9.2 Water transport in multicellular plants Flashcards
What are the 2 reasons water is important for plants, in the context of turgor pressure?
- Turgor pressure resulting from osmosis provides a hydrostatic skeleton to support stems and leaves
- Turgor drives cell expansion - turgor is the force enabling plant roots to push through tarmac and concrete
What are the other 3 reasons (not in relation to turgor) for why water is important in plants?
- Loss of water through evaporation helps keep plants cool
- Mineral ions and products of photosynthesis are transported in aqueous solutions
- Water is a raw material for photosynthesis
What is the exchange surface which plants absorb water through?
Root hair cells
What is a root hair?
Long, thin extension from a root hair cell.
The root hair is a specialised epidermal cell found near the growing root tip.
Why is the microscopic size of a root hair an adaptation?
Can easily penetrate between soil particles
What does each microscopic hair have? (SA:V, amount)
Each root hair has a large SA:V ratio and there are thousands on each growing root tip
Why does each root hair have a thin surface? What does the thin surface contain?
Enables diffusion and osmosis to occur quickly.
Cell wall and plasma membrane
What is the final adaptation of root hairs in terms of solute concentration?
Conc. of solutes in root hair cell cytoplasm maintains a water potential gradient between soil water + cell
Why does soil water have a high water potential?
Bc soil water has low concentrations of minerals
Why is the water potential in the root hair cell lower?
The cell’s cyotplasm + vacuole contains many solvents i.e. sugars, mineral ions and amino acids.
Why does water move into the root hair cells by osmosis?
The cells have a lower water potential than the soil water around them.
What happens after water has moved into the root hair cell?
The water continues to move across the root to the xylem in one of 2 different pathways.
What is the symplast?
Continuous cytoplasm of plant cells connected through the plasmodesmata.
Through what process does water move through the symplast?
Osmosis
