Exogenous application of allelopathic water extracts helps improving tolerance against terminal heat and drought stresses in bread wheat (Triticum aestivum L. Em. Thell.)

The allelopathic water extracts (AWEs) may help improve the tolerance of crop plants against abiotic stresses owing to the presence of the secondary metabolites (i.e., allelochemicals). We conducted four independent experiments to evaluate the influence of exogenous application of AWEs (applied through seed priming or foliage spray) in improving the terminal heat and drought tolerance in bread wheat. In all the experiments, two wheat cultivars, viz. Mairaj‐2008 (drought and heat tolerant) and Faisalabad‐2008 (drought and heat sensitive), were raised in pots. Both wheat cultivars were raised under ambient conditions in the wire house till leaf boot stage (booting) by maintaining the pots at 75% water‐holding capacity (WHC). Then, managed drought and heat stresses were imposed by maintaining the pots at 35% WHC, or shifting the pots inside the glass canopies (at 75% WHC), at booting, anthesis and the grain filling stages. Drought stress reduced the grain yield of wheat by 39%–49%. Foliar application of AWEs improved the grain yield of wheat by 26%–31%, while seed priming with AWEs improved the grain yield by 18%–26%, respectively, than drought stress. Terminal heat stress reduced the grain yield of wheat by 38%. Seed priming with AWEs improved the grain yield by 21%–27%; while foliar application of AWEs improved the grain yield by 25%–29% than the heat stress treatment. In conclusion, the exogenous application of AWEs improved the stay green, accumulation of proline, soluble phenolics and glycine betaine, which helped to stabilize the biological membranes and improved the tolerance against terminal drought and heat stresses.     

兰州百合根及鳞茎水浸液自毒作用的研究

为探讨兰州百合自毒效应机制,明确百合根及鳞茎中主要自毒物质,设置水(CK)、百合根及鳞茎水浸液10、50、100、150mg/mL,共计9个处理,用于自毒作用的生物学实验,采用分光光度法及滴定法测定百合幼苗中的生理生化指标,利用GC-MS技术分析兰州百合根及鳞茎中的主要自毒物质。结果显示,兰州百合根及鳞茎水浸液对自身幼苗生长的影响总体上表现为抑制作用,且存在浓度效应。随着水浸液浓度的增加,SOD、POD、CAT三种酶活性先上升后下降,MDA含量和相对电导率变化趋势则相反。浓度高于100mg/mL时,脯氨酸及可溶性糖含量较对照显著增加(P0.05)。根及鳞茎氯仿萃取液中分别鉴定出23种、14种化合物,主要包括:2,3-二氢茚、萘、2,4-二叔丁基苯酚、对乙烯基愈创木酚、香草醛、月桂酸、丁香醛、肉豆蔻酸、苯基异氰酸酯、对苯二甲酸二辛酯,其中多数被报道为化感自毒物质。兰州百合根及鳞茎水浸液对其幼苗的生长具有明显自毒效应。自毒作用是导致兰州百合连作障碍的重要原因之一。     

作物化感品种对农田杂草的调控

农田施用大量除草剂不仅引起环境和生态问题,而且导致除草剂抗性杂草不断发生。因此,需要建立生态安全的杂草管理策略以改变杂草控制对除草剂依赖的现状。利用作物化感品种调控农田杂草是极具开发潜力的杂草控制策略,这些作物化感品种自身能够产生和释放化感物质调控杂草,从而减少对人工除草剂的依赖。鉴于此,近10余年来,以作物化感品种为中心的农田杂草控制策略一直得到广泛的关注和研发。本文综述了作物化感品种调控农田杂草和相应抑草机制的最新进展,尤其是可商业化种植的作物化感新品种选育及其在除草剂减量控制杂草的实践。在此基础上,阐释了作物化感品种间亲属合作行为以及基于化感物质的新型除草剂研发对解决农田杂草难题的机遇和挑战。     

花生化感物质降解菌的筛选、鉴定与降解特性研究

为筛选高效化感物质降解菌,以花生根系分泌物中的化感物质苯甲酸作为唯一碳源,采用富集培养和稀释平板法从连作花生长期定位试验地的健康花生植株根际土壤中筛选高效花生化感物质降解菌,经形态观察、生理生化分析和16S rDNA序列同源性比较以及系统发育分析对降解菌进行鉴定,并通过单因素试验对降解菌进行降解特性研究。结果表明:筛选到的2株高效降解菌分别为木糖氧化无色杆菌(Achromobacter xylosoxidans HJ-2)和硝基还原假单胞菌(Pseudomonas nitroreducens HJ-3)。降解菌HJ-2降解的适宜pH为6.0～9.0,适宜温度为30～45℃,适宜NaCl浓度为0～6%;降解菌HJ-3降解的适宜pH为6.0～8.0,适宜温度为30～35℃,适宜NaCl浓度为0～4%。两株降解菌都能够降解苯乙酮、硬脂酸、棕榈酸、乳酸、3,5-二甲基苯甲醛和丙三醇等化感物质。研究表明,降解菌HJ-2和HJ-3对苯甲酸有显著降解效果,两个菌株均具有广谱降解化感物质的特性,且降解菌HJ-2对不良环境适应能力较强。     

苦槠叶及根的生化物质对闽楠种子的发芽效应

采用有机溶剂浸提和水授提2种方式分别提取苦槠叶、根的生化物质,并用闽楠种子发芽试验评价苦槠对闽楠的化感作用．结果表明,2种方式浸提的苦槠叶和根的生化物质对闽楠种子的各项发芽指标均表现为一定程度的抑制作用．说明从生化角度看苦槠与闽楠的种间关系并不十分协调．     

Allelopathy and the active metabolites of the endophytic fungus,Alternaria J46, from Platycladus orientalis

The endophytic fungus, Alternaria J46, was isolated from the stem of the medicinal plant, Platycladus orientalis. A suspension of Alternaria J46 mycelial segments and the culture filtrates of the fungi exhibited marked seed germination inhibition against the monocot wheat, large crabgrass, bromegrass, rice and barnyardgrass and weak inhibition against the dicot redroot pigweed and morning glory, but it was safe for use on soybean, rape, cucumber, tomato, lettuce and radish crops. It is possible to use J46 culture filtrates in order to prevent monocot weeds in dicot cropland. Three active metabolites were isolated from an extract of the fungus cultures and elucidated as 3‐acetyl‐5‐sec‐butyltetramic acid (1, tenuazonic acid), 3‐acetyl‐5‐iso‐butyltetramic acid (2, vivotoxin II) and cyclo‐(L‐leucyl‐L‐proline) (3). Among these three compounds, compounds 1 and 2 showed significant phytotoxic effects on the seed germination of large crabgrass, while compound 3 exhibited weak activity, and all were safe for lettuce at 100 μg mL^?1. Accordingly, compounds 1 and 2 were the main active metabolites that were responsible for endophytic fungus Alternaria J46's strong seed germination inhibition against monocotyledons.     

西北干旱荒漠区植物化感作用研究进展

为探明荒漠生态系统中植物之间的化感作用,首次对近年来该领域所取得的研究成果、已报道的化感植物、化感物质以及化感物质释放途径等进行总结,认为:(1)中国有关荒漠植物化感作用的研究才刚刚起步,在该区菊科、豆科、蔷薇科、玄参科、禾本科等科属中发现具有化感潜势的植物。(2)荒漠植物化感物质释放的途径以自然挥发为主,这主要与其生长环境有关,鉴定出的化感物质有生物碱、黄酮类、萜类等化合物。(3)最后指出荒漠生态系统中化感植物研究存在的关键问题,对确定合理的荒漠植物保护措施及荒漠化综合治理提供理论依据和实践价值。     

单体化感物质的作用机理研究概况

摘 要：化感作用研究已从化感现象证明发展到对化感机理的探讨。在作用机理的研究中，以单一化感物质为供体是一条重要途径。本文概述了关于酚类、萜类、生物碱类等单一化感物质作用机理。这几类物质主要影响受体植物种子萌发、物质代谢中的关键酶活性、降低光合效率、损伤细胞超微结构和膜系统的稳定性。今后，对化感物质作用机理的研究应从化感物质处理后的现象描述水平深入到真正作用过程的阐明，并寻找化感物质结构和作用靶标之间的规律性。     

Mechanism of action of insecticidal secondary metabolites of plant origin

Insect pest management is facing the economic and ecological challenge worldwide due to the human and environmental hazards caused by majority of the synthetic pesticide chemicals. Identification of novel effective insecticidal compounds is essential to combat increasing resistance rates. Botanicals containing active insecticidal phytochemicals appear to be promising to address some of these problems. Therefore, there is a continuous need to explore new active molecules with different mechanisms of action. Secondary metabolites present in plants apparently function as defense (toxic), which inhibits reproduction and other processes. The phytochemical biomolecules could be used for maximizing the effectiveness and specificity in future insecticide design with specific or multiple target sites, while ensuring the economic and ecological sustainability. In this article, the current state of knowledge on phytochemical sources and insecticidal activity, their mechanism of action in insects, resistance, and promising advances made in phytochemical research are reviewed.     

不同品种紫花苜蓿酚酸类化感物质含量的研究

 采用高效液相色谱法对１０个品种紫花苜蓿地上部和根水浸提液中的绿原酸、香豆酸、羟基苯甲酸、咖啡酸和阿魏酸５种酚酸类化感物质的含量进行分析。研究表明，无论是地上部还是根水浸提液中，不同品种的紫花苜蓿酚酸类化感物质的含量存在差异，艾丽丝地上部和根水浸提液中绿原酸的含量分别为９４．７２ 和２３．９８μｇ／ｇ，咖啡酸含量分别为３０．４９ 和６．３３μｇ／ｇ，与其他品种相比均较高；艾格地上部和根水浸提液阿魏酸含量分别为４８．９７和６．７５μｇ／ｇ，均明显高于其他品种。紫花苜蓿地上部和根水浸提液羟基苯甲酸含量分别与咖啡酸、绿原酸、阿魏酸含量呈极显著的正相关。紫花苜蓿地上部水浸提液中，香豆酸含量分别与咖啡酸和阿魏酸含量呈极显著的正相关，羟基苯甲酸与香豆酸呈显著正相关；根水浸提液中，咖啡酸含量分别与绿原酸和阿魏酸含量、绿原酸含量与阿魏酸含量呈显著正相关。另外，同一品种紫花苜蓿地上部与根水浸提液中同一种酚酸类含量存在差异。