Postharvest physiology
Zahra Pakkish; Somayeh Mohajerpour; Safoora Saadati
Abstract
Introduction
Fresh fruits and vegetables are physiologically active and perishable after harvest. Continued metabolic processes such as transpiration or respiration may significantly affect their quality and thus shorten their useful life. Since keeping at low temperatures and without freezing for ...
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Introduction
Fresh fruits and vegetables are physiologically active and perishable after harvest. Continued metabolic processes such as transpiration or respiration may significantly affect their quality and thus shorten their useful life. Since keeping at low temperatures and without freezing for a long time effectively reduces the physiological activity of the products, it can be used as a strategy to maintain the quality of the products and increase their life after harvesting. Among the most economically important tropical fruits, ripe green bananas are very sensitive to cold and when stored below the threshold temperature, they show all the symptoms of frost damage. While banana cultivars, maturity stage, and ripening all influence cold sensitivity, there's a growing interest in extending the shelf life of produce using natural, plant-friendly compounds. Gamma-aminobutyric acid (GABA), a naturally occurring four-carbon, non-protein amino acid found in plants, animals, and bacteria, is a promising candidate in this area.Abiotic stresses such as cold, heat, drought, ultraviolet rays and low oxygen can cause the accumulation of GABA in plants. Generally, the purpose of this research was to investigate the effect of gamma-aminobutyric acid treatment to improve freezing and antioxidant properties of Cavendish banana at 5 degrees Celsius for 24 days in 90% relative humidity.
Materials and Methods
Cavendish banana fruits (Musa acuminata cv. Cavendish) at the time of commercial maturity (ripe green) were obtained from a banana garden in Kerman and immediately transferred to the horticultural science laboratory of Shahid Bahoner University, Kerman. Healthy and uniform fruits were selected in terms of size, shape, color, and degree of ripening, and after washing with water and drying them, frost tolerance, malondialdehyde, and antioxidants were measured for zero day. GABA (Sigma-Aldrich, USA) required after weighing was dissolved in water and prepared in two concentrations of 2.5 and 5 mM. The fruits were divided into three groups of 54 and each repetition included 18 fruits. The first and second groups were immersed in GABA solution of 2.5 mM and 5 mM for 5 minutes, respectively. The third group was immersed in distilled water for 5 minutes and was used as a control (Khaliq et al., 2023). Each treatment was repeated three times. Then, all the fruits were dried in the air for one hour and kept for 24 days at 5 degrees Celsius and relative humidity of 85-90%. Biochemical observations were measured on days 0, 4, 8, 12, 16, 20 and 24 of storage.
Results and Discussion
The results of this research showed that frost damage gradually increased during the storage period and the control fruits showed significantly more frost damage symptoms than the fruits treated with GABA. GABA treatments of 2.5 and 5 mM at the end of the storage period reduced the amount of frost damage by 55.64 and 69.95%, respectively, compared to control fruits. As shown in Figure 1b, MDA content as an index of membrane lipid peroxidation in the control and GABA-treated fruit showed an upward trend, which was associated with the destruction of banana fruit membrane under cold stress. Compared to control, banana fruits treated with GABA showed lower MDA accumulation during the entire storage period at 4 degrees Celsius. On the last day of storage, GABA treatment with a concentration of 2.5 mM and 5 mM reduced the amount of MDA in banana fruits by 30.99% and 59.80%, respectively, compared to the control. Post-harvest treatment with GABA reduced frostbite, ion leakage and MDA levels in banana fruits, thereby maintaining fruit quality during low temperature storage. GABA treatment increased the activity of catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD) and superoxide dismutase (SOD) enzymes in banana fruit compared to the control under low temperature storage. The activity of antioxidant enzymes CAT, APX, POD and SOD increased significantly until the 20th day of storage at low temperature, especially in the 5 mM GABA treatment compared to the other two treatments, and then decreased slightly at the end of the storage period. An increase in the concentration of oxygen free radicals, including hydrogen peroxide, leads to an increase in catalase enzyme activity. Catalase enzyme is often present in the peroxisome and causes the decomposition of hydrogen peroxide into water and oxygen. The specific activity of catalase enzyme increased during cold storage, especially in GABA treatments, so it seems that this enzyme is an efficient scavenger for removing hydrogen peroxide and thus causes better protection of cells against peroxidation. In the ascorbate-glutathione cycle, the ascorbate peroxidase enzyme reduces the amount of hydrogen peroxide by using ascorbate as an electron donor. In the present study, the activity of ascorbate peroxidase enzyme in GABA treatment was significantly higher than the control, which indicates the importance of the role of ascorbate peroxidase in plant tissues against oxidative damage. Guaiacol peroxidase enzyme is another antioxidant enzyme that decomposes hydrogen peroxide into water and oxygen. Peroxidase enzyme plays a role in the oxidation of precursors of phenolic compounds, lignin production, and removal of free radicals. The activity of peroxidase enzyme showed a similar trend in all three treatments, although its activity in GABA treatments was more than the control. Therefore, this enzyme effectively eliminated free radicals in banana fruits. In confirmation of these findings, it was reported in research that the activity of peroxidase enzyme increased in fir cuttings during the cold period. In research, post-harvest treatment of GABA with a concentration of 5 mM reduced frostbite and increased the activity of antioxidant enzymes such as CAT, APX, POD and SOD in peach fruits.
Conclusion
The results of this research showed that the applied post-harvest treatments reduced the signs of frostbite and preserved the antioxidant properties of banana fruits. Among the treatments, 5 mM concentration of GABA was the most effective treatment in the storage period. Therefore, GABA treatment can be used as a practical solution to reduce frostbite and preserve the antioxidant properties of Cavendish bananas during long-term storage.
Bahareh Ghorbani; Zahra Pakkish
Abstract
Introduction: Chilling injury (CI) is the primary postharvest problem of orange (Citrus sinensis L.) and many other horticultural crops during storage. Washington Navel orange fruits are susceptible to CI during storage below 5°C, and the main CI symptoms are surface pitting, browning, discoloration ...
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Introduction: Chilling injury (CI) is the primary postharvest problem of orange (Citrus sinensis L.) and many other horticultural crops during storage. Washington Navel orange fruits are susceptible to CI during storage below 5°C, and the main CI symptoms are surface pitting, browning, discoloration and decay. Several promising methods have been developed to alleviate CI symptoms of orange fruit. These include postharvest physical treatments with UV-C, modified atmosphere packaging, temperature conditioning, and chemical treatments with plant growth regulators. Oxidative stress from excessive reactive oxygen species (ROS) has been associated with appearance of chilling damage in fruits. The oxidation of ROS is due to their reaction with numerous cell components coursing a cascade of oxidative reactions and consequent inactivation of enzymes, lipid peroxidation, protein degradation, and DNA damage. Aerobic organisms have evolved well-developed defense systems to establish a fine-tuned balance between ROS production and removal plants are protected against ROS effects by a complex antioxidant system. This involved both lipid soluble antioxidant (α- tocopherol and carotenoids) and water soluble reductants (glutathion and ascorbate) and enzymes, such as catalase (CAT), ascorbate peroxidase (APX), superoxide dismutase (SOD) and peroxidase (POD). Previous studies have shown that there is a positive relationship between the antioxidant enzymes activity and the chilling tolerance in harvested fruits. Nitric oxide (NO) is an important signaling molecule involved in many plant physiological processes. It has also been indicated that NO protects plant cells against oxidative stress by reducing ROS accumulation. When exogenously applied, NO has been shown to result in an improved chilling tolerance and reduced incidence of chilling injury in several fruits. The objectives of this study were to evaluate the effects of NO on chilling injury, lipid peroxidation content, peroxide hydrogen content, and the induction of antioxidant enzymes in Washington Navel orange (Citrus sinensis L.) fruit during storage at 5±1°C.
Materials and Methods: Washington Navel orange (Citrus sinensis L.) fruits were harvested at commercial maturity from a commercial orchard in Kerman, Iran, and transported to the laboratory on the same day. Orange fruits were treated with 0.25 and 0.5 mM nitric oxide for 5 min and then stored at 5±1°C and relative humidity of 85-90 % for 5 months. No nitric oxide use was considered as control. The experiment was arranged in completely randomized design (CRD) with three replicates. Characteristics such as chilling injury, total soluble solids, titratable acidity, pH, ascorbic acid, and activity of antioxidant enzymes (peroxidase and catalase) were evaluated in the present experiment.
Results and Discussion: The results showed that use of nitric oxide in fruits reduced significantly chilling injury, ion leakage, lipid peroxidation and hydrogen peroxide compared to control, though it increased activity of antioxidant enzymes. According to these results, unlike organic acids which decreased in treated and non-treated fruits, total soluble solids, ascorbic acid and pH of the fruits increased during storage, however, nitric oxide treatment reduced the rate of changes, be either reducing or increasing, in the mentioned parameters compared to control. So, fruits treated with 0.5 mMol nitric oxide showed the highest effect on the reduction of chilling injury.
In the present study, the results indicated that NO significantly reduced CI of orange fruits during storage at 5±1 °C. NO has been applied to reduce the development of chilling injury symptoms in a number of horticultural crops. Thus NO has the potential of application in postharvest treatment by alleviating chilling injury and maintaining quality, and the aim of this study was to determine how NO alleviates the anti-oxidative systems, probably one of the mechanisms of improved chilling tolerance, of orange fruit during chilling stress. This indicates that the chilling tolerance of orange fruit was also enhanced by postharvest treatment with NO. Lipid peroxidation and protective enzyme systems are often evaluated in studies of plant mechanisms under various stresses. Low temperature disrupts the balance of active oxygen species metabolism, leading to their accumulation and destruction of scavenging enzymes such as catalase and peroxidase. In the present study, exogenous per-treatment with nitric oxide at 0.25 and 0.5 mM significantly decreased the lipid peroxidation content and electrolyte leakage of cold stored orange fruit compared to untreated fruits. The level of H2O2 was maintained by NO treatment, which led to an increase in chilling tolerance. It has been reported that the improvement of chilling tolerance in harvested horticultural crops is related to the enhancement in activates of antioxidant enzyme. Researchers found that chilling-tolerant mandarins have a higher antioxidant enzyme activity than the chilling-sensitive ones. A number of postharvest treatments that induce chilling tolerance and alleviate chilling injury also enhanced antioxidant enzyme activity. However, to the best of our knowledge, this is the first paper reporting the beneficial effects of NO on CI of postharvest orange fruits. In this study, there was a continuous increase in peel and pulp lipid peroxidation content in all fruits, but the application of NO significantly delayed the increase of lipid peroxidation. Moreover, the change in membrane permeability (revealed by H2O2 content) showed trends similar to lipid peroxidation content; in other words, peel and pulp H2O2 content increased with storage duration, but NO markedly delayed the increase. NO has been considered to be involved in a network of interacting signal transduction pathways, which regulate defense responses to abiotic stress. The detoxification of ROS is dependent on antioxidant enzymes such as CAT and POD. The increase in these enzymes’ activity contributes to the adaptation of plants to cold stress and ameliorates oxidative damage such as lipid peroxidation (lipid peroxidation increase as indicator) and H2O2 content.
Conclusion: In conclusion, application of NO reduced CI of oranges stored at 5±1°C and maintained oranges quality as well. The chilling injury, lipid peroxidation, and peroxide hydrogen were significantly reduced by NO treatment especially at 0.5 mM. Induced cold resistance by NO treatment may be due to the stimulation of antioxidant enzymes, and protection against membrane oxidative damage, decreased lipid peroxidation and H2O2 content in orange fruits. These results may have implications for the use of NO in managing postharvest CI of other subtropical fruits stored at low temperatures.
Soheila Mohammadrezakhani; Zahra Pakkish; Somaye Rafeii
Abstract
Introduction: Recently, strawberry growers have been mostly interested in growing cultivars for the fresh market because of its profitability, but on the other hand it requires more complicated technologies and well-educated workers. High quality of the fruit for the fresh market is an important factor ...
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Introduction: Recently, strawberry growers have been mostly interested in growing cultivars for the fresh market because of its profitability, but on the other hand it requires more complicated technologies and well-educated workers. High quality of the fruit for the fresh market is an important factor attracts customers and determines their choice and prices. Fruit production cost for the fresh market needs to be calculated and efficient methods and technologies also should be taken into consideration. New environmentally friendly mineral-organic fertilizers can improve fruit quality and yield of dessert strawberry cultivars. The desired effects was obtained through the activity of fertilizer’s components, which very often belong to different groups of natural hormones, elicitors, vitamins, flavonoids, amino acids, etc. Numerous breeding programs have been aimed at improving strawberry taste and disease resistance. Three major components of fruit organoleptic quality are flavor, sweetness, and acidity. Several studies have been devoted to strawberry aroma. Fruit with intense flavor also have high titratable acidity and high soluble solids. Numerous studies have addressed strawberry sweetness and acidity. Fruit soluble solids, sugars, titratable acidity, and organic acids at maturity are quantitatively inherited. Moreover, there appears to be genetic variations for these fruit quality traits. Numerous biochemical changes are observed during strawberry development and especially during fruit ripening. The major soluble constituents of maturing and ripe strawberries are soluble sugars and organic acids. The major soluble sugars in strawberries are glucose, fructose, and sucrose. The major organic acid is citric acid. This acid contributes greatly to fruit titratable acidity, which declines gradually during fruit development. The sugar/ organic acid ratio is a major parameter of strawberry taste. Brassinosteroids (BRs) are a class of poly hydroxyl steroids, which have been recognized as a class of plant hormones. These were first explored when Mitchell et al. (1970) reported that cell division and elongation were promoted by the treatment of organic extracts of rape (Brassica napus L.) pollen. Brassinolide (BL) was the first isolated brassinosteroid when Michael et al. (1979) isolated the biologically active molecule. Researches showed that brassinosteroids are essential for many physiological functions in plants, however little is known concerning where and when they are synthesized. In young tomato seedlings BR synthesis activity was observed mainly in apical and root tissues undergoing expansion. In flowers, synthesis activity was observed in the pedicel joints and ovaries, whereas in the fruits it was strongest during early seed development and was associated with the locular jelly and seeds. Quantitative measurements of endogenous BR indicated intense biosynthesis in developing tomato fruits, which were also found to contain high amounts of brassinolide. Moreover, brassinosteroids stimulate cell elongation and cell division, and BR has a specific effect of differentiation. Underling physiological pathways include modification of cell wall properties, effects on carbohydrate assimilation, allocation, and control of aquaporin activities. Brassinosteroids apparently coordinates and integrates diverse processes required for growth, partly via interactions with phytohormones setting the frame for BR responses. The aim of present study was investigation of the role of brassinosteroid on qualitative characteristics improvement of strawberry fruit.
Materials and Methods: In this research the effect of different concentrations (0, 0.25, 0.50, 0.75 and 1 mgl-1) of brassinosteroid sprayat different stages of strawberry growth (30 days after planting, first blooming, green fruit, and pink fruit) on some qualitative characteristics of the strawberry Paros cultivar was considered. This experiment was conducted asfactorial on a randomized complete block design with 4 replications in greenhouse conditions. Parameters such as total soluble solid, inducing sugar, titrable acidity, anthocyanin, phenol, fruit dry weight, fruit water and vitamin C were measured after….
Results and Discussion: Results showed treated plants by brassinosteroid, compared to control, improved fruit qualitative characteristics. So, brassinosteroid application increased total soluble solid, inducing sugar, titratable acidity, anthocyanin, phenol, dry weight, vitamin C.The best effective treatment and the best spraying time was brassinosteroid at 1 mgl-1 in pink fruit stage, respectively for qualitative characteristics improvement. Because, Brassinosteroid growth induced has been related to increase in RNA and DNA content, polymerase activity, protein synthesis carbohydrate fraction, reducing sugars, non-reducing sugars and starch. The yield increase in fruit trees may be related to improvement in the assimilation efficiency of photosynthetic carbon of the sprayed trees. The brassinosteroid application in wheat and mustard plants stimulated photosynthetic activity expressed by acceleration in CO2 fixing, increase protein biosynthesis and in mustard, increased photosynthetic rates that were directly related to growth and seed production. In accordance, researchers explained that BRs have been shown to enhance tracheary element differentiation, stimulate membrane hyperpolarization and ATPase activity, promote ethylene biothynsesis, control microtubule orientation and alter the mechanical properties of cell walls. In addition, brassinosteroid treatment greatly stimulated accumulation of photosynthates in the treated internode. This suggests a possible mobilization role for BR in the intact plant. As well as, in persimmon, grapevine and citrus, reported that BR compound showed, the practical effects for fruit setting. While, showed that brassinolide increased fruit weight and sugar content of oranges. In passion fruit orchards, brassinosteroid increased fruit number of plant and in turn yield per hectare and soluble solids content was 1° Brix greater than the control.
Conclusions: From this study, it is evident that the application of plant biostimulants such as brassinosteroid significantly improved qualitative characteristics. So, brassinosteroid application increased total soluble solid, inducing sugar, titrable acidity, anthocyanin, phenol, dry weight, vitamin C and effective treatment and best spraying was brassinosteroid at 1 mgl-1 at pink fruit stage for qualitative characteristics improvement.
