Plant cell the major classes of cells and tissues of roots, stems, leaves, flowers, and reproductive structures, each of which may be composed of several cell types. Parenchyma cells are living cells that have functions ranging from storage and support to photosynthesis (mesophyll cells) and phloem loading (transfer cells). Apart from the xylem and phloem in their vascular bundles, leaves are composed mainly of parenchyma cells. Some parenchyma cells, as in the epidermis, are specialized for light penetration and focusing or regulation of gas exchange, but others are among the least specialized cells in plant tissue, and may remain totipotent, capable of
Abscission causes leaves in the fall to change colors. Carotenoids in the leaves are slower to degrade than chlorophyll, so autumn leaves appear yellow and orange. Cells under the abscission zone divide and form a layer of cork cells. Situated on both sides of the abscission zone are layers of parenchyma cells, which produce and inject suberin and lignin under the abscission zone into the new layer of cork cells. Suberin and lignin create a durable and waterproof layer for the plant once the organ is detached. This step can occur in a variety of ways depending on the species but