Structure of a Leaf Flashcards
What is the epidermis and how does it affect photosynthesis?
It is a single layer of cells that covers the leaves, flowers, roots and stems of plants.
The epidermis is usually transparent (epidermal cells lack chloroplasts) and coated on the outer side with a waxy cuticle that prevents water loss which would decrease the rate of photosynthesis.
What is the stroma and how does it affect photosynthesis?
It is the fluid filling up the inner space of the chloroplasts which encircle the grana and the thylakoids.
It is clear so it does not block light which increases the rate of photosynthesis. (Allows maximum amount of light to reach the chlorophyll in the thylakoid sacs)
Where are most chloroplasts found?
Most chloroplasts are found near the top of the leaf in (palisade) long cylindrical cells, with the chloroplasts close to the walls of the cell.
How does the location of chloroplasts affect the rate of photosynthesis?
Because they are close to the cell membrane, this reduces diffusion distance of carbon dioxide going into the chloroplast and oxygen going out. These factors combine and lead to more light being received where it can be used to maximize the rate of photosynthesis.
What is beneath the palisade layer and how does it affect the rate of photosynthesis?
There is a spongey mesophyll layers. The cells of the spongy layer are more rounded and not so tightly packed. There are large intercellular air spaces. This maximizes the rate of diffusion of the gases during photosynthesis. (CO2 entering the leaf and O2 leaving it.)
How does the structure of thylakoids affect the rate of photosynthesis?
Thylakoids are positioned in flat stacks called grana which have an increased surface area for the absorption of light.
Where are guard cells found and what are their function?
Specialised guard cells are found mainly on the lower leaf epidermis function to control the movement of gases and water loss. They close stomata to limit water loss and open to let carbon dioxide come in and diffuse through photosynthesis.
How does the number of chloroplasts affect photosynthesis?
Chloroplasts possess the light trapping pigment chlorophyll. The presence of a large amount of chloroplasts allows for enhanced photosynthesis to occur.
What is the importance of chlorophyll?
Chlorophyll is the light trapping pigment, it traps the energy of sunlight and essentially provides a starting point for photosynthesis to take place.
What are thylakoids covered in?
Thylakoids are covered with the chlorophyll pigment, it traps the sunlight so it can be used in photosynthesis.
What is the result of more light being absorbed?
More light = more energy = more photosynthetic reactions taking place.
