Section 4: Gas Exchange in Plants Flashcards
Where are the upper and lower epidermis of a leaf cell?
They are the two outer layers
What does the upper and lower epidermis have?
They have a few chloroplasts and have a thin waxy material called a cuticle on them.
What is a cuticle?
A thin waxy layer on the upper and lower epidermis
What does the cuticle do?
They stop water loss by evaporation and acts as a barrier for disease-causing microorganisms
What is a stomata?
They are pores found on the lower epidermis
What does the stomata do?
They allow CO2 to diffuse into the leaf - get to the photosynthetic tissue. It also allows oxygen and water vapor to diffuse out.
How can guard cells control the stomata?
The stoma is in between two guard cells, these can open and close
Where are the two layers of photosynthetic cells found?
In the middle of the leaf
What is a mesophyll?
The two layers of photosynthetic cells
Where is the palisade layer?
Below the upper epidermis
What is the palisade layer made of?
They are made of elongated cells with hundreds of chloroplasts
Where is the main site of photosynthesis?
In the palisade layer
Why is the palisade layer effective in making chloroplast?
As they are close to the light source; the upper epidermis is relatively transparent
What is below the palisade layer?
A spongy layer
How are the cells organised in the spongy layer?
They are loosely packed with air spaces.
Why does the cells of the spongy layer have air spaces in between them?
So that gas exchange can occur. The air spaces allow gas to diffuse in and out of the cells. The carbon dioxide is absorbed and oxygen and water is released.
What are xylem?
A vessel that supplies water and mineral ions
How is water transported in a plant?
Water is transported through the steam and veins in the leaves in the transpiration stream.
How does water supply mesophyll cells in leaves?
Water leaves the xylem and supplies mesophyll cells
What is the phloem?
It is a transport system that supplies products of photosynthesis, like sugars
What parts does the phloem supply to?
Parts that do not photosynthesis
What transport system do veins contain in leaves?
Both the xylem and phloem tissue
What happens when light intensity increases?
Photosynthesis speeds up, but eventually levels off in very bright light. This causes a lack of CO2 near the leaves and a surplus of oxygen
Describe the concentration of carbon dioxide around a leaf throughout the day?
In the middle of the day, there is a lack of carbon dioxide and lots of oxygen.
In the middle of the night, there is lots of carbon dioxide and a lack of oxygen.
