Biochemical and Physiological Responses of Cucumis sativus L. to Application of Potential Bioinsecticides—Aqueous Carum carvi L. Seed Distillation By-Product Based Extracts

Abstract

The extensive application of synthetic insecticides and herbicides over the past 50 years has led to a number of problems, including negative effects on non-target organisms and the evolution of pesticide-resistant pests. As an alternative means of pest control, plant-based biopesticides have emerged. While developing a new bioinsecticide, allelopathy on both target pests and target crops must be evaluated. We evaluated volatile organic compounds (VOCs), total phenolic content (TPC), total sugars and antiradical activity (ARA), as well as 18 photosynthetic apparatus characterizing functional parameters as stress signaling response to aqueous caraway seed distillation by-product-based extracts. VOCs were detected by headspace gas chromatography mass spectrometry (HS-GC-MS). The caraway extract application decreased “green leaf volatile” C4, C5 and C6 alcohol content in the cucumber leaves. Total phenolic content (TPC), total sugars and antiradical activity (ARA) using high-throughput 96-well plate spectrophotometric methods were tested in dried leaves. No significant changes in these parameters were detected in cucumber leaves after the application of extracts. The caraway extract application did not cause changes in the functioning of the photosynthesis apparatus. Aqueous caraway seed distillation by-product-based extracts can be considered non-phytotoxic to cucumber plants; however, they modify the VOC emissions even ten days after treatment.