عنوان مقاله [English]
Introduction: Fruits and vegetables play a major role in providing vitamins and minerals that are essential in the metabolism. In addition to providing vitamins and minerals compounds, they are called secondary metabolites. Tomatoes are one of the most vegetables in diets of people around the world. Low temperature stress associated with the production of reactive oxygen species causing damage can occur before or after harvest, farm, transportation, storage and marketing. Today, a greater emphasis is placed on post-harvest storage of agricultural products to increase productivity and make better use of labor resources, worker, energy and money, rather than an increase in production. One of the most promising treatments is the use of salicylic acid for prevention of the frost damage of post-harvest fruits and vegetables with different mechanisms such as increased enzymatic and non-enzymatic antioxidant system activity. Salicylic acid is known as a signal molecule in the induction defense mechanisms in plants. SA is a well-known phenol that can prevent ACO activity that is the direct precursor of ethylene and decreases Reactive Oxygen Species (ROS) with increasing enzyme antioxidant activity. Salicylic acid is a natural phenolic compound known as a plant hormone having positive effect on storage life and quality of fruits. This study aimed to investigate the effects of pre- and post-harvest application of salicylic acid on antioxidant properties and quality of tomato and its effect was evaluated on prevention of chilling injury of cherry tomatoes during cold storage.
Material and Methods: This research was conducted in a greenhouse of Horticulture Department of University of Maragheh. Treatments were included before harvest at fruit set stage with the control (distilled water) and 0.75 mM salicylic acid spraying and after harvest, red ripened fruits were used for treatments control and immersion in 0.75 mM salicylic acid. Then all the treated fruits were transferred to 1 °C. Sampling of fruits was done weekly and continued five weeks. In the last week of the experiment, fruits were kept for three days at room temperature (24-25°C) to evaluate the effects of frost on the whole period. To determine the effect of salicylic acid on percentage of cherry tomatoes injury, analysis of variance for a completely randomized design with three replications was used. For other traits factorial experiment with completely randomized design was applied. The treatments included salicylic acid treatment and six periods of storage. Duncan test was used for comparison of means.
Results and discussions: The results showed that the effect of salicylic acid significantly reduced frost damage in cherry tomato fruits during the storage period (P≤0/01). Treated fruit with salicylic acid before harvest showed the lowest damage of chilling in comparison with controls. Titratable acidity is directly related to the concentration of organic acids present in the fruit which is an important parameter in maintaining the quality of fruits. Titratable acidity increased gradually in all treatments except control and it seems to be influenced by the postharvest SA. Cell membrane of injured tissue was exposed to transform from a crystal liquid phase to a solid gel together and thus membrane permeability and ion membrane leak were increased (Wang et al., 2006). Salicylic acid may be used in the pre-harvest cherry tomatoes had a large role in the stability of the membrane and prevention of chilling injury. Salicylic acid was used before conception and chilling injury (Wang et al., 2006). Salicylic acid may be used in the pre-harvest cherry tomatoes that had a large role in the stability of the membrane and prevention of chilling injury.. . Application of salicylic acid before harvest on cherry tomatoes was more effective in maintaining the quality of the fruit and preventing of chilling injury. Organic acids reduce the consumption of sugars that occur during breathing and are directly related to metabolic activities (Jalili Marandi, 1383; Rahemi, 1384). It seems that spraying with 0.75 mM salicylic acid before conception, had a greater impact on the accumulation of proline and resistance in the plants and so the fruit had the lowest percentage of frost and high levels of proline matches. The maximum amount of proline in fruits at low temperature was obtained by increasing the exposure time after fifth week.
Conclusion: The results of the percentage of chilling injury, proline, carbohydrate and indicators related to quality of tomato fruits cherry tomato showed that treatment with salicylic acid can be effective on chilling tolerance during storage. Compared with the control treatments before harvesting frost cherry tomato had the greatest influence on stability by increasing the number of applications of salicylic acid that also reduced the effectiveness of this treatment.