Apoplazmában

Apoplazmában refers to the apoplast, which is the continuous system of non-living porous cell walls, intercellular spaces, and xylem vessels through which water and dissolved substances move in plants. It is one area of the plant where water transport occurs, contrasting with the symplast, which is the living cellular pathway through the cytoplasm. Water and mineral ions entering the root from the soil primarily move across the cortex via the apoplast.

The apoplast plays a crucial role in water uptake by roots. As water moves into the root, it can bypass the cell membranes and travel through the interconnected spaces between cells and within the cell walls themselves. This pathway is generally considered less selective than the symplastic pathway, as it does not require crossing cell membranes for the bulk of the movement. However, the apoplastic pathway is eventually blocked by the Casparian strip in the endodermis. This band of suberin in the cell walls prevents water from moving apoplastically into the vascular cylinder, forcing it to enter the symplast by crossing a plasma membrane. This ensures that the plant can regulate the uptake of minerals and prevents the uncontrolled passage of substances into the xylem.

The apoplast is not merely a passive conduit; it can also be a site of metabolic activity and storage. Enzymes and other molecules can be found within the apoplast, and it can serve as a reservoir for certain substances. The composition and properties of the apoplast can be influenced by various factors, including environmental conditions and developmental stage. Understanding the apoplast is therefore essential for comprehending nutrient and water transport in plants, as well as their interactions with the environment.