Iranian Journal of Seed Research

In order to evaluate the allelopathic effect of aqueous extract of nine weeds species on Anise (Pimpinella anisum) seed germination and seedling growth characteristics, an experiment was conducted in the Laboratory of Yasouj University in 2014. This experiment was carried out as factorial with the aqueous extracts of nine weeds species, as the first factor, in different concentrations (10, 20, 30, 40 and 50 g.l^-1), as the second factor, in a completely randomized design with four replications. The results showed that interactions between different weed aqueous extracts and concentrations had a significant impact on the germination percentage and rate, root and shoot length and weight, and vigor of anise seeds at 1% probability. The most allelopathic effects on germination percentage and rate were observed in 10 g/l of the aqueous extract of Cowherb and Corn Buttercup, in 20 to 30 g/l of Corn Buttercup and Whitetop, and in 40 to 50 g.l^-1 of Corn Buttercup, Whitetop, Wild lettuce and Cowherb, which completely stopped seed germination in Anise.

Highlights:

1.  Allelopathic effects of 9 common weedy types on germination of Anise Seed were studied in Kohgiluyeh and Boyerahmad.
2. The effect of different concentrations of aqueous extracts of weeds on germination characteristics of anise was studied.

Introduction: Allelopathic effects of plant on one another are one of the most important concerns in reclamation and rehabilitation of rangelands in Iran. Allelopathy refers to the deterrent effects of a plant on growth, development or emergence of another plant. One of the rangeland reclamation methods is planting suitable and compatible species. However, without considering the plant’s allelopathis characteristic, it is highly likely that the project will be a failure. The present study sought to investigate the effects of Artemisia sieberi extract on seedling emergence, some morphological characteristics and nutrient uptake of Prosopis cineraria which has hard emergence.
Materials and Methods: The present study was carried out under greenhouse conditions, with 23±5 °C, 60% relative humidity and 70% water-holding capacity of soil. The experimental design was a completely randomized one with four replications. Soil samples were selected from Deging village, located in the city of Khash (Sistan and Baloochestan Province). In order to prepare the plant extract, the A. sieberi samples were dried in the shade and were ground to powder. Then, 190 g of the powder was put in a plastic bottle, then filled with 1 L ethanol and placed on a shaker for 24 hours. The resulting solution was filtered out and the extract was obtained. The planting was carried out in plastic pots with the capacity of 6 kg which were filled with 3 kg of soil. In each pot, 30 seeds were buried, at a depth of 3 cm. The treatments were treated at concentrations of 0.2% (2 ml in 1000 ml distilled water), 0.4%, and zero along with plant irrigation. The parameters measured included emergence percentage and rate, radicle and pedicel length, seedling dry weight, photosynthetic pigments, carotenoid contents and nutrient uptake of P. cineraria.
Results: The results showed that A. sieberi extract significantly decreased plant photosynthetic pigments. The highest chlorophyll a, b, total chlorophyll and carotenoid belonged to the control treatment and by increasing extract concentration, photosynthetic pigments decreased. In addition, the findings were that the highest and lowest nitrogen and phosphorus contents were obtained in the 0.2 and 0.4% treatments, respectively. Potassium and manganese decreased with increases in extract concentration. However, with increases in extract concentration, zinc significantly increased in the plant tissues. In general, the results showed that A. sieberi extract increases P. cineraria emergence in the 0.2% treatment.
Conclusion: In general, morphological traits and photosynthetic pigments of P. cineraria decreased with increases in the concentrations of A. sieberi extract. Artemisia extract had a different effect on the absorption of nutrients by P. cineraria. at low concentrations. It increased nitrogen and phosphorus adsorption and increased concentrations of manganese in high concentrations. The concentration of 0.2% of Artemisia extract had a positive effect on plant emergence. Given the positive effect of A. sieberi on the emergence of P. cineraria, plant extract at low concentrations can be used to increase emergence of P. cineraria, especially given that the P. cineraria has an emergence problem. However, due to the negative effect of A. sieberi on growth and absorption of nutrients in P. cineraria, the cultivation of these two plants is not recommended in dry rangelands.
 

Introduction: Interference caused through weeds’ and crops’ competition for environmental resources and allelopathy brings about damage in crop species. Allelopathy is defined as a direct or indirect inhibiting or provoking effect of a plant on other plants through the production of chemical compounds introduced into the environment. Although the allelopathic effects of the shoot extracts of Xanthium spp and Chenopodium album on the germination of some crops have already been investigated, very few studies have so far been conducted to evaluate their adverse effects on soybean seedling growth. The aim of this study was to investigate the effect of different concentrations of aqueous extract of cocklebur and lambsquarters on germination and soybean seedling growth indices under Petri and Pot conditions.

Materials and Methods: In order to study the allelopathic effects of Cocklebur and Common lambsquarters on germination and seedling growth of soybean, two separate experiments were conducted under petri and pot conditions. In this experiment, the effects of aqueous extract concentrations (25, 50, 75 and 100%) of cocklebur and common lambsquarters were evaluated on seed germination of soybean in a completely randomized design with three replications. In each pot, five soybean seeds were planted with a depth of 2 cm. The extracts were added to the pots for 2 weeks after emergence.

Results: Allelopathic effect of common lambsquarters extract concentrations was higher than that of cocklebur in both experiments. Germination percentage (GP) reduction under 25, 50, 75 and 100% concentrations of common lambsquarters was 57, 84, 96.7 and 100%, respectively. GP reduction under the same concentrations of cocklebur was 17, 20, 34 and 54%, respectively. In the pot culture conditions, the root dry weight of soybean decreased with increases in extract concentration, so that the highest root dry weight belonged to the control treatment with 64 mg and the lowest values belonged to the effect of aqueous extract of weed with a concentration of 100%. The results on the EWRC scale showed that the soybean leaflet damages increased as the extract concentrations increased. The highest leaf damages were obtained in 75 and 100% of cocklebur and Chenopodium concentrations. The negative impacts of common lambsquarters were higher than those of cocklebur.

Conclusion: In general, the results of this study showed that the effects of different concentrations of the lambsquarters extract on germination and soybean growth of the Williams cultivar were higher under both Petri and pot conditions. The percentage of germination in the concentrations of 25, 50, 75 and 100% of the aqueous extract of cocklebur was 17%, 20%, 34% and 54%, respectively, and in lambsquarters, it decreased by 57%, 84%, 96% and 100%, respectively, compared to the control. On the other hand, spraying the extracts of lambsquarters and cocklebur caused necrosis and drying of soybean leaves. According to the results, in the absence of effective control of weeds, especially lambsquarters, in soybean farms, the damage caused by allelopathic elements will lead to a significant reduction in germination and seedling growth.

Introduction: Generally speaking, plants contain various organic compounds which could influence the behavior of plant communities. These compounds are basically secondary metabolites which are found in various parts of plants such as rhizomes, roots, stems, leaves, flowers, fruits and seeds. The objective of the present study was to investigate the hetrotoxicity potential of different organs of Euphorbia maculata weed on traits of germination, chlorophyll and carotenoids pigments of wheat cultivars.

Material and Methods:  In this experiment Euphorbia maculate weed was collected at full maturity stage from the Moghan region, located in Ardebil Province. Then various organs of Euphorbia maculate such as stems, leaves, and fruits were separated from each other. Another treatment namely, a mixture of different organs, was also made. This experiment was carried out as a factorial, adopting a completely randomized design with three replications in Weeds Science Laboratory of Gonbad–e- Kavous University in 2017. The first factor was wheat cultivar at two levels, consisting of Morvarid and Gonbad and organs in 5 levels (control, stem, leaf, fruit and their mixture, with equal amount of each) were the second factor. For the bioassay experiment, from each organ and their mixture, 5% suspension (w/v) was prepared, using distilled water. 10 ml of concentrated extract of each organ was applied on 50 sterilized seeds of cultivars of interest in a petri dish containing filter paper. After 7 days, traits such as rate and percentage of germination, radical length, shoot length, seed length vigor index, chlorophyll a, b and total content and carotenoids content were measured.

Results:  The results showed that unlike the Morvarid cultivar, germination rate and germination percentage of the Gonbad cultivar significantly decreased, using aqueous extract of various organs of Euphorbia maculata and their mixture. The results also showed that the inhibition effect of fruit and leaf organs on the rate and germination percentage of the Gonbad cultivar were higher than that of other organs and their mixture. According to the results, stem, leaf and fruit extracts had a higher toxic effect on the radical length, compared with the shoot length of the Gonbad cultivar. The results of mean comparison also showed that seed length vigor index of the Morvarid and Gonbad cultivars decreased, due to hetrotoxic compounds of all organs of Euphorbia maculate. In terms of this trait, the highest significant decrease was found in the Gonbad cultivar, which was about 84.13%, compared with the control. In this study, the decreases in the photosynthesis pigments of total chlorophyll and carotenoids in both cultivars with aqueous extract of stem, leaf and fruit organs of Euphorbia maculata were different. The highest decrease of pigments was found in the fruit organ of the Morvarid cultivar. However, aqueous extract of mixed organs had a significant decrease and increase on the content of these pigments in the Morvarid and the Gonbad cultivars, respectively, as compared with the control. This may be due to differences in the quantity and quality of some allelochemicals as well as different reactions of the cultivars.

Conclusions:  Given the evidence of the hetrotoxicity potential of various organs of Euphorbia maculata weed on traits of germination as well as the chlorophyll and carotenoids content of wheat cultivars, it is advisable to exploit huge biomass generated by these luxuriantly growing weeds as bio-compounds in sustainable agriculture.

Extended Abstract
Introduction: Plants release much of bioactive chemicals from different parts such as leaves, stems and roots through different mechanisms to their surrounding environement. These biologically active chemicals are often referred to as "allelochemicals". Allelopathic compounds play a major role in reducing germination and the growth of crops.
Materials and methods: In this study, the effect of leaching on the reduction of phytotoxicity effect of soybean, black cumin, dragonhead and dill was investigated on the emergence and early growth of canola (Brassica napus L.). The experiment was conducted as factorial based on a completely randomized design with four replications in 2016. Treatments included four previous crop residue (soybean, black cumin, dragonhead, and dill), and three levels of leaching (without leaching, one-time leaching, and two-times leaching). The leaching-free treatment (control) was sub-irrigated to maintain the uniformity of environment moisture. Five days after the first leaching, the two leaching treatment was irrigated again. Five days after the second leaching, when the soil moisture was suitable for seed planting, 10 seeds of canola were cultivated in each pot at a depth of 3 cm of soil. After three weeks seedlings of canola were removed from the pot and the traits were measured.
Results: The results showed that the growth characteristics of canola, except root length, were affected by the residues of the previous crop. In non-leaching conditions, the residue of the four plants reduced the rate and amount of canola emergence, and the greatest reduction in canola emergence was recorded for the application of black cumin residue (7.5%). In the leaching conditions, the length of canola leaves increased, which was higher in the twice leaching treatment. This trend shows that as the amount of leaching frequency increased, it is highly likely that more inhibitiing materials leave the soil and conditions become suitable for canola germination and growth.. The highest dry weight of canola root was observed in one-time leaching treatment. The dry weight of canola leaf grown in dill and soybean residues was increased as a result of one-time leaching, whereas the dry weight of canola grown in black cumin and dragonhead residues showed a higher increase in two-times leaching. Results show that four studied plants have canola growth inhibiting compounds and leaching can ameliorate this effect. The response of canola in the soil containing black cumin and dragonhead residues is higher in two-times leaching, and in the soil containing plant residues dill, one-time leaching is sufficient. In soils containing soybean residue, the response index was almost similar in case of one and two-times leaching.
Conclusion: Generally, the results showed that the application of leaching before planting canola reduced the inhibitory effects of plant residue on germination and growth of canola. Therefore, it is suggested that in the agricultural ecosystems in which canola is present in crop rotation, cultivation of canola must be avoided in presence of soybean, black cumin, dragonhead, and dill residue to eliminate their inhibitory effects on canola growth. In areas with water restriction, autumn rainfall can act as leaching and reduce the effect of allelopathic compounds. In case leaching is not possible, cultivation of canola inside the residue of these plants must be avoided.
 
 
Highlights:
1-Leaching can reduce the effect of allelopathic compounds.
2- Allelopathic compounds of some plants such as black cumin showed better response to two-times leaching.

Extended Abstract
Introduction: The weed invasion is one of the main yield-reducing factors in crops. They are potent competitors on vital resources which limits the availability of the resources for crops. Allelopathy is one of the weeds' abilities that commonly with inhibitory influences, affects plant communities' behavior. Therefore, the evaluation of these compounds' effects is important on crop plants. Also, the identification of allelopathic plants and their bioactive compounds can be a suitable approach to weed management. Thus, the aim of this study was the evaluation of the allelopathic potential of C. falcate on germination indices of wheat seeds and the mode of action of the extract on some enzyme activities. Furthermore, secondary metabolites in methanolic root extract were identified and reported.
Materials and methods: Germination and seedling experiments of Triticum aestivum var. Sardary seeds were tested by 0, 5%, 10%, 15%, and 20% concentrations of C. falcata root extracts based on CRD with four replications at the research laboratory of Maragheh University during 2018-19. Also, the influence of the extract was studied on enzyme activities of alpha-amylase, catalase, peroxidase, superoxide dismutase, and polyphenol oxidase. Furthermore, chemical compounds of the root methanolic extract identified by GC/MS instruments.
Results: Germination percentage and germination rate decreased significantly with the increase in the concentration of the extract, and germination stopped at concentrations above 15%. The results of seedling growth showed severe inhibitory effects of the extract on radicle and shoot organs of wheat seedlings that associated with reducing of the lengths and weights of the organs, and consequently, the vigor of seedling declined. The extract significantly reduced the activity of alpha-amylase, however, the activities of antioxidant enzymes first increased at low and medium concentrations but at high concentrations, the activities declined. The phytochemical analysis identified 62 compounds in the root of this plant that Octadecatrienal, Dihydro-4H-pyrazolo [3, 4-d] pyrimidin-4-one, Hexadecanoic acid, Hexadecanoic acid, 2-hydroxy-1 (hydroxymethyl) ethyl ester, Isopropyl isothiocyanate, and Cyclohexanone could be effective compounds on seed germination.

Conclusion: C. falcata had a very strong inhibitory effect on the seed viability and seed vigor of the wheat seeds. According to the results, the mode of action of the allelopathic compounds is induced by induction of oxidative stress and inhibition of seed reserves remobilization during germination. The high sensitivity of alpha-amylase activity to allelochemicals was detected in this experiment. The decrease in the activity of all studied enzymes at high concentrations of C. falcata root extract was also significant. Stearic acid and palmitic acid derivatives accounted for about 30% of the compounds, which are very likely to interfere with the activity of the enzymes.

 Highlights:

1. Allelopathy effects of C. falcata root extract on germination indices of wheat were studied.
2. Chemical compounds identified were in methanol extract of the plant roots of C. falcate.
3. Oxidative stress is induced by the allelochemicals of C. falcata.

Extended Abstract
Introduction: Weeds are one of the most important problems in agriculture and cause a lot of damage to crops. Overconsumption of herbicides in recent decades has led to harmful impacts on the environment and living organisms, including humans. In order to deal with these problems today, efforts are being made to reduce reliance on artificial herbicides and change direction towards sustainable agriculture as a part of integrated weed management. Among natural compounds, essential oils, which are components of aromatic and medicinal plants, were investigated to discover new herbicides.
Material and Methods: In order to investigate the effects of yarrow essential oil (Achillea wilhelmsii C. Koch) on the germination and growth of purslane (Portulaca oleracea L.) and rye (Secale cereale L.) seedlings, two factorial experiments were conducted in the form of a completely randomized design in three replicates at Islamic Azad University, Science and Research Branch. The first factor was the type of essential oil in two levels (normal and nanoemulsion) and the second factor was the concentration of essential oil in six levels (0, 100, 200, 400, 800, and 1000 µl L^-1).
Results and Discussion: Scanning electron microscopy images showed the particles were relatively sperhical and their size varied from 1 to 100 nm. The zeta potential of the nanoparticles was -13.8 mV, indicating particle stability. Both type of essential oils reduced germination percentage, germination rate, plumule length, radicel length and seedling dry weight of both weeds and germination percentage decreased significantly with increasing concentration. At a concentration of 200 µl L^-1, purslane treated with essential oil germinated 55.25%, but at the same concentration, the germination percentage of seeds treated with nanoemulsion of essential oil was 30.50%. Nanoemulsion of essential oil at concentration of 800 µl L^-1 was able to completely prevent the germination and growth of purslane seedlings. Nanoemulsion of essential oil at a concentration of 1000 µl L^-1 completely prevented rye seed germination. Germination rate decreased under treatment of yarrow essential oil and there was no difference between two types of essential oils at concentration of 200 µl L^-1, but at a concentration of 800 µl, the germination rate of rye seeds treated with nanoemulsion of essential oil and ordinary essential oil reached to 1.40 and 0.32, respectively which was a significant difference.
Conclusions: The inhibition percentage of the studied traits in both weed species showed that the essential oil nanoemulsion was more effective than the normal essential oil. Yarrow essential oil was more effective on purslane weed compared to rye. Essential oils do not have similar effects on weeds and their inhibitory effects will be different depending on the concentration and species of weeds, and the selectivity of these compounds should be investigated. The production of nano essential oil of yarrow as a natural herbicide is a solution. It offers to control weeds in organic farming systems.

Highlights:
1- Nanoemulsion particles were produced from Yarrow essential oil
 2- Nanoemulsion particles had more inhibitory effects on the investigated weeds than the normal essential oil.

Extended abstract
Introduction: Allelopathy is the same as chemical warfare among plants. Today, global humanitarian efforts in agriculture are moving towards reducing chemical pesticides and introducing new biological methods to control weeds. One of the proposed solutions for weed management is isolating allelochemical compounds from plants and using them as natural herbicides.
Materials and Methods: The present study was conducted to investigate some germination and biochemical properties of the weeds Taraxacum officinale, Achillea millefolium, Rumex acetosa, Althaea officinalis, and Amaranthus retroflexus under the influence of aqueous extract concentrations from the leaves of Thuja orientalis. The experiment was carried out using a completely randomized design with three replications. Aqueous leaf extracts of Thuja orientalis were used at concentrations of 0, 5%, 10%, 20% and 30%.
Results: The results showed that the aqueous leaf extract of Thuja orientalis had a significant effect on all the studied traits, and the highest inhibitory effect was observed at a concentration of 30% extract. In Taraxacum officinale, Achillea millefolium, Rumex acetosa, Althaea officinalis, and Amaranthus retroflexus, the germination percentage (93.33%, 88.55%, 48.3.%, 27.36%, and 40.5%), germination rate (100%, 76.36%, 39.28%, 71.72%, and 57.47%), germination coefficient (100%, 77.5%, 39.56%, 70.9%, and 51.47 %), germination index (57.2%, 72.6%, 84.61%, 72.5%, and 85.6%), peak value (67.9%, 48.7%, 61.4%, 70.9%, and 57%), germination value (43.2%, 39%, 46.9%, 53%, and 59.8%), daily germination speed (100%, 77.5%, 39.56%, 70.9% and 56.02%), seed vigor index (69.9%, 92.7%, 97.5%, 93.2%, and 92.1%), and relative water content (53.1%, 38.35%, 35.37%, 37.65%, and 47.1%) decreased compared with the control, while the mean germination time (51.6%, 71.6%, 50.7%, 60.3%, and 60.5%) and ion leakage (24.23%, 15%, 18.33%, 17.3% and 20.23%) increased compared with the control. The results of this study showed that the seeds of Taraxacum officinale were more sensitive to the inhibitory effects of the aqueous leaf extract of Thuja orientalis compared with the seeds of other studied weeds.
Conclusions: Considering the presence of monoterpene compounds such as alpha-pinene, sabinene, beta-phellandrene, and delta-carene, as well as phenolic compounds in Thuja orientalis, it seems that the allelopathic effects of this plant are mainly due to the presence of these secondary metabolites. The significant allelopathic effects of the aqueous leaf extract of Thuja orientalis at high concentrations can make it a potentially effective and environmentally friendly tool in controlling the studied weed species (Taraxacum officinale, Achillea millefolium, Rumex acetosa, Althaea officinalis, Amaranthus retroflexus) in this study.

Highlights:

1. Leaf extract of Thuja orientalis has significant allelopathic effects on seed germination of studied plants.
2. Among the studied seeds, the seed of the Taraxacum officinale plant is more sensitive to the aqueous extract of Thuja orientalis compared with others.
3. The aqueous extract of Thuja orientalis leaves, by damaging cellular membranes, led to undesirable effects on the growth and seed germination of the studied plants.