扑草净对远志幼苗根系活力及氧化胁迫的影响

以远志(Polygala tenuifolia Willd.)为材料,应用组织化学和生物化学的方法研究不同浓度扑草净(0—400 mg/L)对远志幼苗生长、根系活力、膜脂过氧化、活性氧含量及抗氧化酶活性等的影响。10 mg/L扑草净对远志幼苗根系活力、细胞膜完整性及活性氧的积累几乎无显著影响,而25—400 mg/L扑草净处理则显著增加活性氧的积累,明显抑制根系活力且破坏细胞膜完整性;上述结果进一步被膜脂过氧化、质膜完整性、活性氧产生(O.2-和H2O2)的非损伤组织化学染色所证明。远志幼苗可通过多种抗氧化酶(SOD、POD、CAT、APX等)和非酶抗氧化剂(如脯氨酸)的相互协调作用,清除低浓度扑草净胁迫诱发产生的活性氧,减轻对细胞的伤害。研究结果表明,发芽期是远志对扑草净处理的敏感时期,较为安全的扑草净临界浓度为10 mg/L;25mg/L扑草净处理即引起远志幼苗氧化胁迫和膜脂过氧化,使细胞膜的完整性受到破坏,根系活力下降,抑制了远志幼苗的生长发育。该研究为远志抗除草剂胁迫机制及其栽培过程中除草剂的安全合理使用提供理论依据。

Effect of prometryne on root activity and oxidative stress of Polygala tenuifolia Willd. seedling roots

Following prometryne treatment, Polygala tenuifolia Willd. (Polygala) seedlings were investigated histochemically and biochemically to determine the effects of prometryne on root activity, lipid peroxidation, membrane integrity, reactive oxygen species (ROS) accumulation and antioxidant enzyme activity. There was no significant difference between untreated controls and seedlings treated with 10 mg/L prometryne in terms of root activity, membrane permeability and ROS production. Seedlings treated with 25-400 mg/L prometryne showed significantly accelerated ROS production, enhanced loss of membrane integrity and inhibited root cell viability. Histochemical staining with Schiff's reagent, Evans blue, nitroblue tetrazolium and 3,3-diaminobenzidine was positively correlated with the accumulation of malondialdehyde (MDA), loss of membrane integrity, generation of superoxide radicals (O₂^{· -}) and generation of hydrogen peroxide (H₂O₂), respectively. Prometryne-induced oxidative stress triggered significant changes in the antioxidant defense machinery. At lower prometryne concentrations, the antioxidant defense system of Polygala seedlings demonstrated very efficient and coordinated enzymatic (superoxide dismutase; catalase; ascorbate peroxidase; peroxidase) and non-enzymatic (non-protein amino acids; proline) scavenging of ROS to regulate the cascades of uncontrolled oxidation and protect plant cells from oxidative damage. Higher prometryne levels increase oxidative stress through excessive production of ROS and destruction of antioxidant systems, ultimately leading to seriously damaged Polygala seedlings. The presented results indicate that Polygala seedlings are very sensitive to prometryne exposure during germination; however, the application of 10 mg/L is safe for seedling growth. Treatment at 25 mg/L prometryne can cause significant oxidative stress and lipid peroxidation as well as damage cell membrane integrity, leading to decreased root activity and inhibited seedling growth. These results may provide a theoretical basis for the mechanisms of herbicide resistance and the safe use of herbicides during Polygala cultivation.