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Bioherbicidal Activity of Medinilla magnifica Lindl. Leaf Extract
Abstract
The bioherbicidal activity of kapa-kapa (Medinilla magnifica Lindl.) was studied for the first time. Phenolics from its leaves were extracted with 7:7:6 methanol-acetone-water (MAW). The phenolics of the crude extract were quantified using the Folin-Ciocalteu method and values of 71.86 mg GA∙g-1 extract for total phenolics and 29.58 mg QUE∙g-1 extract for total flavonoids were obtained. The crude extract was subjected to acid hydrolysis and the bioherbicidal activity of the resulting hydrolysate was determined. Lettuce seed germination assay was done and the median lethal dose (LD50) of the extract was determined as 64.69 ppm. This relatively low LD50 value shows that it has great potentials for use against weeds. The extract inhibited the growth of Echinochloa crus-galli, Cyperus iria, and Ludwigia hyssopifolia, with E. crus-galli showing the greatest sensitivity among the three species. Total chlorophyll content of soybean was reduced by the extract. This suggests that the acid-hydrolyzed extract of M. magnifica decreased chlorophyll production, resulting in reduced biomass of the test weeds.
... The crude extract of Medinilla magnifica Lindl. subjected to acid hydrolysis was found to inhibit the growth of E. crus-galli, Cyperus iria, and Ludwigia hyssopifolia weeds, E. crus-galli being the most sensitive weed and its adverse impact on chlorophyll (Chl) production was reflected in reduced biomass of the tested weeds (Tinio et al., 2019). ...
With a changing climate and cultivation of vast agricultural monocultures, the abundance of various pests shows an increase and their activity is shifting, expanding and intensifying. To avoid losses on crops, a variety of synthetic pesticides are increasingly being used to control harmful pests. This trend leads to overuse of pesticides, which has environmental consequences because these toxic chemicals enter the soil and water, can exhibit toxic effects on non-target organisms and could also eventually enter the food chain resulting in adverse impact on human health. Consequently, rapid development of nanotechnologies enabled the reformulation of pesticides into nanosystems, characterized by controlled release, targeted distribution, increased efficiency and reduced dose-dependent toxicity. In addition, so-called biopesticides, i.e. pesticides based on natural compounds, are toxic to specific pests and relatively harmless to non-target organisms and the ecosystem and could be easily formulated also in various types of nanoscale preparations.
This chapter gives a comprehensive overview of recent findings related to the activity and mechanisms of action of biopesticides including plant extracts and essential oils or their constituents, biopesticides produced by microorganisms, peptides obtained in spider venoms and Cry proteins produced by Bacillus thuringiensis in their bulk as well as nanoscale form against noxious weeds and harmful arthropods causing losses of economically important crops. Special attention is paid also to insecticidal activity of green synthesized metal nanoparticles against mosquitoes which are important vectors of many diseases causing annually more than a million deaths in tropical regions.
Keywords: arthropods, biopesticides, essential oils, bioherbicides, bioinsecticides, metals/metal oxides, microbial pesticides, nanoformulations, toxins, weeds
... Blume) Blume [10]. Various studies have also been conducted on the cultivated specimens of the Philippine native and now critically endangered M. magnifica Lindl., which showed herbicidal activity against weeds [122] due to its very high and complex phenolic contents [123,124]. Together, Dissochaeta and Medinilla comprise the melastome genera with high crosscultural consensus on anti-diarrheal use and corroborating evidence for the presence of antimicrobial compounds. ...
Background: Despite the mounting studies on the practical use of species of the pantropical family Melastomataceae, especially their medicinal utility, no attempt at compiling the diverse findings has been made to date. Moreover, most reviews of medicinal flora tend to focus more on the biomedical properties of the plants than their equally meaningful evolutionary and ethnobiological aspects.
Objectives: This review aimed to describe and synthesize the current knowledge from and trends in medicinal studies of locally relevant members of the Melastomataceae. Specifically, it sought to gather, select, assess, and analyze digitally available field studies about the anti-infective potential of the genera of the Melastomataceae that occur in the Philippines using a combined evolutionary and ethnobiological lens.
Methodology: Web-based search was conducted in EBSCO, Google Scholar, PubMed, ScienceDirect, Scopus, and local databases of medicinal ethnobotany for full and original research papers in Filipino or English. Studies were screened and assessed independently based on taxonomic reliability and ethnobiological methodology. Data were analyzed qualitatively using an integrated evolutionary and ethnobiological framework.
Results: Thirty-four ethnobiological studies comprising journal articles and theses that surveyed 41 localities and cultural groups from 12 countries were reviewed. Three Philippine native melastome species are used in treating potentially infectious conditions: Dissochaeta divaricata, Melastoma malabathricum, and M. sanguineum. Other genera native to the Philippines with congeneric species used for anti-infective purposes elsewhere are Medinilla, Memecylon, Osbeckia, and Sonerila. Indications with the most cross-regional consensus include cuts, wounds, and skin infections, diarrhea and dysentery, and buccal, respiratory, and urogenital infections.
Conclusion: This review revealed that Philippine native melastome genera and species are available for infectious disease mitigation and exhibit high use convergence across geographically and culturally divergent communities but remain untapped. Documenting medicinal flora in an area or community based on their evolutionary relationships and ethnomedicinal usage is significant not only in bioprospecting but more importantly, in preserving indigenous knowledge and natural patrimony, especially amid collapsing socio-ecological systems and emerging diseases.
Propyrisulfuron is a new pyrimidinylsulfonylurea herbicide with a fused heterocyclic moiety. Similar to older sulfonylureas, propyrisulfuron inhibits the activity of acetolactate synthase (ALS), the enzyme involved in branched-chain amino acid synthesis. Previous studies have shown that ALS activity, and consequently, the growth of susceptible plants was inhibited when treated with propyrisulfuron. This study was conducted to determine whether or not the addition of branched chain amino acids to the growth medium will alleviate the inhibition of ALS activity and the growth of propyrisulfuron-treated rice and weeds. Visual assessment of injury, shoot height, shoot biomass, in vivo ALS activity and ALS content showed that addition of 100 mg L-1 valine, isoleucine and leucine significantly reversed ALS inhibition and resulted in recovery from ALS and growth inhibition of the propyrisulfuron-treated rice and weeds. Recovery of the weeds, which were more susceptible than rice, was more pronounced than that of rice. Addition of all three amino acids resulted in greater reversal of ALS inhibition and better recovery compared with addition of only two amino acids.
The effects of three allelopathic phenolics, o-hydroxyphenyl acetic, ferulic and p-coumaric acids, on the chlorophyllase activity of rice leaf (Oryza sativa cv. TN67) were investigated. Ten-day-old green seedlings of rice were cultured in greenhouse for 16 d in Kimura's culture solution, which was changed every 4 days, with or without 50, 100 or 200 ppm of the phenolic compounds. Just before changing the culture solution, leaves were harvested to determine their chlorophyll (Chl) and chlorophyllide (Chlide) contents, and their chlorophyllase a and b activities. While the Chl and Chlide contents decreased and increased, respectively, causing the molar ratio of Chlide/Chl to increase, as the phenolic concentrations increased; the chlorophyllase a and b activities drastically increased. This suggests that the consumption-orientation of Chl was significantly stimulated by the exogenously applied phenolics. The order of inhibition of growth of the rice seedlings is: ferulic acid>p-coumaric acid>o-hydroxyphenylacetic acid. The order of inhibition effect on Chl accumulation is: p-coumaric acid>o-hydroxyphenylacetic>ferulic acid. The order of stimulation effect on chlorophyllase a activity is: o-hydroxyphenylacetic acid>ferulic acid>p-coumaric acid. The order of promotion effect on chlorophyllase b is: ferulic acid>o-hydroxyphenylacetic acid>p-coumaric acid. The different responses of chlorophyllase a and b activities to the same concentrations of allelochemical phenolics suggest that they may be two different enzymes. It is apparent that the three phenolics may enhance the activities of enzymes, such as chlorophyllase and Mg-dechelatase, responsible for the Chl degradative pathway. A combination of the present and the preceding data strongly suggest that the three allelopathic phenolics may comprehensively affect the biosynthetic and degradative pathways of Chl.
Discovery starts with objectives. We normally find only what we are looking for. Unexpected detections may occur in rare cases. It is, however, very complicated to rely on unknown events from a business point of view. Agrochemical companies develop their research strategies based on agronomic requirements or demands of the consumer of agricultural products, based on economic expectations, on regulatory restrictions, on company strength and on special company portfolio requirements. Herbicides have been an indispensable tool for farmers in developed countries for more than 50 years. High labour costs, energy prices, erosion as an environmental problem and competition resulted in the reduction of mechanical weed control measures and resulted in a leading role of herbicides as agrochemicals. On a global basis, farmers spent around $17 billion annually for herbicides in 2010 or over 40% of all agrochemical expenditure. In the past, every research driven agrochemical company used to invest heavily in herbicide research. Over the last ten years leading companies' total expenditure was approximately $100 to 300 M annually on herbicide research and development.
Studies on plant growth are interesting because they provide explanations for the factors that influence yield in various crops. The objective of this work was to evaluate growth and yield in corn cultivar AG1051, when in competition with weeds. Cultivar AG 1051 was submitted to two groups of treatments: weed control, and sampling periods for dry biomass evaluation. The weed control treatments consisted of hoeing (two hoeings performed at 20 and 40 days after sowing) and no hoeing. Sampling periods consisted of collecting the above-ground part and roots of corn every fifteen days, until 105 days after sowing (DAS); the first sampling was performed 30 DAS. A completely randomized block design with ten replicates was used. For the characteristics evaluated in a single season, statistical analyses were carried out as a random block experiment. For the characteristics evaluated in several periods, statistical analyses were carried out as random blocks with split-plots (weed control assigned to plots). Fourteen weed species, unevenly distributed throughout the experimental area, were the most important. The growth observed for the above-ground part and root system of corn was 30% smaller in the non-hoed plots, compared to the hoed plots. Lack of weed control increased dry matter of the above-ground part of the weeds and reduced the number of unhusked and husked marketable green ears by 23% and 49%, respectively. Grain yield reduction caused by lack of weed control reached 38%.
Low molecular weight phenolic compounds have been identified in fresh leaves and in soils in which leaves of five varieties of Capsicum annuum L. were decomposing. Six phenolic compounds were tested in laboratory bioassays for their allelopathic effects on germination and seedling growth of six weeds. Ferulic acid, gallic acid, p-coumaric acid, p-hydroxybenzoic acid, vanillic acid, and p-vanillin were bioassayed in concentrations of 10, 1, 0.1, and 0.01 mM. Equimolar mixtures containing all these phenolics were prepared at the final total concentration of 10, 1, 0.1, and 0.01 mM to test for possible interactive effects. Chenopodium album L., Plantago lanceolata L., Amaranthus retroflexus L., Solanum nigrum L., Cirsium sp. and Rumex crispus L. were the selected target weeds. The highest concentration of the compounds inhibited the germination of all these weeds, but lower concentrations had no effect or were stimulatory. However, effects varied with the weed species, the concentration of the compound tested and the compound itself. In assays with the mixture of phenolics we found evidence of some additive effects.
Impact of pesticides use in agriculture: their benefits and hazards
Fundamentals of Weed Science, Fifth Edition, provides the latest information on this constantly advancing area of study. Placing weed management in the largest context of weed research and science, the book presents the latest advances in the role, control and potential uses of weed plants. From the emergence and genetic foundation of weeds, to the latest means of control and environmental impact, the book uses an ecological framework to explore the role of responsible and effective weed control in agriculture. In addition, users will find discussions of related areas where research is needed for additional understanding. Explored topics include the roles of culture, economics and politics in weed management, all areas that enable scientists and students to further understand the larger effects on society. Completely revised with 35% new content Contains expanded coverage of ethnobotany, the specific identity and role of invasive weed species, organic agriculture, and herbicide resistance in GM crops Includes an emphasis on herbicide resistance and molecular biology, both of which have come to dominate weed science research Covers all traditional aspects of weed science as well as current research Provides broad coverage, including relevant related subjects like weed ecology and weed population genetics.
The herbicide glyphosate, N-(phosphonomethyl) glycine, has been used extensively in the past 40 years, under the assumption that side effects were minimal. However, in recent years, concerns have increased worldwide about the potential wide ranging direct and indirect health effects of the large scale use of glyphosate. In 2015, the World Health Organization reclassified glyphosate as probably carcinogenic to humans. A detailed overview is given of the scientific literature on movement and residues of glyphosate and its breakdown product aminomethyl phosphonic acid (AMPA) in soil and water, their toxicity to macro- and microorganisms, their effects on microbial compositions and potential indirect effects on plant, animal and human health. Although the acute toxic effects of glyphosate and AMPA on mammals are low, there are animal data raising the possibility of health effects associated with chronic, ultra-low doses related to accumulation of these compounds in the environment. Intensive glyphosate use has led to the selection of glyphosate-resistant weeds and microorganisms. Shifts in microbial compositions due to selective pressure by glyphosate may have contributed to the proliferation of plant and animal pathogens. Research on a link between glyphosate and antibiotic resistance is still scarce but we hypothesize that the selection pressure for glyphosate-resistance in bacteria could lead to shifts in microbiome composition and increases in antibiotic resistance to clinically important antimicrobial agents. We recommend interdisciplinary research on the associations between low level chronic glyphosate exposure, distortions in microbial communities, expansion of antibiotic resistance and the emergence of animal, human and plant diseases. Independent research is needed to revisit the tolerance thresholds for glyphosate residues in water, food and animal feed taking all possible health risks into account.
Yields from 140 rice trials conducted at CIBA-GEIGY’s Agricultural Research and Development Station in Indonesia were compiled with the aim of determining yield losses in both irrigated transplanted and wet-sown rice in relation to the timing of the elimination of the annual weed flora and its composition.
Relative yield losses due to weeds averaged 50% and were independent of rice production system or season. Actual yield losses were greater in wet season and transplanted rice. While all weed species present contributed to yield losses, the contribution from both grasses and sedges was more significant than that of broadleaved weeds.
Yields increased irrespective of the timing of weed elimination. In particular, elimination of weeds during the period 0–9 DAT/DAS lead to significant yield gains, also when compared with the handweeded check. Such early elimination of weeds was especially beneficial in dry seasons and wet-sown rice.
It is suggested that future studies on rice/weed-competition should pay particular attention to the weed group of sedges as well as to seasonal influences.
Glyphosate (GLY) is a broad spectrum herbicide used for weed control. Presently, sub-lethal impact of GLY on non-target organisms such as insect pollinators has not been evaluated yet. Apis mellifera is the main pollinator in agricultural environments and a well-known model for behavioural research. Moreover, honeybees are accurate biosensors of environmental pollutants and their appetitive behavioural response is a suitable tool to test sub-lethal effects of agrochemicals. We studied the effects of field-realistic doses of GLY on honeybees exposed chronically or acutely to it. We focused on sucrose sensitivity, elemental and non-elemental associative olfactory conditioning of the proboscis extension response (PER) and on foraging related behaviour. We found a reduced sensitivity to sucrose and learning performance for the groups chronically exposed to GLY concentrations within the range of recommended doses. When olfactory PER conditioning was performed with sucrose reward with the same GLY concentrations (acute exposure), elemental learning and short-term memory retention decreased significantly compared to controls. Non-elemental associative learning was also impaired by an acute exposure to GLY traces. Altogether, these results imply that GLY at concentrations found in agro-ecosystems due to standard spraying can reduce sensitivity to nectar reward and impair associative learning in honeybees. However, no effect on foraging related behaviour was found. Therefore, we speculate that successful forager bees could become a source of constant inflow of nectar with GLY traces that could then be distributed among nest mates, stored in the hive and have long-term negative consequences on colony performance.
The purpose of these experiments was to study the effects of various experimental procedures and conditions on bioassay sensitivity in allelopathic studies. The following factors were considered: bioassay methods, choice of test species, the effect of osmotic potential on germination and growth of the test species, growth in dark or in light and the effect of concentrating the extracts in vacuo. Extracts from rape and rye were used in the studies to act as allelopathic agents. Ryegrass appeared as the most sensitive test species when grown horizontally on quartz sand, while radish was the most sensitive test species when grown on filter paper in transparent boxes at a 45° angle. Root length was the most sensitive growth variable measured. Percent germination appeared a more sensitive measure than the speed of germination index, "S", when germinated seeds were counted after one and two days for radish and ryegrass, respectively. A rise in the osmotic potential affected germination more than root length, and radish appeared more sensitive to a rise in osmotic potential than ryegrass. A confounding of germination and root length inhibition may therefore, give misleading results.
Biorational alternatives are gaining increased attention for weed control because of concerns related to pesticide usage and dwindling numbers of labeled products, particularly for minor-use crops. Allelopathy offers potential for biorational weed control through the production and release of allelochemics from leaves, flowers, seeds, stems, and roots of living or decomposing plant materials. Under appropriate conditions, allelochemics may be released in quantities suppressive to developing weed seedlings. Allelochemics often exhibit selectivity, similar to synthetic herbicides. Two main approaches have been investigated for allelopathic weed suppression. One is use of living rotational crops or mulches that interfere with the growth of surrounding weeds [e.g., tall red rescue, Festuca arundinacea Schreb.; creeping red rescue, F. rubra L. subsp. commutata; asparagus. Asparagus officinalis L. var. altilis); sorghum, Sorghum bicolor (L.) Moench; alfalfa, Medicago sativa L.; black mustard, Brassica nigra (L.) Koch; and oat, Avena saliva L.]. Attempts to select germplasm with enhanced suppressive ability have been limited. The second is use of cover crop residues or living mulches to suppress weed growth for variable lengths of time (e.g., winter rye, Secale cereale L.; winter wheat, Triticum aestivum L.; and sorghum). Cover crop residues may selectively provide weed suppression through their physical presence on the soil surface and by release of allelochemics or microbially altered allelochemics. The ability to understand the physiological basis for allelopathy in a crop plant may allow the weed scientist or ecologist to work closely with molecular biologists or traditional plant breeders to selectively enhance the traits responsible for weed suppression.
The production of viable meristem cultures of Medinilla magnifica has proved to be very difficult. This may be due, in part, to a pronounced ‘browning’ response of the tissues on cutting. For this reason the phenolic compounds and the hydrolysable-tannin polyphenol oxidase from Medinilla were studied. The distribution of the compounds was: simple phenols 19% , flavonoids 5% , hydrolysable tannins 69% , condensed tannins 7%. Amongst the simple phenols and phenolic acids, the following were identified: phloroglucinol, p-hydroxybenzoic acid, vanillic acid, protocatechuic acid, gallic acid (both in free and bound form the most abundant simple phenol), syringic acid, trans-p-coumaric acid, trans-ferulic acid and trans-caffeic acid. No kaempferol or quercetin or their derivatives were detected but condensed tannins are present. Methods for the extraction, fractionation and quantitative determination of phloroglucinol and the phenolic acids, as well as correction factors for losses during the extraction, alkali treatment and derivatization, are presented in a supplementary publication. With regard to the hydrolysable tannin polyphenol oxidase activity of Medinilla stems, the enzyme(s) is rather specific since at neither of its two pH optima (6 and 7) could a classical polyphenol oxidase activity be detected. The enzyme was strongly inhibited by 2-mercaptoethanol. Preliminary experiments have further shown that in addition to the hydrolysable tannins of the tissue, the ferrous ions of the medium, and oxygen together with the hydrolysable tannin polyphenol oxidase could play a role in the browning response. Ways to overcome this difficulty have been suggested.
Experiments were designed to test the hypothesis that interference with chlorophyll metabolism may be one mechanism of inhibition of plant growth in allelopathic interactions. Effects of ferulic,p-coumaric, and vanillic acids on soybean and grain sorghum growth and chlorophyll content were quantified and compared after seedlings were treated with these compounds in a nutrient culture. Following a 6-day treatment cycle, dry weights of soybean seedlings were reduced by both 10–3 M and 5 10–4 M treatments of ferulic,p-coumaric and vanillic acids. Soybean weight reductions in each case were paralleled by a significant reduction in the concentration (g Chl/mg dry wt) of chlorophylls a and b and total chlorophyll in the unifoliate leaves. Sorghum seedling growth was also reduced by each of the compounds at the 5 10–4 M level, but leaf chlorophyll concentration was not below that of control plants.
The field experiment was conducted at Students Farm, Sindh Agriculture University, Tandojam, Pakistan during 2004-05. Weed densities tested were: weedy check (control), wheat + Natural weeds (weedy for full season), wheat + mixed weeds ( Chenopodium album , Melilotus alba , Avena fatua , Phalaris minor ) (2:1), wheat + Chenopodium album (2:1), wheat + Melilotus alba (2:1), wheat + Avena fatua (2:1) and wheat + Phalaris minor (2:1). Among the tested weed densities, Chenopodium album , Avena fatua , Phalaris minor , and Melilotous alba were found common and serious weeds in wheat crop and reduced the tillers production, height of plants, seed index, wheat biomass and grain yield. The highest effect of Chenopodium album was recorded which reduced the grain yield by 39.95%, followed by Avena fatua (36.48%), Phalaris minor (35.33%), natural weeds for full season (34.96%), mixed weeds (32.14%) and Melilotous alba (24.01%). It was concluded that weeds exhibit the economic yield losses to the wheat crop, which may range from 24-39.95% and these must be controlled during the full growing season of the crop for achieving satisfactory crop yields.
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