Plant structures and their functions Flashcards
What is the equation for photosynthesis
carbon dioxide + water -> glucose + oxygen
–>
light
Chemical formula for glucose
C₆H₁₂O₆
What is biomass?
The materials in an organism
Where does photosynthesis occur
plants and algae
What kind of reaction is photosynthesis?
endothermic, takes more energy than it releases
What factors affect photosynthesis and how
- Temperature: As temperature increases so does the rate of photosynthesis. This increases until the enzymes denature
- Light intensity: Higher the light intensity, faster the rate of reaction
- Carbon dioxide concentration: As the concentration of CO₂ increases, the rate of reaction increases
What is a limiting factor in terms of photosynthesis?
If one factor which affects the rate of photosynthesis is low(or too high like temperature), the increase in rate of reaction of photosynthesis will be restricted.
The relationship between a factor and the rate of photosynthesis will plateau after a limiting factor stops it.
How can we investigate the effect of light intensity on photosynthesis? (CP)
- Add 20 algal balls to a set amount of hydrogen carbonate indicator. Have many bottles. Cover one in foil as a control.
- Keep each bottle a set distance away from a lamp by using a ruler
- Keep a tank of water between the lamp and the algal balls as a heat shield to prevent temperature being a factor.
- Wait a few days.
- The indicator will show how much CO2 indicator is there in the bottle.
- orange is high
- red is atmospheric
- purple is low
- The higher the CO2 levels, lower the rate of photosynthesis
how does distance affect light intensity
depends on inverse square law which is
light intensity = 1/d^2
How is the root hair cell structured to absorb water and mineral ions?
- Large surface area to diffuse more water and minerals
- mitochondria for energy for active transport of mineral ions
- Large permanent vacuole
- Thin cell walls
What is the xylem?
A tube that carries water and mineral ions (dissolved in water) from the root to the stem and leaves. Goes up. Uses transpiration
How is the xylem adapted to its function
- The xylem is full of dead cells which are joined together without cell walls
- Lignin kills these cells, making them hollow and lignified
- Lignin is deposited in spirals, which provides support for the xylem.
What is the phloem?
Tube which transfers food substances (sucrose) from the leaves to the rest of the plant. Goes up and down. Uses translocation
How is the phloem adapted to its function?
- Made of elongated living cells.
- Small pores in each cell’s end walls to allow things to flow through.
- Each cell has a companion cell which has mitochondria for energy, since translocation requires energy.
What is transpiration?
Loss of water from the plant
How does transpiration work?
- Water leaves the cell through stomata
- Water molecules are attracted to other molecules, causing it to pull more molecules up the xylem. Called capillary action.
- Results in more water coming through the roots
- Leads to a constant transpiration stream.
What are stomata and what does it do
Pores on the surface of a plant. Usually under a leaf. Allow CO2 to diffuse in and out of a leaf
How do guard cells work?
- If the guard cell is turgid, the stomata opens. Allows water and gas to leave
- When flaccid, the stomata close, reducing water loss
What is translocation?
Transportation of food substances, made in the leaves up and down the phloem.
Requires energy supplied by companion cells.
What are the layers of a leaf from top to bottom?
- Waxy cuticle
- upper epidermis
- Palisade mesophyll tissue
- Spongy mesophyll tissue
- lower epidermis
How are plants adapted for photosynthesis and gas exchange? Give a shit ton of reasons
- Thin leaves: carbon dioxide only has a small distance to travel into the leaf and oxygen has a small distance to diffuse out
- Stomata: Close to reduce water loss and open to increase evaporation and gas exchange
- Large surface area: absorb more light at once
- Xylem and Phloem - xylem takes water to leaves, phloem takes away the sucrose
- Waxy cuticle: prevents water loss through evaporation
- Upper epidermis: Transparent so light can reach palisade mesophyll tissue
- Spongy mesophyll: empty space, increases diffusion into and out of leaf cells
What factors affect transpiration and how?
- Light intensity: Brighter light, greater transpiration rate. Stomata close when dark as CO2 is not required because photosynthesis don’t happen.
- Temperature: Warmer, faster transpiration happens. More energy goes to particles, meaning they diffuse out of stomata faster
- Air flow: Good air flow means better transpiration rate. When diffusion happens, water moves outside the leaf. If there is less air flow, the water hangs around the leaf and diffusion is slow. If there is good air flow, the water particles get moved away.
How can you estimate transpiration rates?
- Use a potometer. Air bubble is placed at the start of a capillary tube filled with water. Measure how far the air bubble moves. Divide how far the bubble has moved by the time taken for it to move. This is the rate of transpiration
How do some plants survive in extreme environments?
- Small leaf size: reduces volume of water lost by transpiration
- Has a waxy cuticle: Prevents evaporation of water
- Stomata: fewer stomata or stomata which only open at night.
