Plant Nutrition Flashcards
What is the word equation for photosynthesis?
Carbon dioxide +water ➯ (using chlorophyll and light) glucose + oxygen
What is the chemical equation for photosynthesis?
6CO2 + 6H2O ➯ C6H12O6 + 6O2
How do you test the requirement for light?
- cover part of the leaf w foil or card
- leave another part uncovered
- after being left in sun, test with iodine
- covered section should remain brown, as no sun, so no PS or starch
How do you test the requirement of chlorophyll?
- take a variegated leaf, and test with iodine
- draw pattern of chlorophyll and compare results
- the white sections should stay brown, as they have no chlorophyll for PS, so not starch
How do you test for the production of starch?
- boil leaf in boiling water to denature enzymes in leaf to kill it
- then, using a water bath, boil leaf in boiling ethanol to remove colour
- wash the leaf
- test leaf with iodine. If starch present, goes from brown to blue/black
How do you test the production of oxygen?
- place elodea in a beaker of water, with a test tube on top to catch the oxygen.
- place a funnel around the elodea into the test tube to catch all the oxygen
- as PS append, bubble can be seen and collected
- prove it is oxygen by relighting a glowing splint
How is the leaf adapted for photosynthesis?
- palisade cells have many chloroplasts and are tightly packed, as chlorophyll needed (generally called mesophyll tissue)
- xylem delivers water, as it is needed
- lower epidermis has stomata to allow gas exchange, for CO2 and O2
- phloem transports glucose produced, as sucrose, around plant
Why do plants need nitrogen?
- needed for amino acids, which make proteins needed for growth.
- plant growth stunted, and leaves yellow without
Why do plants need magnesium?
- needed to make chlorophyll, which is needed for PS
* chlorophyll green ∴ leaves look yellow without it
What are possible limiting factors on a plant?
Shortage of water, low light, low temperature, shortage of CO2.
How does light affect photosynthesis?
- when there is not enough light, there will be less photosynthesis
- when light levels have increased, another factor will be the limiting factor
- although PS is higher than before, it is not at peak level
How does CO2 affect photosynthesis?
- at first, when CO2 levels are low, it will be the limiting factor
- when CO2 levels increase, PS will increase, but then another factor will be the limiting factor
How does temperature affect photosynthesis?
- at first photosynthesis increases, as there is more kinetic energy
- if the temperature excedes 40 °C, the enzymes denaturate, so PS rates drop
How do water and minerals reach the xylem?
- water from soil taken in via osmosis in root hair cells
- minerals taken in via active transport in root hair cells, as there are minerals inside the cells, so energy is needed to bring them against the concentration gradient
- water and minerals diffuse to xylem
How is the root hair cell adapted?
- many mitochondria for energy, for active transport of minerals
- long extension, to increase SA, so more osmosis and active transport
- 1 cell thick cell membrane ∴ shorter diffusion distance
- large vacuole for storage
How does water get from the roots to the leaves?
Through the xylem, which uses capillary action.
How do the water molecules get from the xylem to the air?
- water molecules leave xylem vessels
- diffuse through spongy cell layer
- they then evaporate from the stomata into the air
What is transpiration?
Evaporation of water through the stomata
What is a transpiration stream?
Uninterrupted stream of water taken up at the roots and transported in the xylem to the leaves where it evaporates
Pros/cons of open and closed stomata
Open: ➯ allows gas exchange and transpiration ➯ can lead to dehydration Closed: ➯ reduces water loss ➯ reduces CO2 levels(less PS), and plant can overheat
When do the stomata open?
When water moves into the guard cells by osmosis
What causes the stomata to open?
- lots of light
- high temp
- lots of water
What causes the stomata to close?
- little light
- low temp
- not much water
How does light affect transpiration?
• increases it
• more PS
∴ stomata open for CO2
How does temperature affect transpiration?
- increases it
* evaporation increases
How does humidity affect transpiration?
• decreases it
• lower concentration gradient
∴ less evaporation
How does wind speed affect transpiration?
- increases it
- faster air movement removing water vapour
- higher concentration gradient
How do plants prevent water loss?
- Stomata only on one side of leaf
- wilting reduces SA for water loss
- close stomata
- waxy cuticle
How does a potometer work?
- shoot placed in open end of potometer tube
- bung made airtight to prevent evaporation from potometer
- as water moves through planta and evaporates from stomata , air bubble moves along scale
- over time, this gives you the transpiration rate
- you could test the plant with different factors to see how they affect transpiration
What is glucose transported as, and where?
Transported as sucrose, through the phloem
What is glucose stored as? Why?
Starch, as it is insoluble, so osmosis won’t take place, so it wont escape from the cells
What is glucose used for?
- respiration
- lipids, stored in seeds, to make membranes
- amino acids, to make proteins for growth
- cellulose, to make cell walls
What is a tropism?
A growth response in the plant towards a directional stimulus
How do plants bend towards light?
- they have auxin, a hormone required for growth
- this is produced in the tip, and diffuses to shoot
- destroyed by light, so it accumulates on shady side, cause cell elongation to take place
What is phototropism?
- shoots grow towards light source(positive phototropism)
* roots grow away from light source(negative phototropism)
What is geotropism?
- shoots grow away from gravity(negative geotropism)
* roots grow towards gravity(positive geotropism)
What is hydrotropism?
- none for shoots
* some roots grow towards direction of water
What is thigmotropism?
- some shoots grow towards and bend around support(positive thigmotropism)
- roots grow away from object
What are the benefits of geotropism?
- shoot grows away front gravity towards light, for more light, for more PS, for more respiration
- root grows towards gravity to find water and minerals needed in PS and growth, and for anchorage
What are the benefits of phototropism?
- shoots grow towards light, so they get more light for PS, ∴ more glucose, ∴ more PS
- roots grow towards soil for water and mineral ions
What are some benefits of greenhouses?
• increases crop yields
➯ can control temps. + temps mean more KE ∴ more PS ∴ more respiration
➯ control CO2 levels. More CO2 means more PS, as stomata open, so more gas exchange
➯ increase light, so increase PS
➯ fewer pests
Why are fertilisers good?
- increase crop yields, as provides more minerals
* e.g. Nitrogen, which makes plant proteins, so is needed for plant growth
How do you test for the requirement of carbon dioxide?
Fill jar with air but put soda lime at top, which absorbs CO₂ from air ∴ no CO₂ for PS ∴ leaf stays brown
