Section 6 - Plant structures and their functions - Photosynthesis, transport, stomata and transpiration Flashcards
Where does photosynthesis occur in a plant?
Inside chloroplasts which contain chlorophyll which absorb light
Word and balanced chemical equation for photosynthesis?
Carbon dioxide + water –Light + chlorophyll–> glucose + oxygen
6CO2 + 6H2O –> C6H12O6 + 6O2
Three factors that affect rate of photosynthesis?
Light intensity, CO2 concentration and temperature
What plant can be used to measure the effect of light intensity on the rate of photosynthesis?
Canadian pondweed
Inverse square law equation to measure light intensity?
Light intensity ∝ 1 ÷ distance (d)²
What will happen to the rate of photosynthesis if temperature is too high? And the temperature it happens to the enzymes?
Enzymes become denatured
45Cº
Which two factors don’t affect rate of photosynthesis if they are too high?
Light intensity and CO2 concentration
Two types of transport vessels in flowering plants?
Xylem and phloem
What makes root hair cells good for absorbing water and mineral ions from the soil?
A large surface area
What process is water and mineral ions absorbed by in the root hair cells and why for mineral ions?
Water absorbed by osmosis
Concentration of mineral ions usually higher in cell than in soil so mineral ions absorbed by active transport
Structure of phloem tubes?
Made up of columns of elongated living cells with small pores in the end walls to allow stuff to flow through
What do phloem tubes transport and through which process?
Transport food substances made in leaves to rest of plant for immediate use or storage (translocation) and this requires energy from respiration. Transport goes in both directions
Structure of xylem tubes?
Made up of dead cells joined end to end with no end walls between them and a hole down the middle. They’re strengthened with a material called lignin
What do xylem tubes carry and from and to where? What is this movement called?
Carry water and mineral ions from roots to stem and leaves. Movement of water from roots, through xylem and out of leaves is called transpiration stream
What is transpiration and what is it caused by?
Loss of water from the plant
Caused by evaporation and diffusion of water from a plant’s surface. Happens mostly in leaves
What happens when there’s a shortage of water in the leaf? How does a constant transpiration stream of water occur?
More water drawn up from rest of plant through xylem vessels, replacing loss of water, meaning more water drawn up from roots so there’s a constant transpiration stream of water through plant, which carriers mineral ions that are dissolved in water along it
What are stomata and what are they needed for?
Tiny pores on surface of a plant
They allow CO2 and O2 to diffuse directly in and out of a leaf and allow water vapour to escape during transpiration. Needed for gas exchange
What are stomata surrounded by and what does this do?
Surrounded by guard cells, which change shape to control size of pore. When guard cells are turgid, stomata are open. When guard cells flaccid, stomata are closed
3 environmental factors that affect transpiration rate?
Light intensity, temperature and air flow
What happens to the stomata as it gets darker and why?
Stomata begins to close as it gets darker as photosynthesis can’t happen in the dark so they don’t need to be open to let CO2 in. Little water can escape
How does a warmer temperature affect transpiration rate?
When it’s warm, water particles have more energy to evaporate and diffuse out of stomata
How does air flow affect transpiration rate?
If there’s good air flow, water vapour swept away easily, maintaining low concentration of water in air outside leaf so diffusion happens quickly.
What apparatus can be used to estimate transpiration rate? What does it measure
Potometer, measures water uptake by plant
Formula for transpiration rate?
Transpiration rate (mm min-1) = distance moved (mm) ÷ time taken (min)
What is translocation? What does it require from respiration?
When sucrose, which is made in the leaves, is transported to rest of plant for immediate use or storage. Requires energy from respiration
