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Egyptian Journal of Botany http://ejbo.journals.ekb.eg/ techniques, for example, hydro-priming, halopriming, osmo-priming, bio-stimulant inducers, and solid-matrix priming (Rehman et al., 2015). Among the natural biostimulants are plant growth-promoting rhizobacteria, seaweeds, and cyanobacterial extracts (Ruttanaruangboworn et al., 2017). Synthetic substances, such as ascorbic acid, tryptophan, methionine, and phenylalanine, can also be applied to seeds, plants, or soil to stimulate growth (Yan et al., 2020). These substances cause changes in vital and structural environmental processes to induce tolerance to abiotic stresses, improve plant growth, and enhance seed yield and quality (Reche et al., 2018;Gaafar et al., 2020). Cyanobacteria are a diverse group of microorganisms that can live in almost all habitats and can adapt to varied environmental

In the present study chlorella vulgaris and Nostoc muscorum were used as priming solutions for broad bean seeds before cultivation. Presoaking caused a significant (p≤0.05) increase in growth and yield parameters in addition to some metabolites. Treatment with Nostoc muscorum showed highly significant increase in growth parameters, root length (by 30%), shoot length (by 44%), 2fold increase in root fresh weight and 1.5fold fold increase in shoot fresh weight, 67% increase in root dry weight and about 1.6 fold increase in shoot dry weight, also significant increase in photosynthetic pigments, carbohydrates and protein by 52%, 20% and 1.7 fold, respectively, were also recorded.Yield parameters also increased due to algal treatment, the increase was 7% for weight of 100 seeds, 5% for carbohydrates and 32% for protein.Furthermore, algal treatments caused changes in the activity of different antioxidant enzymes (peroxidase and catalase) accompanied with a reduction in lipid peroxidation in the plant

Background: Numerous pesticides and herbicides used in excess cause oxidative stress in plants. These chemicals protect plants from weeds and pests, but they also have very negative side effects, making them common abiotic stressors. One of the most significant nutritional crops in the world is the wheat plant. Conditions of herbicide stress have a negative impact on the plant’s phonological phases and metabolic pathways. Plants primarily make an effort to adjust to the environment and develop oxidative homeostasis, which supports stress tolerance. Methods: When controlling broadleaf weeds that emerge after cereal crop plants have been planted, bromoxynil is frequently used as a selective-contact herbicide. This study looked at the effects of the cyanobacteria Arthrospira platensis and Nostoc muscorum aqueous extracts, tryptophan, and bromoxynil (Bh) alone or in combination on wheat plant growth parameters. Both tryptophan and cyanobacterial extract were used as chemical and natural safeners against Bh application. The antioxidant activity and transcriptome studies using qRT-PCR were assayed after 24, 48, 72, 96 h, and 15 days from Bh application in the vegetation stage of wheat plants (55 days old). Results: In comparison with plants treated with Bh, wheat plants treated with cyanobacteria and tryptophan showed improvements in all growth parameters. Following application of Bh, wheat plants showed reduced glutathione content, as well as reduced antioxidant enzyme activities of superoxide dismutase, catalase, glutathione peroxidase, and glutathione-s-transferase. The combination of different treatments and Bh caused alleviation of the harmful effect induced by Bh on the measured parameters. Additionally, the expression of glutathione synthase and glutathione peroxidase, in addition to those of three genes (Zeta, Tau, and Lambda) of the GST gene family, was significantly upregulated when using Bh alone or in combination with different treatments, particularly after 24 h of treatment. Conclusion: The current study suggests using cyanobacterial extracts, particularly the A. platensis extract, for the development of an antioxidant defense system against herbicide toxicity, which would improve the metabolic response of developed wheat plants.

Taking into consideration, the challenges faced by the environment and agro-ecosystem make increased for suggestions more reliable methods to help increase food security and deal with difficult environmental problems. Environmental factors play a critical role in the growth, development, and productivity of crop plants. Unfavorable changes in these factors, such as abiotic stresses, can result in plant growth deficiencies, yield reductions, long-lasting damage, and even death of the plants. In reflection of this, cyanobacteria are now considered important microorganisms that can improve the fertility of soils and the productivity of crop plants due to their different features like photosynthesis, great biomass yield, ability to fix the atmospheric N2, capability to grow on non-arable lands, and varied water sources. Furthermore, numerous cyanobacteria consist of biologically active substances like pigments, amino acids, polysaccharides, phytohormones, and vitamins that support plant growth enhancement. Many studies have exposed the probable role of these compounds in the alleviation of abiotic stress in crop plants and have concluded with evidence of physiological, biochemical, and molecular mechanisms that confirm that cyanobacteria can decrease the stress and induce plant growth. This review discussed the promising effects of cyanobacteria and their possible mode of action to control the growth and development of crop plants as an effective method to overcome different stresses. Graphical Abstract