B2 Flashcards
Photosynthesis
Process through which plants synthesize carbohydrates from sunlight
6CO2 + 6H2O → light+Chlorophyll C6H12O6 + 6O2
use of carbohydrates
starch: store of energy
cellulose: build cell walls
sucrose: transport in the phloem
nectar: attract insects for pollination
glucose: to use during respiration
Nitrate ions
- produces amino acids
- stunted growth & yellow leaves if deficient
Potassium
- for enzyme function
- yellow leaves w/ dead bits if deficient
Phosphates
- for photosynthesis
- small roots if deficient
Magnesium ions
- makes chlorophyll, forms part of chlorophyll molecule
- yellow leaves if deficient
Testing for starch
ceb
Waxy cuticle
Decreases water loss, transparent so light can pass through
Spongy mesophyll
Site of gas exchange, loosely packed cells with air spaces to allow for diffusion
Xylem
Transports water and mineral ions from roots to shoots (transpiration). Cell walls thickened with lignin to withstand pressure changes.
Phloem
Transports sucrose and amino acids from source to sink (translocation).
Factors influencing transpiration
Temperature, humidity, light intensity, air movement(wind)
How does temperature influence transpiration?
The water molecules gain kinetic energy, and hence more water molecules evaporate from cell surfaces; higher rate of diffusion
How does humidity influence transpiration?
When it is more humid, the concentration gradient of water is decreased, decreasing the rate of diffusion.
How does light intensity influence transpiration?
When light intensity is higher so is the rate of photosynthesis. Hence,
How does air movement influence transpiration?
When there is wind the surrounding water molecules in the air are blown away, which decreases the humidity surrounding the leaf, increasing concentration gradient and hence increasing diffusion.
Water journey through a plant
- From soil, it enters root hair cells via osmosis, mineral ions enter via active transport
- Due to transpiration pull it moves up the plant stem
- Moves into spongy mesophyll
- Evaporates from cell surfaces out of the stomata
Why is water able to travel up the plant?
- Water molecules are cohesive (they stick together)
- Adhesion between water molecules and xylem walls
- When water evaporates, since water molecules are cohesive they travel upwards as well, creating a transpiration stream
Hydrogencarbonate indicator
High -> Low CO2
Purple -> magenta-> red (atmospheric) -> orange -> Yellow
Path of water
Soil -> root hair cell -> root cortex cell -> xylem -> mesophyll cells
Practical: Testing for starch in a leaf
Safety:
- Wear goggles
- Wash hands afterwards
Part 1: Decolour leaf so no other colors will affect viewing results
- Put leaf and dip in water bath (removes waxy cuticle)
- Put the lead in ethanol and place in water bath (5 mins)
Part 2: Testing for starch
- Rinse leaf in cold water, softens
- Cover in iodine
Yellow-brown = no starch, blue-black = starch present
Practical: Testing for rate of photosynthesis
- Place pond weed in a beaker filled with water & sodium hydrogencarbonate, covered by a reversed funnel and boiling tube
- Count the no. of bubbles produced in 1 minute
- change temp/light/other variable and repeat experiment
