作物化感作用研究现状及前景展望

作物化感作用研究是一个相对较新的研究方向，尽管2000年前就有关于植物间克生现象的描述，化感作用在农业生产实践中的应用很有潜力，从化感作用的概念着手总结了近20年来的研究成果，包括化感作用物质研究，作用机制研究，种质资源，生物检测方法和遗传特性研究等，并阐明了作物化感作用的研究意义，研究存在困难以及应用途径与前景。     

植物化感作用类型及其在农业中的应用

本文总结前人研究成果的基础上,对不同植物化感作用类型及其作用机制和在农业中的应用进行了探讨。植物化感作用包括化感偏害作用、自毒作用、自促作用和互惠作用。植物化感偏害作用是由植物根系分泌物介导下的植物与特异微生物共同作用的结果。利用植物化感偏害作用控制田间杂草是一项环境友好型的可持续农业技术,并已在水稻化感抑草研究方面取得了较突出的成果。植物化感自毒作用(作物连作障碍)是造成作物产量降低、生长状况变差、品质变差、病虫害频发的现象。药用植物,特别是以根部入药的药用植物中,连作障碍表现更为突出。近年来研究结果认为根系分泌物生态效应的间接作用及土壤微生物区系功能紊乱是导致植物连作障碍的主要因素。因此,改善土壤生长环境,恢复和修复根际土壤微生物结构平衡,增强生态系统机能是克服作物连作障碍的关键。植物化感自促作用(连作促进作用)是在植物根系分泌物促进下,根际土壤微生物之间此消彼长,有益微生物之间互利协作,土壤肥力和营养补给能力明显改善,从而增强植物根系抗性,促进植物生长发育,提高产量和品质的结果。牛膝的连作促进作用明显,有学者试图通过牛膝与其他不耐连作药用植物间作套种或轮作,实现药用植物生产的可持续发展。植物间的正相互作用(互惠作用)是作物间套种系统超产和养分等资源高效利用的重要机制,根系分泌物在介导根际微生物与植物的有利互作中起到重要作用。最后作者强调指出,存在于根际土壤的微生物群落的宏基因组组成是决定植物能否健康生长的关键。深入研究存在于土壤生态系统中的植物体外基因组的组成与演化机制,将成为借用现代合成生物学原理与技术,定向控制植物根际生物学过程,促进作物生产可持续发展的优先研究领域。     

不同供水水平下间甲酚和间作对小麦、蚕豆耗水特性及产量的影响

通过盆栽试验,研究了3个供水水平(田间持水量的45%、60%和75%)和间甲酚对小麦间作蚕豆耗水量及产量的影响。结果表明:间作总耗水量较相应单作总耗水量的加权平均低12.87%～31.56%,间甲酚对不同作物全生育期总耗水量的作用不显著,但供水和种植模式与作物总耗水量间的相关性极显著。间甲酚对小麦、蚕豆的产量均具有负效应,提高供水量可弱化间甲酚对小麦产量的负效应,但不同供水水平下间甲酚对蚕豆经济产量的化感作用差异不显著。间作生物产量和经济产量较相应单作的加权平均分别高15.3%～37.41%和5.98%～31.27%,间作同时具有弱化间甲酚对蚕豆化感负效应的作用。     

麦类作物化感作用及其分子生态学研究

本文综述了近年来国际上研究麦类作物化感作用的新进展,着重介绍了小麦和大麦的化感作用种质资源的筛选与评价。在此基础上运用现代分子生物标记技术ISSR,分析了麦类化感作用的遗传多样性,并进一步阐明了小麦和大麦化感物质的研究现状。最后根据当前植物化感作用研究的发展趋势,提出化感作用基因表达与信号调控的分子生态学及根际生物学过程是未来麦类作物化感作用的重点领域。     

间作蚕豆根系活力和形态对丁香酚及供水水平的响应

针对干旱和种间作用下,外源化感物质对作物根系作用机制研究薄弱问题,本文以小麦间作蚕豆为参试对象,在不同土壤含水量水平下(田间持水量的75%,60%,45%),研究了小麦根系分泌物丁香酚(2-甲氧基-3-烯丙基苯酚)对单作和间作蚕豆根系形态和活力的影响,以期为通过化感作用途径调控间作群体探索新的思路。结果表明:土壤中浓度为300×10-6mol·kg-1的丁香酚对单作和间作蚕豆根系活力和根体积、根干重和根长等形态特征均具有抑制作用,表现为化感负效应;随供水水平的提高丁香酚对蚕豆根系的化感效应呈减弱趋势,不同供水水平下化感效应绝对值表现为在土壤含水量为田间持水量的45%时最大,60%居中,75%最小。蚕豆根系活力的化感效应值在75%和60%供水水平下,均与45%供水水平之间存在显著差异,单作和间作蚕豆化感效应值在75%供水水平处理下,较45%供水处理分别降低64.0%和56.8%;而种植模式、丁香酚和供水水平对蚕豆根系活力、根体积、根长和根干重的互作效应不显著。因此,生产实践中,可通过优化水分管理达到弱化化感物质对间套作作物间根系的负效应,从而达到克服间套作群体中因某一种作物化感物质累积而造成的毒害作用。     

森林植物他感作用研究进展

阐述了具有他感作用的森林植物种类,他感物质释放方式、种类及作用机理,影响他感作用效果的因素等研究现状以及森林植物他感作用生态学意义及发展方向     

农业生态系统中的化感作用

化感作用体现了植物之间的生化相生相克关系，且广泛存在于农业生态系统之中。由于化感物质的作用，某些种类的作物不宜混种，而有些种类之间实行间作则提高产量。因为自毒作用的影响，重茬种植作物会出现减产，因而选择适宜品种进行轮作可避免此况发生。开发、利用化感物质作为植物源杀虫剂、土壤灭菌剂也已成为当前植保工作的热点。通过杂交和转基因等生物工程手段筛选、培育携带抑草基因的栽培品种，或将普通作物与抑草作用显著的品种进行间作，均可有效减少除草剂的使用。更为直接的方法是将化感物质发展为除草剂，并进一步探讨其人工合成和化学修饰的可能性，从而提高作物产量，减少化学除草剂对农业环境的污染。     

芝麻、花生和田菁秸秆还田的化感效应研究

采用盆栽模拟实验研究了具化感作用的芝麻（Sesamum indicum）、花生（Arachis hypogaea）和田菁（Sesbania cannabina）秸秆全株还田对萝卜（Raphanus sativus）、黑麦草（Lolium multiforum）和黄瓜（Cucumis sativus）生长及土壤养分状况的影响,旨在评价秸秆还田释放养分与化感作用对后茬作物幼苗生长效应的综合影响。结果表明：秸秆还田能改善土壤养分状况,对后茬作物幼苗生长具有较好的促进作用。3种作物秸秆还田促进幼苗生长的大小顺序为花生秸秆〉田菁秸秆〉芝麻秸秆〉对照,其中芝麻秸秆对土壤速效磷、速效钾含量提高最大,而花生和田菁秸秆对土壤有机质、全氮的贡献值远远高于另两种处理。3种秸秆还田均对后茬作物幼苗生长和土壤养分具有促进作用,其释放的养分因子占主导作用,而化感作用并未明显表现出阻碍后茬作物幼苗生长。可能原因在于秸秆还田后导致较高pH和土壤养分利于植物生长,并影响了秸秆化感物质的活性和化感作用的发挥。     

化感作用研究中渗透势对生物测定结果的影响

在不同渗透势的甘露醇溶液培养条件下研究了厚壳桂等对萝卜、黄瓜和白菜化感作用的影响试验结果表明,随渗透势的升高,萝卜幼苗根长和苗高逐渐降低,黄瓜幼苗受抑更明显,而白菜影响极小,未达显著水平。对厚壳桂、锥木和藜蒴的生化他感作用研究中分别以蒸馏水和相同渗透势的甘露醇溶液为对照,其结果化感作用程度普遍降低,有些还发生赁变(化感作用在显著与不显著间转换),故化感生物测定分析中应注意渗透势的影响,以保证结果正确性。     

当归营养期的化感作用

为探讨当归(Angelica sinensis)自毒作用与连作障碍的关系并建立合理的轮作制度,利用4个浓度当归营养期根部及茎叶部水浸液对当归及其种植区常见作物油菜(Brassica campestris)、小麦(Triticum aestivum)和燕麦(Avena sativa)的种子和幼苗进行了生物测定。分析结果表明,当归具明显的自毒作用(敏感指数M3=-0.258 3),茎叶部分的自毒效应强于根部,且作用强度随浓度增加而增强;小麦和燕麦对当归的化感作用有一定的耐受能力,综合敏感指数(M)分别为-0.075 5和-0.144 7;而油菜对当归的化感作用较为敏感,综合敏感指数为-0.307 9,这一结果与实际种植情况不符,推断可能与当归化感物质在土壤中的转化导致化感作用降低有关。在种间化感作用的研究中发现根部的化感作用强于茎叶,并有高抑制低促进的浓度效应。试验结果说明当归的自毒作用是造成连作障碍的原因之一;当归对小麦和燕麦的化感作用较弱,可以用于当归轮作体系,缓解因自毒作用而引起的连作障碍。     

化感作用在杂草控制中的应用

杂草危害农作物的生长和发育,而大量施用除草剂会造成环境污染和增加杂草抗药性。利用植物相互间化感作用控制杂草非常有效,抑草植物通过释放化感物质并与杂草竞争生存环境,进而对杂草发芽和生长产生抑制作用。轮作、耕作等措施影响植物残茬化感物质的释放,造成抑草效果不同。化感育种是解决杂草危害的最有效途径,可使植物具有对杂草抑制作用的化感性状。     

Chemical ecology in wheat plant-pest interactions. how the use of modern techniques and a multidisciplinary approach can throw new light on a well-known phenomenon: allelopathy

A new holistic approach on research into allelopathy was launched in the FATEALLCHEM project. The project was financed by the European Commission in the 5th Framework Programme and involved agronomists, biologists, analytical chemists, organic chemists, environmental chemists, ecotoxicologists, and modelers. Benzoxazinones from wheat (Triticum aestivum L.) were the main group of compounds studied in the project. The project showed that future assessments of an extensive use of allelopathic crops must include the development of validated analytical methods, considerations of relevant concentrations, studies on soil transformation, ecotoxicological studies on individual compounds and mixtures, evaluation on human and mammal toxicity, and joint effect studies on weeds, insects, and pathogens. The project results clearly showed the relevance of optimizing the exploitation of cereal benzoxazinones. Crop rotation is a very traditional practice, which was given less importance for decades but is now regaining its importance in agricultural practice as a means of controlling weed seed banks and soilborne diseases and pests. When using cereals as catch crops and green manure, the allelopathic properties of the cereals could now be much more extensively exploited, choosing varieties with optimal production of benzoxazinones and optimizing the time of sowing in relation to the formation of bioactive metabolites.     

农林复合系统植物竞争研究进展

植物竞争是农林复合系统成功和可持续性的主要决定因素.使资源竞争最小化,资源利用最大化,是农林复合系统提高产量和总生产力的核心.本文对农林复合系统中林木一作物间对光、水分和养分的竞争作用、化感作用及与竞争相关的植物特性进行了综述.一般认为,在湿润地区,农林复合系统地上部分对光的竞争可能是系统生产力的主要决定因素;而在温带地区和半干旱热带地区,地下部分对水分的竞争可能限制着系统的生产力.在农林复合系统中,植物对光的竞争能力由叶面积、冠层结构等决定,对土壤水分和养分的竞争能力则取决于植物根系所占据的土壤空间、根系的形态和生理塑性、植物根系在土壤中的时空分布格局等.今后应加强不同区域农林复合系统中不同组分间的竞争作用的比较、竞争过程及生理机理、化感作用、菌根影响植物竞争的作用和机理、地上部分竞争和地下部分竞争的相互作用、全球变化与植物竞争等方面的研究.     

Biochemical basis for wheat seedling allelopathy on the suppression of annual ryegrass (Lolium rigidum)

The chemical basis for wheat seedling allelopathy on the growth of annual ryegrass was investigated by the identification and quantification of multiple allelochemicals from wheat seedlings. Results indicated that 58 wheat accessions differed significantly in seedling allelopathy and inhibited the root growth of ryegrass from 10 to 91%, depending on accession. Analysis of allelochemicals by GC/MS/MS indicated that allelopathy was significantly correlated with the levels of measured allelochemicals in the shoots and roots of young wheat seedlings. Ryegrass root growth was also negatively correlated with the levels of p-hydroxybenzoic, vanillic, and trans-ferulic acids in root exudates. Wheat allelopathic potential was negatively correlated with the levels of the eight known allelochemicals quantified in the shoots, roots, and water-agar medium, with multiple regression coefficients (r) of -0.61, -0.71, and -0.71, respectively. In comparison with weakly allelopathic accessions, strongly allelopathic accessions produced significantly higher amounts of allelochemicals in the shoots and roots of the wheat seedlings and also exuded larger quantities of allelochemicals into the growth medium. Wheat accessions with strong seedling allelopathy might be useful for management of weeds during the establishment stage, thereby reducing the need for commercial herbicides in early-season application.     

植物化感物质对种子萌发的影响及其生态学意义

化感现象作为植物之间的一种相互作用方式,在农林业生产中广泛存在。合理利用植物之间的化感作用,对于生产实践具有重要的指导意义。研究表明,化感物质可促进或抑制不同物种种子的萌发过程,这对于植物的生长发育、植物群落的组成与分布以及生态系统的平衡有着重要影响。本文从化感物质对种子萌发的影响与其生态学意义两个方面进行了综述。一方面,在阐述化感作用影响种子萌发的基础上,进一步总结了化感物质抑制植物种子萌发的生理生化机制。包括:化感物质通过抑制胚根和胚轴的伸长,破坏亚细胞结构,干扰植物激素及活性氧的合成与代谢,造成细胞损伤,从而阻碍种子萌发;抑制种子中储存物质的代谢,阻碍种子萌发过程中的物质以及能量转换,导致种子萌发受阻等。另一方面,本文从化感作用在抑制农田杂草及影响生态系统稳定性两个方面,阐述了化感物质调控种子萌发的生态学意义。讨论了农作物的化感抑草作用,农林业生产中的化感自毒作用以及化感作用造成的生物入侵等,以期为农林业生产提供借鉴。最后,根据目前研究进展,对本领域未来研究方向进行了展望和讨论。     

A comparision of the competitive effects and nutrient accumulation of fat‐hen and groundsel

The competitive effects of fat‐hen (chenopodium album L.) and groundsel (Senecio vulgaris L.) on tomato (Lycopersicon esculentum Mill), lettuce (Lactuca sativa L.) and cabbage (Brassica oleracea L. var. Capitata) were investigated under glasshouse conditions. Weed competition severely reduced growth of the three food crops, the reduction being more pronounced with the longer exposure to the competition. Chenopodium album and 5. vulgaris were considerably different in their competitive abilities, although similar differences among the three food‐crop species were found. Senecio vulgaris was affected more by the competition than C. album and had lower tissue concentrations of N, K, and Mg. Growth of both weeds was greatly suppressed when tomato emerged two weeks earlier than the weeds, but the crop plants were severely stunted when the weeds had two weeks initial advantage. It appeared that C. album competed with the three food crops more for K than other elements, while S. vulgaris competed better for P. Cabbage was more competitive with both weed species than tomato while lettuce was the least competitor. Some aspects of these differences in competitive ability among the species could be related to their nutrient use.     

Weed management in canola (Brassica napus L): a review of current constraints and future strategies for Australia

ABSTRACT

Weeds are a major constraint to canola (Brassica napus L.) production, reducing grain yield and quality. The repeated use of pre- and post- emergent herbicides to control several grasses and broadleaf weeds has escalated the problem of herbicide resistance in weeds. The development of herbicide-tolerant canola cultivars has increased the flexibility of weed management but has also increased the risks of outcrossing with wild relatives and weed shifts to resistance. Herbicide-resistant weed species, and the related biological repercussions, pose a major threat to sustainable weed management. These developing risks have led researchers to examine integrated weed management (IWM) techniques for sustainable weed control. Weed control strategies using non-chemical tactics have valid roles for managing weeds. However, in broad-acre commercial fields, the effectiveness of several non-chemical selections are less proven than commercial chemical herbicides. Canola competition and allelopathy for weed suppression are potential components for integrated weed management in canola. This review examines current chemical and non-chemical options available for developing IWM strategies for profitable canola production, as well as future research directions.     

基于双注意力语义分割网络的田间苗期玉米识别与分割

为实现复杂田间场景中幼苗期玉米和杂草的准确识别与区域划分,该研究提出改进的双注意力语义分割方法,通过获取形态边界实现玉米幼苗的识别与精细分割,在此基础上采用形态学处理方法识别图像中除玉米外的全部杂草区域。首先对6种当前最高性能的语义分割网络进行对比,确定模型原始架构;建立幼苗期玉米语义分割模型,包括改进深层主干网络增强特征,引入双注意力机制构建特征的场景语义依赖关系,以编码器-解码器结构组建模型并增加辅助网络优化底层特征,改进损失函数协调模型整体表现,制定改进的迁移学习策略;提出图像形态学处理方法,基于玉米像素分割结果,生成杂草分割图。测试结果表明,模型的平均交并比、平均像素识别准确率分别为94.16%和95.68%,相比于原网络分别提高1.47%和1.08%,识别分割速度可达15.9帧/s。该研究方法能够对复杂田间场景中的玉米和杂草进行准确识别与精细分割,在仅识别玉米的前提下识别杂草,有效减少图像标注量,避免田间杂草种类的多样性对识别精度的影响,解决玉米与杂草目标交叠在形态边界上难以分割的问题,研究结果可为智能除草装备提供参考。     

Intercropping of Different Secondary Crops in Maize

Intercropping and bicropping are common cultivation systems in many countries. Maize (Zea mays L.) as a main crop combined with a legume as secondary crop is in general use in many countries. These systems may contribute to a higher biodiversity, and reduced import of fertilizer, concentrates and agrochemicals. The objective of this research was to select an appropriate secondary crop that could be grown with maize in an intercropping system to control weeds while maintaining maize yields. Field beans (Vicia faba L.), crimson clover (Trifolium incarnatum L.), phacelia (Phacelia tanacetifolia Benth.) and thyphon [Brassica rapa L. ar. rapa (L.) Thell] were selected as secondary crops. Acceptable yields of dry matter in maize were obtained regardless of secondary crop. Different yield levels were obtained depending on the morphology of the secondary crop. Thyphon, a high, dense secondary crop with large leaves, shaded the lower maize canopy, and thereby reduced the yield of maize. In contrast, field bean, which is tall and has a narrow canopy, did not reduce maize yield. A negative relation was found between the yield of secondary crop plus weeds in August and October and the yield of maize in October. The secondary crops were not sufficiently competitive against weeds in the first part of the growing season. Thyphon competed too much against maize. Field bean and phacelia resulted in a minimum of competition against maize, and a maximum competition against weeds, compared with the other secondary crops.