【作者】 林瑞余；

【导师】 林文雄；

【作者基本信息】 福建农林大学 ， 生态学， 2008， 博士

【摘要】 植物化感作用是指一个活体植物（供体植物）通过茎叶挥发、淋溶、根系分泌等途径向环境中释放其产生的某些化学物质，从而影响周围植物（受体植物）的生长和发育的化学生态学现象。利用小麦化感作用防除麦田杂草具有剂量小、选择性强、无3R问题，有望成为21世纪环境友好的除草关键技术之一。当前，小麦化感作用研究主要集中在化感种质资源的筛选，化感物质的鉴定，遗传多样性、QTL定位、生理响应和遗传调控等生物学特性上，对小麦化感作用的根际生态学的研究尚少。本文为了阐明小麦化感作用及其根际生态学特征，采用6种方法评价了90份小麦的化感潜力，分析了不同化感潜力小麦的农艺性状、遗传多样性等。同时探讨了小麦抑草作用的化感作用与资源竞争效应、小麦化感抑草的生理特征、化感小麦根际土壤微生物学特性、小麦化感物质多样性与化感活性、土壤微生物和土壤酶对化感物质的响应等，主要结果如下：（1）采用土壤-琼脂三明治法、浸提液生物测试法、琼脂迟播共培法及结合田间调查等6种测试方法，评价了90份来自各地小麦品种的化感潜力，筛选出了3个强化感小麦品种：晋2148、115／青海麦、92L89；3个弱化感作用小麦品种：9813、8401、抗10103，丰富了化感小麦种质资源。试验证明了土壤-琼脂三明治法是评价小麦化感种质资源可行、方便的方法。（2）多元相关分析显示，小麦化感潜力（莴苣根长抑制率IR）与株高、穗长、叶长、叶宽、芒长、茎粗等性状呈负相关，与穗数、实粒数、穗粒数、结实率、千粒重、茎粗等性状呈正相关，但均未达显著水平，表明小麦的化感作用特性与产量与株型等农艺性状的连锁性不大，通过杂交育种获得高产兼具强化感作用的小麦新品种是可能的。（3）为合理评价小麦的化感潜力，采用一种包含4个不同N素营养水平处理的化感-竞争分离法测定了小麦抑草作用的化感作用效应与资源竞争效应，结果表明，供试小麦对伴生杂草看麦娘的化感作用均随氮素浓度的降低而增强。在低氮条件下，强化感小麦抑制伴生杂草生长以化感作用为主，115／青海麦化感效应48.5％，资源竞争效应25.4％；92L89化感效应41.9％，资源竞争27.5％。弱化感小麦抗10103以资源竞争为主，抑制率在化感效应17.8％，资源竞争效应27.7％。强弱化感小麦在干扰伴生杂草上存在生态策略差异。（4）在化感小麦浸提液处理下，对看麦娘的生理生化测定表明，化感小麦能够显著抑制看麦娘植株的生长，化感胁迫下看麦娘发根力、根系活力显著下降，激发了看麦娘体内的保护酶系统，提高了酶活，化感小麦对看麦娘根系的伤害比叶片更为显著，以强化感小麦115／青海麦最为明显，不同浸提液浓度处理的根系中MDA含量是对照的10.88-25.53倍。化感小麦浸提液处理提高了看麦娘叶片和根系中类黄酮、总酚含量。进一步采用沙培法测定化感小麦根系残留物抑制看麦娘生长的生理生化特性表明，不同化感潜力小麦根系分泌残留物处理的看麦娘叶片中MDA含量升高，膜质过氧化作用加强，ABA含量升高，ZR、GA、IAA等生长激素含量降低，抑制了看麦娘根系和植株地上部的生长，显示出小麦化感作用效应。（5）不同化感小麦根际的土壤化感潜力测定表明，土壤灭菌后其化感潜力有所下降，化感小麦根际土壤微生物与其化感潜力间存在一定关联性。不同化感潜力小麦根际土壤微生物区系存在显著差异，种群数量均以细菌为主，80.4-83.9％，真菌数量最少，占0.4-0.6％，放线菌占15.6-19.1％。种植强化感小麦能够促进根际自生固氮菌、反硝化细菌、好气性纤维素分解菌、硫化细菌等主要生理类群的形成。BIOLOG分析结果显示，不同化感潜力小麦根际土壤的AWCD也存在显著差异。利用培养72 h时的AWCD值，进行主成分分析，提取出与土壤微生物碳源利用功能多样性相关的主成分1、主成分2、主成分3，依次解释变量方差的55.8％、31.9％和12.3％；对各主成分起分异作用的主要碳源分别是糖类和氨基酸。不同化感潜力小麦根际土壤脱氢酶、多酚氧化酶等的活性存在一定的差异。进一步提取土壤DNA，采用T-RFLP技术分析强、弱化感小麦根际土壤微生物特征显示，强化感小麦115／青海麦、92L89共有的微生物主要有5个菌属，分别是芽孢杆菌属、固氮螺菌属、赤单胞菌属、李斯特氏菌属、类芽孢杆菌属，主要参与土壤根际微生态系统中的固氮作用、养分循环、农药降解与修复污染土壤等功能，化感小麦对绝大多数细菌、放线菌、固氮菌生长有促进作用，增强了适应性。（6）通过GC／MS分析，从不同化感潜力小麦叶片、根系和根际土壤中鉴定到酚酸类、酸类、醇类、酰胺类、萜类、醚类、酯类、嘌呤类、烃类、酚类、生物碱、酮类和异羟肟酸类等等13大类物质。在小麦叶片、根系和根际土壤中均均检测到了对羟基苯甲酸、对羟基肉桂酸等酚酸类化感物质。室内模拟试验表明，不同浓度的对羟基苯甲酸在土壤中的吸附与解吸作用均可用二次方程Y（μg）=b₀+b₁V+b₂V²得到较好的拟合。（7）室内模拟试验表明，对羟基苯甲酸对看麦娘的生长起到明显的抑制作用；对羟基苯甲酸、肉桂酸能够显著地影响土壤微生物群落组成和土壤酶活性，促进土壤细菌种群数量增长，抑制真菌生长，低浓度的对羟基苯甲酸、肉桂酸能够显著地促进放线菌生长，在中、高浓度时表现出一定的抑制作用。对羟基苯甲酸、肉桂酸能够提高土壤脲酶、蛋白酶、蔗糖酶、磷酸酶活性。T-RFLP分析表明，对羟基苯甲酸、肉桂酸能够促进芽孢杆菌纲嗜热短杆菌、硫化杆菌属、嗜热脂肪芽孢杆菌、优杆菌属，β-变形菌纲伯克氏菌属，δ-变形菌纲除硫单胞菌属、放线菌纲微球菌属，ε-变形菌纲弯曲菌属微生物的生长，有利于土壤物质循环。更多还原

【Abstract】 Allelopathy was one of the most important chemoecological phenomenon, which refers to one plant（donor） impact the growth and development on its neighboring plants （accepter） through the release of secondary metabolism chemical compounds into the environment via volatilization, leaching, excretion, and decomposition. Using wheat allelopathy to control weeds in agroecological system, a low dosage, high selective and without "3R" problems（resistance, rampancy and residue） in weed control, will be a key technology for controling weed friendly in 21st century.Recently, the reaserch for wheat allelopathy was mainly focus on the screning of allelopathic germplasm, identification of allelochemicals, and biological characteristics of allelopathy, such as genetics diversity, QTLs location, physiological response, and its genetic control. Little work was done on the ecology of wheat allelopathy in rhizosphere. In this paper, we aimed to elucidate the ecological characteristics of wheat allelopathy in rhizosphere, 6 screening methods were employed to evalute the allelopathic potential of 90 wheat acessions, their agronomic characters and genetics diversity were tested as well. For the more, allelopathy and resoure competetion between wheat and weeds, the physiological characteristics of weed control, microbal population in rhizospheric soils, allelochemicals in the plant and rhizospheric soils, and allelochemicals effect on the growth of accepter plants, soil microbe and enzyme activities were documented. The result was mainly concluded as below.（1） Six different methods, such as soil-agar-sandwich method（SASM）, aqueous extract screening bioassays（AES）, relay seeding in agar（RSA） and field investigation, were employed to evaluate the allelopathic potentials of 90 wheat acessions introduced from both home and abroad. The result offered three strong allelopathic wheat acessions: Jin 2148, 115/Qinghaimai and 92L89, and 3 weak ones: 9813, 8401 and 10103 for wheat allelopathy reseach. It was also confirmed by experiments that SASM was a simply feasible method for screening allelopathic wheat acessions.（2） Multiple correlation ananlysis was calculated among wheat agronomic characters, yield characters and the IRs of lettuce root length growth showed that IRs were negative correlation with plant height, spike length, leaf length, leaf breadth, arista length. In reverse, IRs were positive correlation with spike number, plump grains, number of grains, setting rate, thousand grains weight and cauline thickness. But all the correlation were not significantly at p<0.05. It suggested that the charater of allelopathy in wheat was not notable linkage to its agronomic and yield characters, and new wheat varieties possess both high yield and strong allelopathic characters can be achieved by hybridize breeding.（3）In order to estimate allelopathy potential resonably, allelopathy-competition separation method （ACS）, a methodology containing four gradient nitrogen application was introduced to evaluate allelopathy and resource competition effects included in the biointerference. The result showed that the allelopathic effect on the growth of Alopecurus aequalis increased with the decline of nitrogen application levels for all the tested wheat acessions. Strong allelopathic wheat acessions suppressing the weed mainly by allelopathic effect, for 115/Qinghaimai, allelopathic effect occupied 48.5% and resoure competition effect was 25.4%. For 92L89 allelopathic effect occupied 41.9%, resoure competition effect was 27.5%. While weak allelopathic wheat acessions Kangl0103 was in reverse, allelopathic effect occupied 17.8% and resoure competition effect was 27.7%. Different ecological strategy in weed suppression was found between strong and weak allelopathic wheat acessions.（4） The physiological response for Alopecurus aequalis was determined by treating the plant with water extracts from allelopathic wheats. The result showed that allelopathic wheat siginificantly suppressed the growth of Alopecurus aequalis, performing low root number, root length, fresh weight of root and low root vigor. Simultaneously, It initiated the protection enzyme system in Alopecurus aequalis, higher enzyme activities of SOD, POD and CAT were detected in the tissue of root and leaf the weed. The higher MDA content in the weed implied that wheat water extracts doharmful to root and leaf of the weed, and root was more sensitve than leaf especially for 115/Qinghanmai. The MDA content in the root tissuse treated with 115/Qinghanmai was 10.88 to 25.53 times as higher as that in control, acompanying with higher flavonoids c and total phenols contents in the tissues of Alopecurus aequalis leaf and root. Further experiments by sand culture showed the same trend in the physiological response for Alopecurus aequalis. higher MDA content was found in the leaf, suggested that obvious lipid peroxidation occurred in the leaf, and reduced the content of ZR, GA and IAA, which pulled down the growth of weed both in root and shoot of the plant, demonstrating the allelopathic effect of wheat.（5） The allelopathic potential declined after the soils were sterilized, it indicated that allelopathy of rhizospheric soils was related to the microbial flora in the soils. The total number and population components of rhizospheric microbial flora showed significant difference among the three wheat cultivars. Among the three major microbial species, bacterium was the predominant one, accounting for 80.4%～83.9% of the total microbial population. The following -up was actinomycete with 15.6-19.1%, and the last one of fungus with only 0.4%～0.6% of the total microbial number. In addition, the cultivation of allelopathy wheat was likely to enhance the abundance of microbal components of azotobacteria, denitrifying bacteria, aerobic cellulose decomposing bacteria, thiobacillus.BIOLOG analysis showed that the value of Average Well Color Development （AWCD） differed significantly among wheat cultivars. According to the AWCD incubated for 72 h, Principal Component Analysis （PCA） identified 3 principal component factors （PCF） in relation to carbon sources, accounting for 55.8%, 31.9% and 12.3% of the variation respectively. Amino acids and carbohydrates were the two main carbon sources separating the 3 principal component factors. Furthermore, soil enzyme activities were found among the rhizospheric siols cultivated with different allelopathic potential wheats.We extracted DNA from the soils, combing the technology of T-RFLP, five common bacteria were found in the rhizospheric soils of 115/Qinghaimai and 92L89, they were putative to be Bacillus, Azoarcus, Blastomons, Listeria, Desulfobacter latus. This bacteria involved in nitrogen fixation, nutrient cycle, pestcise degradation and the rehabilitation of soil contaminated. Allelopathic wheats mostly promoted the population of bacteria, Actinomycete and azotobacteria, which enhance the adaption ability for wheat.（6）Thirteen species of allelochemicals were identified by GC/MS from leaf, root and rhizospheric soils of wheat, they were phenolic acid, carboxylic acid, amine, terpene, aether, ester, purine, hydrocarbon, phenol, alkaloid, ketone and hydroxamic acid. It was found phenolic acids, such as p-hydroxycinnamic acid, p-hydroxybenzoic acid, in all the wheat leaf, root and rhizosperic soils. The simulant experiment in laboratory showed that the absorption and desorption process of p-hydroxycinnamic acid in the soils can be perfectly fitted by the equation of Y（μg） = b₀ + b₁V + b₂V².The bioassay in laboratory showed that p-hydroxycinnamic acid has the suppressing effect on the growth of Alopecurus aequalis. Furthermore, p-hydroxycinnamic acid and cinnamic acid obviously changed the components of microbal flora and enzyme activities in the soils, which enhanced bacteria population, inhibited fungi population, and for actinomycete, it was inhibited at high concentration and enhanced at low concentrtion. At the same time, both p-hydroxycinnamic acid and cinnamic acid promoted the activities of urease, protease, sucrase and Phosphatase. Microbiology ananlysis by the technology of T-RFLP found employed to were found the soils treat with the two phenolic acids was benefitial to the establishment of Brevibacillus, Sulfobacillus, Bacillus stearothermophilu, Eubacterium, Burkholderia, Desulfuromonas, Micrococcus, Campylobacter and the cycling of substances in the soil.更多还原