BI 431 Plant Phys Ch.2

Northern Michigan University, BI 431 Dr. Maki

Transpiration

Evaporation of water from surface of leaves and stems

Specific heat

Amount of energy that can be absorbed for a given temp rise/water has a high S.H.

Heat of vaporization

Energy required to separate molecules from liquid to gas

Cohesion

Mutual attraction between water molecules

Adhesion

Attraction of water to a solid phase, such as a cell wall

Tension

Negative pressure

Tensile strength

Maximum tension that an uninterrupted column of water can handle without breaking

Hydrostatic pressure

Pressure generated by compression of water into a confined space (pascals)

Cavitation

Collapse of tension in a column of water resulting from the formation of tiny gas bubbles

Fick’s first law

The rate of diffusion is proportional to the concentration gradient/fast over short distances but slow over long distances

Bulk flow

Sensitive to the radius of xylem/relies on a pressure gradient to describe water flow

Chemical potential of water

The free energy of water/influenced by concentration and pressure/lessens with solutes

Water potential

Free energy per unit volume of water/measure of pressure (pascal)

Water potential gradient

Water moves from less negative to more negative water potential/pressure in plants are usually negative

Solute potential

The effect of dissolved solutes on water potential/solutes reduce free energy of water

Pressure potential

Effect of hydrostatic pressure on free energy of water

Hydraulic conductivity

How readily water can move across a membrane (m^3 water/m^2 membrane/s^-1 time/ MPa^-1 driving force)

Aquaporins

Membrane proteins that form water channels across a membrane/allows for water movement

Halophytes

Plants native to saline soils that have adapted to extract water without up taking salts