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.
What is an auxin and how does it work
Plant hormones which control growth at the tips of shoots and roots. Move through the plant in a solution. Promotes growth at shoots, inhibits growth at roots. Auxins move away from light
What is phototropism and how does it work and explain its types
- Positive phototropism is when an shoot grows towards the light. The auxins accumulate on the underside of the shoot and make those cells grow, pushing the plant upwards
- Negative phototropism is when a root grows away from the light
What is gravitropism and how does it work, explain its types
- Positive gravitropism occurs in roots, as they follow gravity and move downwards. Auxins accumulate on the lower side and inhibit the growth of that side. Makes other side grow downwards.
- Negative gravitropism occurs in shoots. This is because they grow upwards.
What are gibberellins?
Plant hormones which stimulate germination, stem growth and flowering
What plant hormones are used commercially?
- Auxins
- Gibberellins
- Ethene
Where are auxins used commercially?
- Weed killers: Weedkillers have auxins in them. When put over plants, they target broad leaved plants (weeds). The auxins cause the weeds to grow too fast, killing them.
- Rooting powder: A cutting is taken from the plant. The cutting is placed in the soil. Rooting powder, with auxins, causes the roots to grow fast. Causes the plant to grow like actual plants
Where are gibberellins used commercially?
- Used to make plants flower and/or germinate earlier than they would normally
- Used to make fruits bigger
- Gibberellins can cause unpollinated flowers to grow fruits without seeds.
How is ethene used commercially?
- Ethene makes a fruit ripen
- Helps transport fruit: The fruit is picked when unripe and transported easily because they are still firm. When they reach the supermarket they are sprayed with ethene to ripen them quickly.
