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Dr. Timothy J. Pegg

Assistant Professor
Bolin Hall
Bolin 218 D


Assistant Professor in the Department of Biology. Specializes in botany, confocal light microscopy, electron microscopy, sample preparation, and plant morphology.

Past and present work involves studying chemical and structural alterations to plant root cell wall ultra-structure in response to flooding stress. Focus area in cell wall pectin and hemicellulose biochemistry as revealed with through ultrastructural changes and fluorescence immunolabeling pattern variation.

Classes Instructed:

BIOL 1114, General Life I

BIOL 3213, Botany: Plant Life

BIOL 3534, Plant Systematics

BIOL 4463, Plant Anatomy

Institution Degree Graduation Date
Miami University (Oxford, Ohio) Doctor of Philosophy - Botany 2021
University of Oklahoma Master of Science - Botany 2016
Frostburg State University Bachelor of Science - Biology (1st degree), Chemistry (2nd degree) 2009
Employer Position Start Date End Date
Midwestern State University Assistant Professor 06/01/2022
Marietta College Visiting Assistant Professor 08/23/2021 05/31/2022
Miami University Graduate Teaching Assistant, Ph.D. Candidate 08/16/2016 08/20/2021
University of Oklahoma Graduate Teaching Assistant, M.S. 07/22/2013 07/29/2016
Allegany College of Maryland Adjunct Professor (Biology) 01/23/2012 07/26/2013

Algae to angiosperms: Autofluorescence for rapid visualization of plant anatomy among diverse taxa

Pegg TJ, Gladish DK, Baker RL. Algae to angiosperms: Autofluorescence for rapid visualization of plant anatomy among diverse taxa. Appl Plant Sci. 2021 Jul 2;9(6):e11437. doi: 10.1002/aps3.11437.


Premise: Fluorescence microscopy is an effective tool for viewing plant internal anatomy. However, using fluorescent antibodies or labels hinders throughput. We present a minimal protocol that takes advantage of inherent autofluorescence and aldehyde-induced fluorescence in plant cellular and subcellular structures to markedly increase throughput in cellular and ultrastructural visualization.

Methods and Results: Twelve species distributed across the plant phylogeny were each subjected to five fixative treatments: 1% paraformaldehyde and 2% glutaraldehyde, 2% paraformaldehyde, 2% glutaraldehyde, formalin-acid-alcohol (FAA), and 70% ethanol. Samples were prepared by embedding and mechanically sectioning or via whole mount. A confocal laser scanning system was used to collect micrographs. We evaluated and compared fixative influence on sample structural preservation and tissue autofluorescence.

Conclusions: Formaldehyde fixation of Viridiplantae taxa samples generates useful structural data while requiring no additional histological staining or clearing. In addition, a fluorescence-capable microscope is the only specialized equipment required for image acquisition. The minimal protocol developed in this experiment enables high-throughput sample processing by eliminating the need for multi-day preparations.

Keywords: Viridiplantae; aldehyde; anatomy; autofluorescence; cellular; fixation; methods; microscopy; subcellular; throughput.

Progression of Cell Wall Matrix Alterations during Aerenchyma Formation in Pisum sativum Root Cortical Cells

Pegg, T. J., Edelmann, R. R., Gladish, D. K. 2018. “Progression of Cell Wall Matrix Alterations during Aerenchyma Formation in Pisum sativum Root Cortical Cells” Proceedings of Microscopy & Microanalysis DOI:

Immunoprofiling of Cell Wall Carbohydrate Modifications during Flooding-Induced Aerenchyma Formation in Fabaceae Roots

Pegg, T. J., Edelmann, R. R., Gladish, D. K. 2020. “Immunoprofiling of Cell Wall Carbohydrate Modifications during Flooding-Induced Aerenchyma Formation in Fabaceae Roots” Frontiers in Plant Science DOI:


Understanding plant adaptation mechanisms to prolonged water immersion provides options for genetic modification of existing crops to create cultivars more tolerant of periodic flooding. An important advancement in understanding flooding adaptation would be to elucidate mechanisms, such as aerenchyma air-space formation induced by hypoxic conditions, consistent with prolonged immersion. Lysigenous aerenchyma formation occurs through programmed cell death (PCD), which may entail the chemical modification of polysaccharides in root tissue cell walls. We investigated if a relationship exists between modification of pectic polysaccharides through de-methyl esterification (DME) and the formation of root aerenchyma in select Fabaceae species. To test this hypothesis, we first characterized the progression of aerenchyma formation within the vascular stele of three different legumes—Pisum sativumCicer arietinum, and Phaseolus coccineus—through traditional light microscopy histological staining and scanning electron microscopy. We assessed alterations in stele morphology, cavity dimensions, and cell wall chemistry. Then we conducted an immunolabeling protocol to detect specific degrees of DME among species during a 48-hour flooding time series. Additionally, we performed an enzymatic pretreatment to remove select cell wall polymers prior to immunolabeling for DME pectins. We were able to determine that all species possessed similar aerenchyma formation mechanisms that begin with degradation of root vascular stele metaxylem cells. Immunolabeling results demonstrated DME occurs prior to aerenchyma formation and prepares vascular tissues for the beginning of cavity formation in flooded roots. Furthermore, enzymatic pretreatment demonstrated that removal of cellulose and select hemicellulosic carbohydrates unmasks additional antigen binding sites for DME pectin antibodies. These results suggest that additional carbohydrate modification may be required to permit DME and subsequent enzyme activity to form aerenchyma. By providing a greater understanding of cell wall pectin remodeling among legume species, we encourage further investigation into the mechanism of carbohydrate modifications during aerenchyma formation and possible avenues for flood-tolerance improvement of legume crops.