How do plants protect themselves from insects? A practical laboratory exercise to illustrate the defence mechanisms of the plant through secondary metabolites

ABSTRACT

Despite the growing awareness of the importance of plant secondary metabolites in insect-plant interactions, undergraduate degree content in agronomy and biology generally does not provide a clear concept to students in relation to secondary metabolite induction of plant defences, implying that students do not obtain a good understanding of the secondary metabolism or its functions. To address this deficiency, we have designed a practical exercise where students determine the phytochemical induction of secondary metabolites in aromatic plants subjected to herbivory. This approach involves an experimental laboratory class in which students evaluate the phenolic compounds and main essential oil compound induction in peppermint damaged by an armyworm. By the end of this exercise, based on the results and findings, students will: have a better comprehension of plant defence responses to herbivores; be able to illustrate the consequences of insect herbivory in relation to plant secondary metabolites induction; acquire lab skills related to the use of a spectrophotometer; be able to understand and analyse a GC chromatogram report. Authentic research experiences in the classroom are considered valuable elements for promoting science at undergraduate level, as well as providing motivation for the student and linking research with teaching.

KEYWORDS:

• Herbivory
• insect-plant interaction
• secondary metabolites
• experimental laboratory class
• applied learning

Acknowledgments

The authors thank the teachers, assistants and technical personnel who made it possible to conduct these experimental laboratory classes at the National University of Rio Cuarto. The authors are grateful to Dr. Paul Hobson, native speaker, for editorial assistance.

Ethics statement

The study was undertaken in accordance with the British Educational Research Association’s Ethical Guidelines for Educational Research

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by grants from the Secretariat of Science and Technology of the National University of Río Cuarto (grant code PPI 2020-2022: C529-1; Secretaría de Ciencia y Técnica, Universidad Nacional de Río Cuarto