endodermisbl

The endodermis is the innermost layer of the cortex in vascular plants. It is a single layer of cells that surround the central vascular cylinder, which contains the xylem and phloem. The endodermis plays a crucial role in regulating the movement of water and dissolved substances into the vascular cylinder.

A key feature of the endodermis is the presence of the Casparian strip, a band of waterproof material within the cell walls. This strip prevents apoplastic movement, meaning water and solutes cannot simply flow through the cell walls between endodermal cells. Instead, they are forced to cross the plasma membrane of an endodermal cell and enter the symplast, the continuous network of cytoplasm connected by plasmodesmata. This selective barrier ensures that the plant can control which substances enter the vascular system.

The endodermis is essential for nutrient uptake and transport. By controlling the passage of ions and water, it helps to prevent the entry of potentially toxic substances from the soil. It also contributes to maintaining the proper ion balance within the plant. In some plants, the endodermis may also store starch. The development and structure of the endodermis can vary depending on the plant species and its environment.