Postharvest physiology
Z. Pakkish; S. Mohajerpour; S. 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.
Growing vegetables
S. Parsajoo; F. Dashti
Abstract
Introduction
Plants are sometimes exposed to several stresses during their growth and development. Salinity stress is one of the most common abiotic stresses that significantly reduces the growth and yield of most plant species. A large part of the soils and a significant volume of all water resources ...
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Introduction
Plants are sometimes exposed to several stresses during their growth and development. Salinity stress is one of the most common abiotic stresses that significantly reduces the growth and yield of most plant species. A large part of the soils and a significant volume of all water resources in Iran are affected by salinity to varying degrees. Due to the rapid population growth and the need for more food and the water crisis, the use of unconventional water such as salt water or wells and treated wastewater in agriculture has received more attention. Soil and water salinity is one of the integrative problems in agriculture and is one of the most important barriers to crop production in the world. Salinity stress reduces the ratio of carbon dioxide to oxygen in the leaves by closing the leaves stomata and prevents the stabilization of carbon dioxide. Under these conditions, the formation rate of reactive oxygen species in chloroplasts and mitochondria increases, the electrons produced react with oxygen by photosynthesis and lead to the production of oxygen free radicals. These affects the growth, yield and quality of agricultural products. The use of antioxidant compounds can moderate the effects of this stress. Many compounds have been used to reduce the harmful effects of salinity stress. Ascorbic acid is a water soluble antioxidant and has some effects on plant resistance against environmental stresses by neutralizing free radicals. Researches showed that ascorbic acid increased plant resistance on various stresses such as salinity and drought. It has been widely used to control the effects of salinity stress. The aim of this study was to investigate the effect of ascorbic acid on resistance to salinity stress in bell pepper seedlings.
Materials and Methods
This study was done as a factorial experiment in a completely randomized design including ascorbic acid treatment (0, 1, 3 and 5 mM) and salinity stress of sodium chloride (0 and 100 mM) in 3 replications. The seeds of bell pepper Cv. California Wonder were planted in a seedling tray containing cocopeat. After emergence of cotyledons, they were fertilized with complete fertilizer (N20, P20, K20). At the stage of three true leaves the salinity treatment were started. One week before the beginning of salinity treatment, ascorbic acid was sprayed on plants and repeated two more times by seven days interval. Salinity treatment was applied by irigation for three weeks. After producing 5 leaves, a few growth properties (plant fresh and dry weight, root fresh and dry weight, leaf number and leaf area), biochemical characteristics (amounts of total chlorophyll, proline, soluble proteins, ion leakage and malondialdehyde and activity of Catalase an Proxidase enzymes) and amounts of some elements (K, P, Na, Fe, Zn and Cu) were measured.
Results and Discussion
Based on the results, the simple effect of salinity stress, ascorbic acid and the combined effect of them on ion leakage and amounts of malondialdehyde were significant at the level of 1% probability. Salinity stress increased the amounts of ion leakage and malondialdehyde and application of 5 mM ascorbic acid reduced the amount of these traits to 41.01% and 46.58% compared to the control respectively. The effect of salinity stress, ascorbic acid and the combined effect of them on the concentration of proline and chlorophyll in the leaves of bell pepper were significant at the level of 1% probability. Salinity stress increased the amount of proline but decreased chlorophyll and leaf protein of pepper seedlings and application of 5 mM ascorbic acid increased them to 79.42% and 46.57% compare to control respectively. Under salinity stress the uptake of iron, zinc, copper and phosphorus decreased; using of 5 mM ascorbic acid increasing accumulation of these elements in leaves .On the other hand ascorbic asid could decrease the amounts of sodium accumulation in seedling,s leaves. The results showed that, salinity decreased growth indices (number of leaves, leaf surface, fresh weight of roots and plants) and ascorbic acid reduced the effect of salinity stress on growth parameters. Under salinity stress, 5 mM ascorbic acid treatment increased the leaf surface to 36.30% compared to salinity without ascorbic acid tretment. The effects of salinity stress and the combined effect of salinity stress and ascorbic acid on the amount of catalase and peroxidase enzymes were significant at the level of 1% probability. The effect of ascorbic acid was significant for catalase at 5% probability level and peroxidase at 1% probability level. Although salinity increased the amounts of the antioxidant catalase and peroxidase enzymes but ascorbic acid could increased the activity of them in saline condition.
Conclusion
It seems that application of ascorbic acid as an antioxidant could reduce the effects of salinity stress by increasing the activity of catalase and peroxidase enzymes, reducing sodium uptake and increasing the uptake of phosphorus, potassium, iron, zinc and copper. These could have positive effects on the growth parameters of bell pepper seedlings in salinity conditions. Generally, on based of obtained results, spraying 5 mM Ascorbic acid on bell pepper seedlings modified the resistance of them in salinity stress conditions.
Nasrin Farhadi; Saeideh Alizadeh Salteh
Abstract
Introduction: Allium hirtifolium commonly known as Persian shallot is an important wild medicinal plant from Alliaceae family. Persian shallot commonly known as mooseer in Iran is a perennial diploid plant that is native to Iran and grows as a wild plant throughout in the Zagross Mountains range, western ...
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Introduction: Allium hirtifolium commonly known as Persian shallot is an important wild medicinal plant from Alliaceae family. Persian shallot commonly known as mooseer in Iran is a perennial diploid plant that is native to Iran and grows as a wild plant throughout in the Zagross Mountains range, western and southwestern Iran. It is a bulbous herb and usually consists of a single main bulb or rarely two bulbs. Each bulb has a weight of about 8-15 times of a garlic clove. The bulbs of mooseer has been widely used as a traditional herb and spice plant, added to a variety of foods such as salads, pickles, yogurt and different sauces. Conventionally, Persian shallot propagates through bulbs and seeds but these two methods are not commercially efficient due to low growth rate of bulbs and deep dormancy, low viability and germination rate of seeds. In addition, the natural habitat of this plant is under increasing pressure as a result of excessive incorrect harvest that caused to damage the plant density in Iran rangelands. So, improving the efficiency of A. hirtifolium propagation is necessary. A number of positive effects on the growth and productivity of some plants through cytokinin application have been registered by earlier research. The current study aimed to evaluate the effects of pretreatment and foliar application of forchlorfenuron as a safe cytokinin on improving the bulb production, phytochemical compounds and antioxidant attributes of Persian shallot.
Materials and Methods: This experiment was done at research green house of Tabriz University in 2015-2016. For pretreated of Persian shallot bulbs, they were soaked in 0, 50 and 10 mg l-1 forchlorfenuron solutions for 24 h. Then they were cultured in pots contained perlite and vermicompost with 3:1 ratio. Foliar application was applied 2, 4 and 6 weeks after culture with 0, 50, 100 and 150 mg l-1 concentrations of forchlorfenuron. At the end of growth season the number of leaves, number of bublets, fresh and dry weight of bulblet were recorded. The phytochemical compound (protein, phenol and allicin), antioxidant enzymes (catalase, peroxidase, ascorbate peroxidases and superoxide dismutase) and antioxidant activity of bulbs were assayed with spectrophotometry methods.
Results and Discussion: Foliar applications of plant growth regulators such as cytokinins in agriculture crops are reported to be useful in controlling multiple physiological processes, including flower initiation, shoot elongation, bulb production, fruit set and as well as affected the quality characters of products. In this study despite the bulblets number that did not influence by treatments, pretreatment and foliar application of forchlorfenuron significantly increased the leaves number, fresh and dry weight of bulbs in comparison with control plants. The highest leaves number (4.49 per plant) was obtained from pretreatments. The highest fresh weight (91.77 g) was recorded at 5 and 10 mg l-1 pretreatment and 100 mg l-1 (91.63 g) foliar application. The interaction effect of treatments on dry weight was significant and the highest dry weight (19.75 g) was recorded at 10 mg l-1 pretreatment with 100 and 150 mg l-1 foliar application. Allicin content did not show significant variation between treatments and in average was 0.859 mg g-1 FW. Total phenol content significantly influenced by treatments and the highest phenol content (1.585 mg GAE g-1 FW) was recorded at 5 mg l-1 pretreatment with 100 mg l-1 foliar application. The antioxidant enzymes included catalase, peroxidase and ascorbate peroxidase that showed significant increasing under forchlorfenuron treatments. Due to significant effects of forchlorfenuron on antioxidant compounds and enzymes of Persian shallot bulbs, the assay of antioxidant activity also showed a significant increasing in treated bulbs. The maximum percent of antioxidant activity (74.522) was obtained from 100 mg l-1 foliar application. Exogenous application of cytokinins plays an effective role by protecting the fluidity and integrity of plant cell membranes. They properly mediate enzymatic (SOD, APX, and CAT) and non-enzymatic machinery with the result of preventing cell membrane damage by oxidative stress.
Conclusions: Considerable improvement in biochemical and antioxidant attributes of Persian shallot was recorded with pretreatment and foliar application of forchlorfenuron. The present data support the potential uses of the forchlorfenuron for improving the production of weighty bulbs with the high antioxidants attributes in Allium hirtifolium. Pretreated and foliar application at 5 mg l-1 and 100 mg l-1 concentrations of forchlorfenuron, respectively showed the best results and is recommendable for A. hirtifolim production.
