不同光照强度对兴安落叶松几种主要防御蛋白活力的影响

林木组成抗性对抵御害虫危害发挥着重要作用。为了研究环境因子对其组成抗虫性的影响,以兴安落叶松幼苗为试验材料,通过搭建遮阳棚设置3个光照强度(自然光照作为对照、50%和25%自然光照强度),模拟森林幼苗生长的林缘、林窗和林下3种不同的光环境,分析不同光照强度对其针叶内与植物抗虫性有关的几种主要防御蛋白活力的影响。研究结果表明,不同光照强度对针叶内主要防御蛋白活力有显著影响(P<0.05)。50%和25%光照强度下,POD、SOD、PAL、PPO和CI的活性显著高于自然光照下的(P<0.05),POD和CI的活性在50%光照强度下最高,SOD、PAL和PPO的活性在25%光照强度下最高;自然光照条件下CAT的活性显著高于50%和25%光照强度下的(P<0.05);遮荫处理对TI的活性有显著影响(P<0.05),但在不同月份中波动较大,规律性不明显。相同的光照强度条件下,主要防御蛋白活力在3个月中也有显著变化(P<0.05)。7月和8月份保护性酶POD和CAT的活性显著高于6月(P<0.05);防御性酶PAL、PPO以及蛋白酶抑制剂CI的活性在6月份最高。综合以上研究结果,光照可影响兴安落叶松针叶中几种主要防御蛋白活力,这也说明在较荫蔽的光照环境下,兴安落叶松有较强的抗性。其中SOD、CAT、PAL、PPO和POD是植物次生物质生成过程中的关键酶,其活性的改变在一定程度上表征着植物防御体系在变化。研究环境因子与植物防御之间的关系具有重要的理论和实际应用价值。

Effects of different light intensities on activities of the primary defense proteins in needles of Larix gmelinii

Larix gmelinii is among the most important timber species in northeastern China due to its cold hardiness,drought resistance and rapid growth.It is ecologically and economically very important,but is seriously affected by Lymantria dispar L.,a defoliating insect pest.Plants,including trees,employ an array of physical and chemical constitutive defense mechanisms which play an important role in protection from insect herbivory.Chemical defenses include secondary metabolites and proteins.The primary defense proteins consist of protective enzymes,e.g.peroxidase(POD),superoxide dismutase(SOD) and catalase(CAT);defense enzymes,e.g.polyphenol oxidase(PPO) and phenylalanine ammonia-lyase(PAL);protease inhibitors,e.g.trypsin inhibitor(TI) and chymotrypsin inhibitor(CI).In many organisms.light is a crucial environmental signal influencing natural physiological and developmental processes.There are different effects on the phenotypic and physiological characteristics even if the same plant species with the long-term growth in different light condition.In order to understand the impact of sunlight on the constitutive defenses of Larix gmelinii,sunlight control treatments with three intensities: 100% of natural sunlight(NS),about 50% and 25% of natural sunlight(NS/2,NS/4) were conducted to simulate the light conditions of forest edge,forest gap and understory where the Larix gmelinii grows.Sunlight control was achieved by erecting shade shelters of woven black nylon netting.The activities of the primary defense proteins in the needles of Larix gmelinii seedlings under different light treatments were measured.The activities of POD,SOD,PAL,PPO and CI under 50% and 25% of natural sunlight conditions were significantly(P<0.05) higher than those under 100% of natural sunlight conditions both in June,July and August.The activities of POD and CI were greatest under 50% of natural sunlight conditions while the activities of SOD,PAL and PPO were greatest under 25% of natural sunlight conditions.But the CAT activities were significantly(P<0.05) decreased under the shade conditions.The activities of TI were significantly(P<0.05) changed under different light treatments,but the variation was not regular.The activities of the primary defense proteins showed significant(P<0.05) differences under the same light intensity within the three-month experiment.The activities of POD and CAT in July and August,were significantly(P<0.05) higher than in June.The activities of SOD,PAL,PPO and CI were highest in June.Our results suggested that different light intensities can significantly affect the activities of the primary defense proteins.SOD,CAT,PAL,PPO and POD are the key enzymes in the production of the secondary metabolites of Larix gmelinii.The observed changes indicate the plant defense system has been changed.Our findings therefore suggeste that Larix gmelinii could endure a low light intensity environment and a suitable light deficit might be a feasible means to increase the defensive protein activities of Larix gmelinii.Furthermore,Larix gmelinii could likely be used in forestry systems designed to limit light with increasing forest canopy density or in the schattenseite.Studying the correlation between plant defense and environmental factors may yield both theoretical and practical implications for future studies as well as field applications.