抑制剂和安全剂对高羊茅根中酶活性和菲代谢的影响

以高羊茅(Festuca arundinacea)为供试植物，利用水培体系研究了抑制剂和安全剂对植物根中过氧化物酶(POD)和多酚氧化酶(PPO)活性以及菲代谢的影响。供试安全剂为浓度0.3%的NaCl，抑制剂为浓度2.00 mg/L的Vc。结果表明，2.00 mg/L的Vc作用下，1—16d，高羊茅根的菲含量显著高于对照处理，而供试安全剂对植物根中菲含量的影响不显著。抑制剂作用下植物根部的PPO和POD活性显著降低；16d，抑制剂作用下的植物根部PPO和POD活性为对照组的1/6和1/9，表现出强抑制效应。而安全剂作用下植物根部PPO和POD活性则略高于对照组，但差异不显著（P＜0.05）。植物体内酶的初始活性是影响植物代谢PAHs菲的关键因素。抑制剂主要通过调节酶活性来影响根系代谢菲，其对植物根中PPO和POD活性的抑制效率与根部菲代谢抑制效率显著正相关。

Effects of inhibitor and safener on enzyme activity and phenanthrene metabolism in root of tall fescue

Polycyclic aromatic hydrocarbons (PAHs) are a group of persistent organic contaminants commonly found in the environment. Due to their highly mutagenic and carcinogenic properties, their behaviors and fate in the soil/water plant system are of great environmental concern. Because plants form the basis of human and animal food webs, potentially harmful organic contaminants including PAHs could find their way into human and animal populations via this route. Clearly, increased understanding of how plants take up and accumulate PAHs from the environment could have considerable benefit for risk assessments. In recent decades, considerable interest in the uptake of PAHs by plants has emerged. Plants can be exposed to PAHs in different ways. Foliage uptake of atmospheric PAHs occurs via the deposition of particle-bound compounds and the retention of vapor-phase PAHs on waxy leaf cuticles. The rate and extent of plant root uptake depends on the physiochemical properties of the PAHs, soil characteristics, and plant species and physiology. Recently, metabolisms of PAHs have been observed and proven to be related to the enzyme activities in plant bodies. To this end, how to control and regulate the activity of plant enzymes and PAH metabolism is of worldwide concerns. However, little information is available on this subject. In this work, impacts of inhibitor and safener on the activities of PPO (phenol oxidase) and POD (peroxidase) and the metabolism of phenanthrene as a representative of polycyclic aromatic hydrocarbons (PAHs) in roots of tall fescue (Festuca arundinacea) were investigated utilizing hydroponic cultivation system in a greenhouse. 0.3% NaCl and 2.00 mg/L Vc were chosen as representatives of safener and inhibitor. Root concentrations of phenanthrene were found to be significantly higher with the addition of 2.00 mg/L Vc in 1-16 d. However, no significant difference was seen for root concentrations of phenanthrene with the addition test safener. The activities of PPO and POD in root were much lower with the addition of Vc, and were only 1/6 and 1/9 of the controls without inhibitor or safener, respectively, indicating the strong inhibition of test inhibitor on PPO and POD activity. In contrast, no significant difference was observed between the test enzyme activity with and without the addition of safener (0.3% NaCl). The initial activity of enzyme in roots of tall fescue is a key factor of the phenanthrene metabolism. With the addition of test inhibitor, the inhibition efficiency of enzyme activity was positively correlated to the inhibition efficiency of phenanthrene metabolism. This indicates that the inhibitor affected the metabolism of phenanthrene in root mainly by regulating the enzyme activity. To our knowledge, this is a primary investigation on the inhibitor and safener regulated uptake of PAHs by plant. Results of this work would be of high values in risk assessments of organic contaminants in the environment.