A Descriptive Study of Protective Tissue Formation in Stems of Quercus buckleyi Nixon & Dorr (Fagaceae)
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The epidermis and periderm are two components of the protective tissues that cover plant stems and roots. The epidermis is the first protective layer of the plant, and is later replaced by the periderm, which is typically composed of three different tissues: phellogen, phellem, and phelloderm. The objective of my study was to observe and describe the developmental process of protective tissues in stems of Quercus buckleyi, commonly known as Texas Red Oak. Scanning Electron Microscopy (SEM) is used in this study to examine Q. buckleyi specimens. The epidermis is composed of a single layer of cells that divide anticlinally to compensate for increased diameter. The meristematic phellogen is initiated in the subepidermal layer. The phellogen undergoes both periclinal and anticlinal divisions to create new cells for the periderm. Phellem matures to the outside of the phellogen and is thick walled. It eventually causes the epidermis to slough off during later stages as the periderm replaces the epidermis. No phelloderm to the inside of the phellogen is apparent in the stems of Q. buckleyi.