An at-home Plant Physiology laboratory applied to dark-induced leaf senescence by college students and science teachers

Abstract

Dark-induced leaf senescence is an extreme example of leaf senescence induced by light deprivation. Prolonged dark treatments of individual leaves result in chlorophyll degradation, macromolecule catabolism, and reduction of photosynthesis. In this work, we described an at-home "Dark-induced Leaf Senescence" laboratory exercise for a junior-level undergraduate Plant Physiology course. To perform the dark-induced senescence assay on attached leaves, students may cover individual leaves of an outdoor plant with aluminum foils and record the leaf morphology with controlled vocabularies for [~]9 days. To perform senescence assays on detached leaves, the students may incubate detached leaves in various aqueous solutions (e.g., tap water, sucrose solution, alkali solution, and acid solution) either in the dark or under natural light, and then record the leaf morphology with controlled vocabularies for [~]9 days. This laboratory exercise provides hands-on opportunities for students to understand the relationships among sunlight, chlorophyll, and photosynthesis, in the comfort of students own homes. Specifically, it helps students to comprehend intrinsic and dark-induced leaf senescence mechanisms, the effects of sugars on leaf senescence, and the importance of optimal pH to plant health. This laboratory exercise can be adapted to support inquiry-based learning or be implemented in a middle or high school classroom.