Agricultural scientists are currently focused on producing healthy crops without toxic chemicals because synthetic herbicides are still extensively used in agriculture. There have been limited applications of natural products in this area, but their practical application remains a significant scientific objective. It is crucial to properly formulate natural allelochemicals. The Asteraceae family being a rich source of various phytochemicals, they have found numerous applications in various biological fields. In this study, Russian knapweed was chosen as a biological herbicide because of its allelochemicals. The extracts of plants act as natural chemicals because they have phytochemicals including flavonoids, terpenoids, phenols, polyphenols, amides, aldehydes, and saponins (Kumar et al. 2016). These plants are being used in green synthesis of metal oxide nanoparticles and other area of nanotechnology because of their potential phytochemicals and biological activity. Iron oxide nanoparticles seems to offer some potential to achieve this goal. Different nanoparticles such as iron oxide are successfully synthesized from Asteraceae members (Madivoli et al. 2019). Also In a research, iron oxide nanoparticles were synthesized using weed leaf extract including Tridex procumbance and Achyranthes aspera (Kurdekar et al. 2022). We provide here data indicating that pure and formulated extracts of Russian knapweed have negative effects on wild mustard and wild oat germination and growth.
According to the analysis diagrams including XRD, EDS, VSM, TGA, FTIR and pictures including SEM and TEM show the formulated of iron oxide nanoparticles correctly. The concentration of 200 g L− 1 led to the lowest germination percentage of wild mustard and wild oats (0%), although germination percentage of wheat was still 20% with the same concentration of crude extract, that meaning high concentrations of the substance could be completely inhibitory. Based on germination parameters, a 20% Russian knapweed aqueous extract adsorbed on iron oxide nanoparticles successfully controls wild mustard to a greater extent and wild oats to a lesser extent, that meaning Wheat and wild oats were thus more tolerant to extract. The aqueous extract not just in terms of allelochemicals, but also due to a decrease in osmotic potential that disrupts seeds' water absorption and delays their germination, leading to a lower germination percentage and rate. Germination and vigor are therefore influenced by the seed's internal metabolism and ATP release. The decrease in enzyme activity may be related to a slowdown in germination and emergence (Tokasi et al. 2011).
The results are in agreement with those found in the study (Pannacci et al. 2020). It has been reported that aqueous weed extracts inhibit plant germination significantly (Aziz et al. 2021; Pannacci et al. 2020; Li et al. 2021). Plant extracts inhibit germination by inhibiting imbibition rates, which ultimately inhibits germination and, in particular, cell elongation (El-Mergawi and Al-Humaid 2019). Various weed species demonstrated different capacities, as shown by the results presented. There was a greater sensitivity to wild mustard than to wild oats. Allelochemicals affect plants differently depending on their genetic composition. Strongest growth inhibition was obtained in wild mustard, that indicated sensitivity of wild mustard against of aqueous extract. The difference is caused by the secretion of different metabolites called allelochemicals, which cause nearby vegetation, such as weeds, to reproduce, grow, and develop less efficiently (Soltys et al. 2013), including alcohols, fatty acids, phenolics, flavonoids, terpenoids, and steroids. Weed seed germination is usually negatively affected by extracts with higher concentrations of allelopathic compounds. A negative influence on genetic material might have been caused by allelochemicals, since allelochemicals disrupt protein synthesis and lipid synthesis, and mitochondrial respiration (Cruz-Ortega et al. 1998). The lower inhibitory effect in the low concentration of extract on the germination and growing can be attributed to lower concentration of phenolics and flavonoids in extract (Nadeem et al. 2020).
An effective bioherbicide depends on many factors, including the bioactive compound, the plant growth stage, the formulation type, the spray preparation and the application method. There is a wide variation in allelopathic activity among plant species due to the variations in allelochemicals released by these species.
Germination percentage, seedling length and seedling dry weight in Wild mustard and wild oats was significantly affected by pure extract and Iron oxide nanoparticles formulated with aqueous extract. Based on the results, iron oxide nanoparticles formulated with 20% aqueous showed the highest decrease in weed dry weight. It has been shown that allelochemicals at high concentrations interfere with cell division, hormone biosynthesis, mineral absorption, and mineral transport (Rizvi et al. 1992), membrane permeability (Harper and Balke 1981), stomatal oscillations, photosynthesis (Einhellig and Rasmussen 1979), respiration and protein metabolism (Kruse et al. 2000) as well as plant water relationships, resulting in substantial reductions in growth. Allelochemicals suppress weed growth by their phytotoxic properties. A number of plants were suppressed during germination and growth by flavonoids and phenolic compounds (Sadeghi et al. 2010). Due to the influence of allelochemicals on cell division, plant height is decreased by allelochemicals. According to Jafariehyazdi and Javidfar, (2011) allochemicals lead to reduced water and nutrient uptake by roots, inhibition of photosynthesis, respiration, protein synthesis, cell division, and thickening of seminal roots as well as slow maturation and failure to reproduce. Allelochemicals induced a decrease in plant growth due to a decrease in mitosis divisions of roots, a decrease in catalytic enzyme activity, and disruption of mineral ion absorption (Tokasi et al. 2011).
Formulated iron oxide nanoparticles with 20% aqueous extract reduce wheat germination by only 25%. By increasing the allelochemicals, the water uptake becomes more difficult and root hydraulic conductivity decreases, especially in Gramineae plants. According to (Safahani and Ghooshchi 2014), aqueous extracts of Russian knapweed (Acroptilon repens) reduced the stem dry weight of wheat by significantly altering its morphological characteristics.
The photosynthesis system of a plant directly influences its biomass. By increasing the efficiency of photosynthesis, shoots and roots grow more rapidly, resulting in a greater production of biomass. According to the study, all concentrations used for creating the aqueous extract decreased plant biomass. In general, iron oxide nanoparticle formulations with a 20% concentration were most effective in reducing biomass. Dry weight decreases when the allelochemical extract concentration increases, resulting in a decrease in water and nutrient absorption. When the extract is present in higher concentrations, it likely disrupts the plant's ability to absorb water and essential nutrients, which adversely affects its growth and biomass.