Water Movement in Plants: Endodermis Functions

Study Notes

Water Transport in Plants

The majority of water is transported through the symplast pathway, where water molecules move from cell to cell through plasmodesmata.
The endodermis is the innermost layer of cells in the root cortex, surrounding the vascular cylinder, and acts as a checkpoint for selective passage of minerals into the vascular tissue.
The Casparian strip, composed of suberin, blocks water and solute molecules from crossing the endodermis through the apoplast pathway, controlling what enters the vascular tissue.
The symplast pathway requires repeated crossings of plasma membranes as substances exit one cell and enter the next.
The apoplast pathway is the continuum of cell walls and extracellular spaces.
The transmembrane route involves the transfer of substances from one route to another.

Types of Transport in Vascular Plants

There are three levels of transport: cellular, short-distance, and long-distance transport.
Cellular transport involves the transport of water and solutes from the environment into plant cells.
Short-distance transport involves the transport of substances from cell to cell at the tissue and organ level.
Long-distance transport occurs within the xylem and phloem at the whole plant level.

Absorption of Water by Plants

Water is absorbed by roots, primarily in the root hair zone.
Short-distance transport of water occurs across plasma membranes.

Water Potential

Water potential is a measure of the energy of water in a plant.

Stomatal Closure

Stomata close during the daytime due to environmental stresses such as drought, high temperature, and wind.
When the plant has a water deficiency, guard cells may lose turgor and close stomata.

Xylem Structure and Function

Xylem pipes reduce the risk of collapse and cavitation.
Factors that can interfere with water movement in plants include pressure from high levels of transpiration, air entering the xylem, and freezing.

Phloem Transport

Phloem transport involves the redistribution of photosynthesis products, other organic compounds, and some mineral nutrients.
Sources are exporting regions that produce photosynthate above and beyond their own needs, while sinks are non-photosynthetic organs or organs that do not produce enough photosynthate to meet their own needs.

Description

Explore the functions of the endodermis, the innermost layer of cells in the root cortex, in regulating the movement of water and minerals in plants. Learn about its role as a last checkpoint for selective passage of minerals and how it prevents solutes from leaking back into the soil solution.