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.
Postharvest physiology
Parisa Hayati; Seyyed Mehdi Hosseinifarahi; Gholamreza Abdi; Mohsen Radi; Leila Taghipour; Pedram Assar
Abstract
IntroductionThe Peruvian Groundcherry (Physalis peruviana L.) is a perennial plant that is native to the South American regions and belongs to the Solanaceae family. The harvested fruits are vulnerable to both biotic and abiotic stresses, which can trigger unfavorable physiological and biochemical changes. ...
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IntroductionThe Peruvian Groundcherry (Physalis peruviana L.) is a perennial plant that is native to the South American regions and belongs to the Solanaceae family. The harvested fruits are vulnerable to both biotic and abiotic stresses, which can trigger unfavorable physiological and biochemical changes. As a result, the quality and marketability of the product may decrease by the time it reaches the consumer. The fruit of the Peruvian Groundcherry has a high water content and is sensitive to ethylene, causing rapid ripening with a high respiration rate, making it highly perishable. To ensure quality maintenance after harvest, various postharvest treatments are being studied; however, some methods may not be practical due to low customer preference or lack of effectiveness verification. Therefore, alternative treatments need to be found to prolong shelf life and reduce postharvest losses. Currently, environmentally friendly technologies and treatments are recommended. The aim of this study was to investigate the effects of γ-Aminobutyric acid (GABA) postharvest treatment on the respiration rate, antioxidant activities, and fruit quality of the Peruvian Groundcherry during 21 days of storage, addressing a research gap in this area.Materials and MethodsHandpicked Peruvian Groundcherry fruits were taken from a commercial greenhouse located in Fars province, Iran. The fruits were picked at two stages of maturity based on their color, which was either yellowish green or orange. Following the harvest, the fruits were taken to a horticulture laboratory where they were assessed for appearance, size, color, and any damages. The experimental design was factorial based on a completely randomized design with three replications, each containing 25 fruits. Experimental factors included the GABA concentration (0, 5, 10 and 15 mM), storage time (7, 14 and 21 days) and fruit maturity stage based on color at harvest (yellowish green and orange). Following dip treatments in GABA solutions, fruits were packed in plastic clamshells measuring 20×5×10 cm3 and with a hole ratio of 3%. Fruits were stored at a temperature of 15 ◦C for 21 days, and their quality characteristics and respiration rate were evaluated on a weekly basis.Results and DiscussionThe findings indicated that both groups of treated fruits had a slower increase in respiration rate and lower final respiration rate compared to the control group. The effect of different concentrations of GABA on the final respiration rate of fruits was similar for each stage of fruit maturity. During the storage period, the changes in total soluble solids and total acids of the treated fruits were less than the control group. At the end of the storage period, yellowish green fruits treated with 10 and 15 mM GABA had the lowest amount of total soluble solids; orange fruits had the lowest amount with 15 mM GABA treatment. GABA concentrations had a similar effect on total acids retention of yellowish green fruits, but 15 mM GABA treatment was more effective for orange fruits. Ascorbic acid content and phenylalanine ammonia-lyase enzyme activity were consistently higher in treated fruits than in the control group. In green fruits treated with GABA concentrations, the amount of ascorbic acid increased significantly and continuously, with no significant difference between treatments at the end of storage period. Orange fruits showed a significant increase until the second week of storage, followed by a non-significant decrease. Higher amounts of ascorbic acid in orange fruits were detected by applying higher GABA concentrations. Both groups of fruits had significantly higher amounts of total phenol, carotenoid, and antioxidant capacity in response to increasing GABA concentration, while the minimum amount of these compounds during the storage period was related to the control group. However, orange-colored fruits were more sensitive to treatments compared to yellowish green fruits.ConclusionsThe results of the present study indicate a positive effect of postharvest GABA treatment on reducing respiration rate, improving antioxidant activities, and maintaining the quality and nutritional value of Peruvian groundcherry fruit during a 21-day storage period. Considering the global preference and demand among governments and consumers to use environmentally-friendly treatments of biological origin that pose no risk to human health, we recommend the use of GABA treatment for optimal storage of Peruvian groundcherry fruit. Finally, it is recommended to assess the efficacy of GABA or other safe and environmentally-friendly postharvest treatments on the quality and shelf life of other valuable horticultural commodities.
Growing vegetables
Najme Zeinali Pour; Fatemeh Aghebati
Abstract
Introduction
Portulaca oleraceae is used in many countries for a variety of purposes, including human nutrition and the conversion and pharmaceutical industries. The edible parts of Portulaca oleracea are the young organs, especially the brittle leaves and stems. Over time, this medicinal herb ...
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Introduction
Portulaca oleraceae is used in many countries for a variety of purposes, including human nutrition and the conversion and pharmaceutical industries. The edible parts of Portulaca oleracea are the young organs, especially the brittle leaves and stems. Over time, this medicinal herb has been forgotten. Drought, on the other hand, is a factor in the decline of crops and horticulture around the world. Given the vastness of arid and semi-arid regions in Iran and also the reduction of access to water resources, appropriate arrangements should be made for the optimal use of water in the agricultural sector. Changing the planting pattern and using useful and resistant alternative species such as drought-tolerant medicinal plants can enable the optimal use of limited water resources. GABA is an important non-protein amino acid that plays a positive role in increasing plant resistance to stress.
Materials and Methods
This experiment was carried out in 2020 as a factorial based on a completely randomized design with three replications in the vegetable research greenhouse of the Faculty of Agriculture, Shahid Bahonar University of Kerman. Experimental treatments included different levels of GABA (0, 20, and 40 mM). Treatment with different concentrations of GABA was done in two stages of 6 and 12 leaves of portulaca oleracea and foliar application and application of dehydration stress in three levels of control, medium and severe at irrigation intervals of 7, 14, and 21 days from 6 leaf stage of plants to the end.
Results and Discussion
According to the analysis of variance, the effect of GABA at different concentrations and dehydration stress on plant height was significant at the level of 5% probability. Based on the mean comparison test, the highest plant height was obtained in GABA treatment of 40 mM and irrigation intervals of 7 days (control), and the lowest of this trait was obtained in GABA zero treatment and irrigation intervals of 21 days (highest stress level). The results of analysis of variance showed that the effect of GABA at different concentrations and dehydration stress on vegetative yield was significant, the interaction between irrigation intervals and GABA was significant at 5% level. Based on the mean comparison test, the highest vegetative yield was obtained in GABA treatment of 40 mM and irrigation intervals of 7 days and the lowest in control treatment and irrigation intervals of 21 days. According to the results of the analysis of variance table, the effect of GABA at different concentrations and dehydration stress on the amount of malondialdehyde was significant at the level of 1% probability. Based on the means comparison test, the highest amount of this trait was obtained in the control treatment. Comparison of the mean of the data showed that the effect of GABA at different concentrations and dehydration stress caused a significant difference in the probability level of 1% in the proline content of the data. Based on the mean comparison test, the highest amount of proline was observed in GABA treatment of 40 mM and irrigation intervals of 21 days and the lowest amount was observed in control treatment and irrigation intervals of 7 days. As can be seen in the comparison table of means, the highest activity of superoxide dismutase enzyme was obtained in GABA treatment at 40 mM and irrigation intervals of 14 days and the lowest in control treatment and irrigation intervals was 7 days (Table 2). The results of this study showed that the effect of GABA at different concentrations and dehydration stress on the activity of catalase was significant at the level of 1% probability. As can be seen in the comparison table of means, the highest level of catalase activity was 40 mM in GABA treatment and 21 days irrigation intervals and the lowest in GABA treatment was 40 mM and irrigation intervals were 7 days.
Conclusion
The results of this study indicate that GABA is able to greatly alleviate the oxidative stress caused by dehydration in Portulaca oleracea. This effect is quite evident in oxidative parameters, especially the activity of antioxidant enzymes. The concentration of 40 mM GABA was the most effective treatment in mitigating the effects of irrigation. The results show that the use of GABA makes Portulaca oleracea tolerant to dehydration stress.
