Malath of Abdul Muttalib Hamed

Department of General Sciences

College of Basic Education / Haditha- University of Anbar

Agricultural Sciences - Plant Physiology

Water and salts take two main ways to move from the soil to the inside of the plant

First: the apoplectic route: It is the non-living route, by diffusion through the cell walls by imbibition, as well as through the small spaces between cells. This is the fastest way

The second: through the cells simplistic route: It is the living route, where water passes inside the cells and moves between them, through plasmodesmata, and it is slower than the previous route.

For absorption to take place, water, as well as dissolved salts, must pass through the cells of the root layers, which are in order

1-Root hairs: They are cells that extend from the outer epidermis to the inside of the soil that work to absorb water and mineral salts from the outer periphery

2-Epidermis: The outer cell layer is a group of single-layered cells that cover leaves, flowers, roots, and stems. It forms a boundary between the plant and the external environment. The epidermis has several functions. It protects against water loss, regulates gas exchange, and absorbs (especially in the roots) water and mineral nutrients.

3-Cortex: A wide layer of cells, which is a wide area of ??branchimic cells with thin walls and wide interstitial spaces. This area performs three functions: aeration of the root tissues, the delivery of water and salts to the xylem, and the storage of nutrients.

4-Endodermis: The inner layer of the cortex, which is a single row of cells thickened with suberin, to form what is known as the Casparian strip that is impermeable to water.

Casper's strand is a strand found in vascular plants, chemically composed of suberin. Casper's strand is named after the scientist discovered by Robert Casperi. It is located specifically in the inner epidermis area responsible for regulating the movement of water and salts into the vascular cylinder.

When the salts transported through the cells reach the inner epidermis, they continue their way through plasmonic bonds to the xylem vessels of the vascular bundle, where the water and salts are lifted to the stem and plant parts.

As for the salts that reach the inner epidermis through the passage outside the cells, they face a closed passage, which is (Casper's tape), which prevents their passage to the vascular bundle and changes their way to through the cells.

This stage is very important for the plant, as forcing water and salts to pass through the cells gives the plant the ability to control the quality and quantity of salts entering it, which acts as an electoral pathway for these materials, as well as excluding pathogens that may mix with water. It also works to prevent the return of water and salts from the vascular cylinder to the cortex.