Uptake of Water and Ions Flashcards
What two ways can water be absorbed by root hairs?
By root hairs and other epidermal cells
Water can be absorbed passively into the cell wall or through osmosis into the cytoplasm.
What is the apoplast pathway?
Water movement through the cell wall by diffusion
This pathway allows water to move from cell to cell passively and is the fastest route of transport across the cortex.
What role does the Casparian strip play in water transport?
Prevents continuation of apoplast route
The Casparian strip is a water-proof layer made of suberin that forces water into the symplast route.
What is the symplast route?
Movement of water through the cytoplasm of root hair cells by osmosis
Water moves passively through the cytoplasm and through cells via plasmodesmata.
Fill in the blank: Water can move between the cytoplasm and the large central vacuole through the _______.
vacuolar route
This route is the slowest due to resistance when water crosses membranes.
True or False: The apoplast pathway has high resistance due to membranes.
False
The apoplast pathway has less resistance since there are no membranes to cross.
What substance is the Casparian strip made of?
Suberin
Suberin is a waxy substance that creates a barrier to the apoplast route.
What is the primary function of the cellulose cell wall in the apoplast pathway?
Acts as a sponge for water movement
The cellulose wall allows water to move passively by cohesion.
What is the fastest route of transport across the cortex?
Apoplast route
This route is the fastest due to the permeability of the cellulose cell wall.
What is the process by which water enters epidermal cells?
Osmosis
Water enters the epidermal cells by osmosis through the symplast route.
What type of transport is primarily involved in mineral ion absorption at root hairs?
Active transport
Active transport of mineral ions occurs at root hairs.
What are cations and give two examples?
Positively charged ions
Examples include Ca²⁺ and K⁺.
How do cations enter plant cells?
Ion exchange using a proton pump
Cations such as Ca²⁺ and K⁺ enter through ion exchange at the endodermis.
What are anions and give an example?
Negatively charged ions
An example is NO₃⁻.
How do anions enter plant cells?
Co-transport with H⁺
Anions such as NO₃⁻ enter by co-transport with H⁺ ions.
What is the role of the Casparian strip in ion absorption?
Stops movement via the apoplast route
The presence of the Casparian strip forces all ions to enter the cytoplasm.
What results from the consecutive uptake of minerals into plant cells?
Higher ion concentration in plants than in soil
This leads to a concentration gradient favoring water absorption.
What happens to the water potential when ions are absorbed?
It lowers
This decrease in water potential increases the amount of water absorbed.
Fill in the blank: Ions can move into the _______ along the symplast route.
stele
The movement into the stele increases ion concentration and lowers water potential.
True or False: Most ions enter plant cells through the apoplast route.
False
Most ions enter plant cells through the symplast route.
