Phytotoxic Substances Research Articles

Allelopathy of the Medicinal Plant Dregea volubilis (L.f.) Benth. ex Hook.f. and Its Phytotoxic Substances with Allelopathic Activity

Allelopathic plants and their related phytotoxic chemicals have been explored as alternatives for environmentally friendly weed management. Dregea volubilis (L.f.) Benth. ex Hook.f., a woody vine, is well-known for its uses in various therapeutic treatments, and several bioactive compounds have been isolated from this species. However, to date, no phytotoxic substances from D. volubilis have been reported. Hence, in this research, we aimed to investigate the allelopathic effect of D. volubilis and characterize its phytotoxic substances. Extracts of D. volubilis exhibited significant inhibitory activity against the seedling growth of Italian ryegrass (Lolium multiflorum Lam.) and cress (Lepidium sativum L.). The extracts were purified through several chromatography steps, yielding two phytotoxic substances, and using spectroscopy, their structures were determined as dehydrovomifoliol and loliolide. The compounds inhibited the Italian ryegrass and cress seedlings with the I50 (concentrations needed for 50% inhibition) values ranging from 0.022 to 0.102 mM, for loliolide and 3.24–4.60 mM, for dehydrovomifoliol. These results suggest that both phytotoxic compounds might be responsible for the allelopathy of D. volubilis, and they may be released into the soil through the decomposition of the D. volubilis leaf and probably act as allelopathic active substances. Therefore, the extracts of D. volubilis and its related phytotoxic compounds may be applied as biological agents for controlling weeds.

Phytotoxicity in aqueous methanolic extracts of rice against junglerice and total activities of identified phytotoxic compounds

AbstractThis study examined phytotoxic activities of several Vietnam localised OM rice (Oryza sativa L. OM) cultivars on junglerice (Echinochloa colona (L.) Link), an invasive weed threatening rice production, and identified allelochemicals and their activities for OM 4498, the most allelopathic cultivar. The aqueous MeOH extracts of all rice cultivars inhibited root and shoot growth of junglerice at a concentration as low as 0.01 g ml−1. Inhibitory effects were greatest in OM 380, OM 2395 and OM 4498, with the average effective doses (EDs) of extracts required for 90% inhibition (ED90) on junglerice as low as 0.981, 0.632 and 0.702 g ml−1, respectively. The phytotoxic substances salicylic acid, vanillic acid, p‐coumaric acid, 2,4‐dimethoxybenzoic acid, benzoic acid, p‐hydrobenzoic acid, trans‐cinnamic acid and coumarin were identified in OM 4498 at concentrations ranging from 0.066 to 11.412 mg in 100 g fresh weight of rice tissue. Two of these substances, 2,4‐dimethoxybenzoic acid and coumarin, have never previously been identified in rice. Compared to other compounds, p‐coumaric acid may have the greatest weed‐suppressant potential on junglerice, with the average ED50 being 0.28 mM. The total activities of salicylic acid, vanillic acid, p‐coumaric acid, trans‐cinnamic acid and 2,4‐dimethoxybenzoic acid in an OM 4498 rice plant on junglerice seedlings were 59.60, 0.78, 3.47, 2.52 and 0.61 mM/mM, respectively. The results clearly suggest that OM 4498 rice extract is an excellent source for allelochemicals against junglerice, and this rice cultivar should be considered in rice production areas invaded by junglerice.

Assessment of Allelopathic Potential of Senna garrettiana Leaves and Identification of Potent Phytotoxic Substances

Senna garrettiana (Craib) Irwin & Barneby (Fabaceae) is a medicinal plant known to be rich in biologically active compounds that could be exploited to produce bioherbicides. The present study was conducted to explore the allelopathic potential and phytotoxic substances of S. garrettiana. Extracts of S. garrettiana leaves were found to significantly inhibit the growth of Lepidium sativum L. and Echinochloa crus-galli (L.) P. Beauv. (p ≤ 0.05). The phytotoxic substances were isolated and identified as vanillic acid and ferulic acid by bioassay-directed fractionation and spectral data analysis. The two compounds were shown to significantly inhibit the seed germination, seedling growth, and dry biomass of L. sativum. Based on the concentration required for 50% growth inhibition (defined as IC50), the roots of L. sativum were the most sensitive to the compounds, and the inhibitory effect of ferulic acid (IC50 = 0.62 mM) was >1.3 times more potent than that of vanillic acid (IC50 = 0.82 mM). In addition, a mixture of the two compounds (0.3 mM) resulted in synergistic inhibitory activity against the L. sativum roots compared with the individual compounds. These results suggest that the extracts of S. garrettiana leaves and their phytotoxic compounds have potential as candidate natural herbicides.

​Allelopathic Chemical Screening of Aqueous Extracts of Coir Pith on Seedling Growth of Black Gram (Vigna mungo L.) and Green Gram (Vigna radiata L.)

Background: Black gram (Vigna mungo L.) and Green gram (Vigna radiata L.) were mostly used as chemical residue indicators for testing the persistence of pesticides, fungicides and herbicides, etc. in the soil. Presently, the coir pith was used as a medium of nursery for many seeds and seedling production. This study evaluated the inhibition effects and screening of allelopathic chemicals from aqueous extracts of coir pith and composting coir pith on the back gram and green gram by response index method and GCMS/MS analysis. Methods: The coir pith and composted coir pith soaked the ratio of 1:10 for 24 hrs, filtered through Whatman No.1 filter paper. The inhibition effect tested for germination and seedling growth of black gram and green gram was sown in poly pots. The carbon: nitrogen ratio and the total organic carbon were analyzed by dry combustion method, Kjeldahl method and GCMS/MS analysis. Result: The phytotoxic substances are present in coir pith, which can be exterminated by composting the coir pith for better growth and development of seedlings. The negative response index (RI), high C: N ratio and chemical compounds like tocopherol, fucoxanthin, tetramethyl heptadeca, dichloroacetamide, tetrazole, hydroxyethyl palmitate, neocurdione and uridine derivations present in raw coir may have the phytotoxic effect and produced yellowing symptoms in young plants compared to composted coir pith. This is exterminated by composting the coir pith for better growth and development of seedlings as well as used for various agricultural and horticultural nurseries.

Nutrient dynamics during composting of human excreta, cattle manure, and organic waste affected by biochar.

Ecological sanitation via thermophilic composting could be a promising solution to the lack of sanitation and limited access to fertilizers, particularly in developing countries. Here, we conducted a 185-d thermophilic composting experiment with human excreta, and separately with cattle manure, mixed with kitchen scraps, teff [Eragrostis tef (Zuccagni) Trotter] straw, sawdust, and biochar (BC) by using an appropriate-technology approach. We followed the dynamics of the most important macronutrients (N, P, K), temperature, moisture, pH, electrical conductivity, cation exchange capacity, as well as content of organic matter, organic C, Ca, Mg, and micronutrients throughout the process. Low N (<47%), P (<9%), K (<11%), Ca (<18%), and Mg (<21%) losses and the temperature profile indicated a well-functioning thermophilic composting process. Compost temperature was >60°C for 7, 6, 5, and 8 consecutive days for treatments containing human excreta, human excreta amended with BC, cattle manure, and cattle manure amended with BC, respectively, suggesting a final compost product free of pathogens. The compost mixture with cattle manure and BC reached a significantly higher temperature than the same variant without BC, with a maximum value of 65.9°C on Day 6. For all treatments, final germination index values>100% indicated compost maturity and the absence of phytotoxic substances. Biochar addition reduced losses of organic matter (18-23%), C (33-42%), and N (49-100%) and decreased the amount of extractable NO3 - (32-36%) in the final compost. The tested ecological sanitation concept via thermophilic composting is thus a promising strategy to improve access to cheap fertilizer by safe and sustainable sanitation and waste management.

Allelopathic Activity and Characterization of Allelopathic Substances from Elaeocarpus floribundus Blume Leaves for the Development of Bioherbicides

To help protect the environment as well as increase agricultural production, the use of synthetic herbicides must be reduced and replaced with plant-based bioherbicides. Elaeocarpus floribundus is a perennial, evergreen, and medium-sized plant grown in different areas of the world. The pharmaceutical properties and various uses of Elaeocarpus floribundus have been reported, but its allelopathic potential has not yet been explored. Thus, we carried out the present study to identify allelopathic compounds from Elaeocarpus floribundus. Aqueous MeOH extracts of Elaeocarpus floribundus significantly suppressed the growth of the tested species (cress and barnyard grass) in a dose- and species-dependent way. The three most active allelopathic substances were isolated via chromatographic steps and characterized as (3R)-3-hydroxy-β-ionone, cis-3-hydroxy-α-ionone, and loliolide. All three substances significantly limited the seedling growth of cress, and the compound (3R)-3-hydroxy-β-ionone had stronger allelopathic effects than cis-3-hydroxy-α-ionone and loliolide. The concentrations of the compounds required for 50% growth inhibition (I50 value) of the cress seedlings were in the range of 0.0001–0.0005 M. The findings of this study indicate that all three phytotoxic substances contribute to the phytotoxicity of Elaeocarpus floribundus.

Effects of digestion duration on energy efficiency, compost quality, and carbon flow during solid state anaerobic digestion and composting hybrid process

This study investigated the effects of anaerobic digestion duration on methane yield, net energy production, and humification of compost during solid state anaerobic digestion (SSAD) and composting hybrid process for food waste treatment. Carbon flow and balance were used to evaluate organic methanation and humification inclination of carbon in the whole SSAD and aerobic composting system. Results showed that SSAD for 15 (AD-15) and 21 days (AD-21) could increase net energy production and degraded organic matter contained in the mixtures to achieve high biological stability. The cumulative net energy production between the AD-15 and AD-21 treatments was not significantly different, which was 8.3% higher than that in SSAD for 30 days (AD-30). Furthermore, digestate (AD-15 and AD-21) composting for 3 days reached maturity and absence of phytotoxic substances. Carbon fixed into humus of the AD-21 treatment (11.6%) was not significantly different from that of AD-15 (12.0%). However, the total amount of carbon fixed into compost in AD-15 was 6.6% higher than that in AD-21. Moreover, the CO2 -C loss of the AD-15 treatment (22.9%) was slightly higher than that of AD-21 (20.6%). Thus, AD-21 treatment achieved the most effective use of carbon during SSAD and composting hybrid process for food waste treatment. These results could provide valuable insights for the effective management of food waste in practice.

Chemical Composition of Ambrosia trifida L. and Its Allelopathic Influence on Crops.

Phytotoxic substances released by invasive plants have been reported to have anti-pathogen, anti-herbivore, and allelopathic activity. The aim of this study was to determine the allelopathic influence of the Ambrosia trifida L. on oxidative stress parameters (the lipid peroxidation process; reduced glutathione (GSH) content; and activity of antioxidant enzymes catalase (CAT), superoxide dismutase (SOD), and peroxidase (PX)) and phenolic compounds (total phenolic and tannin content) in maize (Zea mays L.), soybean (Glycine max L.), and sunflower (Helianthus annuus L.) crops to explore the effect of released allelochemicals through A. trifida root on crops. An analysis by HPLC confirmed the presence of protocatechuic acid, p-hydroxybenzoic acid, vanillic acid, and syringic acid as major components in the A. trifida. Based on the obtained results for oxidative stress parameters, it can be concluded that the sunflower was the most sensitive species to A. trifida allelochemicals among the tested crops. The other two crops tested showed a different sensitivity to A. trifida. The soybean did not show sensitivity, while the maize showed sensitivity only 10 days after the sowing.

Three Active Phytotoxic Compounds from the Leaves of Albizia richardiana (Voigt.) King and Prain for the Development of Bioherbicides to Control Weeds

The global population is increasing day by day. To meet the food demand for such a huge number of people, crop production must increase without damaging the environment, and to prevent synthetic chemical herbicides from polluting the environment, controlling weeds using bioherbicides is essential. Accordingly, using phytotoxic substances obtained from plants for biological weed management has attracted attention. The plant Albizia richardiana possesses phytotoxic compounds that have been previously recorded. Hence, we have conducted this research to characterize more phytotoxic compounds in Albizia richardiana. Aqueous methanolic extracts of Albizia richardiana plant significantly restricted the growth of the examined plants lettuce and Italian ryegrass in a species- and concentration-dependent manner. Three active phytotoxic compounds were isolated through various chromatographic methods and identified as compound 1, 2, and 3. Compound 3 exhibited stronger phytotoxic potentials than the other two compounds and significantly suppressed the growth of Lepidium sativum (cress). The concentration of the compounds required for 50% growth reduction (I50 value) of the Lepidium sativum seedlings ranged between 0.0827 to 0.4133 mg/mL. The results suggest that these three phytotoxic compounds might contribute to the allelopathic potential of Albizia richardiana.

Profiles of Compounds in Stover of Rice, Cymbopogon, Desmodium, Mucuna and Maize

Crop residues and mulches release phytotoxic substances into the soil that affect plant growth. An experiment was conducted at the Uganda National Crop Resources Research Institute, Namulonge during 2016, to identify compounds in the stover of potted Cymbopogon nardus, Desmodium uncinatum, Oryza sativa, (NERICA 1), Mucuna pruriens and Zea mays (LONGE 6H) at fourty five days after germination. This marked near the average stationary phase for test crops&amp;rsquo; growth when secondary metabolites are maximum. Organic compounds in the stover were extracted using solid phase micro-extraction. Samples were subjected to analysis using a 7890A Gas Chromatography system. Data files were transferred into a distinct folder and data was uploaded onto XCMS online platform for pair wise comparison and other related statistical analysis in the National institute of Science and Technology library. Ten terpenoids and one ester were identified in cymbopogon stover. Desmodium stover released six terpenoids and three phenols. Rice stover produced six terpenoids, three phenolic compounds and one ester. Mucuna stover released two terpenoids and four phenols. The maize stover produced five terpenoids and four phenolic compounds. Profiled compounds from cymbopogon, desmodium, rice, mucuna and maize could be responsible for the reported negative allelopathic effects such as auto-toxicity and suppression of companion crops expressed in agricultural ecosystems. Allelopathic activity of the profiled compounds should be confirmed through bioassays extracts and residues studies. The development and incorporation of the profiled metabolites into agricultural management system may lead to the production of bio-herbicides that reduce environmental degradation and increase crop productivity.

Phytotoxicity of the novel compound 3-hydroxy-4-oxo-β-dehydroionol and compound 3-oxo-α-ionone from Albizia richardiana (Voigt.) King &amp; Prain

To protect our environment from the toxic effect of herbicides, it is necessary to reduce the application of synthetic herbicides for controlling weeds in crop fields as well as to increase the use of natural herbicides produced from plant sources. Phytotoxic compounds obtained from plant species have gained attention as an alternate biological method for managing weeds. Albizia richardiana was previously reported to contain a number of phytotoxic substances. Therefore, we carried out this study to investigate more allelopathic substances in Albizia richardiana leaves. Aqueous methanol extracts of Albizia richardiana leaves were significantly inhabited the seedling growth of the two test species (alfalfa and timothy) in a concentration-dependent manner. The two most active substances were separated through different chromatographic steps and characterized as a novel compound 3-hydroxy-4-oxo- β -dehydroionol [( E )-6-hydroxy-3-(3-hydroxybut-1-en-1-yl)-2,4,4-trimethylcyclohexa-2,5-dien-1-one], and compound 3-oxo- α -ionone [3,5,5-trimethyl-4-(3-oxo-1-butenyl)-2-cyclohexen-1-one]. The novel compound 3-hydroxy-4-oxo- β -dehydroionol showed relatively stronger growth inhibitory potential compare to the compound 3-oxo- α -ionone and significantly restricted the seedling growth of crees and timothy. The required concentration for 50% reduction in the growth ( I 50 values) of the cress and timothy seedlings varied from 63.78 to 141.61 μ M for 3-hydroxy-4-oxo- β -dehydroionol and 1059.60 to 1616.10 μ M for 3-oxo- α -ionone. The results indicate that these two allelopathic compounds may be responsible for the phytotoxicity of Albizia richardiana leaves. • Isolation and identification of a novel compound 3-hydroxy-4-oxo- β -dehydroionol. • Characterization of another compound 3-oxo- α -ionone and determined their phytotoxicity. • Albizia richardiana might play a vital to control weeds and protect the environment.

Evaluating the Aqueous Phase From Hydrothermal Carbonization of Cow Manure Digestate as Possible Fertilizer Solution for Plant Growth.

Improving the agronomic use of recycled nutrients derived from organic waste is one of the priorities within the measures adopted by the European community to reduce environmental issues but remains an unexplored area of research. This study focused on investigating the possibility of using innovative fertilizer solutions in hydroponic systems for the growth of agricultural plants. To this purpose, a liquid fraction [aqueous hydrothermal carbonization (HTC) liquid (AHL)] derived from HTC of cow manure digestate was chemically characterized (pH, electrical conductivity, mineral elements, and organic compounds such as phytotoxins), diluted with distilled water (1:30, 1:60, and 1:90, v/v) to reduce its potential phytotoxicity, and used to grow hydroponic maize (Zea mays L.) plants instead of the classical full-strength nutrient solution. The results indicated that the dilution ratio 1:30 of the AHL solution maintained a high level of toxicity for the plants (phytotoxic substances, especially Na and alkalinity), inducing the arrest of their growth. Differently, the two other dilution ratios (i.e., 1:60 and 1:90) seemed to considerably limit the levels of toxicity, since they allowed the plants to develop. However, these dilution ratios were poor in nutrient elements, inducing alteration in photosynthesis and an onset of deficiency symptoms such as pronounced leaf chlorosis. In view of an eco-friendly approach, future studies are, therefore, needed to identify the correct species-specific dilution ratio to supply both low levels of phytotoxins and adequate content of essential nutrients for appropriate plant growth and development. Furthermore, in order to lower specific Na phytotoxicity, treatments are of utmost importance before using AHL as a fertilizer solution.

Euphorbia retusa (Forssk.) A PROMISING SOURCE FOR BIOACTIVE COMPOUNDS IN BIOMEDICAL AND AGRICULTURE APPLICATIONS

Euphorbia retusa (family Euphorbiaceae) is an annual plant in the desert of Egypt with a 20 to 60 cm high. The aerial part of the plant containing latex is used in many biological activities. This study aimed to determine the phytochemical constituents, antioxidant, antimicrobial properties and allelopathic activities of aerial parts of E. retusa collected from Wadi Arabah, North Eastern Desert, Egypt. Standard methods were used for the qualitative and quantitative of tannins, saponins, flavonoids, alkaloid, phenolics, steroids, terpenoids, and glycosides. The antioxidant activity was measured based on the reduction of DPPH.Antimicrobial activity was evaluated against pathogenic bacteria, as well as the allelopathic potential against Chenopodium murale was assayed. E. retusa attained the highest values of saponins, tannins, and phenolics compared. In the DPPH test system, the IC50 value of the antioxidant inhibition for E. retusa was 802.74µg mL-1. The data obtained indicated that, the sensitivity of the seedling growth to the extract was higher than the germination of the test species. In addition, the root growth of C. murale was more affected than the shoot system to the inhibitory allelopathic activity induced by E. retusa. At higher concentration (40 g L-1) the germination of the tested seed was highly inhibited by 51.77%, while the shoot and root were reduced by 60.98% and 74.55%, respectively. However, the opposite response was observed at the lower concentration (2.5 g L-1).In conclusion, theextract of E. retusa plant has phytotoxic properties and thus contains phytotoxic substances

Isolation and Identification of Two Potent Phytotoxic Substances from Afzelia xylocarpa for Controlling Weeds

Phytotoxic substances released from plants are considered eco-friendly alternatives for controlling weeds in agricultural production. In this study, the leaves of Afzelia xylocarpa (Kurz) Craib. were investigated for biological activity, and their active substances were determined. Extracts of A. xylocarpa leaf exhibited concentration-dependent phytotoxic activity against the seedling length of Lepidium sativum L., Medicago sativa L., Phleum pratense L., and Echinochloa crus-galli (L.) P. Beauv. Bioassay-guided fractionation of the A. xylocarpa leaf extracts led to isolating and identifying two compounds: vanillic acid and trans-ferulic acid. Both compounds were applied to four model plants using different concentrations. The results showed both compounds significantly inhibited the model plants’ seedling length in a species-dependent manner (p &lt; 0.05). The phytotoxic effects of trans-ferulic acid (IC50 = 0.42 to 2.43 mM) on the model plants were much greater than that of vanillic acid (IC50 = 0.73 to 3.17 mM) and P. pratense was the most sensitive to both compounds. In addition, the application of an equimolar (0.3 mM) mixture of vanillic acid and trans-ferulic acid showed the synergistic effects of the phytotoxic activity against the root length of P. pratense and L. sativum. These results suggest that the leaves of A. xylocarpa and its phytotoxic compounds could be used as a natural source of herbicides.

Evaluation of the nutrients cycle, humification process, and agronomic efficiency of organic wastes composting enriched with phosphate sludge

Composting is now at the core of the environmental policy and the circular economy as one of the best options for recycling organic waste leading to a high-value final product. However, composting organic waste suffers from several drawbacks in the resulting product, such as insufficient maturity, unstable organic matter (OM), accumulation of phytotoxic substances, and low amounts of nutrients. This study investigated the effectiveness of adding phosphate sludge (PS) to improve the green waste (GW) composting process, as well as its effectiveness when combined or not with sugar beet waste (SBW), GW, and oil mill waste (OMW) in the composting process of food waste (FW). The impact on the fertilizer quality of final products was also assessed. Composting treatments and controls were conducted in large-scale trials for 150 days. The composting process parameters, nutrient dynamics, phytotoxic effect, and agronomic capacity of the compost product were evaluated. The physicochemical analyses demonstrated that the addition of PS increased the pile temperature and prolonged thermophilic period by two weeks compared to controls. The PS addition brought pH, electrical conductivity (EC), and carbon to nitrogen ratio (C/N) values of FW and GW composts to maturity acceptable level. The results also indicate that adding PS alone or in combination stimulated the nitrification process in FW composting with a nitrate concentration of 69.91 mg/L recorded in the treatment received the combined addition of PS and GW. The results of Fourier-transform infrared (FT-IR) spectroscopy analysis showed a significant increase in humification by adding PS in mixtures of FW and GW. The resulting treated composts showed high total content of nutrients, no phytotoxic effect on seed germination, and growth enhancement of tomato plant compared to control compost, NPK fertilizer, and no amended soil.

Phytotoxic Substances Involved in Teak Allelopathy and Agroforestry

Teak (Tectona grandis L.f.) is one of the most valuable timber species, and is cultivated in agroforestry systems in many countries across the tropical and subtropical regions of the world. The species is also one of the most essential trees in home gardens in South Asia due to its wood quality and medicinal value in folk remedies. It is a deciduous tree species, and the amount of litter that falls from teak trees is huge. The decomposition rate of the litter is relatively fast in tropical humid conditions. The interactions between teak and weeds, or crops, under the teak trees have been evaluated in terms of allelopathy. Evidence of allelopathy is documented in the literature over the decades. The leachate and extracts of teak leaves suppress the germination and growth of several other plant species. Phytotoxic substances, such as phenolics, benzofurans, quinones, terpens, apocarotenoids and phenylpropanoids, in the teak leaves, were isolated and identified. Some phytotoxic substances may be released into the soil under teak trees from leaf leachate and the decomposition of the litters, which accumulate by annual leaf fall and can affect the germination and growth of undergrowth plant species as allelopathic substances. The allelopathy of teak is potentially useful for weed management options in agroforestry and other agriculture systems to reduce commercial herbicide dependency. It was also reported that agroforestry systems with teak enhance income through the production of crops and woods, and provide energy efficiency for crop cultivation.

Laboratory and Field Evaluation of the Phytotoxic Activity of Sapindus mukorossi Gaertn Pulp Extract and Identification of a Phytotoxic Substance

Interest in finding plant-based herbicides to supplement synthesized herbicides is increasing. Although the extract of Sapindus mukorossi Gaertn has been reported to have herbicidal activity, little is known about phytotoxic substances and their efficacy of weed control in the field. To identify phytotoxic substances, the bioassay-guided fractionation by column chromatography and high-speed counter-current chromatography (HSCCC) was carried out. The phytotoxic activity assay, performed by the agar medium method, showed that the 70% ethanol fraction exhibited strong root growth inhibition against Trifolium pratense with an 50% inhibitory concentration (IC50) value of 35.13 mg/L. An active compound was isolated from the 70% ethanol fraction and identified as hederagenin 3-o-β-D-xylopyranosyl-(1→3)-α-l-rhamnopyranosyl-(1→2)-α-l-arabinopyranoside (Compound A). Compound A had an IC50 value of 16.64 mg/L. Finally, a new formulation was prepared based on the 70% ethanol fraction, which exhibited good efficacy against broadleaf weeds in a carrot field. The fresh weight control efficacy was 78.7% by 45 days after treatment at the dose of 1500 g a. i./ha. Hence, the extract of S. mukorossi pulp could be a promising supplement to the synthesized herbicides. Furthermore, compound A from S. mukorossi may be responsible for its phytotoxic activity.

A Fumigation-Based Surface Sterilization Approach for Plant Tissue Culture.

Plant tissue culture has led to breakthroughs in understanding and applying the fundamental knowledge towards harnessing more from plants. Microbial contamination is one of the serious problems limiting the successful extrapolation of plant tissue culture practices. Sources of in vitro contamination include culture containers, media, explants, equipment, the environment of the culture room and transfer area, and operating personnel. The successful initiation of in vitro culture mostly depends on surface sterilization of explants because this is the primary source. Usually, surface sterilization is done using chemicals, or toxic nanomaterials, this is the first time such an approach has been demonstrated. Numerous surface microflora attached to plant surfaces grow faster than the cultured explants and release phytotoxic substances into the culture media, hindering positive outcomes. In the current work, for the first time, the applicability of turmeric and benzoin resin-based fumigation of explants is demonstrated. The results showed that fumigation methods for surface sterilization were promising and could lead to fifty and even 100% contamination-free plant tissue culture. Nanoparticulate carbon was identified in the turmeric and benzoin smoke and coined the key player in the surface sterilization effect. These studies open a whole new avenue for the use of fumigation-based methods for riddance of microbial contamination.

Phytotoxic Activity and Growth Inhibitory Substances from Albizia richardiana (Voigt.) King &amp; Prain

Albizia richardiana, a fast-growing, large deciduous tree belonging to the Fabaceae family, grows well in hot and humid areas but mainly grows in the tropics of the Old World. The medicinal and other uses of Albizia richardiana are well documented, but the phytotoxic effects of this tree have not yet been investigated. We conducted this study to investigate the phytotoxic activity of Albizia richardiana leaves and to identify growth inhibitory substances for controlling weeds in a sustainable way. Aqueous methanol extracts of Albizia richardiana leaves greatly suppressed the growth of cress and barnyard grass seedlings in a concentration- and species-dependent manner. Two phytotoxic substances were separated using several purification steps and characterized through spectral analysis as dehydrovomifoliol and loliolide. Dehydrovomifoliol and loliolide significantly arrested the seedling growth of cress in the concentrations of 0.1 and 0.01 mM, respectively. The extract concentrations needed for 50% growth inhibition (I50 values) of cress seedlings were 3.16–3.01 mM for dehydrovomifoliol and 0.03–0.02 mM for loliolide. The results suggest that these two allelopathic substances might play a vital role in the phytotoxicity of Albizia richardiana leaves.

Characterization and phytotoxicity of ophiobolins produced by Bipolaris setariae.

The Bipolaris setariae NY1 strain, isolated from a diseased green foxtail plant in Henan Province, China, showed strong pathogenicity towards green foxtail. In order to clarify the role of phytotoxic substances in the fungal pathogenicity, bioassay-directed isolation and bioactivity assays of secondary metabolites produced by the fungal strain were carried out. Five ophiobolins were obtained: 3-anhydro-ophiobolin A, 6-epi-ophiobolin A, 6-epi-ophiobolin B, 3-anhydro-6-epi-ophiobolin B and ophiobolin I. Bioassays on punctured and intact detached leaves of green foxtail indicated that 3-anhydro-ophiobolin A was the most phytotoxic, followed by 6-epi-ophiobolin A. The other three ophiobolins appeared to be inactive against green foxtail. The effects of 3-anhydro-ophiobolin A and 6-epi-ophiobolin A were synergistic. The symptoms on green foxtail caused by 3-anhydro-ophiobolin A or its mixture with 6-epi-ophiobolin A resembled those caused by the fungus. 3-Anhydro-ophiobolin A and 6-epi-ophiobolin A are likely the main pathogenic determinants of B. setariae. 6-epi-Ophiobolin A caused cytotoxicity against five kinds of human cancer cells: human colon adenocarcinoma cells (HCT-8), human liver cancer cells (Bel-7402), human gastric cancer cells (BGC-823), human lung adenocarcinoma cells (A549), and human ovarian adenocarcinoma cells (A2780). The results provide information for the development of herbicides and antitumor potential of the ophiobolin sesterterpenes.