chapter 7: water movement

shoots

Where does most of the water absorbed by the roots get lost?

large surface area

increase the H2O loss

transpiration

more than 90% of the water entering a plant passes into leaf air spaces and then evaporates through the stomata into the atmosphere

water potential

the potential energy of a volume of water, expressed as a pressure

less

Is high water potential more or less negative?

more

Is low water potential more or less negative?

high to low

How does water move?

negative

Is water potential always positive or negative?

cohesive

water molecules stick to each other

adhesive

water sticks to other things

tracheids

tube-shaped cells that carry water and minerals up from the roots

vessel elements

Structures that, along with tracheids, make up xylem

vessel elements

A short, wide, water conducting cell found in the xylem of most angiosperms and a few nonflowering vascular plants

photosynthesis

requires open stomata and the intake of CO2

stomata

open during the day and closed at night

high humidity

Reduces transpiration

abscisic acid

causes stomatal closure

high temperatures and high CO2

What causes stomata to close?

potassium

increased ______________ inside the guard cell draws water in from the surrounding epidermal cells by osmosis

cuticle

retains H2O, thicker the better

trichomes

reflect light and keep leaf temperature down

sunken stomata

increases the boundary layer and decreases transpiration

leaf abscission

decrease transpiration by dropping leaves when H2O and temperature becomes limiting