1108 F24 4.04 Plant Transport in Xylem

Water Potential (Ψ)

Measurement combining solute concentration and pressure.

Solute Potential (Ψs)

Osmotic potential; inversely proportional to solute concentration.

Pressure Potential (Ψp)

Physical pressure exerted on a solution.

Osmosis

Diffusion of water across a membrane.

Transpiration

Loss of water vapor from plant leaves.

Apoplast Pathway

Water travels through cell walls and extracellular space.

Symplast Pathway

Water moves through the cytoplasmic continuum.

Transmembrane Pathway

Water moves out of one cell into another.

Root Pressure

Positive pressure pushing water up from roots.

Capillary Action

Water movement due to surface tension and adhesion.

Cohesion-Tension Theory

Water pulled up by evaporation and cohesion.

Guttation

Exudation of water droplets from plant leaves.

Xylem

Vascular tissue responsible for water transport.

Turgor Pressure

Pressure from fluid in plant cells maintaining rigidity.

Flaccid Cell

Cell lacking turgor pressure, wilting appearance.

Plasmolyzed Cell

Cell that has lost water and shrunk.

Xylem Vessels

Conducting tubes for water in plants.

Environmental Effects

Soil conditions affecting water potential gradients.

Hydraulic Pressure

Pressure exerted by fluids in a closed system.

Stomata

Pores on leaves for gas and water exchange.

Xerophytes

Plants adapted to survive in dry environments.

Lignin

Structural polymer providing strength to xylem.

MegaPascals (MPa)

Unit of pressure used to measure water potential.

Water Transport Challenge

Mechanisms enabling water movement in tall plants.

Water Potential Gradient

Difference in water potential driving water movement.

Evaporation

Process of water vapor loss from plant surfaces.

Surface Tension

Cohesive force at the air-water interface.

Adhesion

Attraction between water and other substances.

Solute Concentration

Amount of solute in a given volume of solution.