6.4- GAS EXCHANGE IN THE LEAF OF A PLANT Flashcards
What do all plant cells require during respiration and what do they produce?
require oxygen
produce carbon dioxide
What do plants cells take in during photosynthesis and what do they produce?
take in carbon dioxide
produce oxygen
When photosynthesis is happening where does some of the carbon dioxide come from?
respiration of cells
Where is most of the carbon dioxide for photosynthesis obtained?
from external air
For respiration in plants where does some of the oxygen come from?
some oxygen from photosynthesis
What happens to most of the oxygen produced from photosynthesis?
most of it diffuses out of plant
Example of when photosynthesis is not occuring?
in the dark
What does oxygen do when photosynthesis is not occuring?
oxygen diffuses into the leaf
Why does oxygen diffuse into the leaf when photosynthesis is not occurring?
as it’s constantly being used by cells during respiration
What happens to carbon dioxide produced from respiration?
diffuses out
How is gas exchange in plants similar to that of insects?
no living cell far from external air- so source of oxygen + carbon dioxide
diffusion happens in gas phase (air), which makes it more rapid than if it were in water
What is the diffusion pathway like in plants?
short, fast diffusion pathway
What do the air spaces inside a leaf have?
large SA compared with volume of living tissue
Is there a specific transport system for gases?
no- simply move in + through plant by diffusion
Where does most gaseous exchange happen in plants?
occur in leaves
What adaptations do leaves have for rapid diffusion? (3)
many small pores, called stomata
numerous interconnecting air-spaces that occur throughout mesophyll
large SA of mesophyll cells
How is many small pores, called stomata an adaptation of leaves for rapid diffusion?
so no cell far from stoma + so diffusion pathway short
How is numerous interconnecting air-spaces that occur throughout mesophyll an adaptation of leaves for rapid diffusion?
so gases can readily come in contact with mesophyll cells
How is large SA of mesophyll cells an adaptation of leaves for rapid diffusion?
for rapid diffusion
What are stomata?
minute pores
Where do stomata occur?
occur mainly, but not exclusively on leaves, especially on underside
What is each stoma surrounded by?
pair of special cells (guard cells)
What can the guard cells do to the stomatal pore?
can open or close stomatal pore
What can the guard cells control as they can open/close the stomatal pore?
can control rate of gaseous exchange
Why is it important that the guard cells can control the rate of gaseous exchange?
as terrestrial organisms lose water by evaporation
How have plants evolved to balance the conflicting needs of gas exchange + control of water loss?
by closing stomata at time when water loss would be excessive
