Journal of Plant Process and Function

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Melatonin (N-acetyl-5-methoxytryptamine) is an indole metabolite derived from tryptophan which is synthesized in plant cells in the chloroplasts and mitochondria. Melatonin is present in all plant species, with large variations in its level depending on the plant organ or tissue, and is a molecule endowed with a multitude of functions that makes it worthy to be referred to as a plant growth regulator. One of the main functions of melatonin in plants is its substantial influence on plant hormones such as auxin, gibberellins, cytokinins, and abscisic acid. Melatonin functions in plants are similar to the antioxidant activities of auxin. Melatonin has many beneficial actions, generally improving physiological responses such as seed germination and growth, photosynthesis (pigment content, photorespiration, stomatal conductance, and water economy), seed and fruit yield, osmoregulation, and the regulation of the different metabolic pathways. Its ability to strengthen plants subjected to abiotic stress such as drought, cold, heat, salinity, chemical pollutants, herbicides, and UV radiation makes melatonin an interesting candidate for use as a natural bio-stimulating substance. In addition, melatonin is involved in numerous cellular functions as an antioxidant. It acts as an excellent scavenger of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in plants. The studies showed that melatonin act as a direct antioxidant, neutralizing several ROS/RNS and other radical species harmful to the cell, and also acts as an activator of the antioxidant response, up-regulating various transcription factors that triggers the activity of antioxidant enzymes such as superoxide dismutases, catalases, peroxidases, and those involved in the ascorbate-glutathione cycle. Melatonin also acts as a circadian regulator, cyto-protector, and growth promoter, rhizogenesis, cellular expansion, and stress protection, in plants. All these data lead us to the idea that exogenous melatonin treatment might help crops resist under biotic and abiotic stressful environmental conditions. 

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Salicylic acid (SA) is a key molecule that alleviates abiotic stress in many plant species. In this study, the role of SA was examined to moderate lead (Pb) toxicity in the basil (Ocimum basilicum). The experimental design was a randomized complete block design with 4 levels of PbNO3; 0 (control), 100, 200 and 300 mg kg^-1 of soil as the first factor, and the foliar application of SA at 3 levels of 0, 50 and 100 mL L^-1 comprised second factor that were applied with four repetitions. The experiment was conducted during 2013 at research greenhouse of the Zabol University. Addition of Pb at a rate of 300 mg.kg-1 significantly reduced the carotenoids by 45.5 percent and organic acids by 49.3 percent, while it caused an increase in anthocyanins, flavonoids, electrolyte leakage and antioxidant enzymes, including lipoxygenase and glutathione peroxidase. In addition, SA spraying had a significant influence on all traits. In this study, the interaction effects between SA and Pb was significant on carotenoids, anthocyanins, flavonoids, electrolyte leakage, organic acid, and lipoxygenase and glutathione peroxidase, and play a moderating role and reduce the harmful effects of Pbtoxicity. The results of this experiment suggested that the application of SA in basil caused a reduction in oxidative damage originated by Pb toxicity and induce the synthesis of photosynthetic pigments, such as carotenoids.


 

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To investigate the influence of humic acid on the amount of absorption and allocation of elements on different parts of Satureja khuzestanica under salinity stress conditions, a greenhouse experiment was done as factorial based on a randomized complete block design in four replications. Factors included humic acid (zero, 10, 20, 30 and 40 mg kg^-1 soil), and salinity stress (zero, 25, 50, 75 and 100 mM NaCl). It was found that the shoot dry weight was decreased with increasing the intensity of salinity stress; at a level of 100 mM sodium chloride, the average of this trait was reduced by 16%. In contrast, the use of humic acid, particularly 60 mg/kg soil, increased the shoot dry weight by 25% compared to the control. The effect of humic acid, salinity, and their interaction were significant (P≤0.01) on measured characteristics except stem and leaf nitrogen. Results showed that among organs (root, stem and leaf), the highest amount of sodium, potassium, phosphorus, zinc and nitrogen (5064, 9000, 13, 19.92 and 3.91 mg kg^-1 dry weight) were observed in leaf in the S₁H₅, S₂H₂, S₁H₄, and S₁H₅ treatments, respectively. Among different organs, maximum iron content (759.9 mg kg^-1 of dry weight) was observed in roots under S₂H₁. In general, with increasing salinity and decreasing humic acid, the concentration of salts such as sodium increased whereas the concentration of useful and essential elements for the plant decreased. According to the results, it can be stated that probably soil application of humic acid at high amounts (40 and 60 mg/kg soil) can moderate the effects of salinity stress by affecting the nutrient changes of plant organs.

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Damask rose is one of the oldest and most valuable rose varieties that to some extent, tolerates water deficiency. However, the selection and identification of genotypes that are more tolerant to drought stress will be effective in development of cultivation of the plant. In this case, an experiment was performed under in vitro conditions using polyethylene glycol at five levels (0, 25, 50, 75 and 100 g L^-1) on four genotypes of Damask rose (Maragheh, Urmia, Pakdasht and Kashan) and the tolerance of genotypes to drought stress was measured based on water relations traits of the plant via response surface method (RSM). Results showed that as the severity of drought stress increased, the percentage of dry matter was increased in genotypes of Maragheh, Urmia and Kashan compared to the control. At concentration of 100 g L^-1 PEG, Maragheh genotype had the highest fresh and dry weight, total chlorophyll, chl a and chl b and the lowest leaf number and height compared to the other genotypes. Carotenoid contents in Urmia and Maragheh genotypes were higher in 100 g L^-1 PEG than other genotypes. As water deficiency increased, leaf water content in Maragheh, Kashan and Urmia genotypes decreased. Maragheh genotype with high values ​​of relative leaf water content, on the other hand, with a decrease in water moisture reduction, relative water loss and saturated water deficiency, showed a better protection mechanism against drought stress than the other three genotypes. After Maragheh genotype, Pakdasht genotype was partially resistance to drought stress up to 75 g L^-1 polyethylene glycol.

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In order to investigate the effects of nanosilicon in salinity stress amelioration in miniature garden rose 'Sanaz' a factorial experiment as a completely randomized design were done with three replications at greenhouse of University of Maragheh in 1399. At the present study for improving in quantitative, qualitative and biochemical traits of miniature garden roses under salt stress (0, 25 and 50 mM NaCl), SiO₂-NPs spray were used at different levels (0, 50, 100, 150 and 200 mg L^-1). Results showed that all measured traits were decreased severely at 50 mM salinity compared to controls and the least amount of each parameter were recorded at 50 mM level of salinity. While SiO₂-NPs spray at 50 mM salinity caused to preserve chlorophyll index and led to increase in the number of plant leaves (62.4%), maximum florescence (55.4%) and variable florescence (more than 3 folded). Also, SiO₂-NPs spray decreased the minimum florescence (44%) at 50 mM salinity. Nanosilicon by stimulating growth and increasing in the activity of the antioxidant enzymes resulted in a decreased lipid peroxidation, malondialdehyde amount and, subsequently decreased oxidative stress in plant cells. Spray of nanosilicon under salinity stress, increased the amount of proline and decreased the oxidative damage to the protein. It seems that according to the present results foliar application of SiO₂-NPs especially at 200 mg L^-1 under salinity stress can be recommended in garden roses. 

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In order to investigate the effect of brassinosteroid foliar application on the growth characteristics and content of sodium and potassium ions of summer savory (Satureja hortensis L.) under salt stress, a factorial experiment was conducted based on randomized complete block design with three replications in the greenhouse of Payam Noor University in Lorestan in 2020. The factors were salinity stress at three levels (0, 40 and 80 mmol/L NaCl) and foliar sprays of brassinosteroid at three levels (0, 0.5 and 2 μmol/L). The largest mean values of plant height (32.56 cm), root length (22.02 cm), shoot fresh weight (5.89 g/plant), shoot dry weight (2 g /plant), root dry weight (0.87 g/plant), and potassium content in plant shoot (16.39 mg/g dry matter) were observed under control conditions (without salinity). These traits declined by 32, 21, 19, 17, 31, 23 and 79%, respectively, under salinity conditions (80 mmol /L NaCl). However, spray of brassinosteroid, especially at 2 μmol /L, increased mean plant height (30.46 cm), root length (21.7 cm), fresh and dry weights of shoot (5.95 and 2.06 g/plant, respectively), and potassium content of aerial organs (10.63 mg/ g dry matter).The interaction effects of the salinity and hormone spray indicated that increases in salinity level significantly improved sodium content of plants (sodium content was 10.93 mg/g dry matter in the treatment of applying 80 μmol/L NaCl and no hormone spray). This led to a drastic reduction in the potassium/sodium ratio (the mean value of this trait was 0.2 in the treatment of applying 80 mmol/L NaCl without hormone spray); however, spray of brassinosteroid somewhat reduced sodium absorption (the sodium content in the treatment of applying 80 mmol/L NaCl and 2 μmol/L of the hormone was 6.56 mg/g dry matter). In general, salinity decreased the studied plant growth traits by disrupting potassium absorption and strongly reducing plant potassium /sodium ratio, but brassinosteroid spray improved the fresh and dry weight of summer savory plants.

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Salinity stress is one of the most important abiotic stresses in arid and semi-arid climates that limit crop plants' growth and development. Salicylic acid (SA) is an endogenous plant growth regulator that can regulate physiological processes and improve the plant's tolerance to stress. A factorial experiment based on a completely randomized design was carried out to investigate the effects of different levels of SA (0, 0.5, and 1 mM) on some growth and biochemical parameters of spinach under salinity stress (0, 40, and 80 mM). Our findings showed that salinity negatively affected growth traits and photosynthetic pigments while SA increased them. For example, under severe salinity stress, a concentration of 1 mM SA increased shoot length by 23%, and 0.5 mM SA enhanced both the fresh and dry weight of the root by 26%. Also, under moderate and severe salinity stresses concentration of 1 mM SA increased shoot dry weight by 130 and 69%, shoot fresh weight by 52 and 42%, chlorophyll a by 53, and 86%, chlorophyll b by 79 and 112%, total chlorophyll by 63, and 96%, carotenoids by 63 and 64%, soluble sugars by 44 and 13%, anthocyanin by 48 and 25%, respectively in comparison to the control plants. In conclusion, a concentration of 1 mM SA decreased negative effects of salinity stress on evaluated growth and biochemical parameters more than 0.5 mM, and improved tolerance of the spinach plants to the salinity stress by an increase in plant growth, total chlorophyll and carotenoids, soluble sugars, and anthocyanin. 

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Salinity is one of the important environmental factors that reduces the growth and performance of plants, especially in arid and semi-arid regions of the world. Damask rose (Rosa damascena Mill.) is one of the most important medicinal and ornamental plants in the country. Considering that the expansion of plants tolerant to salinity stress is one of the important goals of breeding and production programs, in this case a factorial experiment in a completely randomized design with three replications was done during 2020–2021 in the laboratory of the Department of Science and Engineering, Faculty of Agriculture, University of Maragheh, under in vitro conditions on four Damask landraces including Atashi, Bikhar, Chaharfasl and Kashan at 5 salinity levels of 0, 25, 50, 75 and 100 mM NaCl and the physiological and biochemical traits of them were evaluated. The results showed that the physiological and biochemical characteristics of Damask landraces caused an increase in antioxidant enzyme activities and compatible osmolytes. The Atashi landrace with high photosynthetic pigments, relative water content, proline, total soluble protein and the highest increase in antioxidant enzymes activity and, on the other hand, the lowest amount of hydrogen peroxide and electrolyte leakage, was more tolerant to salinity compared to other landraces. Compared to other genotypes, the Atashi genotype was the most favorable and tolerant, with the highest optimal level of antioxidant activity and the accumulation of compatible osmolytes, as well as a high concentration of total soluble protein. The tolerance threshold of Atashi landrace to the in vitro-induced salinity was estimated at 75 mM NaCl.

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Soil salinity is one of the most important abiotic factors that has an adverse effect on plant growth. Despite the difference in salt tolerance among different varieties and species of roses, saline soils contain a significant concentration of salt, which can damage rose species in green spaces irrigated with saline water. This research was conducted in order to investigate the effect of different levels of pistachio tree biochar on some biochemical properties of rose, based on a factorial experiment with a 3x4 arrangement and a completely randomized design with four replications. This research included two factors: biochar at four levels (no application, 25, 50 and 100 gr per 1 kg of potting soil) and salinity from sodium chloride salt at three levels (0, 75 and 150 mM). The results showed a decrease in petal anthocyanin as well as an increase in proline and total phenol following the increase in salinity. However, the use of biochar in the amount of 3 kg at a stress of 75 mM increases petal anthocyanin, potassium, and the ratio of potassium to sodium by 1.17, 1.02, and 1.26 times, respectively, and decreases proline, total phenol, and sodium, respectively. It was found to be 0.87, 0.41 and 0.81 times higher compared to the control treatment. 75 mM salinity increases carbohydrates, antioxidants, and flavonoids by 1.03, 1.02, and 1.02 times, respectively, and decreases calcium and iron by 0.92 and 0.71 times, respectively, compared to the control (no use). from Biochar) On the other hand, biochar at the level of three kilograms caused a significant decrease in flavonoids by 0.99 times and an increase in iron by 1.22 times compared to the control. In general, it can be said that three kilograms of biochar had a significant effect on reducing the negative effects of salinity stress resulting from irrigation on rose plants. For this reason, the use of biochar in order to reduce the adverse effects of salinity stress in salinity-sensitive plants, including roses, and considering the expansion of saline lands in the world and especially in Iran, is important and plays a significant role in compensating for the resulting damage. Therefore, it is suggested that it be tested on a larger scale (farm level) as well as other stress factors such as cold, heat and drought.

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The accumulation of heavy metals throughout the ecosystem is now a major environmental problem that threatens the quality of life of all living organisms. In a factorial experiment based on a completely randomized design, the effect of sodium nitroprusside on the physiological and biochemical responses of tomatoes under nickel stress was investigated. Tomato plants were grown in two concentrations of sodium nitroprusside (zero and 100 µM) and three different nickel concentrations (zero, 25, and 50 µM) with three replications under hydroponic conditions. The results showed that 50 μM nickel sulfate without sodium nitroprusside significantly reduced the relative water content of leaves (43.1%) compared to the same treatment with-sodium nitroprusside. An increase in electrolyte leakage and malondialdehyde were observed as an indicator of oxidative damage in plants under nickel sulfate stress. In response to oxidative stress caused by nickel sulfate, the amount of chlorophyll decreased and carbohydrate and proline concentrations increased compared to the control. Application of sodium nitroprusside resulted in higher concentrations of chlorophyll b (4.54%) and total chlorophyll (3.57%) under non-nickel sulfate stress than the control. Antioxidant, peroxidase, and catalase activity increased by 62, 37, and 38%, respectively, under nickel sulfate stress when treated with 100 µM sodium nitroprusside compared to non-sodium nitroprusside treatment. According to the results, sodium nitroprusside at a concentration of 100 µM can reduce the negative effects of nickel exposure on the growth characteristics of tomato plants such as the number of leaves and dry weight of the plant, by increasing the antioxidant activity (increasing the activity of the enzymes catalase and peroxidase) and also the positive effect of proline accumulation on the RWC, so the use of this substance is recommended for tomato plants growing under nickel conditions.

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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.

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A factorial experiment using a randomized complete block design with three replications was carried out at Payame Noor University of Lorestan Province to study the effects of potassium sulfate sprays on the traits of Thymus daenensis  under salinity stress. The factors were salinity stress (0, 50 and 100 mM sodium chloride) and potassium sulfate sprays (0, 1 and 2 g/L). In the 100 mM sodium chloride treatment, total chlorophyll and chlorophyll a and b contents and leaf relative water content were at their lowest levels (6.7, 4.3 and 11 mg/g fresh weight and 57.8%, respectively). Application of potassium sulfate sprays, especially at 2 g/L, significantly improved these traits. In the 100 mM sodium chloride treatment, carotenoid and proline contents increased by 94% and 195%, respectively, compared to the treatment with no salinity stress, whereas carotenoid and proline contents increased by 17% and 16%, respectively, compared to the control when potassium sulfate was applied at 2 g/L. The highest hydrogen peroxide content was recorded in the treatment in which the plants were under salinity stress (100 mM sodium chloride) and potassium sulfate was not applied. However, application of potassium sulfate (1g and 2 g/L) decreased hydrogen peroxide contents by 22% and 44%, respectively. The highest rates of superoxide dismutase and ascorbate peroxidase activity (9.60 and 0.910 units/mL enzyme extract) were observed under the treatment of salinity stress (100 mM sodium chloride) and the application of potassium spray (2 g/L). In general, salinity levels, especially the 100 mM sodium chloride treatment, led to a decrease in chlorophyll content and relative leaf water content and an increase in carotenoid and proline content traits, hydrogen peroxide, malondialdehyde content, and the activity of superoxide desmutase and ascorbate peroxidase enzymes. On the other hand, the application of potassium sulfate foliar application could greatly reduce the negative effects of stress.    

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The purpose of this study was to investigate the metabolism and role of gamma-aminobutyric acid as an effective compound in inducing stress tolerance in plants, in cultivars of strawberry ʻ Camarosaʼ (heat-sensitive) and ʻKurdistanʼ (heat-tolerant). For this purpose, the strawberry plants were transferred to Isfahan University of Technology on 15 November 2021 and with a fully expanded 5–6 leaf stage, they were transferred to growth chambers with temperatures of 25, 30, 35 and 40 ºC, relative humidity of 70% and 1200 lux of light. After 10 hours of temperature stress, the plants were taken out of the growth chamber and some physiological, biochemical and molecular traits were measured. In order to investigate the expression of the Succinic semialdehyde dehydrogenase gene, sampling was done at 0, 2, 5 and 10 hours after the start of a temperature stress of 40 ºC. This research was conducted as a completely randomized mixed-analysis experiment. The results of the experiment showed that high temperature (40 ºC) in cultivar ʻCamarosaʼ significantly 20.43% decrease the content of gamma-aminobutyric acid and 12.19% the amount of soluble carbohydrates, as well as 43.81% increased the percentage of ion leakage, 20.66% proline, and 200% in injury rating value compared to the control (temperature of 25 ºC). In contrast, High temperature stress (40 ºC) in the cultivar ʻKurdistanʼ caused a 17.78% increase in gamma-aminobutyric acid compared to the control treatment. Injury rating value was statistically non-significant in the cultivar ʻKurdistanʼ at a temperature of 40 ºC compared to the control. The expression level of the SSADH gene (the key gene in the entry of GABA into the tricarboxylic acid pathway) was constant in cultivar ʻCamarosaʼ, but in cultivar ʻKurdistanʼ, the gene expression level increased significantly 2 hours after heat stress.