Please enable JavaScript.
Coggle requires JavaScript to display documents.
Plant structure and their function I - Coggle Diagram
Plant structure and their function I
Photosynthesis
Process that plants use to make their own food (glucose)
Uses energy from the sun to convert carbon dioxide and water into glucose and oxyen
Photosynthetic organism are the main producers of food and therefore biomass.
Biomass is the mass of living material at a particluar stage in a food chain, this energy works its way through the food chain as animals eat them and then eahcother
Where does it happen?
Takes place in chloroplasts
Contain pigments called chlorophyll that absorb light
Happens in the leaves of all green plants
Carbon dioxide + Water --> Glucose + Oxygen
Endothermic reaction
Limiting factors
What is a limiting factor?
The rate of photosynthesis is affected by light intensity, CO2 concentration and temperature
All three must be at the right temperature to allow the plant to work as quickly as possible
If any of the factors is too high ot too low, it will become a limiting factor
A factor which is stoppping photosynthesis from happening any faster, even if other factors are increased, the rate won't increase
CO2 concentration
CO2 is one of the raw meterials needed fro photosynthesis
Rate of photosynthesis increases as the carbon dioxide concentration increases
The amount of CO2 will only increase the rate up to a point
If the conentration increases, but the rate doesn't then CO2 conentration isn't the limiting factor
At this point either light intensity or temperature are
Temperature
Photosynthesis gets faster as the temperature increases, but only up to a certain temperature
If the temperature gets too hot, the rate slows down
Ezymes increase the rate of photosynthesis, the speed at which the enzymes works is affected by temperature
If the temperature is too low, the enzymes will work more slowly
If plants get too hot, the enzymes become damaged
Light intensity
Light provides energy for photosynthesis,higher the light intensity, the faster the rate of reaction
After a certain point, increasing light intensity won't make a difference to the rate
Temperature or CO2 concentration will be the limiting factors
Investigating the rate of photosynthesis
Aim: To investigate how light intensity affects the rate of photosynthesis
Method
1) Place 20 agal balls in the same volume of sodium hydrogencarbonate indicator and place the lid
2) Use a ruler to measure the place the agal balls at specifc distances from the lamp
3) Set up a control variable, by placing the agal balls in a dark cupboard, to show that its light light that will cause a colour change
4) Leave the agal balls for 1 hour
5) In a table record the distance and pH of each bottle
Conclusion
As distance increase, light intensity falls
Photosynthesis rate decreases
This is because enegry transferred by light is needed for photosynthesis to take place
Closer to the light, more photosynthesis will occur, so less CO2 and a lower pH sicne CO2 is an acidic gas, purple in colour
Further away from the light, there will be more CO2 and a lower more acidic solution, yellow in colour
Inverse square law
Rate of photosynthesis is direcctly proportional to light intensity
Rate of photosynthesis and distance from a light source are inversley proportional
Light intensity is proportional to 1/distance squared
A measure of light
Xylem
Made from dead cells
No cells walls between cells and a hole in the middle
Strengthened with lignin, prevents them collapsing
Carry water and mineral ions from the roots to the stem and leaves
Transpiration
The loss of water by evapouration from the leaves.
The movement of water from the roots to the leaved is called the transpiration stream
Transpiraiton stream
Water vapour evapourates from leaves through the stomata
This draws water up from the rest of the plant though the xylem
This means more water is drawn from the roots, so there's a constant transpiration stream of water though the plant
Stomata
Found on the lower surface of the leaf
Allow CO2 and oxygen to diffuse directly in and out of the leaf
When the plants have lots of water, guard cells fill with water and become turgid, this opens the stomata so gases can be exchanged for photosynthesis
When the plant is short of water, the guard cells lose water and become flaccid. closing the stomata, this helps to stop stoo much water vapour escaping, they are also on the underside of the leaf
Guard cells are light sensetive, so dont open at night to prevent water loss
Factors affecting transpiration rate
Light intensity
Guard cells are light sensetive, so during the day when they open the stomata, the transpiration rate is highest
During the night when the stomata are closed, the rate is low
Air movement
Wind blows moist air away from the plant
Causes a high concentration gradient leading to an increase in transpiration rate
Will eventually plateau because all the stomata are open
Temperature
Water particles have more kinetic energy at higher temperatures
More evaporation and more diffusion leads to more pull through the plant
Will eventaully plateau as the rate can't keep up
Humidity
At high humidity, the is alot of water in the air
Causes a low concentration gradient between he air and the plant
Water wont diffuse out of the plant, and the rate is low
At low humidity, there is a high concentration gradient and a high rate
Using a potometer
Measure the rate of transpiration
1) Note the position of the air bubble on the ruler before you start
2) Note the position of the bubble on the ruler after the experiment
3) Divide the distance moved by the bubble by the time taken, the further the bubble moves, the great the transpiration rate
Phloem
Made from living cells
Transport products of photosynthesis (sucrose) made in the leaves to the plant
Travels in both directions
Process is called translocation
Translocation
The transport of sucrose around a plant for immediate use or storage
Dissolved sugars are transported through the phloem
Sucrose is produced from in the leaves from glucose formed during photosynthesis
Dissolved sucrose is transported to areas that need it
Location of sources and sinks depends on the season, in the spring the source could be in the roots and the sink in the leave, in the summer
Adaptations
Cell walls of each cell form sieve plates allowing the movement of subsances for cell to cell
Cells are alive
Energy cells need is supplied by the mitochondira
Leaf Adaptations
Epidermal tissues of the leaf are covered with a thick waxy cuticle, which helps reduce water loss from the leaf by evapouration
Upper epidermis - transparent so that light can pass through
Palisade cells - contain lots of chloropasts, where photosynthesis takes place, they are near the top of the leaf where they get the most light
Xylem and Phloem - Form a network of vascular bundles, to deliver water and nutrients to the entire plant, they support the structure. Xylem cells contain lignin, which strengthens the cells
Leaves - Large surface area exposed to light for photosynthesis
Lower epidermis - full of stomata for gas exchange
Spongy mesophyll - air spaces increase the rate of diffusion
Root Hair cell - Large surface area for water absorbtion, have mitochondira with provide energy from transpiration for the active transport of mineral ions to root hair cells
Stomata - Able to close to minimise wate rloos and open to increase evapouration and transpiration, Stomata allows gas exchange to occure when they open