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Presentation Type
Presentation
Start Date
12-4-2023 1:30 PM
End Date
12-4-2023 2:30 PM
Description
Video of Josh Turner's presentation at REDay 2023 for his work on the Cleared Leaf Epidermis (CLE) Technique. This work was supervised by Dr. Qin Leng. The effectiveness of the technique was demonstrated using Metasequoia leaf samples as examples and explain its applications to (paleo)botanical and climate change research.
The Cleared Leaf Epidermis (CLE) Technique: An Improved Method for Botanical and Paleobotanical Studies
Video of Josh Turner's presentation at REDay 2023 for his work on the Cleared Leaf Epidermis (CLE) Technique. This work was supervised by Dr. Qin Leng. The effectiveness of the technique was demonstrated using Metasequoia leaf samples as examples and explain its applications to (paleo)botanical and climate change research.
Comments
A leaf epidermis is comprised of cells with a thickened cell wall and also covered with a cuticular membrane. Cuticles are composed mainly of a very stable chemical known as cutin, which is why they are most commonly found in the fossil record. To prepare a clean cuticle (CC) is the most conventional technique for botany and paleobotany to obtain leaf epidermal characteristics for the purposes of identification, classification, physiological studies, and ecological reconstruction, etc. (Dilcher 1974). However, as a cuticle only reveals the surface structure of the epidermis, its usage is constrained to two-dimensional (2D) applications. The cleared leaf (CL) technique involving the use of chemicals to de-color the whole leaf and turn it transparent (cleared) was thus invented to observe three-dimensional (3D) structures of the leaf. However, as a leaf has many layers of cells between the two epidermises, this method is inadequate for the recently established ancient CO2 reconstruction models, which require the understanding and precise measurements of the epidermal structures because the CL samples under the microscope is obscured by layers of cells. To circumvent these issues, we developed a cleared leaf epidermis (CLE) technique in our Laboratory for Terrestrial Environments at Bryant University based upon the CL technique (Liang et al. 2022a and 2022b). As leaf epidermal cells are more persistent than mesophyll cells due to their thickened cell wall and cuticle, we can carefully choose chemicals and their appropriate concentration to treat the leaf, not only to de-color the leaf but also to partly decay the mesophyll cells. Then we can take one step further to “open” the leaf like a book to be read under microscope. With careful treatment, most mesophyll tissue can be removed chemically and mechanically, leaving the upper and lower epidermises almost completely prepared with all 3D cellular structures intact. The resulting microscopic slides thus can show complete micromorphological and anatomical characteristics of stomatal complexes and epidermal cells, rendering information for various botanical and paleobotanical studies. For example, cuticular types in both modern and fossil samples can be clearly identified and stomatal parameters necessary for leaf-gas exchange models (such as the Franks Model) to estimate atmospheric concentrations of CO2 can all be accurately measured. In addition, this technique uses more economical chemicals and allows for the technician to obtain larger pieces of leaf samples for necessary statistical analysis. In the past couple of years, our lab has used this technique to reconstruct early and middle Miocene atmospheric CO2 from fossils collected from China and the US. In this presentation, we demonstrate the effectiveness of the technique using Metasequoia leaf samples as examples and explain its applications to (paleo)botanical and climate change research.