Effect of Application of Salicylic Acid, Thiofer Natural Antifreeze and Soybean Oil on the Phenological Characteristics of Sweet Cherry under Cold Stress Conditions

Sweet cherry is very popular due to its early maturity, high transportability, attractive appearance and good taste of the fruit. The high content of sugars, ascorbic acid, vitamins, carbohydrates and organic acids in the fruit increases the interest in this product both in industrial gardening and home gardening. The damage caused by cold in the critical stages of plant growth is one of the important factors in reducing the yield of plants all over the world. Salicylic acid is one of the phenolic compounds that is produced by the roots, and by reducing the activities of reactive oxygen species, it increases the resistance of plants to various environmental stresses (Mahmoudi et al., 2019). Salicylic acid not only plays an important role in determining the quality, color and taste of grape fruit (Hajivand & Rahmati, 2018), but also in the plant's response to environmental stresses such as drought (Miura & Tad, 2014), cold (Kosova et al., 2014) salinity (Noreen et al., 2014) and heavy metal stress (Mahmoudi et al., 2019) are effective. Commercial compounds such as plant growth regulators, including antiperspirant and antifreeze substances, are also used to increase cold resistance or delay the breaking of bud stagnation in horticultural crops (Mahmoudzade et al., 2012). Another way to reduce spring cold damage is to use Natural Plant Antifreeze. These materials either act as a mechanical barrier to prevent the formation of ice crystals on sensitive plant tissues or activate cold resistance systems in the plant (Hajivand & Rahmati, 2018).

In order to investigate the effect of the application of growth regulators, on the cold resistance of the cherry tree variety "Siah Daneh Mashhad", a factorial experiment was conducted in the form of a randomized complete block design with 3 factors of growth regulators each at 3 levels. (salicylic acid: zero, 1.5 and 3 mM), (natural antifreeze Thiofer: zero, 2.5 and 5 per 1000) and (soybean oil: zero, 2.5 and 5 per 1000)} and in 4 repetitions It was performed in a commercial garden located in Serain city in 2018 and 2019.

The results of the variance analysis revealed that the three-way interactions of the experimental factors significantly influenced the percentage of healthy pistils and the duration of flowering cessation at the 1% probability level. The highest percentage of healthy pistils, reaching 69.25%, was observed in the treatment involving foliar spray application of salicylic acid (1.5 mM) combined with soybean oil (5/1000) and foliar spraying of Thiofer natural antifreeze (5/1000). Furthermore, the combined effect of salicylic acid and natural antifreeze was found to be the most effective in delaying the onset of flower opening. The highest amount of ion leakage percentage was observed in the control treatment and the lowest amount was observed in the 3 mM salicylic acid foliar treatment along with soybean oil (5 per 1000) Thiofer. According to the data variance analysis table (Table 1), the ion leakage index was affected by the simple effect of salicylic acid, soybean oil and antifreeze and the interaction effect of salicylic acid oil × salt, salicylic acid × soybean oil, and soybean oil × antifreeze. The activity of malondialdehyde was affected by the simple effect of salicylic acid and soybean oil and the interaction effect of salicylic acid × year and year × soybean oil (Table 1). The total phenolic content was also affected by the simple effect of salicylic acid and soybean oil (Table 1). According to Figure 11, increasing the concentration of salicylic acid increased the content of total phenol, so that the highest content of total phenol (53.22%) was obtained in the treatment of 3 mM salicylic acid, while there was no significant difference in the treatment of 1.5 mM salicylic acid. . To adapt to the cold, phenolic compounds accumulate in plants, which are related to the antioxidant capacity of the plant (Mozafari &Yazdan Panah, 2018). A decrease in temperature increases the accumulation of phenolic compounds in the plant and can act as a mechanism to adapt and overcome the oxidative stress caused by low temperature (Balasundram et al., 2007). Balasundram and colleagues (Balasundram et al., 2007) noted that grape plants exhibit an accumulation of phenolic compounds and proteins while maintaining membrane stability at low temperatures. This accumulation leads to reduced production of malondialdehyde, enhancing the plant's adaptability and tolerance to cold temperatures, thereby reducing the risk of freezing. Similar observations of increased phenolic compound levels during cold adaptation have been reported in pistachios (Palonen, 1999) and apples (Huang & Wang, 1982). Chen and Tian (Chan & Tian, 2006) reported an increase in phenolic compound accumulation following enhanced activity of phenylalanine ammonia-lyase enzymes in grapes treated with salicylic acid. From their findings, they concluded that salicylic acid plays a pivotal role in the biosynthesis of phenolic compounds and the activation of plant defense genes.

According to the observations of this research, it can be concluded that the use of salicylic acid along with soybean oil and natural antifreeze of Thiofer is a suitable solution in order to delay the opening time of flowers and also to increase the indicators of cherry cold resistance against The tension is cold.