)value)and antioxidant system indexes(SOD activity,POD activity,and MDA content)of leaves,and there are also relatively strong correlations ofΦ_(PSⅡ)value and chlorophyll content with antioxidant system indexes.In conclusion,‘Zhongshanshan 406’and T.distichum exhibit certain growth adaptability to low concentration(1.25μmol·L^(-1))Cr stress,and‘Zhongshanshan 406’shows stronger resistance to medium and high concentrations of Cr stress.Relatively strong PSⅡphotochemical performance,antioxidant capacity,and PSⅡheat dissipation ability under Cr stress are important mechanisms for‘Zhongshanshan 406’to maintain a relatively high growth rate and defend against photoinhibition and photodamage.