TRANSPIRATION Flashcards
TRANSPIRATION
1) movement of water in plants which was released in vapor form
2) energy dependent process (transformation of liquid to gas)
3) 97-99% of water taken up is lost in transpiration
IMPORTANCE OF TRANSPIRATION
1) keeps cell hydrated
2) maintains favorable turgor pressure for nutrient transport
3) cools plants
TYPES OF RESPIRATION
(BASED ON AVENUE OF EXIT OF VAPOR)
1) cuticular transpiration
2) lenticular transpiration
3) stomatal transpiration
CUTICULAR TRANSPIRATION
1) loss of water through cuticle
2) 5-10% water loss
LENTICULAR TRANSPIRATION
1) through pores in outer layer of woody plant stem
2) water loss are quite substantial
STOMATAL TRANSPIRATION
1) through stomata
2) 90% water loss
FACTORS AFFECTING DIFFUSION OF WATER FROM LEAF TO ATMOSPHERE
1) relative humidity
2) vapor pressure deficit
RELATIVE HUMIDITY
1) actual water vapor in air
2) water vapor pressure in leaf
3) 100% in leaves
4) 90%in atmosphere
VAPOR PRESSURE DEFICIT
1) vapor pressure at saturation
2) at 0 VPD, there is no net water movement
3) low RH = high VPD = high transpiration rate
MOVEMENT OF WATER FROM SOIL TO ROOT XYLEM
1) extracellular (apoplastic route)
2) intracellular
EXTRACELLULAR ROUTE OF WATER
1) water moves through non-living parts
=> capillary spaces of cell wall
=> intercellular spaces
INTRACELLULAR ROUTE OF WATER
1) symplastic
=> plasmodesmata
2) transmembrane (transcellular)
=> vacuolar membrane (tonoplast)
=> plasma membranes
MOVEMENT OF WATER FROM ROOT XYLEM TO LEAF XYLEM
transpiration-cohesion-adhesion theory
MOVEMENT OF WATER FROM LEAF XYLEM TO AIR
1) influenced by RH and VPD
2) towards lower water potential
PLANT FACTOR AFFECTING TRANSPIRATION
1) efficiency of evaporative surface
2) efficiency of water absorption
3) other surface/stomatal modifications
4) phytohormones
5) canopy structure
