Topic 3 - Transpiration Flashcards
What does the xylem transport
Water and inorganic ions
What does the phloem transport
Organic molecules
What is transpiration
The process whereby water vapour is lost from plants
What is cuticular transpiration
When water is lost through the cuticle
What is stomatal transpiration
When water is lost through the stomata
What are internal factors that affect rate of transpiration
Increased surface area increases, due to more stomata being exposed to air
Greater density of stomata, less transpiration occurs
The thicker the cuticle, the less cuticular transpiration
What are external factors that affect rate of transpiration
High temperatures increase rate of transpiration
Increased air movement increases rate of transpiration
Brighter light increases rate of transpiration
Less water, less transpiration
What is the difference between the apoplast and Symplast pathways
Apoplast is where water moves along the cellulose fibrils in the cell wall
Symplast is when water diffuses from the cell cytoplasm to cell cytoplasm through plasmodesmatas
What are some structural adaptations of hydrophytes
Thick cuticle to increase waterproofing
Few stomata to reduce water loss
Sunken stomata reduces the diffusion gradient out of the leaf
Water storage cells for when the plant is in drought
Spines prevent grazing
Extensive root networks cause for greater uptake of water
What is the process of water uptake
Root hairs provide large surface area, high to low water potential
Either apoplast or Symplast pathways, apoplast is faster so more moves through it
Apoplast along cells walls
Water cannot pass through apoplast, so casparian strip means water travels via Symplast
What is the casparian strip
A barrier so that water can only travel via the Symplast pathway into xylem vessels
What is the process of movement of water through the stem
Water is pumped into the xylem in the root, causing root pressure
Water creeps along the walls of the xylem vessels by capillarity due to adhesive water
Water molecules attract more water molecules
Adhesion and cohesion are caused by the polarity of water molecules
Water column forced upwards by negative pressure in the lead
Water is drawn out of xylem vessels in the leaf
What are some structural adaptations of hydrophytes
Thick epidermis layer
Stomata on the upper epidermis to allow gas exchange without the leaf being flooded
Air spaces for easier diffusion
