Introduction
Aging seed can be defined as loss of seed quality, viability and vigor. This process is irreversible over time and its intensity increases with increasing temperature and humidity. Aging seed is one of the major factors reducing quality and quantity in the agricultural sector, especially oilseeds. The use of antioxidants can reduce the damaging effects of aging. Ellagic acid is a natural plant antioxidant that can play a role in reducing the effects of stress on plants. This substance is a phenolic compound and among different antioxidants, due to its polyphenolic properties, it is one of the best scavengers for oxygen free radicals.
Materials and Methods
To investigate the effect of ellagic acid on improving the quality of plants obtained from normal and aged soybean seeds, an experiment was conducted in the research farm of Shahroud University of Technology during the two cropping years 2019 and 2020. In this study two sets of seeds including control seeds (un-aged) and aged seed were used and ellagic acid (50 mg. l^-1) was applied for control, seed pretreatment, foliar spray and seed pretreatment+foliar spray. Farm research was conducted a factorial experiment based on a randomized complete block design (RCBD) in three replications. Soybean seeds var. DPX were collected from Mazandaran agricultural research center. The water content of seeds was 12%. The seeds were those that harvested in the same year and kept in a controlled storage room at the temperature between 14 to 17 °C and relative humidity of 30 to 40% at the Agricultural Research and Training Center and Natural Resources of Mazandaran Province. To prepare aged seeds in the laboratory, the seeds were incubated at 41°C and 95% relative humidity for 72 hours. Seed pretreatment with a concentration of 50 mg.L^-1 ellagic acid was performed under ventilation condition for 6 hours. The seeds were then dried in the shade and used to continue testing and measuring traits compared to normal seeds. Foliar application was done early in the morning at the beginning of flowering (R1) and in favorable environmental conditions.
Results and Discussion
The results showed that aging reduced the mean daily seedling field emergence by 61.39% compared to normal seeds. The ratio of chlorophyll a to b, total chlorophyll, stomatal conductance and membrane stability index in the leaves of plants from aged seeds decreased by 9.9, 6.3, 7.0 and 28.9%, respectively, compared to the control. The amount of free amino acids and soluble sugars in the leaves of plants from aged seeds increased compared to normal seeds. Pretreatment of normal and aged seeds with ellagic acid increased the mean daily seedling field emergence by 23.1% and 19. 7%, respectively. The content of insoluble sugars were increased with application of both pretreatment and foliar spray of ellagic acid 32.0% respectively. The highest oil yield in both conditions was observed with application of both pretreatment and foliar spray of ellagic aicd. The yield seed increased with ellagic acid compared to the control 23.6%. Grain yield was higher than 23.2% in the plants that had received ellagic acid in a form foliar spray. In the end, the pretreatment+foliar spray of ellagic acid had the highest grain yield, which increased to control 55.5%.
Conclusion
However, in this study, the application of ellagic acid as a seed pretreatment and foliar spray had a positive effect under normal and aging conditions, but in the scope of the research, the combined application of ellagic acid as seed pretreatment and foliar spraying can be recommended to increase seed yield and seed oil yield in soybean. In general, ellagic acid can be introduced as a powerful antioxidant in aging conditions to reduce some of the destructive effects of the reactions involved in aging.