Topic 6 - Plant Structures And Their Functions Flashcards
What is the equation for photosynthesis?
Carbon dioxide + water –> glucose + oxygen
6CO2 + 6H2O –> C6H12O6 + 6O2
Is photosynthesis an endothermic or exothermic reaction?
Endothermic - energy is taken in during the reaction
Where does photosynthesis take place?
The chloroplasts
What does chlorophyll do?
It absorbs light
Energy is taken transferred to the chloroplasts by light
What are the three factors that affect photosynthesis?
Light intensity, the concentration of CO2 and the temperature
What is a limiting factor in photosynthesis?
Something that is stopping photosynthesis from happening any faster
What does not having enough light have to do with the rate of photosynthesis?
Not having enough light slows down the rate of photosynthesis
What does not having enough carbon dioxide have to do with the rate of photosynthesis?
Too little carbon dioxide slows down the rate of photosynthesis
How does temperature affect the rate of photosynthesis?
The temperature has to be around the optimum temperature for photosynthesis to happen quickly
The enzymes cannot work best if the outside temperature exceeds their optimum temperature
If this happens, the enzymes will denature and photosynthesis cannot take place
What is the purpose of root hair cells?
To take in minerals and water
What do phloem tubes transport?
Transport food - mainly sucrose - around the plant
Give an adaptation of root hair cells
They have microscopic hairs on the surface of the plant roots which stick out into the soil
This gives the roots a larger surface area, and the plant is therefore more able to absorb minerals and water quicker
How are minerals absorbed in root hair cells?
Active transport
How is water absorbed in root hair cells?
Osmosis
Give an adaptation of phloem tubes
They are made of elongated living cells with small pores to allow substances to flow through easily
What is the purpose of xylem tubes?
They take water up the plant
What is transpiration?
The loss of water from a plant
What is transpiration caused by?
Evaporation and diffusion
How does transpiration allow more water to be drawn up through the roots?
The loss of water creates a slight shortage of water in the leaf, and so more water is drawn up from the rest of the plant through xylem vessels in order to replace it
This in turn means that more waterside drawn up from the roots and so there’s a constant transpiration stream of water through the plant
How do you calculate light intensity?
1 (divided by) distance (d)^2
What are stomata used for?
Gas exchange
What are stomata? What gases diffuse out of them?
Tiny pores on the surface of a plant. They are mostly found on the lower surface of leaves.
Carbon dioxide and oxygen diffuse directly out of the leaf through the stomata, as well as water vapour during transpiration
What surrounds stomata to open and close them?
Guard cells
What three environmental factors affect the transpiration rate?
- Light intensity
- Temperature
- Air Flow
How does light intensity affect transpiration?
Brighter the light, the greater the transpiration rate. Stomata close as it gets darker. Photosynthesis can’t happen in the dark, and therefore they don’t need to let CO2 out.
How does temperature affect the transpiration rate?
The warmer it is, the faster transpiration happens. When it’s warm the water particles have more energy to evaporate and diffuse out of the stomata
How do you estimate the transpiration rate?
Using a potometer. It measures water intake in the plant, but it is assumed that water uptake is directly related to water loss from the leaves
What are leaves adapted for?
Photosynthesis and gas exchange
Leaves are broad. Why is this a good adaptation?
Because it means they have a larger surface area exposed to the light, making photosynthesis happen faster
How is the palisade layer adapted for photosynthesis?
It is very close to the surface and they have lots of chloroplasts, so they can get the most light
How is the upper epidermis adapted for photosynthesis?
it is a transparent layer so that light can pass through easier
How has the waxy cuticle adapted?
it is a waxy layer which helps reduce water loss
Why are air spaces good in photosynthesis?
it gives a larger surface area for gas exchange and diffusion
Give 3 adaptations of plants living in warm climates
Small leaves - reduces surface area for water loss
Curled leaves - reduces air flow which traps water vapour near the surface
Thick waxy cuticles - reduces water loss
Thick stem - stores water
Fewer stomata which only open at night - reduce water loss by evaporation
Name 3 plant hormones
Auxins
Gibberellins
Ethene gas
What do auxins do?
Plant hormone that controls growth at the tip of shoots and roots. They move through the plant in a solution
They change the direction of shoot and root growth
What is positive and negative phototropism?
Where a shoot or root either grows towards or away from the light
Positive - grows towards the light
Negative - grows away from the light
What is positive and negative geotropism?
Where a shoot or root either grows towards or away from gravity
Positive - grows towards gravity
Negative - grows away from gravity
What are roots - phototropic / geotropic?
Positively geotropic
Negatively phototropic
What are shoots - phototropic / geotropic?
Positively phototropic
Negatively geotropic
How do auxins cause shoots and roots to move?
Auxins accumulate on the shaded side of the shoot or root, which makes the cell elongate faster on the shaded side so it bends towards the light
What plant hormone is in selective weed killers?
Auxins
What plant hormone is in rooting powder?
Auxins
What plant hormone is in the control of fruit and flower formation?
Gibberelins
What plant hormone is used in producing seedless fruits
Gibberellins
What plant hormone is involved in the ripening of fruits?
Ethene gas
What plant hormone is in controlling seed germination?
Gibberellins
