Facts About the Cell Types for the Plant Kingdom

Each plant cell type functions differently within the plant.

Like animals, plants are composed of eukaryotic cells, though the cells of most plants are somewhat more complex. The cellular structure of plants consists of general and specialized cell types. These cell types work together in order to keep plants functioning and healthy. Plants feature different types of cells, each with a different function. The cell types collectively make up the various tissues of the plants.

Parenchyma

The parenchyma cells in plants lack a specialized function but still hold importance in a plant. Parenchyma cells comprise the majority of the contents of ground tissue, or tissue on the interior, and can also be found within vascular tissue. These cells are alive upon the maturity of a plant and feature thin, semi-flexible cell walls. Parenchyma cells conduct photosynthesis to produce food for the plant and act as storage cells for nutrients. The palisade parenchyma cells reside below the epidermis of a plant, while the spongy parenchyma, or spongy mesophyll, sits below the palisade parenchyma.

Collenchyma

Collenchyma cells provide support to a plant, such as the stringy bits of celery. Like the parenchyma cells, they live during the maturity of a plant and can be found within ground tissue. However, the collenchyma cells feature a thicker primary cell wall, or cell wall which develops as the cell grows. In prepared slides, where parenchyma cells stain green, collenchyma cells stain red. Collenchyma cells clump together in bundles beneath the epidermis of a plant.

Sclerenchyma

Similarly to collenchyma cells, sclerenchyma cells give plants support, stain red on prepared slides and can be found within ground tissue. However, most of these cells die by the time a plant reaches maturity. They have a thick secondary cell wall, or a cell wall which develops post-maturity of the cell. Two types of sclerenchyma exist: fibers and schlerids. Fibers like the fibers of hemp feature longer, thinner cells. Schlerids have shorter, irregularly-shaped cells, such as nut shells, seed shells and the harder parts of pears.

Xylem

Xylem cells make up part of the vascular tissue, or tissue which acts similarly to the veins of a plant. Xylem carries water and minerals from a plant's environment up from the roots to the leaves. The secondary cell walls of xylem are thicker and often times uneven to allow for stretching. These cells are dead once the plant reaches maturity. The first type of xylem, tracheids, exist in all vascular plants as long and thin cells that are connected by pits. Vessels, the second type of xylem, only exist in angiosperms and are shorter, wider cells.

Phloem

The counterpart to xylem, phloem occurs in vascular tissue of plants. It carries nutrients from the leaves to the roots of a plant. Unlike xylem, phloem cells are alive. Sieve-tube cells transport sucrose to the other parts of a plant and lack a nucleus. Companion cells have a nucleus and are thought to control the function of sieve-tube cells. Of the two vascular cell types, phloem cells reside closest to the surface of the plant, while xylem can be found beneath phloem.

References

• State University of New York: The Biology Web: Plant Structure; Michael J. Gregory, PhD.; 2006
• University of Illinois at Chicago: Plant Structure and Function
• Estrella Mountain Community College: Plant Structure; M.J. Farabee; 2007