Theme 4 Part 5 Gas Exchange In Plants Flashcards
Why do plants do gas exchange
They need co2 for photosynthesis and need to dispose o2 as waste
How have leaves adapted for gas exchange
It is done by simple diffusion (same as animals)
The distance between the cells and external environment is short which maximizes rate of diffusion
Thin leaf, large area and gas filled space in the leaves
They do gas exchange through the stomata
When stomata pore is open ?
When closed?
Turgid
Flaccid
How does the uptake of co2 cause water loss
In photosynthesis the co2 enters the cell and o2 leaves through the open stomata
The water Vapor leaves the leaf through a diffusive gradient
What is the spongy mesophyll layer
Where the gas exchange happens
What does the cuticle covered epidermis do
Reduces water loss from leaves and stems
Limits co2 diffusion from photosynthesis (so water doesn’t leave) (stomata closed)
What is the transpiration photo synthesis compromise
To limits water loss pores close but now photosynthesis doesn’t happen
To do photosynthesis they need to open the stomata but then water is lost but co2 is absorbed
They open and close the stomata to control gas exchange depending on the environmental conditions
How is the stomatal opting and closing controlled
By active transport of k+ into and out of the guard cells
The water follows (solutes) k so if k leaves water leaves and stomata is flaccid (closed)
What happens to the stomata under water stress
If roots get less water, the roots make abscisic acid which is a hormone signal for closing stomata
Closes stomata and stops excess water loss
The mesophyll cells take up the ABA from the xylem and realease it
Where is the potassium when stomata is closed
H pumped in actively to make less electronegative stomata
k gone and water gone makes flaccid
K is in the epidermal cells
Where is the potassium when stomata is open
first h is pumped out (actively) to make the cell electronegative
K goes in guard cells and water follows.
Cell turgid , open
Potassium content in open stomata
High
Water is in making it turgid so k is in
