Destructive Weeds Research Articles

Baseline Survey on Sorghum (Sorghum bicolor L.) Production in Southern Taraba State

A baseline survey was carried out to assess sorghum production practices namely; years of production, cropping system, hectarages cultivated, identification of important pests, diseases and weed species infesting the crop and other cultural practices measures used by the farmers during sorghum cultivation in Taraba state. The study aimed at gathering information on the production status of sorghum in the state. Questionnaires were administered to 12 farmers carefully selected in 5 wards from each of the 5 Local Government areas sampled. This gave a total of 300 farmers. The survey shows that most of the farmers cultivate less than 3 ha of sorghum usually intercropped with maize or millet and most recently with groundnut. Striga hermonthica was identified to be the most destructive weed and one of the major limiting factor to sorghum production in the study area. It was also observed that most of the farmers produced sorghum without application of fertilizer and pesticide generally. In conclusion, there is urgent need to sensitize farmers in this part of the country on the need for the use of proper pesticides to control pests and diseases in sorghum, application of organic and inorganic fertilizers alongside the incorporation of crop residues to improve soil fertility for higher yield of sorghum in this survey area. Also there is need to sensitize them on the practice of cereal-legumes intercrop for sustainable crop production, instead of the commonly practiced cereal-cereal intercrop system. Moreso research effort on finding solutions to the challenges of striga hermonthica in sorghum is strongly advocated in the state. This will encourage the farmers to cultivate more hectarages of sorghum, to burst food security in the state

Effect of the tillage system on the floristic composition and the emergence of weeds in Allium sativum

In fragile environments, no-tillage (0T) instead of conventional tillage (CT) is desirable to prevent agroecosystem degradation, but there is little information on its implementation in horticulture. This study aimed to investigate the effects of replacing CT with 0T on floristic composition and weed emergence dynamics in a garlic crop, under the hypothesis that the implementation of a 0T system alters the weed community during the initial stage of the transition. Two experiments were carried out following a randomized complete block design with two treatments (garlic crop grown under 0T and CT). In two subsampling per plot, biweekly destructive weed surveys were carried out. Although both tillage systems presented a similar diversity between systems, these weed communities varied by 36% in their species identity, and it was recorded a higher total weed density under CT (P>0.05). Under 0T, anemophilous Asteraceae, such as Conyza bonariensis and Sonchus oleraceus, tended to increase their presence. Under CT, there was a greater amount of indehiscent fruiting Brassicaceae such as Raphanus sativus and Rapistrum rugosum. The implementation of Vicia villosa as a predecessor crop led to many births due to its capacity for natural reseeding. It is concluded that there are important changes in the species composition and weed emergence patterns immediately after the implementation of 0T compared to CT, suggesting that the filtering pressures exerted by each tillage system favor certain weed species over others. By understanding weed community shifts and critical stages of weed emergence, farmers can improve herbicide application, thereby reducing the excessive use of chemicals and minimizing environmental impact. In addition, this information can help to schedule labor and machinery more efficiently, saving time and production costs.

Biological treatment of Climbing Hempweed biomass through optimized composting technologies - Toxicity assessment and morphological study of Abelmoschus esculentus.

Climbing Hempweed (CH) is one of the top ten most obnoxious weeds on the planet, as well as one of the most destructive weeds. Its disastrous spread on the agricultural field has hampered the production of a wide range of crops. Various management techniques have been used to eradicate the weed, but none have been completely successful. As a result, management through the use of weed biomass will aid in the eradication of the weed as well as the production of a value-added product. To utilize invasive weed CH for the production of rotary drum compost (R1) and rotary drum followed by vermicompost (V1), two composting technologies were used. These technologies are being compared on several physicochemical parameters to determine their efficacy. V1 compost had the highest total Kjeldahl Nitrogen (TKN) (3.01%), potassium (3.45%), and total phosphorus (16.42g/kg) levels, while R1 compost had 2.58% TKN, 2.8% potassium, and 14.25g/kg total phosphorus. Subsequently, the increasing trends in mitotic index (%) of R1 and V1 samples imply that the cytotoxic effects of CH were decreased due to composting and vermicomposting processes. Genotoxicity assessment revealed that an aberration percentage of 1.64 was observed in 100% concentration of V1 (after 30 days) and 4.34% in R1(after 20 days). R1 and V1 were used to evaluate the performance of Abelmoschus esculentus where the highest fruit harvest was seen at 25% amended R1 compost and 35% amended V1 compost. The application of 25-35% R1 compost and 35-40% V1 compost was found to be the most beneficial for the development of Abelmoschus esculentus. There was no significant difference in heavy metal (Mn, Fe, Cu, Co, and Zn) content in the fruit of Abelmoschus esculentus post-application of R1 and V1 compost.

Recent CO2 levels promote increased production of the toxin parthenin in an invasive Parthenium hysterophorus biotype.

Recent carbon dioxide (CO2) concentrations promoted higher parthenin concentrations in an invasive Parthenium hysterophorus biotype. Mean concentrations of parthenin, an allelopathic and defensive sesquiterpene lactone, were 49% higher at recent (~400 ppm) than at mid-twentieth-century (~300 ppm) CO2 concentrations, but did not vary in a non-invasive biotype, suggesting that recent increases in atmospheric CO2 may have already altered the chemistry of this destructive weed, potentially contributing to its invasive success.

Botanical Pharmacognostical Study of Al-Booda (Striga hermonthica) Distributed in Gezira State, Sudan

Striga hermonthica is an invasive and destructive weed which is usually infects crops as well as pasture and wild grasses. It is widely distributed in many African countries including Sudan and it is traditionally been used as abortifacient, for pneumonia, fungal infections, as contraceptive, mosquito repellent and anti-diabetic. This study was aimed to identify morphology of whole plant and microscopic characteristics of the root, stem, and leaf and powder microscopy to support its botanical pharmacognostical characterization. Morphological and microscopic study was carried out using fresh and dry whole plant, the root, stem and leaves. The results of present macroscopic and histomicroscopic features of root stem and leaves of S. hermonthica and powder microscopic were reported which may provide useful information for the regulatory aspects of the quality control measures of the crude drugs.

Multi-source spatial data-based invasion risk modeling of Striga (Striga asiatica) in Zimbabwe

ABSTRACTMonitoring of destructive invasive weeds such as those from the genus Striga requires accurate, near real-time predictions and integrated assessment techniques to enable better surveillance and consistent assessment initiatives. Thus, in this study, we predicted the potential ecological niche of Striga (Striga asiatica) weed in Zimbabwe, to identify and understand its propagation and map potentially vulnerable cropping areas. Vegetation phenology from remote sensing, bioclimatic and other environmental variables (i.e. cropping system, edaphic, land surface temperature, and terrain) were used as predictors. Six machine learning modeling techniques and the ensemble model were evaluated on their suitability to predict current and future Striga weed distributional patterns. The mentioned predictors (n = 40) were integrated into six models with “presence-only” training and evaluation data, collected in Zimbabwe over the period between the 12th and 28th of March 2018. The area under the curve (AUC) and true skill statistic (TSS) were used to measure the performance of the Striga modeling framework. The results showed that the ensemble model had the strongest Striga occurrence predictive power (AUC = 0.98; TSS = 0.93) when compared to the other modeling algorithms. Temperature seasonality (Bio4), the maximum temperature of the warmest month (Bio5) and precipitation seasonality (Bio15) were determined to be the most dominant bioclimatic variables influencing Striga occurrence. “Start of the season” and “season minimum value” of the “Enhanced Vegetation Index base value” were the most relevant remote sensing-based variables. Based on projected climate change scenarios, the study showed that up to 2050, the suitable area for Striga propagation will increase by ~ 0.73% in Zimbabwe. The present work demonstrated the importance of integrating multi-source data in predicting possible crop production restraints due to weed propagation. The results can enhance national preparedness and management strategies, specifically, if the current and future risk areas can be identified for early intervention and containment

The rhizosphere microbiome and biological control of weeds: A review

The productivity of important grain crops wheat, rice and maize is adversely affected by various biotic and abiotic stresses. Weeds and phytopathogens are the major biotic stresses involved in biomass reduction and yield losses of these cereal crops. Various weeds compete with crop plants for natural resources viz. light, moisture, nutrients and space, and cause yield losses to agricultural produce. Weeds also increase harvesting costs and reduce quality of the farm produce. Weed management strategies include crop rotation, mechanical weeding or treatment with different herbicides. Although, sprays of different herbicides control various destructive weeds but their excessive use is environmentally unsafe and uneconomic. Indiscriminate use of these agrochemicals for weed control has resulted into considerable pollution of soil, groundwater and atmosphere. Therefore, effective biological weed management is an attractive approach for achieving the increased crop production to meet the food demands of the escalating global population. Many bacteria and fungi have been identified from the plant rhizospheres, which suppress the growth of weeds. The production of indole acetic acid, aminolevulinic acid, toxins and hydrogen cyanide has been correlated with the growth suppression of various weeds. Interestingly, inoculation with bioherbicides results in creation of biased rhizosphere leading to resource partitioning of nutrients towards growth stimulation of crop plants. Thus, inoculation of plants with bioherbicides has been found to increase germination percentage, seedling vigor, root and shoot growth, seed weight and increased grain, fodder and fruit yields. These environment-friendly biocontrol strategies for management of weeds are highly compatible with the sustainable agriculture.

Bacterial leaf spot on Convolvulus arvensis caused by Pseudomonas sp.

Field bindweed (Convolvulus arvensis) is considered as one of the most destructive weeds in the fields and gardens worldwide. In summer 2017, during the investigation carried out in Mazandaran province, a significant number of field bindweed indicated the leaf spot symptoms. Hence, the samples were collected and brought to the phytobacteriology lab for further examination. Then, isolation, purification and biochemical characterization of fifteen isolates were performed based on the standard bacteriological methods. The pathogenicity test of selected isolates on field bindweed plant were evaluated as positive. In order to validate the results, partial of 16S rRNA region were sequenced and phylogenetic trees constructed as well. According to the phenotypic and molecular characteristics, field bindweed isolates were identified as Pseudomonas sp. To the best of the authors’ knowledge, the present study is the first report of bacterial leaf spot on Convolvulus arvensis caused by Pseudomonas sp. in Iran.

Review: Rice momilactones, potential allelochemical for weeds suppression

Abstract. Estiati A. 2019. Rice momilactones, potential allelochemical for weeds suppression. Asian J Agric 3: 6-15. Weeds become one of the important biological constraint declining the productivity and quality of rice. Among the weeds, barnyardgrass is reported as the most destructive weed species. Synthetic herbicides are preferred method to control weeds. However, the excessive and continuous use of synthetic herbicides can have a negative impact on the environment, health and even the emergence of herbicide-tolerant weeds. Therefore, another alternative to overcome weed problems become the concern of scientists. Rice plants have been proven to be able to suppress the growth of weeds nearby by secreting secondary metabolites called allelochemicals. In this article, the achievements of research on rice allelochemicals at laboratory level will be reported. Among rice allelochemicals, momilactones are potential growth inhibitor. The biosynthetic pathway of momilactones and its coressponding genes have been extensively investigated in rice. OsCPS4, OsKSL4, CYP99A2, CYP99A3 and OsMAS are genes that co-regulated in momilactones biosynthetic pathway and production, and they form a gene cluster which is located on chromosome 4. Reverse genetic approach by inserting genes knock-out of OsCPS4 and OsKSL4 into two rice cultivars from Japonica subspecies showed that insertional mutant lines harboring cps4 or ksl4 exhibited a significant loss in inhibition potential due to the lack of momilactones production.

Host lignin composition affects haustorium induction in the parasitic plants Phtheirospermum japonicum and Striga hermonthica.

Parasitic plants in the family Orobanchaceae are destructive weeds of agriculture worldwide. The haustorium, an essential parasitic organ used by these plants to penetrate host tissues, is induced by host-derived phenolic compounds called haustorium-inducing factors (HIFs). The origin of HIFs remains unknown, although the structures of lignin monomers resemble that of HIFs. Lignin is a natural phenylpropanoid polymer, commonly found in secondary cell walls of vascular plants. We therefore investigated the possibility that HIFs are derived from host lignin. Various lignin-related phenolics, quinones and lignin polymers, together with nonhost and host plants that have different lignin compositions, were tested for their haustorium-inducing activity in two Orobanchaceae species, a facultative parasite, Phtheirospermum japonicum, and an obligate parasite, Striga hermonthica. Lignin-related compounds induced haustoria in P.japonicum and S.hermonthica with different specificities. High concentrations of lignin polymers induced haustorium formation. Treatment with laccase, a lignin degradation enzyme, promoted haustorium formation at low concentrations. The distinct lignin compositions of the host and nonhost plants affected haustorium induction, correlating with the response of the different parasitic plants to specific types of lignin-related compounds. Our study provides valuable insights into the important roles of lignin biosynthesis and degradation in the production of HIFs.

West African Arthropods Hold Promise as Biological Control Agents for an Invasive Tree in the Pacific Islands

African tulip tree, Spathodea campanulata Beauv. (Bignoniaceae), is a large tree of secondary forests, forest edges and savannas that is indigenous to Central and West Africa (Bidgood 1994). It has been widely utilised as an ornamental plant due to its beautiful flowers, fast growth and relative ease of cultivation, as a shade tree in parks and coffee plantations, and as a living fencepost (Francis 1990). Naturalisation has often followed cultivation of the plant, which is now established outside of the native range in Africa (Hedberg et al. 2006), the Caribbean (Francis 1990; Labrada & Medina 2009) and many Pacific islands (Meyer 2004), including Hawaii, Papua New Guinea, Fiji, Samoa, Tonga,Vanuatu and Tahiti (Lowe et al. 2000; Dovey et al. 2004; Labrada & Medina 2009). On some of these islands it has become a destructive weed, invading indigenous forests and having a severe impact on agricultural production (Labrada & Medina 2009; Larrue et al. 2014). This has resulted in African tulip tree being recognised as one of the 100 worst alien invasive species worldwide, along with only 30 other terrestrial plants (Lowe et al. 2000).

Weed Allelochemicals and Possibility for Pest Management

Purpose: Weed interference is a constraint in agricultural practice. The crop-weed interaction has been extensively described in literature, but the weed-weed interaction and their potential usage in crop production have not much been understood. In this paper, the interactions of allelochemicals of the weeds which cause troublesome in crop production and ecosystem against weeds, crops, and pathogens are described. Principal results: Weed allelochemicals are classified into many chemical classes, and the majority is consisting of phenolics acids, alkaloids, terpenes, flavonoids, long chain fatty acids, lactones, and other volatile compounds. Type of weed allelochemicals and their doses are varied among weed species. Some allelochemicals such as catechin (+/-) have been reported to be responsible for weed invasiveness. Some crops exude germination stimulants to parasitic weeds such as Striga spp. and Orobanche spp. In contrast to their negative impacts on crop production, many weeds can be exploited as promising sources to control harmful insects, fungi, bacteria, and weeds. For instance, Ageratum conyzoides is a destructive weed in crop production, but it exerted excellent insecticidal, antifungal, and herbicidal capacity and promoted citrus productivity in A. conyzoides intercropped citrus orchards. Major conclusions: In general, weeds compete with crops by chemical pathway by releasing plant growth inhibitors to reduce crop growth. Weed allelochemicals may be successfully exploited for pest and weed controls in an integrated sustainable crop productoiin. Some weed allelochemicals are potent for development of natural pesticides.

Weed Allelochemicals and Possibility for Pest Management

Purpose: Weed interference is a constraint in agricultural practice. The crop-weed interaction has been extensively described in literature, but the weed-weed interaction and their potential usage in crop production have not much been understood. In this paper, the interactions of allelochemicals of the weeds which cause troublesome in crop production and ecosystem against weeds, crops, and pathogens are described.Principal results: Weed allelochemicals are classified into many chemical classes, and the majority is consisting of phenolics acids, alkaloids, terpenes, flavonoids, long chain fatty acids, lactones, and other volatile compounds. Type of weed allelochemicals and their doses are varied among weed species. Some allelochemicals such as catechin (+/-) have been reported to be responsible for weed invasiveness. Some crops exude germination stimulants to parasitic weeds such asStrigaspp. andOrobanchespp. In contrast to their negative impacts on crop production, many weeds can be exploited as promising sources to control harmful insects, fungi, bacteria, and weeds. For instance,Ageratum conyzoidesis a destructive weed in crop production, but it exerted excellent insecticidal, antifungal, and herbicidal capacity and promoted citrus productivity inA. conyzoidesintercropped citrus orchards.Major conclusions: In general, weeds compete with crops by chemical pathway by releasing plant growth inhibitors to reduce crop growth. Weed allelochemicals may be successfully exploited for pest and weed controls in an integrated sustainable crop productoiin. Some weed allelochemicals are potent for development of natural pesticides.

Cenchrus biflorus Roxb. (Indian sandbur), a blessing or curse in arid ecosystems: a review

AbstractAlthough a widely used forage plant in arid areas, Cenchrus biflorus is viewed by many scientists as an invasive weed that has a serious negative impact on agriculture and biodiversity in arid and semi‐arid environments. It has risen from insignificance as a forage and famine cereal crop to its recent status as one of the most economically destructive weeds in many regions of the world. Numerous features like high nutritional value, prolific seed production, tolerance to high temperature and prolonged drought conditions contributed greatly towards its success as a potential forage species in arid environments. But, evidence from agriculturalists shows that it is a destructive invader which disrupts cultural practices and reduces natural biodiversity. Unfortunately, limited knowledge is available about its ecology and management in natural habitats and agro‐ecosystems. In this paper, we provide a comprehensive review of its ecology, biology, agricultural impact, management and utilization. This review also provides future directions for research on C. biflorus in arid environments.

Antibacterial properties of extracts of Solidago canadensis and their potential use as dietary supplements in red swamp crayfish (Procambarus clarkii)

Canadian goldenrod (Solidago canadensis )i s one of the most destructive invasive weeds in South- eastern China. To evaluate its potential application as dietary supplement in red swamp crayfish (Procambarus clarkii), the antibacterial properties of aqueous and ethanol extracts of this plant against three major pathogenic bacteria in crayfish aquaculture were examined. Inhibition zone tests and determination of minimum inhibitory concentration revealed that the extracts had lower antibacterial activity than extracts from two traditional medicinal plants that possess antibacterial properties, garlic (Allium sativum) and cortex phellodendri (Phello- dendron chinense). However, they did exhibit greater antibacterial effects than extracts from another widely used medicinal plant, Sophora flavescens, and an aquatic weed, Alternanthera philoxeroides. Aqueous extracts of Cana- dian goldenrod gave greater inhibition than the ethanol extracts. Crayfish fed a diet with 2% these aqueous extracts exhibited significantly higher enzyme activity of alkaline phosphatase, catalase and phenoloxidase (P<0.05). Based on the results of this study, we conclude that aqueous extracts of Canadian goldenrod are highly promising for the development of new dietary supplement for use in crayfish aquaculture.

Allelopathic potential of rice residues of selected rice varieties (Oryza sativa L.) against Echinochloa crus-galli

Allelopathic potential of rice residues of selected rice varieties (Oryza sativa L.) against Echinochloa crus-galliAbstract Allelopathic compounds will play a vital role in sustainable weed control in paddy cultivation in future. Exploitation and implementation of this technology in weed management has been considered as ecologically sound, resource conserving and economically viable method. The objective of this study was to assess the allelopathic traits of rice residues of selected (Bg359, Ld365, Bg407, At401, Bg358, At362, At402, Bg450, Bg300, Herathbanda and Handiran) rice cultivars to control of barnyard grass (Echinochloa crus-galli) one of the most destructive weed in Sri Lankan paddy ecosystem. Completely Randomize Design was used with three replicates for each cultivar. According to the research findings, significant differences (p≤0.05) were observed among cultivars and amount of residue mixed with sand (2.0, 4.0, 6.0g of ground residue per 500.0g of sand) in terms of barnyard grass plant height, number of leaves, germination and total dry weight. Among those measured variables germination and dry matter of barnyard grass showed significant reduction when increasing amount of rice residue. Among different cultivars used Ld365 showed the highest inhibition % for all above measured variables and the lowest was the Herathbanda. As an example the inhibition percentages of plant height, seed germination and shoot dry weight of Ld365 were 60%, 56% and 65% respectively. In contrast, rice cultivar Herathbanda caused 27%, 26% and 26% inhibition respectively for above mentioned parameters. When comparing three levels of rice residue mixture 63% dry weight reduction was observed in 6.0g rice residue and (51%) 4.0g and 27% with 2.0g mixture. Furthermore percentage germination also reduced with increased amount of rice residue mixture. It indicated that highest in 6.0g, which is 49% closely followed by 4.0g (41%) and the lowest is 2.0g by 12%. Therefore, it could be suggested that the allelopathic potential of rice residue significantly changes with cultivar and amount of residue mix with soil. Knowledge of rice allelophathic properties of rice residue will offer several possibilities for ecological management of weeds in paddy fields of Sri Lanka. Keywords: - Allelopathy, Echinocloa crus-galli, Inhibition, Oryza sativa

Effect of crop species and mixed ratios on morphological plasticity and competitiveness of Phalaris minor Retz

入侵植物小子虉草(<i>Phalaris minor</i> Retz.)为农田恶性杂草, 对其科学、有效的控制与管理是世界性难题。本文以小子虉草为试验对象，在温室条件下采用de Wit取代法，研究了其与小麦、蚕豆和油菜3种农作物在不同混种比例下, 小子虉草的表型可塑性与竞争效应, 以提高农田生态系统对该入侵物种的预警和控制能力。结果表明, 除混种比例对小子虉草的分枝数和主穗长度影响不显著外(<i>P</i>≥0.05), 作物种类、混种比例以及二者交互对小子虉草的株高、主穗种子数、剑叶面积和生物量有显著或极显著影响(<i>P</i>≤0.05或0.001)。在油菜混合种群中, 小子虉草的株高显著大于按同等比例与小麦、蚕豆的混合种群及其单一种群的株高, 但分枝数、主穗长、主穗种子数、剑叶面积和生物量则显著小于按同等比例与小麦、蚕豆混种时植株的上述指标。3种作物按不同比例与小子虉草混种时, 小麦、蚕豆和油菜的相对产量均小于1.0, 表明3种作物与小子虉草在田间以种间竞争为主; 小子虉草与蚕豆以各种比例混种、与小麦以1∶1和1∶2混种时, 其相对产量均大于1.0, 表明此时以其种内竞争为主; 油菜混合种群中小子虉草的相对产量均小于1.0, 表明此时以种间竞争为主。在混种比例大于1∶1时, 小子虉草与油菜的竞争平衡指数显著小于0, 表明此时油菜的竞争能力大于小子虉草, 而供试其他条件下小子虉草与供试作物的竞争平衡指数均显著大于0, 说明小子虉草对小麦、蚕豆及低密度种植条件下的油菜具有很强的竞争能力。本研究结果显示油菜对小子虉草具有较强的竞争抑制作用, 在油菜混合种群小子虉草的分枝数、主穗长、主穗种子数、剑叶面积和生物量显著降低, 因此在小子虉草入侵地大面积种植油菜有抑制小子虉草的效果。

Effects of the Residues of Cuscuta campestris and Mikania micrantha on Subsequent Plant Germination and Early Growth

Cuscuta campestris, a dodder, can parasitize and suppress a scrambling herbaceous to semi-woody perennial vine, Mikania micrantha, one of the most destructive weeds in the world. To assess the effects of the mixed residue of C. campestris and M. micrantha on the subsequent plant community, we conducted a one-year experiment on the germination and seedling growth of subsequent plant community after the application of C. campestris. Seven treatments of varying proportions of C. campestris and M. micrantha residue on 21 subject trees and shrubs, which were commonly found in South China, resulted in a germination rate of 35.3% for all 8 715 seeds from 18 species, ranging from 5.7 to 81.9%; the remaining 3 species failed to germinate. ANOVA analysis showed that the residue did not affect the germination, growth, or mortality of the trees and shrubs. The germinated C. campestris seeds from the residue coiled the seedlings of most of the species, but less than 4% host death caused by C. campestris. In addition, the residue did not affect the germination of the herbaceous seedlings originating from the loam, and the similarity coefficients of the germinated seedlings between the treatments were very high. These results suggested that the residue had no negative impact on the germination and early seedling stages of the tree, shrub and grass species of the subsequent plant community. The use of C. campestris residue had a positive effect on the growth of M. micrantha, but it did not change the trend of M. micrantha being suppressed because re-parasitization occurred soon after the growth restarted. No negative effect was detected on the other species as a result of the parasitization of C. campestris or by the use of the mixed residue. This suggests that C. campestris is likely to be an effective and promising ecologically safe native herbaceous agent for controlling M. micrantha.

Inhibitory effects of leachate from Eupatorium adenophorum on germination and growth of Amaranthus retroflexus and Chenopodium glaucum

Amaranthus retroflexus L. and Chenopodium glaucum L. are two widely distributed destructive weeds. Their strong adaptability and massive seed production make them the hardest weeds to deal with. This present study intended to investigate the effect of leachate from Eupatorium adenophorum on the growth of these weeds and explore the potential to develop an environmental friendly strategy to use the leachate to control the weeds. Seeds of A. retroflexus L. and C. glaucum L. were soaked in solutions containing 0%, 0.6%, 1.25%, 2.5%, and 5% leachate from E. adenophorum leaves. A. retroflexus and C. glaucum seedlings grown in pots were sprayed with leachate solutions in the same concentration range. The effects of these leachate solutions on membrane permeability and germination of seeds, and growth and physiological characteristics of the seedlings were investigated. The highest concentration of leachate (5%) caused significant damage to the cell membrane of seeds of both weed species, whereas lower concentrations (0.6%) promoted repair of the membrane system, as reflected by higher and lower than control in relative conductivity (RC), respectively. Different concentrations of leachate showed distinct allelopathic inhibitory effects on the two weed species; lower concentrations showed weak inhibitory or even positive effects, whereas higher concentrations showed stronger inhibitory effects. Higher concentrations of leachate (2.5% and 5%) delayed germination and significantly decreased the emergence rate of the seeds, survival rate, and dry matter accumulation of the seedlings. When treated by 5% leachate, the emergence date of A. retroflexus was delayed by 3.6 d, emergence rate of the seeds and survival rate was 69.1% and 70.6% of the control, respectively, seedling dry matter was 48.6% less than the control; In the case of C. glaucum, the emergence date was delayed by 2.7 d, emergence rate of the seeds and survival rate was 45.1% and 58.6% of the control, respectively, seedling dry matter was 44.7% less than the control. There were significant interactions among the different concentrations of leachate and the length of treatment period with respect to activities of antioxidant enzymes, malondialdehyde (MDA) contents, and chlorophyll contents. Seedlings treated with 0.6%, 1.25%, or 2.5% leachate solution for 24–72 h showed increased superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities. When seedlings were treated with leachate solutions for 96 h, antioxidant enzyme activities and chlorophyll content decreased in A. retroflexus, but only CAT activity decreased in C. glaucum. When seedlings of the two weed species were treated with 5% leachate solution, CAT activity and chlorophyll content decreased and MDA content gradually increased with longer treatment times (from 24 to 96 h). The two weed species showed different allelopathic responses to E. adenophorum; A. retroflexus was more sensitive than C. glaucum. Based on the investigation, it could be speculated that the delayed germination and low germination rate of the weeds after treatment by leachate could be due to the fact that leachate damaged the membrane system of the seeds. By delaying germination, lowering the germination rate of the weeds and inhibiting seedling growth, leachate from E. adenophorum could provide an effective way of controlling the weeds.

Targeted metabolomics in an intrusive weed, Rumex obtusifolius L., grown under different environmental conditions reveals alterations of organ related metabolite pathway

This study was intended to analyze the metabolic pathway of Rumex obtusifolius L. (Broad-leaved dock), destructive weeds worldwide, in relation to major environmental factors (light and temperature). It was found that R. obtusifolius can be classified as plants in accumulating major organic acids such as oxalate in leaves and citrate in stems (Miyagi et al., Metabolomics 6:146–155 2010). The organ specific accumulation of certain metabolites was dissected by metabolomics approach in relation to metabolic pathway. Light or dark experiments showed that in the case of the oxalate accumulation, the major or the most dominated pathway was found to be the citrate-isocitrate-oxalate shunt. Furthermore, under the dark and/or low temperature (5°C) leaves showed sustainable growth with normal accumulation of TCA metabolites. Unlike leaves, there was a different pattern of metabolite accumulation in stems. Other metabolites such as amino acids also showed the organ specific alterations under the different ambient environments.