Transport of Water and Solutes in Plants

Flashcards about water and solute transport in plants.

Water Potential

A measure of the potential energy in water, expressed as the Greek letter Ѱ (psi) and measured in megapascals (MPa).

Factors Influencing Water Potential

Solute concentration, pressure, gravity, and matrix effects.

Water Movement

Water moves from an area of higher potential to lower potential.

Water Potential Gradient

Ψsoil > Ψroot > Ψstem > Ψleaf > Ψatmosphere

Solute Potential

Related to solute concentration; calculated using the van 't Hoff equation: Ψs= –Mi RT.

Solute Potential in Plant Cells

Solute potential is negative in plant cells and zero in distilled water.

Pressure Potential

The higher the pressure, the more potential energy in a system.

Positive and Negative Pressure Potential

Compress increases water potential, tension decreases water potential.

Gravity Potential

Always reduces water potential; pulling downward towards the soil. Plants cannot manipulate it.

Matric Potential

Always negative to 0; binding of water to a matrix removes potential energy. Typically ignored in well-watered systems.

Transpiration

The loss of water through evaporation at the leaf surface; main driver of water movement through xylem.

The Control of Transpiration

Drives transpiration rate, cuticle prevents some water loss, and stomata & guard cells regulate gas exchange & water loss.

Adaptations to Water Loss

Prevent water loss.

Photosynthates

The products of photosynthesis, typically in the form of simple sugars like sucrose.

Sources

Structures in the plant that produce photosynthates (leaves).

Translocation

Transporting photosynthates to the growing parts of the plant.

Sinks

Points for sugar delivery (roots, shoots, developing seeds).

Photosynthate Production and Transport

Photosynthates are produced in the mesophyll of leaves and transported AGAINST its concentration gradient to reach phloem sieve tube elements (STE).