摘要:稀土污染已成为制约农业发展的一种重要因素，为探讨外源过氧化氢（H₂O₂）缓解裸燕麦镧（La）胁迫伤害的光合生理机制，以'白燕7号’裸燕麦幼苗为材料，采用砂培方法，研究了5 mmol/L H₂O₂喷施预处理对1.20 mmol/L La³⁺胁迫下裸燕麦幼苗生长、叶片叶绿素荧光参数和碳同化关键酶活性的影响。结果表明：La胁迫下，H₂O₂预处理的裸燕麦幼苗根长、株高和生长量的降幅及叶片叶黄素循环脱环氧化状态（A+Z）/（V+A+Z）显著下降，PSⅡ最大光化学效率（F_v/F_m）、实际光化学效率（Φ_PSⅡ）、光化学猝灭系数（qP）和吸收光能用于光化学反应的份额（P）显著提高，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（E_x）和双光系统间激发能分配不平衡偏离系数（β/α-1）明显降低，同时1，5-二磷酸核酮糖羧化酶（Rubisco）、1，7-二磷酸景天庚酮糖酯酶（SBPase）和1，6-二磷酸果糖醛缩酶（FBAase）活性显著提高，但转酮醇酶（TKase）活性无显著变化。表明外源H₂O₂能够通过提高PSⅡ光化学效率和碳同化关键酶活性而非依赖叶黄素循环的热耗散来减轻La胁迫导致的光抑制，从而缓解La胁迫幼苗生长的受抑程度，增强裸燕麦对La胁迫的适应性。



Abstract:Pollution with rare earths has become an important factor restricting agricultural development. The objective of this study was to analyze the photosynthetic physiological mechanism of exogenous hydrogen peroxide (H₂O₂) mitigating lanthanum (La) induced stress damage in naked oat (Avena nuda) seedlings. Seedlings of naked oat cultivar ‘Baiyan 7’ were used in a sand culture experiment to investigate the effect of spraying 5 mmol/L H₂O₂ on seedling growth, leaf chlorophyll fluorescence parameters, and photosynthetic carbon assimilation enzyme activities upon a 1.20 mmol/L La³⁺ treatment. The results showed that root length, plant height, and biomass, and the leaf de-epoxidation extent of xanthophyll cycle (A+Z)/(V+A+Z) of naked oat seedlings sprayed with the H₂O₂ decreased significantly, and PSⅡ maximal photochemistry efficiency (F_v/F_m),practical photochemical efficiency(Φ_PSⅡ),photochemical quenching coefficient (qP), and quotient of absorbed luminous energy used for photochemical action (P) apparently increased. However, PSⅡ non-photochemical quenching coefficient (NPQ), regulated energy dissipation Y(NPQ), non-regulated energy dissipation Y(NO), quotient of absorbed luminous energy used for antenna heat dissipation (D), quotient of absorbed luminous energy used for non-photochemical dissipation (E_x) in reaction center of PSⅡ, and unbalanced distribution of coefficient deviation on excitation energy between two photosystems (β/α-1) decreased significantly under La stress. Moreover, the activities of ribulose 1, 5-biphosphate carboxylase (Rubisco), sedoheptulose-1,7-bisphosphatase (SBPase), and fructose-1,6-bisphosphate aldolase (FBAase) increased significantly. However, there was no significant change in transketolase (TKase) activity. These results show that exogenous H₂O₂ can decrease photoinhibition caused by La stress through improving PSⅡ photochemical efficiency and carbon assimilation key enzyme activity, but not based on the xanthophyll cycle-dependent energy dissipation, which showed to mitigate inhibition of La stress on seedling growth and enhanced adaptability of naked oat to La stress.





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