Conyza Canadensis Research Articles

Study of weeds and field plants of vegetable crops using the example of common potatoes

This paper presents the results of a study showing that in an area with moldboard tillage there are 16 species of weeds belonging to the following families: Roaceae B., Polygonaceae J, Chenopodiaceae V., Amaranthaceae J., etc. It has been established that with no-mouldboard tillage soils in the study area grow 33 plant species belonging to different families, such as Roaceae B., Polygonaceae J, Chenopodiaceaevent, Rubiaceae, etc. It was revealed that the dominant plant species in the study area were: Amaranthus Retroflexus L., A. blitoides S. Watson, Conyza canadensis (L.) Crong and other harmful cosmopolitan perennials, such as: Convōlvulus arvēnsis, Euphorbia waldstéinii, Cīrsium setōsum.

The effect of herbicides on arbuscular mycorrhizal fungi associated with annual invasive Asteroideae weeds

Invasive plants Galinsoga parviflora and Erigeron canadensis are common in crops and adjacent territories. One of the factors contributing to their spread is the community of arbuscular mycorrhizal fungi associated with these species. The nature of the symbiotic relationship between the host plant and AMF is determined by their phylogenetic position and place of growth. The aim of this work was to determine the level of mycorrhizal colonization of E. canadensis и G. parviflora growing in arable fields and along them. For plants at the flowering stage, high rates of frequency and intensity of mycorrhization were revealed. It has been shown that the level of mycorrhizal colonization of E. canadensis and G. parviflora is significantly influenced by the range of herbicides applied. The application of 2.4 D slightly reduced the intensity of colonization, but significantly stimulated the formation of arbuscules in plant roots. In turn, metribuzin prevented the formation of mycorrhiza. AMF associated with these plants formed a separate clade. This group, in our opinion, is responsible for more effective symbiosis with invasive plants of the Asteroideae subfamily and requires further closer study.

CONSIDERATIONS REGARDING THE VASCULAR FLORA OF SOME FRUIT ORCHARDS IN DOLJ COUNTY, ROMANIA

Through the environmental requirement imposed by inter-rows, the eco-scheme contributes to the CAP objective of biodiversity conservation, as well as increasing the soil's carbon sequestration capacity and improving the quality of the soil structure, the main natural resource in agricultural activity. The present work aimed to analyze the vascular flora from some fruit orchards in Dolj County, Romania following a taxonomic study, starting from the need to establish a vegetal soil cover with spontaneous plants, both specific to the region and environmentally friendly. Following the observations made, it was found that the floristic composition of the grassy cover in the orchards in Dolj County is variable depending on the age of the orchard and the works that were carried out between and on the rows of trees. In orchards where human intervention is low, there is a good representation of taxa belonging to the Fabaceae family (eg Trifolium repens, T. pratense, Medicago arabica, M. sativa). On the other hand, isolated species are present in well-maintained orchards, especially from the category of weeds that can be difficult to fight (e.g. Sorghum halepense, Xanthium italicum, Conyza canadensis, etc.). Observations will be continued to consider the effect of wild plants on the environment and to establish an area-specific varietal soil cover for keeping the row spaces grass-covered.

Potential allelopathic interactions from canola and pennycress postharvest roots and stubble

AbstractWinter oilseed Brassica plants have several documented allelochemicals; however, most literature revolves around the application of seed meal to fields, or the use of aerial parts of the plant. It is not clear if these chemicals interact with the surrounding environment to the same extent if the winter oilseeds are harvested as a cash crop in the spring. To determine this, we conducted a preliminary study bioassay using water extractable compounds from canola (Brassica napus L.) and pennycress (Thlaspi arvense L.) roots diluted to 25 and 50% (v/v). These four extracts, as well as deionized water for control, were used to irrigate plates with the seeds of soybean (Glycine max L.), Palmer amaranth [Amaranthus palmeri (S.) Watson], and mare's tail (Erigeron canadensis). We measured germination percent per plate and seedling radicle and hypocotyl lengths after 8 days of treatment. Mare's tail germination was lowered by 40% on day 4 by 50% pennycress extracts, and root length was stunted by both canola and pennycress extracts by 3–5 mm. Palmer amaranth root length was stunted by 10–15 mm by both species’ extracts, as well as shoots lengthened by 5–10 mm. Extract treatments did not affect soybean germination or growth. These interactions indicate potential for allelopathic interactions in the field following harvest of dual cropped winter oilseed and herbicide‐resistant weeds and warrant further study into the topic.

ALLELOPATIC INFLUENCE OF WEEDS ON THE GERMINATION OF WINTER WHEAT SEEDS

The article summarizes the results of the phytotoxic effect of water-soluble extracts from various weeds on the germination processes of winter wheat seeds. Competitive relations between plant organisms begin with chemical interaction. Therefore, the competitive properties of the participants of the cenosis and the level of productivity of its components will depend on the starting conditions that are formed during the germination of the seeds of the crop. The research was carried out in the laboratory of plant physiology of VNAU. The purpose of the research was to establish in laboratory conditions the allelopathic effect of water extracts from the most common weeds of the Vinnytsia region: Convolvulus arvensis L., Sonchus arvensis L., Cirsium arvense L., Erigeron canadensis L., Matricaria perforata Merat, Capsella bursa pastoris, Erodium cicutarium L., Chenopodium album L., Galium aparine L., Stellaria media L. Water extracts from the stems, leaves and root system of weeds were prepared at a concentration of 1:10. During the experiment, it was established that the presence of allelopathically active substances of all experimental weed species of this concentration negatively affects the germination energy of winter wheat seeds. In the control version, all the seeds of the culture germinated on the 4th day, and in the experimental versions, 1-3% of the wheat seeds were in the swelling phase. Water extractions of different types of weeds had different inhibitory effects on winter wheat seed germination and subsequent growth of the root system and sprout stems. The negative effect of water-soluble secretions from Erodium cicutarium L., Cirsium arvense L. and Sonchus arvensis L. reduced the height of wheat seedlings by 5.8-4.0%. And the length of the root system of the culture was smaller by 5.7, respectively; 5.8 and 5% compared to the control variant. Water-soluble extracts from Stellaria media L. and Matricaria perforata Merat. had the least influence on the growth processes of winter wheat. The difference in sprout height from the control variant was 1.3% and 2.0%, respectively. The length of the germinal root of wheat was shorter by 1.8% and 3.8% under the influence of water-soluble secretions of asteraceae and chamomile. The total length of the root system of winter wheat was inhibited by them by 2.4% and 2.6%, respectively, in relation to the control. The results of the conducted research provide justification for the appearance of unfriendly seedlings and the lag in the growth of winter wheat plants on weedy areas.

Historical evidence for context-dependent assessment of Erigeron canadensis invasions in an 18th-century European landscape

Understanding the historical roots of invasion science provides insights into early perceptions of invasive species, allows us to trace the evolution of the discipline over time, and helps contextualize modern research. This paper analyzes work by Christian Ludwig Krause, published 250 years ago, on the invasion of an 18th-century European landscape by Erigeron [Conyza] canadensis (Canadian horseweed), one of the most common invasive species today and a widespread agricultural weed. Here an analysis is conducted of the ecological consequences and underlying mechanisms Krause described, how he evaluated E. canadensis invasions in different land-use systems and how his insights align with existing knowledge. Krause identified copious seed production and long-distance dispersal by wind as key mechanisms for the formation of dominant stands on degraded sandy soils. He recognized various ecosystem services associated with population establishment, such as erosion control, increased soil fertility, and the facilitation of other species. While Krause highlighted the benefits of E. canadensis invasions for the recovery of degraded grasslands and fields, he also acknowledged this introduced species as a troublesome weed in gardens. Thus, Krause’s work is not only an early report on the invasion of a cultural landscape subject to wind erosion but also an early example of a context-dependent invasion assessment, illustrating both positive and negative impacts of the same species in different environments. Krause’s perspective may encourage current assessments of E. canadensis not solely based on its presence or frequency, but on documented ecological and socioeconomic effects and their associated benefits or harms. As Krause impressively demonstrated 250 years ago, these effects can differ starkly in different environments, necessitating multiple responses to the same species.

Lawn or spontaneous groundcover? Residents' perceptions of and preferences for alternative lawns in Xianyang, China.

Within urban green spaces, spontaneous groundcovers, as potential alternatives for traditional lawns, have garnered attention due to their ecological adaptability. However, little attention has been paid to whether spontaneous groundcovers can serve as suitable replacements for lawns in terms of the aesthetic values and human preferences for each. Based on questionnaires accompanied by photo elicitation, this study explored the perceptions of and preferences for seven kinds of lawns and six kinds of spontaneous groundcovers in China. The effects of social backgrounds on people's perceptions of and preferences for ground covers were also analyzed. The results indicated a general equivalence in preferences for the lawn and spontaneous groundcover. The Taraxacum mongolicum - Cynodon dactylon - Conyza canadensis community was significantly preferred most among all of the selected ground covers. Spontaneous groundcovers were regarded as more natural, wild, variable, and species-richer compared to lawns, while lawns were perceived as better kept than spontaneous groundcovers. Ground covers were preferred which were perceived to have high ecological aesthetic value and low wildness. Industry and attention to herbaceous plants mostly affected human perceptions and preferences among the social background factors, and gender, age, education level, and occupation also had significant effects. The results thus provide the support for the application of spontaneous groundcovers in moderately developed cities, but such application should consider the comprehensive development of ecological aesthetic value and the applicability of different groups of residents.

A first-in-class dimethyl 2-acetamido terephthalate inhibitor targeting Conyza canadensis SHMT1 with a novel herbicidal mode-of-action

IntroductionHerbicide application is a highly efficiency method of weed control that boots agricultural output and assures food security. The development of novel herbicides focuses on improved bioactivity and new modes of action. The amino acid biosynthesis was validated as a promising novel mode of action for herbicidal compounds. However, the amino acid biosynthesis enzyme remains largely unexplored for herbicidal targets. ObjectivesSerine hydroxymethyl transferase (SHMT) is an essentialenzyme in the photorespiratory cycle. The study aims to explore Conyza canadensis SHMT1 (CcSHMT1) as a promising target for herbicide discovery. MethodsStructure determination of CcSHMT1 was resolved by X-ray crystallography. Virtual screening docking experiments were performed with Glide version 5.5. Novel derivatives of dimethyl 2-acetamido terephthalate were further designed, synthesized, and bioassay. The druggability of the inhibitor was evidenced by ultrastructural changes in mitochondria, in vivo and vitro enzyme activity assays, and genetics analysis. ResultsCcSHMT1 has a typical PLP-dependent enzyme 3D structure. The dimethyl 2-acetamido terephthalate-containing compounds had herbicidal activity. Dimethyl 2-(2-(4-(2-(4-bromo-2-chlorophenoxy) acetyl)piperazin-1-yl)acetamido) terephthalate (Compound 9ay, EC50 = 193.8 g a.i./ ha) exhibited the highest herbicidal activity on tested weed among the synthesized compounds. Compound 9ay had no obvious adverse effect on the growth of maize and honeybees. Compound 9ay was verified to target CcSHMT1 as an herbicide candidate. ConclusionA first-in-class CcSHMT1 inhibitor that could be developed as a potent herbicide with a new mode of action and provide an avenue for discovering novel inhibitors of pyridoxal-5-phosphate-dependent enzymes.

Impacts of landscape pattern on plants diversity and richness of 20 restored wetlands in Chaohu Lakeside of China

The recovery of wetland function and biodiversity conservation aroused considerable interest in the past decades. Although many advances have been achieved in revealing disturbing factors on plants diversity, the knowledge of biodiversity manipulation, landscape configuration and ecosystem process in restored wetlands remains incomplete. To address this issue, the landscape of 20 restored wetlands' vegetation was classified into five vegetation formations including: upland plants, wet grassland, emergent plants, floating plants and submerged plants. Meanwhile, the configuration of landscape, plants' function traits and the structure of plants communities of each wetland were analyzed. A total of 142 herbaceous plants were identified from 399 samples of 20 lakeside wetlands. The top five predominant species were Typha orientalis, Alternanthera philoxeroides, Phragmites australis, Echinochloa caudata, and Erigeron canadensis. The highest of diversity index was observed in upland plants with Shannon-Wiener index (H) of 0.92 while higher richness of plants was obtained in wet grassland with species of 88. In dry year, the immigration of upland xerophyte and obligated aquatic species to facultative area increased the biodiversity of the ecotone. Meanwhile, this change may also aggravate the diffusion risk of exotic invasive species Erigeron canadensis. Additionally, the results indicated that number and evenness of landscape outweighed Shannon diversity index (SHDI) of wetlands in shaping the richness and diversity of wetland plants. Whereas, the high value of maximum proportion of landscape (Pmax) have reduced the landscape evenness and species richness. A suggested Pmax of <0.5 was benefit for the stability and biodiversity of restored wetlands.

Invasive alien plant biomass-derived hard carbon anode for sodium-ion batteries

In the context of rampant growth of invasive plants, finding suitable ways for resource utilization has become the optimal choice for invasive plant management. In the field of energy storage, sodium-ion batteries have been limited by the lack of appropriate anode materials, and hard carbon stands out as the most promising candidate. Therefore, this study focuses on the preparation of biomass-derived carbons from three invasive plant species, namely Spartina alterniflora Loisel., Solidago canadensis L., and Erigeron canadensis L., through high-temperature carbonization. The resulting biomass carbons are then subjected to cleaning and activation processes to prepare sodium-ion anode materials. The internal structure of the materials was characterized using SEM, TEM, XRD, XPS, Raman spectroscopy, and BET. The materials exhibited a significant amount of pore structures, with interlayer spacing around 0.37 nm, which is larger than the original graphite interlayer spacing. The plant anode materials were assembled into full batteries for cyclic charge/discharge tests. The results show that all three anode materials have good multiplicative performance and excellent cyclable charge/discharge. After 100 cycles at a current of 50 mA in the voltage range of 0–3.0 V, the reversible capacities of the three materials reached 245.3, 207.19, and 227.12 mAh/g, respectively. Among them, the material derived from Spartina alterniflora maintained a capacity of 141.63 mAh/g even after 1000 cycles at a current of 200 mA, demonstrating the best capacity performance.

What Are the Most Efficacious Herbicides Applied Postemergence for Control of Multiple-Herbicide-Resistant Canada Fleabane [Conyza canadensis (L.) Cronq.] in Corn?

Multiple-herbicide-resistant (MHR) Canada fleabane [Conyza canadensis (L.) Cronq.] control has become a major concern for corn producers in Ontario. Postemergence (POST) herbicides are critical for the control of emerged MHR Canada fleabane in corn. A study that consisted of five field experiments was conducted in southwestern Ontario in fields with confirmed MHR Canada fleabane to evaluate various herbicide mixtures applied POST for the control of MHR Canada fleabane in corn. Glyphosate + 2,4-D amine, glyphosate/2,4-D choline, glyphosate + clopyralid, glyphosate + S-metolachlor/mesotrione/bicyclopyrone, glyphosate + tolpyralate + atrazine, glyphosate + dicamba, glyphosate + dicamba/atrazine, glyphosate + S-metolachlor/mesotrione/ atrazine, glyphosate + mesotrione + atrazine, glyphosate + bromoxynil + atrazine, glyphosate + S-metolachlor/ mesotrione/bicyclopyrone/atrazine, glyphosate/S-metolachlor/mesotrione + atrazine, glyphosate/dicamba + tembotrione, glyphosate + tembotrione + bromoxynil, glyphosate/dicamba + tembotrione + atrazine, and glyphosate + tembotrione + atrazine applied POST provided 63-99% control, 77-100% density reduction, and 88-100% shoot biomass reduction of MHR Canada fleabane in corn. MHR Canada fleabane interference reduced corn yield up to 58%; reduced MHR Canada fleabane interference with all herbicide treatments resulted in corn yield similar to the weed-free control. Results of this study indicate that among the herbicide mixtures evaluated glyphosate + mesotrione + atrazine, glyphosate + bromoxynil + atrazine, glyphosate + S-metolachlor/ mesotrione/bicyclopyrone/atrazine, glyphosate/S-metolachlor/mesotrione + atrazine, glyphosate/dicamba + tembotrione, glyphosate + tembotrione + bromoxynil, glyphosate/dicamba + tembotrione + atrazine, and glyphosate + tembotrione + atrazine applied POST provided the most consistent control of MHR Canada fleabane in corn.

Contributions of shading, soybean (Glycine max) row width, and planting green on horseweed (Conyza canadensis) management compared with soil-applied residual herbicides

AbstractGlyphosate-resistant (GR) horseweed is a problematic weed for Michigan soybean growers. Additionally, rosette- and upright-horseweed growth types have been observed co-emerging during mid- to late summer in several Michigan fields. In the greenhouse, shade levels from 35% to 92% reduced rosette- and upright-horseweed biomass 31% to 99% compared with the upright growth type grown under 0% shade. Greater reductions in biomass occurred under 69% and 92% shade. Thus, increased shading by planting in narrow rows and/or planting green into cereal rye may improve horseweed suppression. A field experiment conducted over 3 site-years compared the effect of fall-planted cereal rye terminated with glyphosate 1 wk after planting (WAP; planting green) with a preemergence residual herbicide program (glyphosate + 2,4-D + flumioxazin + metribuzin) on horseweed control in soybean planted in three row widths (19, 38, and 76 cm). Planting green or applying a residual herbicide program across all row widths reduced horseweed biomass 86% to 91% and 95% to 99%, respectively, compared with soybean planted with no cover in 76-cm rows, 4 to 6 WAP. At soybean harvest, when a noneffective postemergence herbicide (glyphosate) was applied, horseweed biomass was 42% and 81% lower by planting green or applying a residual-herbicide program compared with no cover, respectively. Similarly, planting soybean in 19-cm rows reduced horseweed biomass compared with 38- and 76-cm rows. When an effective postemergence program was applied, similar horseweed biomass reductions were observed by planting green or applying a residual herbicide across all row widths. Additionally, soybean yield and economic returns were similar between planting green and applying a residual herbicide in 1 of 2 site-years. Integrating planting green and an effective postemergence herbicide program offers an alternative horseweed management strategy to applying a residual preemergence herbicide program.

Bioherbicidal Activity of Albifimbria verrucaria (Formerly Myrothecium verrucaria) on Glyphosate-Resistant Conyza canadensis.

The effects of the bioherbicidal activity of the fungal phytopathogen, Albifimbria verrucaria (AV), formerly Myrothecium verrucaria, on glyphosate-resistant and -susceptible Conyza canadensis (horseweed) were examined in greenhouse and field studies. Spray applications of mycelial formulations of AV infected both glyphosate-resistant and -susceptible C. canadensis plants at various growth stages. Young plants in the rosette leaf stage of growth were controlled more efficaciously than were older plants that had bolted or that were in the inflorescence stage; nevertheless, severe injury and mortality also occurred in mature plants. The results indicate that this bioherbicidal fungus can infect and control C. canadensis, thereby demonstrating the potential of this fungus as a bioherbicidal agent against this troublesome weed, which has become resistant to various herbicides.

EcAGL enhances cadmium tolerance in transgenic Arabidopsis thaliana through inhibits cadmium transport and ethylene synthesis pathway

Cadmium (Cd) is a highly toxic heavy metal with severe impacts on plant growth and development. Although a multitude of plants have acquired strong tolerance to Cd stress, the underlying molecular mechanism has not been fully elucidated. Here, we identified a Agamous-like MADS-box gene (EcAGL) from Erigeron canadensis. The expression of EcAGL was obviously raised under Cd stress and subcellular localization indicated EcAGL was localized in the nucleus. Overexpression of EcAGL in Arabidopsis thaliana showed marked alleviation of the Cd-induced reduction; Compared to wild-type lines, the antioxidant enzymes activities were increased in EcAGL overexpressing lines under Cd stress. The roots Cd content of transgenic lines was not different with the control plants, whereas significant reduction in shoots Cd content was detected in the transgenic lines, indicating that this gene can enhance Cd tolerance by reducing Cd accumulation in Arabidopsis. Moreover, the expression levels of heavy metal ATPase (AtHMA2 and AtHMA3) and natural resistance-associated macrophage protein (AtNRAMP5) genes in the root of transgenic lines decreased under Cd stress, indicating that EcAGL likely hampered the Cd transport pathway. Gene expression profiles in shoot showed that EcAGL likely modulates the expression of 1-aminocyclopropane-1-carboxylic acid synthase gene (AtACS2), which is involved in the ethylene synthesis pathway, to strengthen the tolerance to Cd. Collectively, these results indicate that EcAGL plays a significant role in regulating Cd tolerance in E. canadensis by alleviating oxidative stress, Cd transport and affecting the ethylene biosynthesis pathway, providing new insight into the molecular mechanism underlying plant tolerance to Cd stress.

Heavy metal pollution is more conducive to the independent invasion of Solidago canadensis L. than the co-invasion of two Asteraceae invasive plants

Allelopathy is one of the primary factors that affects the successful invasion of invasive plants. Two invasive plants can often co-invade the same habitat. However, increasing amounts of heavy metal contamination can alter the independent allelopathy and co-allelopathy of two invasive plants that co-invade the same habitat. However, research on the co-allelopathy of two invasive plants treated with different types of heavy metals is limited. This study aimed to analyze the independent allelopathy and co-allelopathy of the two Asteraceae invasive plants horseweed (Conyza canadensis [L.] Cronq.) and Canadian goldenrod (Solidago canadensis L.) on the seed germination and seedling growth of the horticultural Asteraceae species lettuce (Lactuca sativa L.) treated with different types of heavy metals, including the independent contamination with copper (Cu), the independent contamination of lead (Pb), and the co-contamination of Cu and Pb. The aqueous extract of S. canadensis leaves triggers stronger allelopathy than that of C. canadensis. There is an antagonistic effect for the co-allelopathy of the two Asteraceae invasive plants compared with their independent allelopathy. Both types of heavy metals can significantly intensify the independent allelopathy of S. canadensis and the co-allelopathy of two Asteraceae invasive plants but weaken the independent allelopathy of C. canadensis. Thus, the increase in heavy metal contamination can favor the independent invasion of S. canadensis and the co-invasion of two Asteraceae invasive plants by intensified allelopathy. The intensity of influence of co-allelopathy of both invasive plants was lower than that of the independent allelopathy of S. canadensis treated with heavy metals. Thus, heavy metal contamination is more conducive to the independent invasion of S. canadensis than the co-invasion of the two Asteraceae invasive plants.

Weed infestation of switchgrass (Panicum virgatum L.) crops

Purpose. Determination of the species composition of weeds in switchgrass crops and their influence on the formation of biomass productivity. Methods. Field, laboratory, quantitative-weighing, calculation-comparative, mathematical-statistical. Results. The results of studies on weed infestation of switchgrass crops and methods of their control are highlighted. A mixed type of weediness was observed in the crops, consisting of 19 species from 8 families, with a predominance of annual dicotyledonous species (75.0-87.2%). While in the third (91.7-95.1%) and fifth (61.0-91.7%) years of vegetation, perennial dicot species such as Erigeron canadensis, Lactuc aserriola L., Artemisia annua L., thistles ones, annual dicotyledons were not present. When analyzing the quantitative composition of weeds in the first year of vegetation on the weedy control, high level of weed infestation was observed, which amounted to 176 pcs./m2, in the second and third years 103-105 pcs./m2, in the fourth – 74 pcs./m2 and in the fifth – 39 pcs./m2 . In the variants where weed control was used in the third and subsequent years a decrease in the number of weeds by 83.5-88.4% was noted compared to the control. The use of herbicides on crops ensured efficiency in the first year of vegetation at the level of 72.3-76.9%, while in the fifth year it was 95.3-96.2%. Weed control allowed increasing the biomass yield to 10.7-10.8 t/ha, while the weeded control yielded 8.8 t/ha. Conclusions. The use of herbicides (Dialen super 464 SL, Caliber 50) led to a decrease in the number of weed plants from 28.6% in the first year of vegetation to 88.3% in the fifth year, providing a 72.3-97.6% efficiency depending on the year of vegetation of the crop. Weed controll in the fifth year of crop vegetation made it possible to obtain 11.0 t/ha of dry biomass, 11.9 t/ha of solid fuel, 220 GJ/ha energy from fuel.

Allelopathic Effects of Conyza canadensis Water Extract on Seed Germination and Seedling Growth

In order to investigate the effects of allelo-pathic substances of Conyza canadensis on seed germination and seedlings, this study was designed to explore the allelopathic effects of Conyza canadensis water extract (CCE) on pakchoi, spinach and lettuce. Germination rates of three crops (pakcholi, spinach, and lettuce) during the seed germination, root length, seedling height, and fresh weight of two crops (pakcholi and lettuce) during the seedling were measured under different concentrations of CCE treatment (20, 40, 60, 80, 100 g/L). The allelopathic effect index was also calculated. The results showed that CCE had a varying degree of inhibitory effect on the germination rate of the seeds of the three crops. Spinach and lettuce have significant allelopathic effects from C. canadensis. At higher concentration of CCE, the germination rate of spinach and lettuce significantly decreased (P&lt;0.01). After germination, the root length, seedling height, and fresh weight of the crop were measured, and the allelopathic effects were also calculated. It was found that the CCE had a significant inhibitory effect on root length, but it showed a promoting effect on seedling height and fresh weight of pakchoi, and CCE had a "low promotion-high inhibition" effect on seedling height and fresh weight of lettuce.

Native plant community characteristics explain alien species success in post-industrial vegetation

Biological invasions are one of the major challenges to the restoration of post-mining sites. Most post-mining sites are under technical reclamation with only a few left to spontaneous vegetation processes. Therefore, we know little about alien plant species on spontaneously-vegetated post-coal mine heaps and how native community characteristics predict their establishment. To fill the knowledge gap, we aimed to determine the drivers of alien species colonisation on post-coal mine heaps. Specifically, we asked: (i) Which alien species are the most successful on post-coal mine heaps and why? (ii) What are the drivers of alien species richness and cover, and how are they affected by the native community? (iii) What does it mean for predicting threats from alien species and management? We recorded vascular plant species and their abundance across 400 plots on post-coal mine heaps in Upper Silesia, Poland. We calculated plant community taxonomic and functional characteristics and, using mixed-effects models, we estimated predictors of alien species richness and cover. We found 65 alien species on post-coal mine heaps, comprising 20.4% of all recorded species, including 36 neophytes and 29 archaeophytes. Amongst them – Erigeron canadensis, Solidago gigantea, Solidago canadensis, Erigeron annuus and Impatiens parviflora – were the most frequent on the studied heaps. We showed that native functional richness significantly predicts alien species richness and cover. Similarly, native community-weighted mean (CWM) seed mass and plant height predict alien species cover. However, CWM of specific leaf area for native species marginally predicts alien species richness. We showed that alien species cover decreases with native species cover. Our findings revealed the ecological significance of niche-filling and the biotic acceptance hypotheses on post-coal mine heaps. We demonstrated how exploring native community characteristics can help in understanding the invasibility and management of post-industrial vegetation.

Monitoring weed mechanical and chemical damage stress based on chlorophyll fluorescence imaging.

Currently, mechanical and chemical damage is the main way to carry out weed control. The use of chlorophyll fluorescence (CF) technology to nondestructively monitor the stress physiological state of weeds is significant to reveal the damage mechanism of mechanical and chemical stresses as well as complex stresses. Under simulated real field environmental conditions, different species and leaf age weeds (Digitaria sanguinalis 2-5 leaf age, and Erigeron canadensis 5-10 leaf age) were subjected to experimental treatments for 1-7 days, and fluorescence parameters were measured every 24h using a chlorophyll fluorometer. The aim of this study was to investigate the changes in CF parameters of different species of weeds (Digitaria sanguinalis, Erigeron canadensis) at their different stress sites under chemical, mechanical and their combined stresses. The results showed that when weeds (Digitaria sanguinalis and Erigeron canadensis) were chemically stressed in different parts, their leaf back parts were the most severely stressed after 7 days, with photosynthetic inhibition reaching R=75%. In contrast, mechanical stress differs from its changes, and after a period of its stress, each parameter recovers somewhat after 1 to 2 days of stress, with heavy mechanical stress R=11%. Complex stress had the most significant effect on CF parameters, mainly in the timing and efficiency of changes in Fv/Fm, Fq'/Fm', ETR, Rfd, NPQ and Y(NO), with R reaching 71%-73% after only 3-4 days of complex stress, and its changes in complex stress were basically consistent with the pattern of changes in its chemical stress. The results of the study will help to understand the effects of mechanical and chemical stresses and combined stresses on CF parameters of weeds and serve as a guide for efficient weed control operations and conducting weed control in the future.

Filago pyramidata Tolerant to ALS-Inhibiting Herbicides: A New Invasive Weed in Olive Groves of Southern Spain

Weeds that usually grow in non-agricultural areas have become increasingly common invading perennial crops. Species of the genus Filago, in addition to invading Spanish olive groves, have developed certain levels of natural tolerance to the acetolactate synthase (ALS) inhibiting herbicide flazasulfuron. The objective of this study was to determine the level and the mechanism involved in the tolerance to flazasulfuron in Filago pyramidata L., which occurs in olive groves of southern Spain, as well as to identify possible cross- or multiple-tolerances by evaluating alternative herbicides for its control. A population resistant (R) to flazasulfuron and a susceptible (S) one of Conyza canadensis were used as references. The accessions of F. pyramidata presented LD50 values (from 72 to 81 g active ingredient (ai) ha−1) higher than the field dose of flazasulfuron (50 g ai ha−1), being 11–12.5 times more tolerant than the S population of C. canadensis, but less than half the R population (170 g ai ha−1). Enzymatically, F. pyramidata was as sensitive to flazasulfuron (I50 = 17.3 μM) as the S population of C. canadensis. Filago pyramidata plants treated with flazasulfuron, combined with 4-chloro-7-nitro-2,1,3-benzoxadiazole, had a growth reduction of up to 85%, revealing the participation of glutathione-S-transferases in herbicide metabolism. Filago pyramidata presented cross-tolerance to the different chemical groups of ALS inhibitors, except triazolinones (florasulam). Synthetic auxins (2,4-D and fluroxypyr) presented good control, but some individuals survived (low multiple resistance). Cellulose synthesis, 5-enolpyruvylshikimate-3-phosphate, 4-hydroxyphenylpyruvate dioxygenase, protoporphyrinogen oxidase, photosystem I, and photosystem II inhibitor herbicides, applied in PRE or POST-emergence, presented excellent levels of control of F. pyramidata. These results confirmed the natural tolerance of F. pyramidata to flazasulfuron and cross-tolerance to most ALS-inhibiting herbicides. The mechanism involved was enhanced metabolism mediated by glutathione-S-transferases, which also conferred low multiple tolerance to synthetic auxins. Even so, herbicides with other mechanisms of action still offer excellent levels of control of F. pyramidata.