Influence of iron leaf nutrition on chlorophyll content and some antioxidant enzyme activities of strawberry fruit cv. Camarosa

Iron is considered as a micro-element with essential roles in plant metabolism and also, is a cofactor in the function of antioxidant enzymes. The strawberry is one of the favorite fruits throughout the world and maybe classified as a functional food as it is a rich source of phytochemicals and vitamins. Therefore, nutrition of foliar minerals is of particular importance for the rapid supply of plant nutrients. The aim of this study was to the determination of optimum concentration and evaluation of the pre-harvest application of iron on some antioxidant enzyme activities and qualitative characteristics of strawberry fruit during developmental stages.

The experiment was factorial based on a randomized complete block design with three replications. This experiment was carried out at the University of Zanjan in the spring and summer of 2018. Firstly, in a pretest, the effect of different amounts of iron was investigated (0-200-400-600-800-1000-1200-1400-1600-1800 and 2000 μmol/L) at 3, 6, 9 and 12 days after the foliar application in some of the characteristics. Then, the concentration of 1400 μmol/L was considered as the optimum concentration. Finally, data analysis was done using SPSSver 22, and means were compared by Duncan’s multiple range tests at 5% level of Probability.

Results showed that chlorophyll a, chlorophyll b, catalase, peroxides, and ascorbate peroxidase were significantly increased by iron treatment in comparison to the controls. Besides, strawberry fruits treated with iron in comparison to the controls exhibited lower, MDA, and H2O2 content. But it had no significant effect on SOD enzyme, pH, and soluble protein. In addition to the above results, the application of 1400 μmol/L iron accelerated fruit ripening for several days. The main reasons for the effect of the treatment can be related to the increase in iron content in the plant, the decrease in competition between vegetative and reproductive growth, as well as better photosynthetic efficiency. According to the results, the application of iron during the fruit growth stage increased the activity of most antioxidant enzymes and improved the quality of strawberry fruit. These results are in agreement with those obtained by Pestana et al. (2013) and Zaerei et al. (2016) of strawberry growth and crop yield improved by foliar application of iron chelate. The experiments demonstrated the beneficial effects of foliar Fe-EDTA application on some antioxidant enzyme activities and qualitative characteristics of strawberry fruit during developmental stages. Generally, for the production of strawberry greenhouses and its cultivation in hydroponic, according to the results of this study, a concentration of 1400 μmol/L can be suggested by the spraying method.