Biology term 2 Photosynthesis and Transpiration Flashcards
What is the balanced symbol equation of photosynthesis?
6H2O+6CO2=C6H12O6+6O2
What are the three limiting factors in plants?
Light intensity, Carbon dioxide concentration and temperature.
What are the limiting factors on a rate of photosynthesis- light intensity graph that increases before plateauing?
On the slope, light intensity.
On the flat, carbon dioxide concentration or temperature.
What are the limiting factors on a rate of photosynthesis- carbon dioxide concentration graph that increases before plateauing?
On the slope, carbon dioxide concentration.
On the flat, light intensity or temperature.
What are the limiting factors on a rate of photosynthesis- temperature graph that increases, peaks, then decreases?
On the slope up and down, temperature.
On the peak, light intensity or carbon dioxide concentration.
Explain the shape of a rate of photosynthesis- light intensity graph that increases, then plateaus.
When the line is diagonal light intensity is limiting the rate of photosynthesis. On the plateau, light intensity is no longer the limiting factor, either carbon dioxide concentration or temperature is.
What is glucose from photosynthesis used for?
Energy for respiration.
To be stored as starch.
Proteins for growth.
Strengthens cell wall.
Produces fat/oils for storage in seeds.
Why does the leaf that has been in the light have starch, while the leaf that has been in the dark doesn’t?
The green chlorophyll is needed to absorb light energy for photosynthesis, converting carbon dioxide and water into glucose which is stored as starch.
What is a stoma and what is its function in a leaf?
A stoma is a microscopic hole on the leaf between two guard cells.
Its function is to open/close to control gas exchange in the leaf.
How do stoma open?
Guard cells fill with water via osmosis.
As guard cell expands, thick inner wall doesn’t stretch as much as thin outer wall.
Results in the guard cell bending in a banana shape.
The whole between the two guard cells is a stoma.
What are the features and functions of the xylem?
A hollow, continuous tube made of dead cells that transports water and mineral ions up the plant.
Part of the transpiration stream.
What are the features and functions of the phloem?
A chain of living cells that transports sucrose and amino acids up or down a plant.
Part of the translocation process.
Describe the transpiration stream.
- Water enters the root hair cell via osmosis.
- Water moves across the root one cell at a time via osmosis.
- Water enters the xylem of the stem, and flows up it.
- Water leaves the xylem and enters the leaf cells via osmosis.
- Water moves across the leaf one cell at a time via osmosis.
- Some of the water is used in photosynthesis.
- Remaining water evaporates into air spaces in the spongy mesophyll.
- Water diffuses out of the stomata and evaporates.
Describe translocation.
- Sugars are made in the leaf cell by photosynthesis.
- Sugars are moved via active transport from leaf to companion cell.
- Sugars diffuse from companion cell into phloem vessel.
- The high concentration of sugars at the top of the phloem causes water to also enter the phloem via osmosis.
- The movement of water into the phloem vessel causes the translocation of sugars to the root.
- In the root sugar leaves the phloem vessel and is stored as starch.
Where are the xylem and phloem located inside vascular bundles?
The phloem is always on the outside of the xylem.
How would you use a potometer to measure the rate of transpiration in a plant?
Set up the apparatus underwater to prevent air bubbles other than the one used for measuring.
As water is drawn up by the transpiration stream and lost via transpiration, the air bubble will move along the scale.
This is not a perfect measure as some water will be used in photosynthesis and won’t leave the plant via transpiration.
