
Controlled by guard cells

Flaccid
Little water
 Limp


Turgid
Fill with water
 Bend


http://academic.kellogg.edu/herbrandsonc/bio111/animat
ions/0021.swf

Triggered by blue light


Activates proton pump



Yellow pigments located in membrane (?)
H+ out, creates electrochemical gradient
K+ diffuses in through ion channels,
Cl- follows
K+, Cl- accumulate in vacuoles, water
moves in




K+ concentration in guard cells decrease
during day
Sucrose increases, maintains osmotic pressure
As sucrose concentration decreases, water
leaves
Pores close

Blue Light

Low CO2 concentration

Water stress

Hormones

Abscisic acid

Transpiration
99% of water plants take in is lost by evaporation
 Open stomata


Rate of Transpiration affected by:
Humidity
 Temperature
 Wind


Guttation

Liquid water forced out when transpiration negligible

Allows water to move from roots to leaves

Shedding of leaves


Conifers lose needles yearround
Deciduous trees




Survive low temp of winter
Water uptake inhibited
Prevents continuous water
loss by transpiration
Controlled by hormones:
Ethylene





Essential organic compounds & minerals move
to other parts of plant for storage
Chlorophyll breaks down, other pigments seen
Cork forms protective layer on stem side of
abscission zone of petiole
Enzymes dissolve middle lamella in abscission
zone of petiole
Leaf detaches in breeze