棉铃虫持续取食对棉花三种防御酶活性的作用

The effects of Helicoverpa armigera herbivory on the activity of phenylanlanine ammonialyase,lipoxygenase and polyphenol oxidase in cotton seedling leaves

昆虫取食作为一种关键的生物胁迫因子对棉花防御机制产生了重要影响。植物对昆虫取食产生的防御响应,在昆虫与植物的生态关系中具有重要作用。为了明确棉铃虫Helicoverpa armigera取食与棉花防御性之间的动态互作关系,本文研究了棉铃虫持续取食下及停止取食后,棉花中3种防御相关酶活性变化的时间效应。在明确了棉花受损程度与棉铃虫取食时间关系的基础上,分别考察了棉铃虫持续取食2、6、12、18和24h,对棉花中苯丙氨酸解氨酶(PAL)、脂氧合酶(LOX)和多酚氧化酶(PPO)活性的影响。针对棉铃虫持续取食棉叶12h后停止取食,研究了去除虫害胁迫后0、6、12、24和36h,棉花体内PAL、LOX、PPO活性的变化。结果表明:在棉铃虫持续取食棉叶24h内,棉花中3种防御酶的活性响应有所不同,其中,棉铃虫持续取食2和6h对棉花体内PAL活性没有产生显著影响,而持续取食12h显著诱导了PAL活性,持续取食24和36h,均极显著诱导了PAL活性;棉铃虫持续取食2、6、12、和18h均显著诱导了棉花体内LOX活性,持续取食24h极显著诱导了LOX活性;棉铃虫持续取食6h极显著诱导了棉花体内PPO活性,持续取食24h显著诱导了PPO活性。棉铃虫取食12h后停止取食,在去除虫害除胁迫后0、6、12、24和36h,棉花体内PAL活性均显著升高;而LOX活性则呈现出先升高后恢复正常的现象;PPO活性开始无变化,但在胁迫去除后12和24h显著增高,到36h恢复正常。可见,棉花体内PAL、LOX和PPO活性对棉铃虫取食产生的防御响应,与其受虫害持续取食胁迫时间的增长呈正相关,随着取食时间和受危害的程度加大而升高。并且,在虫害胁迫去除后的一定时间内,棉花体内PAL、LOX和PPO活性依然会保持较高的活性状态,而同等程度机械损伤后的棉叶内PAL、LOX、PPO活性均没有发生显著性变化。说明棉花对于棉铃虫取食胁迫的防御与棉花生理生化性质的改变有关,且具有持续性。

Defense-related enzymes of cotton are greatly influenced by various environmental stresses,including insect herbivory.The defense response to insect herbivory plays an important part in the ecological relationship between insects and plants.In order to explore the dynamic interaction between plant defense and Helicoverpa armigera herbivory,the effect of H.armigera herbivory and the cessation of herbivory on the activity of three defense related enzymes in cotton seedlings was investigated.Changes in the activity of phenylanlanine ammonialyase （PAL）,lipoxygenase （LOX） and polyphenol oxidase （PPO） in the leaves of cotton seedlings were measured after these had been fed on by H.armigera for 2,6,12,18 and 24 hours.Changes in PAL,LOX,and PPO activity were measured after removing H.armigera that had been feeding for 12 hours.The results indicate that the three enzymes responded differently to H.armigera herbivory.After 2 h and 6 h,PAL activity had not changed significantly but this increased markedly after 12,18 and 24 h.LOX activity increased significantly after 2,6,12,18 and 24 h,and PPO activity increased after 6 and 24 h.After removing H.armigera that had been feeding for 12,PAL activity increased until 36 h,whereas LOX activity increased until 24 h then returned to normal.PPO activity increased only at 12 h and 24 h.There was a positive correlation between changes in PAL,LOX and PPO activity in cotton seeding leaves and the duration of feeding by H.armigera.The activities of the three defense related enzymes also increased after removing H.armigera.In contrast,mechanical injury of leaves did not induce change in the activity of the three defense related enzymes comparing to the untreated control.This suggests that the activities of the three defense related enzymes were influenced by insect herbivory,and that this may change the physiological and biochemical properties of cotton leaves.