antioxidant enzymes

Drought stress as a non-biological stress in nature has several dimensions and affects plants at different levels. During prolonged drought stress, the amount of water in the plant cells decreases and causes thorogenesis, which eventually leads to plant death. The concentration of solutions in the cytosol and extracellular matrices increases due to drought stress in plants and cell development decreases as a result, which leads to growth inhibition and failure to reproduce. Subsequently, the plant withers with the accumulation of abscisic acid and compatible osmolytes such as proline. Overproduction of reactive oxygen species and formation of scavenging compounds of radicals such as ascorbate and glutathione take place at this stage. Drought stress also affects stomatal closure, physiological traits, gas exchange, reduced transpiration, and reduced carbon assimilation (photosynthesis). Drought stress also affects stomatal closure, physiological traits, gas exchange, transpiration reduction, and carbon assimilation reduction (photosynthesis). Negative effects on mineral metabolism and nutrition (absorption and transport of nutrients) reduce leaf area and change the distribution of assimilates between organs.
Organic matter is essential for fertility and preservation of soil biological, chemical and physical properties. Recently, much attention has been paid to the possibility of using organic matter to improve plant growth. Humic substances (humic acid and folic acid) are among the organic substances that are used as growth regulators under suitable irrigation conditions and drought.
In recent years, the number of studies on melatonin in plants has increased significantly. The wide range of functions in different organisms indicates the potential of this substance in plant physiology. Its role as an anti-stress agent against stressors such as water, salinity, low temperature and high temperature, UV and toxic chemicals has been analyzed. The antioxidant role and growth promoter (among other melatonin functions in the plant) is very important. Melatonin is a polar molecule with diverse physiological and cellular functions. Melatonin has received a great deal of attention in recent years, as research has shown that melatonin is widely found in the leaves, roots, stems, fruits, and seeds of all plant species.
To date, numerous applications of fulvic acid and melatonin in agriculture, food industry and animal sciences have been proposed, but unfortunately few studies have been conducted on the simultaneous use of fulvic acid and melatonin in agriculture, which necessitates research in this area. Therefore, considering the economic importance and increasing demand for small fruits, especially strawberries, in this study, the effect of fulvic acid and melatonin on the biochemical properties of strawberries under water stress was investigated.

This experiment was performed in Bostanabad city (East Azerbaijan province) in Iran. Strawberry seedlings (Kamarosa cultivar) were obtained from a commercial strawberry growing greenhouse in Urmia in October and transferred to the greenhouse in cultivation trays. Laboratory studies were performed in the laboratories of the Department of Horticulture and Soil Science, Faculty of Agriculture, Mohaghegh Ardabili University. This experiment was performed as a factorial experiment in a completely randomized design with 3 factors in 4 replications. Factors include water stress at three levels of 100 (full irrigation (control), 25 and 50%, maintainable water drain), fulvic acid at three levels (control, 200 and 400 mg/l) and melatonin at three levels (control, 75 and 150 μM). After complete establishment and cooling of plants, melatonin and fulvic acid were applied to the treatments in three stages through foliar application. The first stage was performed after complete establishment of the plant (15 days after planting), the second stage was performed 10 days after the initial time of treatment and the third stage was performed 10 days after the second stage of foliar application. It should be noted that distilled water was used to treat the plants in the control group.
In order to apply water stress to the plants, at first the soil is completely dried (to decrease the effect of moisture on the weight of the soil in the pot), then the same amount of coarse sand was poured on the floor after weighing to create sufficient drainage in the pots. The pots were then placed on a scale (accurate to one tenth of a gram) and the soil mixture was poured into all of them. Then one of the pots was selected randomly and the soil inside it was completely submerged and covered with plastic and allowed the gravity water to come out. Because this part of the soil moisture is useless for the plant and must be drained. The pot was weighed and taken daily for a week (until the weight of the pot was fixed) after the soil moisture reached the field capacity. Then the soil inside the pot was emptied in a special container and the mass of the container along with the soil inside it was recorded and dried in an oven at 105 ° C for 24 hours. After removing from the oven, the soil with the container was weighed again and the difference between these two masses (before the oven and after the oven) showed the mass of water (Mw) of the soil in the pot in the last stage of the experiment. The mass of the container was deducted from the mass of the soil sample along with the container after the oven and the mass of dry soil (Ms) was calculated. Finally, the mass moisture content (θm) was obtained using the following equation.
Measurement and amount of Mw according to the relationship between humidity (mass moisture (θm)) at that stage, was obtained after obtaining moisture in the last stage of the experiment and adding the mass difference of the pots in each time period. (Given that the difference in the mass of the pots on each successive day indicates the amount of water evaporated and the amount of dry soil at each stage is constant). By obtaining the mass of the pot and the mass moisture, a linear relationship between them was drawn by Excel software. The moisture content of the pots was calculated by the regression relationship with the mass of the pots at the stress levels.

Analysis of variance of data showed that the effect of drought stress and its interactions with fulvic acid and melatonin treatment on yield, RWC, electrolyte leakage and antioxidant enzymes activity were statistically significant. The interactions between treatments (drought stress, fulvic acid and melatonin) were statistically significant and only the triple effects of catalase were not statistically significant. The results showed that the drought satress (25 and 50%, maintainable water drain) without the application of fulvic acid and melatonin ecreased yield, RWC and increased electrolyte leakage. But application of fulvic acid and melatonin increased the yield and RWC under drought stress conditions. Furthermore, the application of fulvic acid and melatonin reduced the oxidative damage (electrolyte leakage) in the plants through increased enzymatic activity under drought stress conditions. Generally, the highest and lowest yield was obtained in control plants (full irrigation) with foliar spraying with melatonin (150 µM) and 50%, maintainable water drain which were 693.54 and 504.78 g, respectively. The highest and lowest ascorbate peroxidase activity was obtained in 50%, maintainable water drain with foliar spraying melatonin (75 µM) and control plants (full irrigation) with foliar spraying melatonin (75 µM) and fulvic acid (400 mg/l) which were 2.929 and 1.426 µmol min-1 gFW-1, respectively. The highest and lowest peroxidase activity was obtained in 50%, maintainable water drain with foliar spraying melatonin (75 µM) and fulvic acid (200 mg/l) and control plants (full irrigation) with foliar spraying fulvic acid (400 mg/l) which were 2.411 and 0.58 µmol min-1 gFW-1, respectively. The highest and lowest superoxide dismutase activity was obtained in 50%, maintainable water drain with foliar spraying melatonin (150 µM) and fulvic acid (400 mg/l) and control plants (full irrigation) with foliar spraying fulvic acid (200 mg/l) which were 96.93 and 36.18 µmol min-1 gFW-1, respectively. The highest and lowest level electrolyt leakage leaves also were observed in 50%, maintainable water and control plants (full irrigation) with foliar spraying melatonin (150 µM) and fulvic acid (200 mg/l) which were 96.93 and 36.18 respectively. The highest and lowest relative water content (RWC) were obtained control plants (full irrigation) with foliar spraying with melatonin (150 µM) and 50%, maintainable water drain which were 95.35 and 53.92%, respectively. The highest and lowest catalase activity was obtained in 50%, maintainable water drain with foliar spraying fulvic acid (400 mg/l) and control plants (full irrigation) which were 0.7108 and 0.4946 µmol min-1 gFW-1, respectively.

Overall, the results of the present study suggest that the use of melatonin and fulvic acid may be an effective approach to improve the yield of strawberry plants under drought stress. Melatonin and fulvic acid helped to strengthen the antioxidant enzymes system of strawberry plants, which reduced the oxidative damage. Also, foliar application of melatonin and fulvic acid had a protective role on strawberry plants grown under drought stress and its optimal concentration will be useful in increasing drought tolerance in many crops.

Copper, as a micronutrient, is essential for the synthesis of enzymes and proteins. However, excessive copper concentrations can be highly toxic and inhibit the photosynthetic and metabolic pathways in plants, ultimately leading to reduced biomass, delayed flowering and fruiting. Sodium nitroprusside (SNP) (as a nitric oxide donor compound) plays a significant role in plant growth and development, from germination to organ senescence, signal transduction, regulation of antioxidant defense systems, and reduction of heavy metal toxicity. In the present study, the combined effects of two levels of copper sulfate (600 and 1200 µM) and sodium nitroprusside (150 µM) were investigated on some physiological and morphological activities of okra (Abelmoschus esculentus L. cv. Clemsonspineless) is grown hydroponically. The experiments were conducted in a complete randomized design with three replications. Based on our results, the high copper concentration resulted in a reduction in chlorophyll content, essential nutrients, growth parameters and an increase in malondialdehyde, hydrogen peroxide, electrolyte leakage, total protein, proline, soluble sugars, peroxidase enzyme activity and copper content in both the roots and leaves of okra compared to the control plants. Conversely, SNP foliar spray led to an increase in total chlorophyll, uptake of essential elements, peroxidase enzyme activity and a decrease in copper concentration, malondialdehyde and hydrogen peroxide content, as well as ion leakage in okra plants. Therefore, it seems that the application of SNP was able to mitigate the negative effects of copper sulfate stress significantly and enhance the tolerance of okra plants to copper stress conditions.

Copper, as a micronutrient, is essential for the synthesis of enzymes and proteins. However, excessive copper concentrations can be highly toxic and inhibit the photosynthetic and metabolic pathways in plants, ultimately leading to reduced biomass, delayed flowering and fruiting. Sodium nitroprusside (SNP) (as a nitric oxide donor compound) plays a significant role in plant growth and development, from germination to organ senescence, signal transduction, regulation of antioxidant defense systems, and reduction of heavy metal toxicity. In the present study, the combined effects of two levels of copper sulfate (600 and 1200 µM) and sodium nitroprusside (150 µM) were investigated on some physiological and morphological activities of okra (Abelmoschus esculentus L. cv. Clemsonspineless) is grown hydroponically. The experiments were conducted in a complete randomized design with three replications. Based on our results, the high copper concentration resulted in a reduction in chlorophyll content, essential nutrients, growth parameters and an increase in malondialdehyde, hydrogen peroxide, electrolyte leakage, total protein, proline, soluble sugars, peroxidase enzyme activity and copper content in both the roots and leaves of okra compared to the control plants. Conversely, SNP foliar spray led to an increase in total chlorophyll, uptake of essential elements, peroxidase enzyme activity and a decrease in copper concentration, malondialdehyde and hydrogen peroxide content, as well as ion leakage in okra plants. Therefore, it seems that the application of SNP was able to mitigate the negative effects of copper sulfate stress significantly and enhance the tolerance of okra plants to copper stress conditions.

The use of plant symbiosis with arbuscular mycorrhizal fungi (AMF) and Plant-growth-promoting rhizobacteria (PGPR) is one of the ways to reduce drought stress that has recently been used in agriculture. In the present study, the response of lemon balm (Melissa officinalis L.) plants to microbial inoculation of plant growth-promoting rhizobacteria (PGPR, Azospirillum brasilense) and arbuscular mycorrhizal fungus (AMF, Glomus mosseae) and co-inoculation (AMF+PGPR) under well-irrigated (100% field capacity) or drought stress (50% field capacity) conditions were investigated. This study was conducted in 2020 in the greenhouse of Ayatollah Amoli Branch, Islamic Azad University, Amol, Iran as a factorial experiment based on a completely randomized design with five replications. The results of the present study showed that drought stress by reducing the relative water content (RWC, 17.8%), declined transpiration rate (E, 62.2%), stomatal conductance (gs, 36.8%), intercellular CO2 concentration (Ci, 22.5%), and net photosynthesis (Pn, 48.5%) of the plant compared to control plants. Drought stress also induced oxidative stress by increasing the accumulation of hydrogen peroxide (2.1-fold) and methylglyoxal (2-fold), resulting in damage to bio-membranes and photosynthetic apparatus and reduced growth of lemon balm. However, microbial inoculation, especially co-inoculation of PGPR and AMF, by improving the proline content and RWC, restored Ci, E, gs and Pn under drought stress. Microbial treatments by increasing the activity of antioxidant enzymes and the glyoxalase system reduced the level of hydrogen peroxide and methylglyoxal and alleviated drought stress-induced oxidative stress, which increased the growth of lemon balm under drought stress by protecting bio-membranes and photosynthetic pigments. Therefore, the results showed that the application of G. mosseae and A. brasilense alleviated the negative effects of drought stress on lemon balm.

Sweet basil is a popular culinary herb used in food and oral care products and medical herb. Today it has become important to increase crop production to feed the growing world population. A cold atmosphere or low-pressure plasma is a potential tool to increase crop production The number of potential applications of cold plasma in agriculture has grown significantly in recent years. Cold plasma treatment is thought to be a fast, economic and pollution-free method to improve seed performance, plant growth and ultimately plant production . This study exposed plant seeds to DBD cold plasma for 45 (P1) and 90 (P2) seconds. The amount of fresh and dry weight of the plant increased significantly in the P1 treatment compared to the control, decreasing in the P2 treatment. Germination percentage remained unchanged compared to the control. Total chlorophyll increased in P1 treatment and decreased in P2 treatment. The protein contents increased by 37% and 42%, respectively, in P1 and P2 treated plants compared to the control. The soluble sugar contents in the P2-treated plants increased by 6% compared to the control, while its amount remained unchanged in the P1-treated plants compared to the control. The proline content in the P2-treated plants increased two times compared to the control, while its amount remained unchanged in the P1-treated plants compared to the control. Catalase and peroxidase enzyme activity increased in p1 and p2 treatments compared to the control. Cold plasma technology has a significant potential to increase seed and plant growth.

Japanese barberry or ornamental barberry (Berberis thunbergii) belongs to the Berberidaceae family. This family have several properties, including antioxidant, antimicrobial and anticancer activities. The healing properties of barberry have been known and studied for thousands of years. In order to study the changes in the physiological-biochemical characteristics of Japanese barberry under the influence of abiotic elicitors, an experiment was conducted in the form of a completely randomized design in the greenhouse and laboratory of the Faculty of Agriculture and Natural Resources of Imam Khomeini International University in 2018-2019. The treatments included methyl jasmonate elicitors, salicylic acid, titanium dioxide and no elicitor (control) in four replications. In this research, the amount of leaf photosynthetic pigments and antioxidant enzymes of leaf and root tissues of Japanese barberry plant were extracted and measured. The results showed that the effect of the experimental treatments on the amount of photosynthetic leaf pigments and antioxidant enzymes in the two studied tissues was significant at the 1% probability level. Comparison of the means showed that salicylic acid treatment increased the amount of chlorophyll a and total leaf chlorophyll compared to the control by 20.9% and 21.3%, respectively. Salicylic acid and methyl jasmonate increased 29.9 and 19.1 percent of carotenoid content in leaves, respectively, compared to the control. The highest protein content of the root was produced with the use of salicylic acid, which increased by 38.6% compared to the control. The activity of catalase enzyme in the root increased by salicylic acid and titanium dioxide elicitors by 76.8 and 52.2%, respectively, compared to the control. In leaves, salicylic acid and methyl jasmonate elicitors increased catalase enzyme activity by 104.1% and 57.1%, respectively. From this research, it was concluded that salicylic acid had the greatest effect in increasing the amount of pigments and the activity of antioxidant enzymes of the Japanese barberry plant, which can be used for medicinal products.

Heavy metals are part of the most important and dangerous environmental pollutants due to their long shelf life, non-degradability by soil microorganisms, and high potential for absorption by plants and entering the food chain. Cadmium is one of the toxic metals for organisms such as plants. The purpose of this research was to investigate the effect of cadmium on the ability of the common daisy plant. In this research, the effect of different amounts of cadmium (0, 10, 20 and 30 mgl-1) had done in a completely randomized design with three replicates. The results showed that the increase of the cadmium hadn’t any significant effect on common daisy plant fresh weight and length. Also, plant dry weight, shoot total chlorophyll, shoot and root carotenoids contents, total protein contents, plant translocation factor and bioaccumulation factor decreased with the increase of cadmium concentration, significantly. While shoot and root proline, and cadmium contents and catalase, peroxidase and ascorbate peroxidase activity increased, significantly. According to this research, the common daisy isn’t suitable for planting in studied cadmium concentrations.

In order to investigate the effects of different Pseudomonas bacterial strains, including fluorescens, Chloraphis and Putida strains, on the morpho-physiological characteristics and performance of Sante variety potato under drought stress in the Jiroft region, an experimental study was conducted in the form of a split-plot design with a randomized complete block design with three replications for two years, 2019–2020 and 2020–2021. The main factor of the experiment consisted of three levels of drought stress (40, 65, and 90 mm of evaporation from the evaporation class A pan), while the sub-factor included four levels of Pseudomonas bacterial strains (control, strain T12 (Pseudomonas fluorescens RO7), strain T13 (Pseudomonas putida RO3) and strain T17 (Pseudomonas chlororaphis RO1). The results showed that the applied drought stress treatments had no effect on the chlorophyll a content. The use of Pseudomonas bacteria strains increased the content of chlorophyll b and total chlorophyll (a+b). The carotenoid content of leaves at 90 evaporation from the Class A pan with the application of bacteria strain T17 showed the lowest amount compared to the treatment without bacteria and strains T12 and T13. Application of bacteria strain T13 showed the highest superoxide dismutase (SOD) enzyme activity at different drought stress levels. There was no significant difference in peroxidase enzyme activity between different Pseudomonas bacterial strains and the treatment without bacterial application at various drought stress levels. The highest catalase enzyme activity in the leaves was observed in the application of Pseudomonas bacterial strains T12 and T17. The application of Pseudomonas bacterial strains led to a significant increase in shoot dry weight, tuber dry weight, and total tuber weight in potato plants compared to the treatment without bacterial application at all drought stress levels.

Sesame (Sesamum indicum L.) is one of the most important oil seed crops used by humans and accounts for a remarkable portion of global high-quality oil production. In this study, the effect of the same osmotic pressure provided by NaCl (salt stress) and by PEG600 (osmotic stress) on the biochemical reaction of sesame was evaluated. Results showed that the activity patterns of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and peroxidase (POD) enzymes were similarly affected by these stresses. Means comparison results indicated that the activity of POD was similar in both root and shoot tissues under both conditions. Also, the activity of SOD and APX enzymes was higher under salinity than under osmotic stress in both sesame tissues. The CAT activity was higher under salinity as compared with the osmotic stress in sesame roots, while in shoots, its activity was higher under osmotic stress compared with salinity. No significant difference was observed in Malondialdehyde accumulation in roots, while it reached its maximum under salinity in shoots. The bioinformatics analysis of the SiSOD gene family revealed that it can be classified into three clusters and into two major groups. Genes belonging to the first cluster have the CU/ZN-SOD domain, while genes belonging to the second cluster have the Mn/Fe-SOD domain. In conclusion, our findings indicated that sesame was more affected by salinity than osmotic stress, which could be due to both osmotic and ionic pressure created by NaCl. Therefore, the response of sesame defense systems to both studied stresses can be relatively different.

In order to investigate the effect of using salicylic acid, antifreeze and soybean oil, on the cold resistance of the flower of the sweet cherry tree cultivar "Siah Tak Daneh Mashhad", a factorial experiment in the form of a randomized complete block design with 3 factors (salicylic acid: zero, 1.5 and 3 mM), (natural antifreeze: zero, 2.5 and 5 per 1000) and (soybean oil: zero, 2.5 and 5 per 1000) and in 4 repetitions was conducted in a commercial garden located in Sarein city in 2018 and 2019. The results of the variance analysis of the data showed that the three-way effects of factors on proline are significant at the 5% probability level and on soluble carbohydrates and protein at the 1% probability level. The highest amount of proline (70.85% compared to the control) was observed in the treatment of salicylic acid foliar spraying 3 mM along with soybean oil (5/1000) and Thiofer antifreeze (5/1000 foliar treatment). The bilateral effects of salicylic acid and soybean oil on glycine betaine were different at the 1% probability level and on the activity of the catalase enzyme at the 5% probability level. The highest accumulation of glycine betaine (27.27% compared to the control) and also the highest activity of the antioxidant enzyme catalase (36.84% compared to the control) in salicylic acid (1.5 mM) foliar treatment with soybean oil (5 in 1000) were obtained. According to the observations of this research, it can be concluded that the use of salicylic acid foliar treatment (3 mM) along with soybean oil (5/1000) and 5/1000 foliar treatment of Thiofer natural antifreeze in flower buds. It is a suitable solution to increase the cold resistance indices of cherries against cold stress.

Low irrigation is one of the ways to reduce water consumption in heat-loving and water-loving crops. On the other hand, the use of mycorrhiza as a biofertilizer is also one of the effective solutions in increasing the absorption of water and nutrients in the conditions of water shortage stress. In addition, the selection of varieties compatible with the region in order to achieve production potential is another way to deal with drought stress in each region. For this purpose, the effect of irrigation regime at three levels of 80 (control), 120 (mild stress) and 160 (severe stress) mm of evaporation from the evaporation pan of class A and biofertilizer including application and non-application of mycorrhiza on three grain sorghum cultivars Kimia, Payam and Sepideh It was investigated in the form of randomized complete block design in the form of a split plot in the summer cultivation of 2016 in Kohdasht city of Lorestan. The results showed that the amount of zinc, copper, manganese and iron in the seeds decreased with the increase in water shortage, but the crude protein content of the seeds increased. The application of mycorrhiza mainly increased the essential elements in shoots and seeds and helped to moderate water deficit stress. The presence of interaction between the factors indicated the different response of cultivars at the levels of mycorrhizal application to water deficit stress in terms of many traits; so, in the conditions of extreme stress of water shortage, the highest increase in catalase and peroxidase observed in Kimia cultivar without mycorrhiza application and Sepideh cultivar with mycorrhiza application, respectively. Also, Sepideh variety with mycorrhiza application showed the highest reduction in chlorophyll b and total chlorophyll. In total, Sepideh cultivar with the use of mycorrhiza under the conditions of mild stress of water shortage while producing the highest grain yield and crude grain protein, saved irrigation water consumption.

Salinity is one of the most important environmental stresses, the increasing spread of which reduces the growth and yield of agricultural plants, in this regard, identifying sugar beet cultivars tolerant to salinity stress to improve quantitative and qualitative yield is of particular importance. For this purpose, research was conducted to investigate the physiological characteristics of some sugar beet genotypes under salt stress in 2019. This experiment was carried out factorially in the form of randomized complete blocks with three replications in Mohaghegh Ardabili University under greenhouse conditions. The experimental factors included different genotypes of sugar beet (9 genotypes) as the first factor and salinity stress as the second factor at four levels (control and 4, 8 and 12 dS/m). The results showed that the effects of salinity stress on chlorophyll content, soluble protein, proline content, soluble sugars and the activity of antioxidant enzymes (catalase, peroxidase and polyphenol oxidase) of different sugar beet cultivars were significant. Higher levels of salinity stress (12 dS/m) caused a significant increase in soluble protein, proline content, soluble sugars and activity of catalase, peroxidase and polyphenol oxidase enzymes compared to other levels of salinity stress and the control treatment. Whereas, the highest content of chlorophyll a, b and total chlorophyll was observed in cultivars number 15 and 4 in the treatment of not applying salt stress. Among the studied genotypes, genotypes No. 6, 15 and 20 had the highest activity of antioxidant enzymes under the condition of 12 dS/m salinity stress. Therefore, at higher levels of salinity stress, resistant sugar beet cultivars prevent the reduction of photosynthetic pigment content by improving the content of compatible osmolytes and antioxidant activities through correct membrane structure.

In this research, the effect of foliar spraying of brassinosteroid (0, 0.077 and 0.384 mg/liter) on grain yield and some physiological characteristics of wheat (Sirvan cultivar) under drought stress conditions (100% control) and 50% F.C.) was investigated in a factorial arrangement based on a randomized complete design with four replications at the research greenhouse of the Agriculture faculty, Shahid Bahonar University of Kerman on 2016. The results showed that drought stress caused a significant reduction in the biomass, yield and yield components of wheat and the decrease of these traits compared to the control was 31.7%, 29.6% and 20.3% respectively. On the other hand, brassinosteroid foliar spraying caused a significant increment of biomass, yield and yield components by approximately 22.7%, 22.4% and 12.5%, respectively, compared to the plants which were treated with distilled water under stress conditions. Drought stress had a significant effect on increasing of antioxidant enzymes activity (peroxidase, ascorbate peroxidase, catalase and superoxide dismutase) and the concentration of malondialdehyde, hydrogen peroxide, as well as the accumulation of carbohydrates and proline in wheat leaves. Spraying of brassinosteroid in both stress and non-stress conditions increased the activity of antioxidant enzymes and osmolytes accumulation (protein, carbohydrate and proline) and conversely reduced the amount of hydrogen peroxide and malondialdehyde, and this effect was more noticeable under drought stress condition. It seems that the effect of brassinosteroid application on modulating drought stress and improving wheat yield can be related to enhancement of osmotic regulation (through the accumulation of osmolytes) and increasing the activity of the antioxidant defense system mechanism in wheat.

In the present study, the effect of foliar spraying of strigolactone (0, 5, and 10 μM) on the physiological and biochemical responses of Thymus daenensis Celak plant under drought stress (90, 60 and 30% of field capacity (FC)) was examined in a factorial experiment based on a completely randomized design with three replications in the Agriculture and Resources Campus Natural Sciences of Tehran University, Karaj. This study provided compelling evidence of increased drought stress tolerance in the Thymus daenensis Celak plant when treated with exogenous strigolactone at the flowering stage. Plants exposed to drought stress exhibited a significant decline in growth and development, as evidenced by shoot growth characteristics, photosynthetic pigments, and antioxidant enzyme activities. Drought stress led to a strong increase in hydrogen peroxide (212%) and malondialdehyde (151%), and these changes were strongly linked to growth retardation. The highest value of total phenol (56.49 mg GA.g-1 DW), flavonoid (96.24 mg Q.g-1 DW), proline (4.147 μmol g-1), superoxide dismutase (24.26-unit mg-1 protein), catalase (44.5-unit mg-1 protein), and peroxidase (26.9 unit mg-1 protein) enzymes activity as well as the highest amount of essential oil (0.48% by volume/weight) and the highest amount of thymol (1.93%) in Foliar spraying of 10 micromolar strigolactones under irrigation conditions of 30% of the agricultural capacity of Thymus daenensis Celak were obtained with Foliar spraying of 10 micromolar strigolactones under deficit irrigation 30% EFTc. In conclusion, strigolactone reduced the negative effects of deficit irrigation on Thymus daenensis Celak by improving water relations, increasing photosynthetic pigments, increasing secondary metabolites, osmotic adjustment, and enhancing antioxidant enzymes activities that regulated the homeostasis of reactive oxygen species. To our knowledge, this is the first study on the role of strigolactone in the mechanism of tolerance to drought stress in Thymus daenensis Celak. Also, based on the results of this research, strigolactone can be used as an efficient biological elicitor to improve quantitative and qualitative yield in thyme. It is recommended that these compounds be used as the best option for achieving sustainable agricultural goals and reducing environmental risks.

This study was conducted to investigate the growth and physiological responses of tomato (Solanum lycopersicum) plants to long-term foliar application of zinc oxide (ZnO) and salicylic acid (SA) in low concentration. This experiment was carried out under the pot conditions in cocopeat and perlite medium and Hoagland's nutrient solution was used to irrigate tomato seedlings. Tomato seedlings were sprayed with two concentrations (0 and 5 mg/l) zinc oxide and/or two dose (0 and 5 mg/l) of salicylic acid with three-day intervals during two months. Single and combined foliar application of salicylic acid and zinc oxide improved plant growth and fruit fresh weight. The applied treatments increased plant height, shoot fresh weight, root fresh weight, and fruit fresh weight. Individual and combined treatments of salicylic acid and zinc oxide also significantly increased the content of photosynthetic pigments, including chlorophyll a (Chla), Chlb, and carotenoids. A significant increase in the activity of catalase enzyme was recorded due to the foliar spray of zinc oxide and salicylic acid, especially the combined treatment. Peroxidase enzyme activity also showed an increasing trend in response to foliar application of zinc oxide and salicylic acid. Overall, this study provided physiological evidence on how the application of ZnO and salicylic acid in appropriate concentration can improve primary metabolism and antioxidant system. It is obvious that performing further researches, especially at molecular levels, can improve our knowledge in the field.