Transport in plants and transpiration Flashcards
What is the stele?
Vascular cylinder containing xylem and phloem (vascular tissue)
What does xylem transport?
Water and mineral salts
What does phloem transport?
Sugars e.g. sucrose
What are some characteristics of xylem vessels?
Highly specialised for transport of water and minerals
No end walls
No cell contents
Are dead
Secondary walls are thickened with lignin
What is the purpose of pits?
Allows movement of water between adjacent vessels and surrounding cells
What are 2 important properties of lignin?
Strength - prevents vessels from collapsing under the pressure of transpiration
Waterproof - prevents leakage of water
What is the definition of transpiration?
Evaporation of water from the mesophyll surface and subsequent diffusion of H2o vapour through the stomata and into the atmosphere.
What are the 3 main stages of transpiration?
Into and across the root
Up the root and stem into the xylem
Through the leaf and evaporation of water from the leaf
Explain the movement of water through roots:
Vast majority plants are terrestrial
Need to conserve water - waxy cuticle
Cannot absorb water over general surface
What helps root absorb water?
Root hairs
What does a root hair look like?
Long
thin
extension of a root epidermal cell
How long will a root hair be functional?
A few weeks
What is the main function of root hair cells?
Exchange surfaces in plants responsible for absorption of mineral ions and water
Why are root hairs efficient exchange surfaces?
A large surface area - occur in thousands of each root branch
Thin surface layer - substances can move easily
Does the soil have a low or high water potential and why?
High - soil solution is mostly water