Leaf damage from insects may improve antioxidant levels in produce

Plants can respond to the environment by activating the secondary metabolites as part of a defense mechanism or as part of an adaptation process. Research scientists at Texas A&M have discovered that insects wounds on the leaves of fruit and vegetable crops may create stress responses and cause the plant to produce more antioxidants prior to harvest. The results of the research are published in Scientific Reports From Nature.

The researchers used strawberries as a crop model and applied various levels of wounding to the leaves—mimicking the attack of insects—a few days before harvesting. Immediately after harvest, the berries were evaluated for quality by measuring physicochemical parameters—weight, color, firmness, and soluble solids concentration. In addition, the researchers analyzed the total phenolic compounds and total vitamin C.

The researchers found that the average fruit weight, firmness, and color at harvest was the same after seven and 14 days of applied wounding. For soluble solids (soluble sugars and organic acids), they reported a 19.7% increase in the fruit from plants that were wounded with 100 perforations per plant two weeks before harvest. Additionally, the amount of total phenolics in fruits of all treated plants increased significantly, 12.8% and 10.7% over the control, when wounding occurred one and two weeks, respectively, before harvest.

They saw a significant increase in the level of specific phenylpropanoids and tannins derivatives in fruit from plants wounded with 100 perforations per plant two weeks before harvest compared with the control, including ellagic acid (+58%), epicatechin (+100%), gallic acid (+68%), quercetin (+190%), and rutin (+137%).

“The results support the idea that higher levels of phytochemicals reported in organic fruits and vegetables could be due to the wounding component of the biotic stress attributed to herbivore insects feeding on leaves, to which the plant is exposed,” concluded the researchers in the study. “As a technological application of the present results, the controlled mechanical wounding applied during preharvest in leaves could be used to increase phytochemicals in fruit. Further studies are recommended in other crops as well.”

Study