Water Transport and Xylem Function

A set of flashcards covering key concepts related to water transport, xylem function, and stomatal regulation in plants.

Water potential (Yw)

The potential energy of water in a system, comprised of solute potential (Ys), pressure potential (Yp), and gravitational potential (Yg).

Solute potential (Ys)

The effect of solute concentration on water potential, calculated as Ys = -RT Cs, where Cs is solute concentration in moles/liter.

Pressure potential (Yp)

The hydrostatic pressure exerted by water in a plant cell; can be positive in phloem, negative in xylem under tension.

Turgor pressure

The pressure exerted by fluid in a cell that pushes the plasma membrane against the cell wall, essential for maintaining structure.

Transpiration

The process of water vapor loss from plant leaves through stomata, contributing to water movement from roots to atmosphere.

Cavitation

The formation of gas bubbles in xylem vessels due to negative pressure, which can disrupt water transport.

Guard cells

Specialized cells that control the opening and closing of stomata, regulating gas exchange and water loss in plants.

Apoplastic pathway

Water movement through the cell walls and extracellular spaces, bypassing the plasma membrane of cells.

Symplastic pathway

Water movement through the cytoplasm of cells connected by plasmodesmata, allowing for cellular communication.

Transmembrane pathway

Water movement across cell membranes via aquaporins, facilitating selective transport into and out of cells.

Permanent wilting point

The water potential at which plants cannot regain turgor pressure and start to undergo wilting.

Root pressure

Positive pressure in the xylem resulting from water uptake when transpiration rates are low, leading to guttation.

Xylem

Tissue responsible for the conduction of water and dissolved minerals from roots to leaves in vascular plants.

Stomatal resistance (rs)

The resistance to water vapor flow through the stomatal pores, affected by their aperture size and environmental conditions.

Callose

A polysaccharide that forms in the walls of plasmodesmata, regulating their permeability.

Surface tension (T)

The cohesive force at the surface of water that creates a negative pressure potential in the xylem.