gas exchange in plants Flashcards
(19 cards)
What is the word equation for photosynthesis?
Carbon dioxide + water → glucose + oxygen
What is the chemical equation for photosynthesis?
6CO2 + 6H2O → C6H12O6 + 6O2
Where does photosynthesis take place?
in the chloroplasts.
When does photosynthesis take place?
in the presence of light
What is the word equation for respiration?
glucose + oxygen → carbon dioxide + water + energy released
What is the chemical equation for respiration?
C6H12O6 + 6O2 → 6CO2 + 6H2O + 38ATP
Where does aerobic respiration take place?
in the mitochondria.
What are leaf adaptations for photosynthesis?
- Large flat surface area - to absorb light.
- Leaves are arranged to maximise light absorption (optimum leaf mosaic) - to absorb light.
- Network of veins, containing xylem and phloem - for transport, help support leaf blade - to absorb light.
- Thin - for gas exchange.
- Stomata allows gas exchange - for gas exchange, which may close to reduce water loss, most are on the lower epidermis.
- Large air spaces - for gas exchange.
- Transparent - to absorb light, waxy cuticle - to reduce water loss.
- Upper epidermis is thin and transparent - to absorb light.
What are adaptations of the palisade mesophyll?
- Cylindrical cells arranged end-on to upper epidermis - to absorb light.
- Large number of chloroplasts - to absorb light.
- Large vacuole to restrict location of chloroplasts to cell edge - to absorb light, and for gas exchange.
- Chloroplasts can be moved around the cell - to absorb light.
- Thin cell walls and narrow air spaces between the cells to provide a large surface area - for gas exchange.
What are adaptations of the spongy mesophyll?
- Irregular packing with large air spaces - for gas exchange.
- Large surface area of moist cell wall - for gas exchange.
- Fewer chloroplasts than palisade cells.
What is the role of guard cells in stomata?
- Each stoma is surrounded by 2 guard cells.
- Guard cells turgid = pore open to allow gas exchange.
- Guard cells flaccid = pore closed to reduce water loss.
What is the structure of guard cells?
- Unevenly thickened cell wall.
- Cellulose microfibrils arranged as hoops around the guard cell.
- As the guard cell becomes turgid it mainly increases in length.
- Thin outer walls bend more easily.
- Guard cells become ‘banana shaped’ and curve apart, opening the stoma.
What is the mechanism of a stoma opening?
- ATP used to actively transport K+ into the guard cell.
- Starch is converted into malate.
- This lowers water potential in guard cell.
- Water enters by osmosis down the water potential gradient.
- Guard cells become turgid and stoma opens.
What are xerophytes?
Xerophytes are plants which live in environments where there is little water.
What are leaf adaptations of xerophytes to reduce water loss through transpiration?
- High water vapour potential in air space.
- Stoma at base of pit.
- Water vapour collects in pit or under hairs.
What are halophytes?
Plants which live in environments where the soil water is very salty.
cross section of a leaf
simple drawing that includes structures like the waxy cuticle, upper epidermis, palisade mesophyl, spongy mesophyl, lower epidermis, waxy cuticle + stoma
Stomata function diagram
SEM of stomata
