Module 3: Transport of water and features of the leaf Flashcards
What are the 2 routes in which water can travel to the xylem through?
State how they differ
symplast route-between the cytoplasms of cells through plasmodesmata
apoplast route-between cells via their cell walls
Name the 3 main functions of the casparian strip
-prevents harmful substances entering the xylem
-prevents leakage of water from xylem vessels
-aids development of root pressure
How does the casparian strip prevent harmful substances entering the xylem?
2 points
it forces water moving through the apoplast pathway to diffuse into the cytoplasm of cells and enter the symplast pathway
-in the symplast pathway water passes over membranes which won’t let harmful substances cross due to their selective permeability
Describe the first two steps of the transport of water from roots to xylem
1)mineral ions from the soil enter the root hairs by active transport which lowers the water potential in the root hairs
2)creates a water potential gradient between inside and outside the root hair so water moves into root by osmosis down its water potential gradient
Describe the next two steps of the transport of water from roots to xylem
3)water continues to move through the root , the epidermis and cortex via either the symplast or apoplast route
4)water flowing through the apoplast route will reach the endodermis and be stopped by the casparian strip
Describe the final 2 steps of the transport of water from the roots to the xylem
5)water in the apoplast route diffuses into the cytoplasm of endodermis cells and enters the symplast route
6)water moves into the xylem by osmosis as the water potential inside the xylem is smaller than in the endodermis
How is the waxy cuticle involved in photosynthesis?
How is the upper epidermis involved in photosynthesis?
its waterproof to prevent water evaporating out of cells
its transparent to allow light required for photosynthesis to pass through
How is the palisade mesophyll involved in photosynthesis?
How is the spongy mesophyll involved in photosynthesis?
contains lots of chloroplasts that are required for photosynthesis
has many air gaps/pockets for gas exchange and diffusion of oxygen and carbon dioxde
How is the lower epidermis involved in photosynthesis?
contains stomata and guard cells that control gas exchange
How are the xylem and phloem involved in photosynthesis?
xylem-made of dead cells to allow an uninterrupted flow of water flow to the leaves
phloem-transports amino acids and sucrose(assimilates) from the leaf to other parts of the plant where they are required
What do endodermal cells move into the xylem by active transport?
This results in production of movement of water by osmosis , what does this water movement result in?
mineral ions
root pressure-this gives water a push up the xylem
Give 3 pieces of evidence that can be used to support the role of active transport in root pressure
-poisons such as cyanide affect mitochondria so effect production of ATP , if applied to root root pressure disappears
-root pressure increases with temp rise and vice versa , suggesting chemical reactions are involved
-if oxygen levels or respiratory substrates fall , root pressure falls
