盐胁迫对八角金盘光合生理特性的影响

Effects of Salt Stress on the Photosynthetic Characteristics of Fatsia japonica

以八角金盘(Fatsia japonica)幼苗为试材,设置CK(0 g/L NaCl)、S6(6 g/L NaCl)、S12(12 g/L NaCl)和S24(24 g/L NaCl)4种盐浓度进行盆栽处理,探讨盐胁迫对八角金盘幼苗光合特性及相关生理指标的影响。结果表明:(1)低浓度(S6)盐胁迫下,八角金盘的净光合速率及气孔导度显著降低(P<0.05),但光系统Ⅱ(PSⅡ)最大光化学效率(Fv/Fm)、叶绿素含量、抗氧化酶活性、丙二醛(MDA)含量和可溶性蛋白含量等均无显著变化;(2)中浓度(S12)盐胁迫下,八角金盘的净光合速率、叶绿素含量、光合电子传递速率(ETR)、过氧化物酶(POD)和PSⅡ光化学效率(YⅡ)显著降低(P<0.05),MDA含量显著增加(P<0.05),其通过调节非光化学淬灭系数(QN)及提高过氧化氢酶(CAT)、超氧化物歧化酶(SOD)和抗坏血酸过氧化物酶(APX)3种抗氧酶活性来积极主动响应中浓度盐胁迫;(3)高浓度(S24)盐胁迫下,MDA含量显著上升(P<0.05),而POD和CAT酶活性降低,过氧化胁迫加重,Fv/Fm及YⅡ值降至最低,净光合速率亦较其他处理组更低。因此:低浓度盐胁迫对八角金盘幼苗的光合系统有一定抑制作用,但其可以通过调节自身的PSⅡ和抗氧化系统来积极应对;高浓度盐胁迫对八角金盘幼苗的光合生理具有较强的毒害作用,导致PSⅡ受损严重,抗氧化系统调节失效,生长受到严重抑制。

In this study,the seedlings of Fatsia japonica were used as the research materials,and four salt stress treatments(e.g.,CK(0 g/L NaCl),S6(6 g/L NaCl),S12(12 g/L NaCl)and S24(24 g/L NaCl))were carried out to investigate the effects of salt stress on the characteristics of the photosynthetic and physiological indexes.The results showed that:(1)under low salt stress(6 g/L NaCl),the seedlings of Fatsia japonica exhibited significant decrease in net photosynthetic rate and stomatal conductance,while no obviously variations in photosystem Ⅱ(PS Ⅱ) maximum photochemical efficiency(Fv/Fm),chlorophyll content,antioxidant enzyme activity,malondialdehyde content(MDA) and soluble protein content.(2) Under the moderate salt stress(12 g/L NaCl),the net photosynthetic rate,chlorophyll content,photosynthetic electron transfer rate(ETR),peroxidase(POD)activity and PS Ⅱ photochemical efficiency(Y Ⅱ)of the Fatsia japonica seedlings decreased significantly,while MDA content increased significantly. Besides,the Fatsia japonica seedlings could positively adapt to the salt stress by enhancing the photochemical quenching coefficient(QN)and improving the activities of catalase(CAT),superoxide dismutase(SOD),and ascorbic peroxidase(APX).(3)Under the heavy salt stress(24 g/L NaCl),the Fatsia japonica seedlings showed heavy tperoxidation stress,which indicated by the higher MDA content and the lower POD and CAT activities.Moreover,the values of Fv/Fm,YⅡ and the net photosynthetic rate were lowest at the S24 salt stress,which suggested that the photosynthetic mechanism of Fatsia japonica seedlings were severely impaired. It can be concluded that:salt stress has certain effects on the photosynthetic and physiological characteristics of Fatsia japonica seedlings.Fatsia japonica seedlings can positively respond to the low salt stress by regulating the PSⅡ and the antioxidant system,although the low salt stress can inhibit the photosynthetic system.In addition,the photosynthetic and physiologic characteristics of Fatsia japonica seedlings were hit by serious toxic effects under higher concentration of salt stress,which was reflected by the serious damage to the PSⅡ,the antioxidant system,and severe inhibition of the growth of the seedlings.