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The endodermis is the boundary between the cortex and the stele. In many seedless plants, such as ferns, the endodermis is a distinct layer of cells immediately outside the vascular cylinder (stele) in roots and shoots. In most seed plants, especially woody types, the endodermis is present in roots but not in stems.
The discovery of the Casparian strip dates back to the mid-19th century, and advances in the understanding of the endodermis of plant roots. [15] In 1865, the German botanist Robert Caspary first described the endodermis of the root of plants, found that its cell wall was thickened, and named it Schuchtzscheide.
The endodermis in the root is important in the development of root pressure. The endodermis is a single layer of cells between the cortex and the pericycle. These cells allow water movement until it reaches the Casparian strip, made of suberin, a waterproof substance. The Casparian strip prevents mineral nutrient ions from moving passively ...
In plants undergoing secondary growth, the pericycle contributes to the vascular cambium often diverging into a cork cambium. [citation needed] In angiosperms certain molecules within the endodermis and the surrounding vasculature are sent to the pericycle which promotes the growth of the root meristems. [citation needed]
The earliest vascular plants had stems with a central core of vascular tissue. [3] [4] This consisted of a cylindrical strand of xylem, surrounded by a region of phloem. Around the vascular tissue there might have been an endodermis that regulated the flow of water into and out of the vascular system. Such an arrangement is termed a protostele.
Roots are specialized for the uptake of water, nutrients (including ions for proper function). [12] Similar to the endodermis, the exodermis contains very compact cells and is surrounded by a Casparian band, two features which are used to restrict the flow of water to a symplastic fashion (through the cytoplasm) rather than apoplastic fashion which (through the cell wall) flow through passages ...
Early plants sucked water between the walls of their cells, then evolved the ability to control water loss (and CO 2 acquisition) through the use of stomata. Specialized water transport tissues soon evolved in the form of hydroids, tracheids, then secondary xylem, followed by an endodermis and ultimately vessels. [33]
Root hairs form an important surface as they are needed to absorb most of the water and nutrients needed for the plant. They are also directly involved in the formation of root nodules in legume plants.