Primary Cortex

Primary Cortex

 

the peripheral part of the stem and root of a plant, located away from the epidermis (in the stem) or the epiblem (in the root). The primary cortex surrounds the conducting cylinder. In stems it becomes differentiated from the tunica and the corpus; in roots it arises from the periblem. The primary cortex consists of living parenchymatous cells with intercellular spaces; active metabolism and the accumulation of various metabolites occur there. Cells of the primary cortex of the stem form layers of chlorenchyma and mechanical tissue known as collenchyma. Cells of the inner layer of primary cortex of the stem (endodermis) are rich in secondary starch. The primary root cortex, which is multilayered and wider than the cortex of the stem, is marked by intensive transport of water and mineral substances from the absorptive layer to the conducting cylinder. The root endodermis plays an important regulatory role in the process. In plants found in humid regions, large intercellular cavities, or aerenchymas, develop in the primary cortex of the root.

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