外源H2O2对镉胁迫下酸枣幼苗生长及生理特性的缓解效应

Alleviative Effects of Exogenous H2O2 on Growth and Physiological Characteristics of Zizyphus jujuba Seedlings Under Cadmium Stress

通过温室盆栽土培试验,研究不同浓度(0,0.02,0.04,0.06,0.08,0.1,0.3 mmol/L)的外源H2O2处理对0.05 mmol/L Cd胁迫下酸枣幼苗生长、光合系统和荧光特性等的影响。结果表明:(1)Cd胁迫下,酸枣幼苗生长受到抑制,经H2O2处理后,酸枣幼苗对镉抗性系数、光合绿素含量、净光合速率(Pn)、蒸腾速率(Tr)和气孔导度(Gs)均升高,过氧化氢(H2O2)、丙二醛(MDA)含量和胞间CO2浓度(Ci)则出现不同程度的下降;(2)低浓度H2O2(≤0.08 mmol/L)处理后,酸枣叶片和根系内抗氧化酶[过氧化物酶(POD)、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)]活性增强,叶片内1,5—二磷酸核酮糖羧化酶(Rubisco)、1,1—二磷酸景天庚酮糖酯酶(SBPase)和1,6—二磷酸果糖醛缩酶(FBAase)活性最高显著上升38.24%,42.15%,84.08%,但转酮醇酶(TKase)活性无显著变化;(3)酸枣叶片内PSⅡ最大光化学效率(Fv/Fm)、实际光化学效率(ΦPSⅡ)、光化学猝灭系数(qP)和吸收光能用于光化学反应的份额(P)在H2O2处理下最大分别提高37.52%,135.95%,53.10%和98.36%,PSⅡ非光化学猝灭系数(NPQ)、调节性能量耗散Y(NPQ)、非调节性能量耗散Y(NO)、吸收光能用于天线热耗散的份额(D)、PSⅡ反应中心非光化学耗散的份额(Ex)和双光系统间激发能分配不平衡偏离系数(β/α-1)分别降低34.13%,35.15%,30.26%,35.52,32.30%和53.43%,缓解效果显著,但随着外源H2O2喷施浓度的增加,缓解效应有下降趋势。综合分析发现,H2O2对酸枣镉毒的缓解作用与其改善酸枣光合作用、维持抗氧化系统高活性和提高PSⅡ光化学效率等多种生理过程有关。其中以0.08 mmol/L H2O2提高酸枣的修复效率最佳,可作为植物修复的强化措施。

Through a pot soil-culture experiment in greenhouse, the effects of exogenous H2O2 treatment with different concentrations (0, 0.02, 0.04, 0.06, 0.08, 0.1, 0.3 mmol/L) on the growth, photosynthetic system, and fluorescence characteristics of Z. jujube seedlings under the stress of 0.05 mmol/L Cd were studied. The results showed that: (1) Under Cd stress, the growth of Z. jujube seedlings was inhibited. After H2O2 treatment, the Cd resistance coefficient, photosynthetic chlorophyll content, net photosynthetic rate (Pn), transpiration rate (Tr), and stomatal conductance (Gs) of Z. jujube seedlings increased, while H2O2, malondialdehyde (MDA) content, and intercellular CO2 concentration (Ci) decreased with different degrees. (2) The activities of antioxidases (Peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT)) in the leaves and roots of Z. jujube enhanced after treatment with low concentration of H2O2 (≤0.08 mmol/L), and the activities of ribulose—1,5—bisphosphate carboxylase/oxygenase (Rubisco), sedoheptulose—1,1—bisphosphatase (SBPase), and fructose 1,6—diphosphate aldolase (SBPase) in the leaves increased significantly by 38.24%, 42.15%, and 84.08%, respectively. However, there was no significant change for the activity of transketolase (TKase). (3) The maximal photochemistry efficiency (Fv/Fm), actual photochemistry efficiency (ΦPSⅡ), photochemical quenching coefficient (qP), and the share of absorbed light energy for photochemical reactions (P) in the leaves of Z. jujube increased by 37.52%, 135.95%, 53.10%, and 98.36% respectively under the treatment of H2O2. The PSⅡ non-photochemical quenching coefficient (NPQ), regulatory energy dissipation Y (NPQ), non-regulatory energy dissipation Y (NO), the proportion of absorbed light energy used for antenna heat dissipation (D), the proportion of non-photochemical dissipation of PS II reaction center (Ex), and the unbalanced deviation coefficient of excitation energy distribution between two optical systems (β/α-1) decreased by 34.13%, 35.15%, 30.26%, 35.52, 32.30%, and 53.43%, respectively. The mitigate effect was significant, but the mitigation effect tended to decline with the increase of exogenous concentration of H2O2. Comprehensive analysis showed that the mitigate effect of H2O2 on cadmium toxicity of Z. jujube was related to many physiological processes, such as improving photosynthesis of Z. jujube, maintaining the high activity of antioxidant system and improving photochemical efficiency of PS II. Among them, 0.08 mmol/L H2O2 was the best way to improve the repair efficiency of Z. jujube, which could be used as a strengthening measure of phytoremediation.