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What is the difference between simple permanent tissues and complex permanent tissues?

Permanent tissues are tissues that contain non-dividing cells. As a result, they stay around for a long time and are relatively static, as opposed to meristematic tissues that contain dividing cells and are therefore usually in a state of growth and expansion.

Simple permanent tissues are comprised of a single type of cell, usually in many layers; there are four major types, parenchyma (functional cells), collenchyma (flexible structure), sclerenchyma (rigid structure), and epidermis (outer skin).

Complex permanent tissues are comprised of two or more types of cell in combination, usually with a complex structure that makes the cells interact with one another (otherwise they would probably be considered different tissues). Xylem and phloem are the two major types of complex permanent tissues.

There are also special or secretory tissues, which form glands that excrete different substances. These three categories comprise all the different types of permanent plant tissues.

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