苯甲酸和肉桂酸对番茄幼苗根部保护酶及膜质过氧化的影响

研究了苯甲酸和肉桂酸对番茄幼苗根部保护酶及膜质过氧化的影响.以珍珠岩作为基质,通过施加不同浓度的苯甲酸和肉桂酸研究在番茄苗期,不同浓度自毒物质主要成分对其根部超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)、丙二醛(MDA)的影响.结果表明:两种物质的作用与其浓度和作用时间密切相关,不同浓度的苯甲酸和肉桂酸都促进了MDA含量的增加,其中以10 mmol/L的苯甲酸在第20天时促进作用最为明显;不同浓度的苯甲酸和肉桂酸在处理后的第5天使SOD的活性显著升高,但是从第10天开始苯甲酸促进作用减弱,5 mmol/L和10 mmol/L的苯甲酸转为抑制作用,而肉桂酸则在第20天转为抑制作用;两种自毒物质使POD的活性在处理后的第5和第10天显著高于对照水平,并且低浓度促进作用明显大于高浓度,但是在第20天急剧下降;不同浓度的苯甲酸和肉桂酸使CAT的活性在处理后的第10天达到最高,但是在第20天完全低于对照水平.可见,苯甲酸和肉桂酸的施用打破了番茄根部保护酶系统原有的平衡,造成了根系的膜质过氧化.     

放线菌对对羟基苯甲酸的降解作用及草莓生长的影响

通过液体培养及温室连作草莓土壤修复试验,从自毒物质降解角度研究了4株放线菌对草莓连作障碍的修复作用及对草莓生长的影响。结果表明:在液体培养条件下,7 d后4株供试放线菌对对羟基苯甲酸的降解率达到97.6%～98.7%。同样,在温室连作条件下,4种供试放线菌制剂对草莓根区土壤中的对羟基苯甲酸有明显的降解作用。与对照相比,在草莓种植结束时,251、252、40号菌剂处理的草莓根区土壤中对羟基苯甲酸含量显著下降。供试放线菌接种处理后,草莓根系总重量及新根较对照分别增加28.5%～50.4%及25.7%～80.2%,表明其对草莓根系生长和新根形成有明显促进作用。菌剂还能有效降低草莓植株死亡率和发病率,相对防效达到51.9%～56.3%。但他们对连作温室草莓植株总重量、叶面积及叶片PPO活性影响不明显。     

毛栓菌27-1漆酶对酚酸类化合物降解的效能分析

探究毛栓菌27-1漆酶对酚酸类化合物的降解效能,为竹林地酚酸类自毒物质降解提供依据。采用超高效液相色谱检测法,通过测定菌液处理后酚酸含量变化,研究毛栓菌27-1漆酶对10种酚酸类化合物的降解特性。结果表明,毛栓菌27-1漆酶能完全降解酚酸类化合物中的香草酸、咖啡酸和芥子酸;丁香酸、阿魏酸和龙胆酸的降解效果一般,降解率50%左右;原儿茶酸的降解效果较差,降解率达35%;不能降解香豆酸、对羟基苯甲酸和绿原酸。研究不同条件下毛栓菌27-1漆酶降解酚酸类化合物丁香酸的效能,发现在pH 5、温度30℃、丁香酸初始浓度小于100 mg/L时,菌株对丁香酸具有高效降解能力,ABTS溶液作为介体物质加入降解体系后降解效果更好,在浓度为0.5 mmol/L时,降解率可达到100%。毛栓菌27-1产生的漆酶对酚酸类化合物具有良好降解效能。     

2株放线菌对土壤中苯甲酸和对羟基苯甲酸的降解作用

【目的】研究2株放线菌对土壤中草莓根泌自毒物质苯甲酸和对羟基苯甲酸的降解效果。【方法】以2株对草莓有促生作用的放线菌Act11和Act12为材料,将其接种于含有定量苯甲酸和对羟基苯甲酸的土壤中,模拟自然条件下培养,定期测定其对土壤中苯甲酸和对羟基苯甲酸的降解量和相对降解率。【结果】①供试放线菌在模拟田间条件下对土壤中苯甲酸和对羟基苯甲酸有较强的降解能力。培养150 d后,Act11和Act12对苯甲酸的降解量分别达到700~888和747~867 mg/kg,对对羟基苯甲酸的降解量分别达到94~218和117~118 mg/kg。②在土壤中加入有机质对2种酚酸相对降解率的影响不同,其中有机质对苯甲酸的相对降解率无显著影响;但Act11在培养15,60,150 d及Act12在培养60 d时,加入有机质能显著提高对羟基苯甲酸的相对降解率。③所有接菌土壤中,苯甲酸与对羟基苯甲酸平均降解速度较CK均有所提高。【结论】供试放线菌对土壤中的苯甲酸和对羟基苯甲酸有较强的降解能力,加入有机质对对羟基苯甲酸的降解有明显促进作用。     

Autotoxicity of Phthalate Esters in Tobacco Root Exudates:Effects on Seed Germination and Seedling Growth

Autotoxicity is one of the major factors that impede continuous cropping. It is defined as the toxic influence of chemicals released from one plant species on the germination and growth of individuals of the same species. Here, in order to exam the autotoxicity of tobacco root exudates, root exudates were collected from tobacco plants grown both in cultural solution and on natural soil. Using ultraperformance liquid chromatography coupled with triple-quadrupole tandem mass spectrometry, main autotoxic chemical substances in the root exudates were identified. The autotoxic effects of suspected autotoxins on seed germination (including germination rate, germination potential, germination index, and vigor index) and seedling growth were analyzed. Dibutyl phthalate (or diisobutyl phthalate), dioctyl phthalate, and diisooctyl phthalate were identified in tobacco root exudates. It was observed that high concentrations (greater than 0.5 mmol L^-1) of each identified phthalate ester caused significant (P < 0.05) inhibition of tobacco seed germination and seedling growth. It can be concluded that phthalate esters such as dibutyl phthalate, diisobutyl phthalate, and diisooctyl phthalate in tobacco root exudates may play an important role in tobacco autotoxicity.     

Etiology of asparagus replant-bound early decline

Asparagus replant-bound early decline (ARED) was characterized and its etiology was elucidated in experiments under greenhouse and field conditions. Selective soil treatments were used to differentiate between autotoxic compounds and soil-borne pathogens as causal agents. In greenhouse experiments, there were symptoms of ARED within 12—15 weeks. Asparagus plants grown in soil formerly used for asparagus (asparagus soil) showed brown lesions on primary and secondary roots, and many secondary roots had rotted. Root weights of plants grown in asparagus soil were lower than those of plants grown in fresh soil.Fusarium oxysporum f. sp.asparagi (Foa) was by far the most common species among the fungi isolated from roots with lesions. Under greenhouse and field conditions, there were similar symptoms, which indicates that the results obtained under greenhouse conditions are similar to those in the field. The vertical distribution of the ARED-causing factor(s) was studied in a greenhouse experiment in which plants were grown in soil from three layers: 0–30, 30–60, and 60–90 cm. For all four asparagus soils tested, there were ARED symptoms and similar disease severity in samples from all three depths. The causal factor persisted at least 11 years after soil was no longer used for asparagus. When asparagus soil was diluted with fresh soil to give mixtures with 100%, 80%, 50%, 20% and 0% asparagus soil, disease severity did not decrease with increasing dilution of the asparagus soil from 100% to 20%. Disease severity of all mixtures with asparagus soil was significantly higher than that for fresh soil. The results imply that ARED is caused by a pathogen colonizing the soil rather than inhibition by autotoxins released from residues of the preceding asparagus crop. This conclusion is supported by the results of greenhouse and outdoor experiments with heat and fungicide treatments of soil. ARED was nullified by heat treatments of 30 min at 55 or 60 °C but not 45 and 50 °C, eliminating autotoxins as an important cause of ARED because they are heat-stable. Foa is eliminated by a 30-min soil treatment at 55–60 °C but not 50 °C. Prochloraz, known for its toxicity toF. oxysporum, also nullified ARED. Disease severity level was related to the density of Foa in soil. The results provide conclusive evidence thatF. oxysporum f. sp.asparagi is the main cause of ARED in the Netherlands, which largely removes the need to discriminate between early decline and replant-bound early decline, because Foa is the main cause of both diseases.     

自毒物质胁迫下不同草莓品种枯萎病抗性变化的研究

通过盆栽试验研究了17个亲本不同的草莓品种在自毒物质—对羟基苯甲酸胁迫下对枯萎病的抗性变化及其与抗病性相关生理指标的影响,采用HPLC法分析了3种抗病类型的草莓品种根系分泌物中氨基酸成分的差异。结果表明:不同抗性品种在自毒物质胁迫下发病程度均加重,病情指数上升最多的是‘红玫瑰’和‘丰香’,分别为24.44和24.86,上升幅度高达77%和69%;病情指数变化较小的为‘石莓1号’和‘土特拉’,上升幅度均小于4。对羟基苯甲酸处理使不同抗性草莓品种根系分泌物中氨基酸的含量和种类发生变化,表现为降低了对枯萎病菌"抑制型"氨基酸如天冬氨酸含量,提高了"促进型"氨基酸种类和含量。对羟基苯甲酸处理后,‘土特拉’根系分泌物中天冬氨酸含量降低了0.009mg/gDW,而‘丰香’根系分泌物中"促进型"丝氨酸含量却升高0.114mg/gDW。总之,自毒物质胁迫下根系保护酶活性和分泌氨基酸的差异可能是不同草莓品种抗枯萎病强弱的重要原因。     

作物重茬连作障碍中自毒物质的研究进展

在设施农业的大背景下，连作障碍普遍存在于粮食作物、经济作物、蔬菜、林木及中药材等各种植物中，严重制约了种植业的可持续发展。大量研究表明自毒作用是导致重茬连作障碍的主要原因之一，系统介绍了自毒物质的来源和种类、作用特点及机理，概述了自毒物质的提取、活性检测、降解功能菌株分离筛选等研究方法，系统归纳了土壤改良、耕作模式改良、生物防治等消减连作障碍的措施，并提出了现有研究中存在的问题和今后发展重点，为自毒作用的深入研究提供新思路。