جستجوی مقالات مرتبط با کلیدواژه « پلی فنل اکسیداز » در نشریات گروه « کشاورزی »

 Citrus fruits are susceptible to a number of fungal diseases that cause significant losses in the citrus industry in the postharvest stage. Worldwide, diseases have been primarily controlled for many years by the application of conventional fungicides. However, human health risks and environmental contamination associated with chemical residues and the proliferation of resistant strains of the pathogens are major problems associated with the continuous and widespread use of conventional postharvest fungicides. Heat and UV radiation treatments are the most common physical means used to control postharvest diseases of fresh fruits. The aim of this study was to investigate the effects of UV-C radiation and Hot Air Flow (HAF) treatment on decay control and some biochemical properties in Thomson navel oranges at cold storage.

In this experiment, the effects of heat treatments (37 °C for 24 hours), UV radiation (7.98 kJ / m2) and combination treatment (HAF*UV) on the storage life of Thomson oranges were investigated. The statistical model of factorial experiment was in the form of a completely randomized design in which two factors of storage time and treatments were considered. After treatment, the fruits were stored at 5 ° C for 90 days during the storage period, the percentage of decay, fruit weight loss, and some biochemical properties and enzymatic activity were investigated. Statistical analysis of data was performed using SAS software and the mean data were compared using Duncan's multiple range test at a five percent probability level using MSTATC software.

The results showed that radiation and heat treatment effectively reduced fruit rot . the lowest and highest percentage of cumulative rot was observed in the combined treatment with an average of 3.8% and the control treatment with an average of 12.7%, respectively.The control treatment and the combined treatment with the average of 5.68 and 2.94, respectively, had the highest and lowest fruit weight loss. During fruit storage, TSS, TA, TSS/TA and pH increased and TA decreased The amount of ascorbic acid in fruits treated with hot air flow with an average of 35.54 mg per 100 g of fresh material was higher than the control treatment with an average of 30.67 mg per 100 g of fresh material. Antioxidant activity increased at the beginning of the period, however, the treatments did not have a significant effect on inhibiting DPPH radical activity in fruit flesh The amount of total phenol, peroxidase and polyphenol oxidase enzyme activity in fruit flesh under the influence of heat treatment, initially increased with the period, which the enzyme activity decreased with increasing storage time.

The results showed that radiation and heat treatment were effective in controlling post-harvest decay of Thomson oranges. Radiation had no significant effect on the biochemical changes of Thomson Novel orange fruit. According to the evaluated traits, heat and combination treatment succeeded in reducing the rate of rot and increasing the biochemical properties of the fruit during storage, so it can be considered as a suitable practical option.

In recent years, Urtica dioica L. has attracted the attention of researchers due to its significant effect on many diseases, especially diabetes. However, more research needs to be done in the field of tissue culture and the effect of elicitors on antioxidant properties and the production of its secondary metabolites. This research aimed to investigate the best hormonal combination and light conditions effective on nettle callogenesis and the effect of methyl jasmonate elicitor on its biochemical properties.

For this purpose, using stem explants, the effect of different levels of auxin hormones, naphthalene acetic acid (NAA) (1.5 and 3 mg/l) and 2,4-dichlorophenoxy acetic acid (2,4 D) (0.5 and 1.5 mg/l) and cytokinin hormone, benzylaminopurine (BAP) (0.5 and 1.5 mg/l) were evaluated in two light conditions (light and dark) by measuring fresh weight, dry weight and percentage of callogenesis. The nettle plant's callus growth curve was obtained using liquid culture. After starting the suspension culture, methyl jasmonate treatment was applied with three levels of 1, 0.1 and 0.01 mM, and sampling was done at 24, 48 and 96 hours. The enzyme activity of phenylalanine ammonialyase and polyphenol oxidase and total protein content by extracting in 50 mM Tris-HCl buffer with 8.8 acidity and total phenol, total flavonoid content by extracting in 80% methanol was measured using spectrophotometric and standard methods for control samples and those under different treatments of methyl jasmonate. Also, three metabolites of quercetin, kaempferol and rutin were measured using an HPLC device with a UV detector and 18C column stationary phase. Data from the callogenesis experiment were analyzed in a two-factor experiment in a completely randomized design. The data from the biochemical and HPLC experiments were analyzed in a split-plot in time design, and the means were compared with Duncan's test.

According to the results, the best hormonal combination to produce fresh and dry weight in light conditions includes 1.5 mg/l of NAA and 1.5 mg/l of BAP and in dark conditions, it includes 1.5 mg/l naphthalene acetic acid and 0.5 mg/l of benzyl aminopurine. Also, according to the results, naphthalene acetic acid (62.5%) performed better than 2,4-D (43.5%) in the nettle callogenesis percentage. Lighting was determined as the best light condition for callogenesis in nettle, so the amount of fresh and dry weight and percent of callogenesis in light compared to darkness increased by 4.79, 4.91 and 1.92 times, respectively. There was an increase in polyphenol oxidase enzyme activity, total phenol and total protein in some samples treated with methyl jasmonate compared to the control, and no significant increase was observed in the activity of phenylalanine ammonialyase enzyme and total flavonoid content. According to the HPLC results, the highest amount of rutin metabolite was obtained in 96 hours after the addition of the elicitor and at the concentration of 0.01 mM methyl jasmonate.

The naphthalene acetic acid hormone was more effective than the 2,4-D hormone and light conditions than darkness in nettle callogenesis. Methyl jasmonate elicitor increased the antioxidant property of nettle (48 hours after treatment) by increasing the polyphenol oxidase enzyme activity. However, compared to the control, it had no significant effect on the phenylalanine ammonialyase enzyme activity and total flavonoid. It is suggested that other concentrations of methyl jasmonate be tested to reach optimal conditions for increasing the production of secondary metabolites in nettle in vitro culture conditions.

Guar (Cyamopsis tetragonoloba) is an annual plant from the legume family and tolerant to salinity and drought, which can be used as an alternative product in low water plains. Ascorbic acid is one of the antioxidants involved in the defense mechanisms of plants against various stresses, including drought, which plays a role in ROS detoxification. Calcium is also an essential element for plant growth, which, despite being immobile, has many electrochemical, structural and catalytic functions in plants. It has been reported that calcium ions can increase drought tolerance in plants by participating in the drought signal transduction process and stimulating abscisic acid synthesis. Therefore, this research was conducted with the aim of investigating the effect of foliar spraying of ascorbic acid and calcium on some morpho-physiological traits of guar under drought stress conditions. In order to investigate the morpho-physiological responses of guar to foliar application of ascorbic acid and calcium under drought stress conditions, a factorial experiment was conducted with two factors in the form of a randomized complete block design with three replications in the research greenhouse of Saravan Higher Education Complex in 2020. The experimental treatments included three levels of drought stress (70, 50 and 30% of field capacity) and three levels of foliar application (no foliar application, foliar application with calcium carbonate and ascorbic acid with a concentration of 3‰). The results showed that in 50 and 30% of the field capacity, compared to the treatment of 70% of the field capacity, plant height, number of pods per plant, number of seeds per pod, pod length, leaf dry weight and total protein showed a decreasing trend, but traits of reducing sugar, Polyphenol oxidase (PPO) enzyme activity and root length showed an increasing trend. The increase of reducing sugars is considered a mechanism to deal with drought in plants because reducing sugars are osmolytes that play a role in plant cells as regulators of the osmotic potential of the intracellular environment. Similarly, the increase in PPO activity during drought stress is justified by the increase in radical oxygen species generated during this stress, because the increase in the activity of antioxidant compounds as a defense mechanism is essential to maintain cellular processes and prevent the damaging effects of free radicals on plant physiological processes. Foliar application with ascorbic acid did not significantly change plant height and number of pods per plant compared to non-sprayed plants but increased leaf dry weight, total protein, reducing sugar and root length by 22%, 11%, and 21%, respectively. While, calcium foliar application significantly increased plant height, number of pods per plant and leaf dry weight by 16%, 24%, and 42%, respectively compared to non-foliar application and 8.5%, 12%, and 17.5% compared to foliar application with ascorbic acid, but total protein, reducing sugar, root length and dry weight of root remained statistically unchanged in calcium spraying respect to foliar application with ascorbic acid. However, both ascorbic acid and calcium application than no-foliar application showed a significant increase in the amount of total protein, reducing sugar, root length and dry weight of root and a decrease in PPO enzyme activity. The decrease in PPO activity can be considered as a result of reducing the harmful effects of drought stress caused by the application of calcium and ascorbic acid. In general, it seems that the availability of moisture in less than 70% of the field capacity has caused the formation of mechanisms to deal with drought stress in the guar, but foliar application with ascorbic acid and calcium can somewhat to be effective in modulating the effects of drought stress on this plant.

In order to study the effect of using salicylic acid in inducing tolerance mechanisms to drought stress, a research was carried out in the field of Moghan Agriculture and Natural Resources Research Center in 2014 and 2015 as a split factorial in three replications. The main factor includes irrigation treatments based on evaporation from class A evaporation pan (100, 135 and 170 mm evaporation) and secondary treatments including soybean genotypes (Williams, L17 and D42X19) and salicylic acid foliar spraying (0, 0.4 and 0.8 mM). The results of composite analysis showed that drought stress significantly reduced plant height, number of nodes per stem, days to flowering and days to maturity in soybean genotypes. Seed yield was reduced by 38% in moderate stress and 46% in severe stress compared to control. Drought stress and application of salicylic acid, especially at a concentration of 0.4 mM, increased the concentration of amino acids such lysine and methionine. The highest amount of lysine was observed in Williams genotype under severe stress conditions and the highest amount of methionine was observed in D42XI9 genotype under moderate stress conditions. The highest level of activity of polyphenol oxidase enzymes in D42XI9 genotype and the highest level of glutathione reductase enzyme activity in Williams genotype was observed under severe drought stress conditions. Foliar spraying with salicylic acid (0.4 mM) increased the activity of these enzymes in both stressed and non- conditions. Intensity of stress caused an increase in concentration trihalose. But the effect of stress on the amount of trihalose in Williams genotype was more than other genotypes. With the application of salicylic acid, the concentration of trihalose increased in all genotypes, and the effective concentration of salicylic acid to increase trihalose was 0.8 mM. Drought stress and application of salicylic acid increased flavonoid accumulation in all genotypes and especially in L17 genotype. Drought stress significantly reduced plant height, number of nodes, days to flowering, days to maturity and seed yield in soybean genotypes, while the use of 0.4 mM salicylic acid improved the above traits, especially in the Williams genotype. In this study, Williams showed less sensitivity to drought stress (12% more seed yield than L17 genotype and 6% more than D42XI9 genotype) due to higher antioxidant enzyme activity and higher seed yield compared to other genotypes, and the use of salicylic acid in non-stressed and stressed conditions increased seed yield in soybean genotypes.

One of the research requirements in agriculture is to find a new and practical method for sustainable production that brings the highest efficiency and the least harm to humans and the environment. In order to investigate the effect of different levels of carbon dioxide and ethanol foliar spraying on the physiological and biochemical characteristics of basil (Ocimum basilicm cv. Keshkeni luvelou), a factorial pot experiment based on a completely randomized design with three replications was conducted in the research greenhouse of the Department of Horticultural Sciences and Landscape of Ferdowsi University Mashhad in 2018. The factors included ethanol spraying at 4 levels (0, 10, 20, and 30% v/v) and carbon dioxide at 3 levels (380, 700, and 1050 µmol mol−1). The results showed that the highest relative water content (RWC) of leaf, photosynthesis rate, transpiration rate, stomatal conductance, and leaf protein were observed in the treatment of 20% v/v ethanol foliar application with the application of 700 µmol mol−1 of carbon dioxide, as they increased by 45%, 295%, 684%, 83%, and 328% compared to the control, respectively. Fresh and dry biomasses of shoot parts increased significantly with increasing carbon dioxide concentration and ethanol spraying. Thus, the highest fresh and dry biomasses of shoot parts were obtained in foliar spraying of 30% v/v of ethanol and 700 µmol mol−1 of carbon dioxide which increased by 176% and 76%, respectively, compared to the control. The highest activity of polyphenol oxidase and guaiacol peroxidase, stomatal resistance, and electrolyte leakage were related to spraying 30% v/v of ethanol with an application of 1050 µmol mol−1 of carbon dioxide which showed an increase of 2%, 4%, 65%, and 76%, respectively, compared to the control. Overall, the results showed that foliar spraying of 20 and 30% v/v of ethanol along with the application of 700 µmol mol−1 carbon dioxide had the greatest effect in increasing photosynthesis and finally the fresh and dry biomasses of basil.

Microplastics (MPs) have been reported as emerging contaminants. There was little information about their effect and behavior on soil properties. This study aimed to investigate the changes in exchangeable concentrations (extracted with 1 M ammonium acetate) and water-soluble (ratio of 1 to 2.5 soil to water) of sodium (Na), potassium (K), calcium (Ca), and magnesium (Mg) elements under the presence of Low-Density Polyethylene MPs particles in the soil. The experiment was performed as a factorial experiment based on a completely randomized design with three replications. Experimental factors included the amount of MPs particles (zero, 1, 2, and 4% w/w) and incubation time (3, 17, 31, 45, 90, and 180 days). The results showed that MPs particles affected exchangeable and water-soluble elements. MPs particles reduced the exchangeable amounts of Na, K, and Ca. The largest decrease was related to the level of 4% MPs. Briefly. In the level of 4%, the amount of exchangeable Na, K, and Ca decreased by 7.2, 5.7 and 2.6 %, respectively, in comparison with control soil (without MPs). On the other hand, water-soluble K and Ca under the influence of MPs particles (4% MPs level) decreased by 6.97 and 8.4 % respectively, as compared with control. MPs particles reduced water-soluble Na in the first (3 days) to fourth (45 days) incubation periods. Also, MPs particles reduced the amount of exchangeable and water-soluble Mg, but it was not significant. In summary, the presence of MPs particles in the soil, especially in higher amounts (ex: 4%), can affect the availability of cationic elements such as Na, K, Ca, and Mg.

In order to investigate the effect of gibberellic acid, magnetic field and temperature on strawberry, this research was conducted in form of split plot on based of randomiz completely design and treatments include gibberellic acid, magnetic field and temperature stress in three levels. The results of analysis of variance of the data showed that the interaction effect on all studied traits was significant. The comparison of the averages showed that the highest amounts of chlorophyll a (14.95 mg of protein per minute) and total chlorophyll (28.54 mg of protein per minute) in the treatment of 100 mg/L gibberellic acid, magnetic field of 10 millitesla and temperature of 2 degrees and the highest of chlorophyll b (9.26 mg of protein per minute) and polyphenol oxidase enzyme (57.52 mg of protein per minute) were obtained in the treatment of 50 mg/L of gibberellic acid, 10 milliTesla magnetic field and 8 degrees. The highest amounts of peroxidase (53.6 mg of protein per minute) in the treatment of 100 mg/liter of gibberellic acid acid, magnetic field of twenty millitesla and temperature of twenty degrees Celsius and the highest values of titratable acidity (0.89 percent) and pH (6.9) were obtained in the treatment of no use of gibberellic acid, no use of magnetic field and temperature of 20 degrees. In terms of the triple interaction effect, the best effective treatment on increasing the storage time of strawberries was the combined treatment of 50 mg/L gibberellic acid and 10 milliTesla magnetic field and 8 degrees Celsius temperature.

 Narcissus (Narcissus tazetta) has high demand in flora markets due to its beauty, having a multi-floret flowerhead and delicate fragrance. The appearance quality and vase life of cut flowers decreased after harvest due to flower senescence, loss of petals turgor, reduced water absorption, transpiration, fresh weight loss, and reduced water potential which reduces the economic and ornamental value of flowers at the consumer. One of the important reasons for the poor postharvest quality of Narcissus tazetta is the loss of turgor and their high sensitivity to browning of the petals. Browning mechanisms are chemically divided into enzymatic and non-enzymatic browning reactions. Enzymatic browning, which causes important reactions and discoloration, is one of the important factors affecting the quality and shelf life of fresh produce. Previous studies have shown that the activity of polyphenol oxidase (PPO) and peroxidase (POD) is positively correlated with browning during the postharvest storage of fruits and vegetables. Nitric oxide (NO) is recognized as a biological messenger in plants. It is a highly reactive gaseous free radical. Optimum NO levels could delay the climacteric phase of many tropical fruits and prolong the post-harvest shelf life of a wide range of horticultural crops by preventing ripening and senescence. Nitric oxide also could prevent the activity of PPO, phenylalanine ammonialyase (PAL) and POD, and keep the highest activity of superoxide dismutase (SOD).

Narcissus (Narcissus tazetta L. cv. Shahla e-Shiraz) cut flowers at their commercial maturity stage (Goose-neck) were harvested from a production field in Farse province and. then they were transported to the laboratory. Healthy and uniform cut flowers with the same number of buds, a similar size and growth status were selected. Cut flowers were subjected to pulsed treatment of sodium nitroprusside for 24 hours on two levels (25 and 50 μM) and then kept in containers. Samples were stored at 20 ± 2 °C, relative humidity of 70-60%, with light cycle of 12 hours light and 12 hours dark. In this experiment, various physiological and biochemical indices including apparent quality (wilting index), cell membrane stability index (%), petal relative water content (%), color index and browning using a colorimeter, relative weight using digital scale (g), flower diameter, PPO and POD were examined. 

Sodium nitroprusside treatment reduced the browning process by reducing the activity of POD and PPO enzymes. The effect of sodium nitroprusside was concentration-dependent. Sodium nitroprusside maintains membrane stability by protecting the membrane and preventing lipoxygenase activity and scavenging free radicals that have attacked the membrane. Sodium nitroprusside-maintained flower diameter due to its role in eliminating free radicals, delaying the aging process and maintaining flower quality. Discoloration and browning reactions of cut flowers reduce their appearance quality, leading to economic loss. The browning of the petals due to senescence is one of the important factors limiting the vase life of narcissus. It has been shown that PPO and POD are the key enzymes for the oxidation of the phenolic substrate (especially simple phenols) and the production of the brown compounds. It has also been suggested that the stability index of the cell membrane, which represents the ion leakage of the tissues, is diminished extremely as the longevity is increased. Another effective factor in determining the quality and vase life of cut flowers is the water-holding ability and water balance of the cut flowers petals. Changes in the cut flower fresh weight could also be regarded as one of the most important postharvest physiological disorders that affected the quality, vase life and commercial value of the cut flowers. Fresh weight loss, which is one of the most important reasons for the wilting of the flowers, is due to the less water uptake and more respiration rate.

 Sodium nitroprusside treatment maintained the quality of Narcissus tazetta L. cv. Shahla e-Shiraz by increasing the relative water content of the petals and maintaining the cell stability index, as well as reducing the activity of browning enzymes (PPO and POD).Of course, the concentration used was very important.The best results were observed at lower concentrations (25 μM) of sodium nitroprusside.

Button mushroom (Agaricus bisporus L.) is one of the most popular and widely consumed edible mushrooms that is grown all over the world. However, button mushrooms have a short shelf life of about 3 to 4 days after harvest and lose their commercial value within a few days due to browning of the tissue, water loss, aging and microbial attack. Tissue browning is caused by the activity of polyphenol oxidase (PPO) in plastids on phenolic compounds in the vacuoles as a substrate. Therefore, enzymatic browning is intensified by the loss of membrane integrity due to aging and tissue deterioration and as a result of physical connection between the enzyme and the substrate. The use of some techniques such as the chemicals and physical treatments gives promising results in delaying Browning and increasing the shelf life of edible mushrooms. Cinnamic acid (CA) is an organic acid that occurs naturally in plants and has low toxicity and a wide range of biological activities. Cinnamic acid and its derivatives are widely used in food industry. This compound acts as an inhibitor of polyphenol oxidase activity. On the other hand, cinnamic acid in low concentration has been proposed as an activator of the antioxidant system and its positive effects on reducing the effects of environmental stresses in various plants have been proven in several experiments. Therefore, in the present study, the effect of cinnamic acid treatment on reducing the browning of the tissue and maintaining the quality of white button mushrooms in the post-harvest period has been investigated. 

Treatments included exogenous application of cinnamic acid at four levels (control, 100, 200 and 400 μM trans cinnamic acid) and storage time at five times (0, 4, 8, 12 and 16 days after storage). Cinnamic acid treatment at the mentioned concentrations was applied by top application 24 hours before mushroom harvest. Distilled water was used for control treatment. At the time of picking, infected, very large and small mushrooms were removed and the same mushrooms with a cap diameter of 40 to 45 mm were collected for each experimental treatment. After harvesting, the mushrooms were placed in a polyethylene box covered with cellophane and after weighing, they were transferred to an incubator at 4°C. In the post-harvest period, different traits were measured with a four day interva.

The results showed that by increasing storage time, the activity of polyphenol oxidase and peroxidase increased and consequently the browning of the tissue also had an increasing trend. Also, with increasing storage time, weight loss percentage, hydrogen peroxide and malondialdehyde increased and total phenol and total antioxidant capacity were decreased. The use of cinnamic acid treatment in all three concentrations (100, 200 and 400 μM) reduced the activity of peroxidase and polyphenol oxidase activities and reduced tissue browning. The application of cinnamic acid also improved the quality traits of edible mushrooms such as total phenol, total antioxidant capacity and visual quality index. These findings suggest that application of cinnamic acid, especially at a concentration of 400 μM, could have the potential of inhibiting tissue browning and thus maintaining the mushrooms quality at the postharvest period

In the present study, first, an in vitro experiment was conducted to study the effects of Thymus vulgaris L., Foeniculum vulgare Mill., Rosmarinus officinalis L., and Mentha piperita L. water extracts on reducing the growth of Fusarium rot disease factor of cucumber (Fusarium oxysporum f. sp. radicis-cucumerinum (forc)) by the saturated paper disk method. According to the results, the water extracts of Th. vulgaris, F. vulgare, R. officinalis, and M. piperita at a concentration of 250 ppm with the inhibitory zone diameter of 24.66, 17.33, 11.66, and 10.33 mm, respectively, showed the highest antifungal activity compared to the control (the inhibitory zone diameter of 3.66 mm). Then, it followed by a greenhouse experiment to investigate the effects of Th. vulgaris and F. vulgare water extracts on the cucumber cv. Nagene treated with F. oxysporum. The water extract of Th. vulgaris at a concentration of 200 ppm with the disease index of 31% showed the greatest reduction in the disease symptoms compared to the infected control and the F. vulgare treatment with the disease indices of 82.66 and 42%, respectively. Study on the activity of polyphenol oxidase, β-1, 3-glucanase, and peroxidase enzymes under the greenhouse conditions showed that the activity of all three enzymes had an increasing trend. So that the activity of enzymes in the combined treatment of Th. vulgaris water extract (200 ppm) and pathogen increased respectively from 1.12, 1.11, and 0.27 ΔOD/min/mg protein on the first day after the inoculation to 5.25, 4.81, and 2.88 ΔOD/min/mg protein on the 12th day, and it had a significant difference with the control. Considering the results of this research, it was found that the water extract of Th. vulgaris, in addition to the direct fungicidal effect, could increase the activity of defense enzymes in the cucumber plants resulted in the host plant resistance induction against the pathogen.

Yew is valuable medicinal plant because of the paclitaxel. However, due to the slow growth of endangered yew plant and low amounts of paclitaxel, the extraction of taxol from the plant is expensive and need appropriate substitute. Optimization of both biomass and metabolite culture media, is one of the main goals of invitro culture of yew plant. The present study was conducted to investigate the effect of some elicitors on the activity of enzymes involved in paclitaxel biosynthesis with the aim of optimizing the production of this compound in vitro conditions. In order to produce callus, explants of T. baccata and T. brevifolia were cultured in B5 medium containing NAA (2 mg / l), 2,4-D (0.2 mg / l), kin (0.2 mg / l). The callus was cultured in media containing elicitors including salicylic acid (80 mg / L), methyl jasmonate (100 μM), cinnamic acid (0.25 M), and a combination of them. The effect of phenylalanine (0.1 mM) as a precursor of phenylalanine-ammonialase was also investigated. The experiment was performed in a completely randomized design with three replications. Finally, the effect of the mentioned treatments on the activity of polyphenol oxidase, superoxide dismutase and phenylalanine ammonialyase enzymes of the treated calli was evaluated. Results showed that the application of experimental treatments as well as their interaction significantly affect the activity of the studied enzymes. The results showed that methyl jasmonate increased the activity of phenylalanine ammonialyase and polyphenol oxidase. Also, in the interaction of methyl jasmonate and salicylic acid, the activity of superoxide dismutase was higher than the control. Also, the activity of the studied enzymes was different without considering the effect of the treatment under the influence of the species.

Effect nanocomposite-based packaging was prepared by blending polypropylene (PP) with nano-Ag, nano Silica on the quality attributes and postharvest life of the fresh-cut fruits nectarine (cv. Red Gold) during storage at 0-1 0C with 90-95% RH for 21 days were studied. The factorial experiment was performed in a completely randomized design with 4 replications. Decay incidence, weight loss, total acidity, total soluble solids, browning index, polyphenol oxidase (PPO) and peroxidase (POD) activities were evaluated. Compared with the control (PP), nano packaging significantly reduced the fruit decay and weight loss rate (p<0/01). Polyphenol oxidase (PPO), peroxidase (POD) activities and Browning index were decreased in nano packaging fruit. Nano packaging retained total acidity. Compared with the control (PP), nano packaging retained the fruit total soluble solids rate. These results indicate that nano-Ag+ Silica active packaging could be a viable technique to reduce fruit decay and maintain quality and increase the shelf life in “Red Gold” fresh-cut nectarine during postharvest storage.

Aiming at finding a suitable treatment for maintaining the fruit quality and increase the shelf life of strawberry, effects of ascorbic acid and essential oil of Thymbra spicata were evaluated. Fruits were dipped in 10 and 15 mM of ascorbic acid and essential oil of T. spicata (400 and 600 ppm) for two minutes, and after drying at room temperature, were packed by cellophane in the polyethylene container and transferred to 4 °C. Some of the qualitative, quantitative and biochemical parameters were measured at 7 and 14 days after storage. Results of analysis of variance showed that there were significant differences among the treatments in most of the evaluated parameters. Strawberry fruits treated with ascorbic acid and essential oil showed lower weight loss and lower fruit browning, while they had higher marketability than control plants. Ascorbic acid and essential oil treatments also led to decreases in polyphenol oxidase activity, total phenol content and electro leakage, while the vitamin C content and antioxidant capacity were significantly higher than control plants. Generally, ascorbic acid (15 mM) and essential oil (400 ppm) compounds reduced fruit’s degradation during cold storage and these treatments have the potential to be used as practical postharvest treatments to retain the quality of strawberry fruits.

In order to study the effects of foliar application of nano iron oxide particles and biofertilizers on root growth, antioxidant enzymes activity in two parts of root and leaf, as well as some other physiological characteristics of black cumin (Nigella sativa L.) a pot experiment with factorial arrangement in randomized complete block design with three replications was carried out in 2017 growing season at the Faculty of Agriculture, University of Shahrood. The first factor was foliar applications of nano iron oxide at three levels (F0= control, F1= 1.5 and F2= 3 g /1 l water) and the second factor was biofertilizers at five levels (B0= Control, B1= Glomus Intraradices, B2= Glomus mosseae, B3= Azospirillum and B4= Azotobacter solution). The results showed that activity of antioxidant enzymes catalase, polyphenol oxidase in two parts of root and leaf was influenced by two factors of biological fertilizers and foliar application of nanoiron oxide particles, so that the use of biofertilizers reduced and with increasing iron oxide concentration, activity they increased. The highest activity of ascorbate peroxidase in leaf was obtained from F2B0 treatment. The interaction effect of foliar application of nanoiron oxide particles and biofertilizers had a significant effect on photosynthetic pigments and aerial dry weight, so that the highest amount of chlorophyll a was obtained from F2B1 treatment, chlorophyll b, aerial dry weight and iron of aerial from F2B2 treatment. According to the results of the experiment, the symbiosis with G. intrarardits fungus caused a significant increase in the absorption of nitrogen and iron elements in the plant.

Melon, like other members of cucurbitaceae family, is sensitive to cold stress. Applying different cultivation techniques in the nursery can provide some degree of tolerance to environmental stresses in the plants. In the other words, applying stress conditions on plants may cause them to withstand subsequent stresses, this is so called a cross-adaptation or cross-tolerance. For example, Whitaker (1994) showed that cold stress damage can be mitigated by temperature pretreatment. This technique was then used to improve stress tolerance in different plants. In this regard, heat treatment has been used to increase the chilling tolerance in fruits and vegetables. Therefore, in this study, the possibility of increasing cold stress tolerance in melon seedlings using heat shock was investigated.

The experiment was conducted in a completely randomized design (CRD) with three replications and five treatments (including control and spraying with water at temperatures of 20, 45, 50 and 55 °C for 90 seconds) in Faculty of Agriculture of Ilam University in 2019. Heat treatments where used as foliar spray by heated water. After applying different levels of heat treatment and recovery at 24 hours, seedlings were exposed to chilling stress at 3 °C for 6 h in 6 consecutive days. All seedlings were transferred to greenhouse and after 72 hours, the related traits were measured.

Results showed that pre-treated seedlings had higher growth rate than control seedlings at the end of chilling period. Heat shock pretreatment significantly increased the content of chlorophyll, proline and hydrogen peroxide and reduced the amount of malondialdehyde compared to the control. The lowest amount of malondialdehyde (1.14 nmol g-1 fresh weight) was observed in the 50 °C treatment, which was 50% lower than the control. Similar to other environmental stresses, low temperature usually leads ROS production and oxidative stress. Malondialdehyde content is an index to measure membrane lipid peroxidation and its measurement is a criterion of damage to plants in stress conditions. Reduction of malondialdehyde has been reported to increase cell membrane stability and increase stress tolerance in plants. In the present study, heat shock reduced the accumulation of malondialdehyde compared to the control, indicating a decrease in cold effects on the plant. Mei and Song (2010) investigated the effect of heat pretreatment on increasing high temperature tolerance in barley, and reported that using this method by stimulating the synthesis of antioxidant enzymes prevented the increase of malondialdehyde in the plant under heat stress. Therefore, maintaining the membrane structure and decreasing the accumulation of malondialdehyde in melon seedlings under cold conditions indicates an improvement of plant defense responses induced by heat shock. Environmental stresses including cold stress by producing hydrogen peroxide and other free radicals lead to oxidative stress and damage plant cells. Hydrogen peroxide is converted to water by ascorbate peroxidase, peroxide redoxin, glutathione peroxidase and guaiacol peroxidase groups. Therefore, increasing the activity of antioxidant enzymes in plants is one of the most important mechanisms of the plant to cope with stress conditions. In the present study, heat shock pretreatment significantly increased peroxidase (POD) and poly phenol oxidase (PPO) activity and increased the amount of proline and hydrogen peroxide. In this regard, it has been reported that hydrogen peroxide has a dual role in plants and its increase in stress conditions by regulating the production of antioxidant enzymes helps plants to enhance their tolerance to the stress conditions. Our results is in consistent with Ao et al. (2013) report that stated hardening pretreatment of Jatropha curcas seedlings caused to increase the antioxidant enzymes activity, plant glutathione and ascorbate content. The increases in antioxidant enzymes activity by heat shock might be a positive mechanism, which facilitate the scavenging of ROS and induce plant growth and development under chilling stress. These results indicate that antioxidant defense system has a specific role in enhancing plant tolerance to stress conditions and hydrogen peroxide play an important signaling role in plant adaptive responses.

In general, the results showed that heat shock (especially at 50 and 55 oC) caused positive physiological changes in melon seedlings and could increase their tolerance to cold stress conditions.

Understanding the reaction form and biochemical response of wheat cultivars about the salinity stress can help to better understand the defense mechanisms and identify the indicators and biomarkers of tolerance screening for salinity stress in this strategic plant and other field crop. For this purpose, biochemical traits related to salinity tolerance of wheat cultivars were evaluated as a factorial experiment based on a completely randomized design with tree replications. Experimental factors included wheat cultivars (Sarc 6 as tolerant cultivar and Chinese spring as susceptible cultivar) and sampling time series (control, 6, 12, 24, 48, 72 and 96 hours) after salinity stress. Salinity stress with a concentration of 250 mM of sodium chloride was applied to uniform 10-day seedlings in the two-leaf stage and sampling of shoot and root was performed. The studied traits included the ratio of potassium to sodium (K+/Na+), malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), and polyphenol oxidase (PPO). The results of analysis of variance showed that the effects of the cultivar (excluding peroxidase), the effects of time and the interaction of cultivar and time in all the studied traits, were significant. In one hand, the interaction results of cultivar and time indicated that the trend of changes in the studies traits were different, depending on the type of cultivar, the studied plant part and the sampling time. On the other hand, they also specified that the salinity stress was generally reduced the K+/Na+, increased the MDA and surged the activity of antioxidant defense enzymes in shoot and root of the studied cultivars as compared to control conditions (zero time). The results of group comparisons not only confirmed the efficiency and dominance of the Sarc 6 tolerant cultivar antioxidant defense system against the sensitive cultivar of Chinese springs, but it also emphasized the benefits of K+/Na+, SOD, and CAT biomarkers for wheat screening.

Pistachio is one of the most important horticultural produce is used both in dry and fresh form. The fresh pistachio is very perishable due to its high respiration, heat production and moisture resulting to short shelf life. Therefore, in order to maintain quality and improve the shelf life of this produce, a factorial experiment with two treatment factors (control, 2 g activated carbon sachets, 4 g activated carbon, 2 g activated carbon impregnated with potassium permanganate saturation, 4 g activated carbon impregnated with potassium permanganate Saturation) and storage time (0, 20 and 45 days) was designed in a complete block with four replications on pistachio cultivar Ahmad Ahaghei. The results showed that different indices of evaluated fruit quality included weight loss, hull firmness, total chlorophyll, lightness, total color changes, antioxidant activity, anthocyanin, hull and kernel phenolic compounds and PPO activity was affected by the treatments. hull firmness, total chlorophyll, lightness, antioxidant activity, anthocyanin, phenolic compounds decreased during storage time but weight loss, total color changes, and PPO activity increased then control and treatments maintained these traits. Among the treatments 4 g activated carbon impregnated with potassium permanganate had the most effective on maintaining the quantitative and qualitative characteristics of this pistachio cultivar.

Oxalic acid (OA), as a natural antioxidant, delays the ripening and senescence of fruits. In this research, the effect of different concentration of OA (0, 2, 4, 6, and 8 mM) investigated on storage life and postharvest quality of loquat fruit at 5°C and 90±5% relative humidity for 28 days. Traits such as browning index, biochemical and qualitative characteristics and activity of polyphenol oxidase (PPO) and peroxidase (POD) enzymes of fruit at harvest (0), 7, 14, 21 and 28 days after storage were analyzed. With increasing storage time, the level of browning index, total soluble solids (TSS), ratio of TSS/titratable acidity (TA) and the activity of PPO and POD enzymes increased in all treatments, while firmness, ascorbic acid, total phenol and flavonoids content and antioxidant activity decreased (p˂0.05). OA application significantly reduced the level of browning index and the activity of enzymes responsible for tissue browning (PPO and POD) compared to control (p˂0.05). At the end of storage, fruits treated with different concentration of OA had a more firmness tissue and higher level of ascorbic acid, total phenol and flavonoids content and antioxidant activity in comparison to the control fruits (p˂0.05). Overall, OA application effectively reduced fruit softening and browning index with diminished the activity of PPO and POD enzymes during cold storage. Thus, OA treatment (6 mM) can be used as an effective method for cold storage of loquat fruit.