Topic 6- Plant Structures And Their Functions Flashcards
Photosynthesis word equation and then symbol equation
Carbon dioxide + water > glucose + oxygen
6CO2+ 6H2O > C6H12O6 + 6H2O
What type of reaction is photosynthesis
Endothermic
Bio mass
Mass of living material
Where do photosynthetic organisms get their energy from?
What do they store it as?
They get their energy from the sun to form glucose which is stored as starch (larger, complex molecule)
Photosynthetic organisms role in the food chain
Main producers of nearly all life on earth as animals eat it and then are eaten.
Where does photosynthesis take place?
In the chloroplasts
Containing chlorophyll which absorbs light and so energy
What affects the rate of photosynthesis
Water availability Carbon dioxide availability Light intensity Temperature Chlorophyll availability
How to test for starch
Boil a leave in water for 30 secs.
Then boil in ethanol for a few mins which is heated using a water bath
Dry with distilled water and place on white tile
Add iodine solution from a pipette which will detect starch after a few minutes by turning black.
What does boiling the leaf in water do?
Stop chemical reactions from occurring
What does boiling in ethanol do?
Decolorisation
Needs water bath as ethanol is flammable
How do you distract a plant
Leave in the dark for a few hours
How to investigate the effects of light intensity on rate of photosynthesis
- ) set up apparatus (including gas syringe, ruler, conical flask w water in and light source) and put sodium hydrogencarbonate into water.
- ) place light source at specific distance away from the plant
- ) leave to photosynthesise for a set time
- ) as it photosynthesises, released oxygen will collect in the gas syringe to accurately measure volume of gas produced
- ) repeat w different distances away from light
Why is sodium hydrogen-carbonate added to the water?
To provide it with CO2.
Is a control variable that can be controlled by set amount of sodium hydrogen-carbonate mixed with set amount of water.
Rate of oxygen produced
Volume produced/ time taken
Control variables in investigation into effect of light intensities on rate of photosynthesis
Carbon dioxide concentration (sodium hydrogencarbonate amount)
Temperature (putting in water bath)
Law of limiting factors
When a process depends on 2 or more factors, the rate of that process is limited by the factor which is in short supply.
Light intensity’s effect on photosynthesis graph
At first, no gas is released as rate of photosynthesis= rate of respiration (compensation point) Then the (as light intensity increases), rate of photosynthesis steadily increases up to a certain point in which it plateaus as another factor limits the rate.
Light intensity
Proportional to 1/ distance squared
Relationship between light distance and intensity of light
Inversely proportional
Carbon dioxide’s effect on photosynthesis rate graph
As CO2 concentration increases, so does rate of photosynthesis until plateaus as other factor limits rate.
This is because CO2 is a raw material needed for photosynthesis.
Temperature ‘s effect on photosynthesis rate graph
As temp increases, rate increases (as it gives more kinetic energy to enzymes to carry out photosynthesis) until it reaches an optimum temperature in which it then begins to steadily decrease (enzymes are becoming denatured by the too hot temp)
Temp in which all photosynthesis enzymes are denatured
45 degrees Celsius
2 types of plant transport vessel
Xylem and phloem (go to every part of plant totally separate)
What do root hairs take in and how?
Advantages of a root hair cell?
Minerals and water.
active transport for minerals
Diffusion for water
They have a large surface area
What do phloem tubes transport and how?
Food (ph vs f) - mainly sucrose which is made in leaves
Uses TRANSLOCATION and requires energy from respiration to transport food in both directions to rest of plant for immediate use/ storage.
What are phloem tubes made up of?
Elongated living cells w pores in end walls for stuff to get through.
What does xylem transport and how?
water and mineral ions
They use the TRANSPIRATION STREAM in which transported from roots to the stem to the leaves
What are xylem tubes made up of?
Dead cells joined end to end (no end walls) and hole down middle.
Strengthened with lignin
What’s transpiration
loss of water from the plant, caused by evaporation and diffusion of water from plant surface.
Mainly happens @ leaves.
Creates small shortage of water in leaf, drawing more water up through xylem vessels to replace it.
Is constant transpiration stream throughout which carries minerals dissolved in water
Stomata
Where are they found?
Tiny pores on the surface of a plant, mostly found underneath leaves.
Function of stomata
Allow CO2 and O2 to diffuse directly in and out of a leaf while also allowing water vapour to escape for transpiration.
Exchange gases easily.
Why does transpiration occur?
Because there’s more water outside the plant than in the air outside so they diffuse via the stomata.
What are stomata surrounded by?
What do they do?
2 guard cells
They change shape to control the size of the pore.
What happens when the guard cells are turgid?
The stomata open because they have enough water
What happens when the stomata are flaccid?
The stomata is closed and so they need more water.
V little water can escape
What’s transpiration rate affected by?
Light intensity
Temperature
Air flow
How does light intensity affect transpiration rate?
Brighter light = greater transpiration rate
Stomata begin to close as it gets darker as photosynthesis Cant occur in dark.
How does temp affect transpiration rate?
Warmer= faster transpiration
Warm means particles have more energy to evaporate and so diffuse out of stomata
How does air flow affect transpiration rate?
Greater airflow= greater transpiration
If there’s good airflow (like strong wind), water vapour is swept away, maintaining a low concentration of water in air outside leaf for diffusion.
How do you estimate transpiration rate?
1.) set up apparatus (beaker of water with a capillary tube coming from it and a scale that leads to reservoir water tube and a tube with a plant’s head outside and cork around stem)
Record the starting position of the air bubble.
2.) start a stopwatch and record distance moved by bubble per unit time . Calculating air bubble movement speed gives an estimate of transpiration rate.
Potometer
A piece of apparatus measuring water uptake which correlates to transpiration.
Technically is used to estimate transpiration.
Top layer of leaf
Waxy cuticle
How’s the plant’s surface adapted for photosynthesis?
It has a large surface area for more light needed in photosynthesis and the waxy cuticle helps reduce water loss by evaporation.
Cells underneath the waxy cuticle
Adaptations?
Upper epidermis
Transparent so light can get to palisade layer
Cells under upper epidermis
Adaptations?
Palisade mesophyll (middle) tissue Has many chloroplasts so are near top of leaf for light
Cells under the palisade mesophyll tissue?
Adaptations?
What cells are next to this?
Spongy mesophyll tissue
Contains air spaces which increase diffusion rate of gases in and out.
They are next to xylem/phloem cells
Purpose of xylem and phloem
Form network of vascular bundles providing leaf with water for photosynthesis and taking glucose produced.
Help to support structure.
Cells under spongey mesophyll tissue
Lower epidermis and guard cells w stomata
Desert plants adaptations
Small leaves and spines (reduces surface area for water evaporation and prevent animals drinking from it)
Curled leaves/ hairs (reducing air flow next to leaf to prevent diffusion)
Thick waxy cuticles (reduce evaporation )
Thick, fleshy stem (stores water)
Fewer stomata (only open at night sometimes for less evaporation)
Sunken stomata (reduces air flow)
Translocation
Starch produced via photosynthesis in day and broken down at night, products moved to cytoplasm to make sucrose (soluble) moved via active transport into companion cells w many mitochondria and sieve cells, (no nucleus and v little cytoplasm). Pressure differences move contents up/down.
