B5 - Plant nutrition Flashcards
Photosynthesis definition
The process by which plants manufacture carbohydrates (as nutrition) from raw materials using energy from light
- conversion of light energy from the sun into chemical energy
Photosynthesis balanced equation
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Use of carbohydrates in plants (name 4)
- Converted into starch molecules which act as an effective energy store
- Converted into cellulose to build cell walls
- Glucose can be used in respiration to provide energy
- Converted to sucrose for transport in the phloem
- As nectar to attract insects for pollination
- Converted into lipids for energy storage in seeds
- Combined with nitrate minerals to make amino acids (proteins)
Carbon dioxide
- raw material gas found in the atmosphere
- absorbed by stomata of the leaves and used in chloroplasts for photosynthesis
Oxygen
- through photosynthesis: water is transformed into oxygen by the movement of electrons
- diffused as a waste product through the stomata
Chlorophyll and its function
- Green pigment that is found in chloroplasts within plant cells
- it is this pigment which gives plants their characteristic green colour - Transfers energy from light into energy in chemicals, for the synthesis of carbohydrates
- is essential for photosynthesis to occur
Nitrogen ions in plants
- majorly used to make amino acids (the building blocks of proteins)
- are also a part of chlorophyll
Magnesium ions in plants
- major component in making chlorophyll in chloroplasts
- therefore necessary in photosynthesis
Nitrate ion deficiency in plants
Causes stunted growth and yellowing leaves from a lack of chlorophyll
Magnesium ion deficiency in plants
Causes yellowing between the veins of the leaf (chlorosis)
Sunlight use in photosynthesis
Provides the initial light energy that starts the process of photosynthesis and is then transferred into chemical energy
What effects the rate of photosynthesis? (3)
- light intensity
- carbon dioxide concentration
- temperature
Minerals in plants
Nitrogen, magnesium, phosphorus, potassium
- Plants obtain these elements in the form of mineral ions actively absorbed from the soil by root hair cells
Protein synthesis
The formation of proteins by using information contained in DNA and carried by mRNA
- happens subsequent to photosynthesis
Testing for the presence of starch (5 steps)
- A leaf is dropped in boiling water to kill the cells and break down the cell membranes
- The leaf is left for 5-10 minutes in hot ethanol in a boiling tube. - This removes the chlorophyll so colour changes from iodine can be seen more clearly
- The leaf is dipped in boiling water to soften it
- The leaf is spread out on a white tile and covered with iodine solution
- In a green leaf, the entire leaf will turn blue-black as photosynthesis is occurring in all areas of the leaf
Investigating the need for carbon dioxide
- Destarch two plants by placing in the dark for a day
- Place one plant in a jar which contains a beaker of sodium hydroxide (which will absorb carbon dioxide from the surrounding air)
- Place the other plant in a jar which contains a beaker of water (control experiment), which will not absorb carbon dioxide from the surrounding air
- Place both plants in bright light for several hours
- Test both plants for starch using iodine
- The leaf from the plant placed near sodium hydroxide will remain orange-brown as it could not photosynthesise due to lack of carbon dioxide
- The leaf from the plant placed near water should turn blue-black as it had all necessary requirements for photosynthesis
Investigating the need for light in photosynthesis
- Plant needs to be destarched by placing in a dark cupboard for 24 hours
- this ensures that any starch already present in the leaves will be used up and will not affect the results of the experiment
- Following destarching, a leaf of the plant can be partially covered with aluminium foil (which resists light) and the plant placed in sunlight for a day
- The leaf can then be removed and tested for starch using iodine
- the area of the leaf that was covered with aluminium foil will remain orange-brown as it did not receive any sunlight and could not photosynthesise, while the area exposed to sunlight will turn blue-black
Investigating the need for chlorophyll (variegated leaf)
- The white areas of the leaf contain no chlorophyll and when the leaf is tested only the areas that contain chlorophyll stain blue-black
- The areas that had no chlorophyll remain orange-brown as no photosynthesis is occurring here and so no starch is stored
Investigating the rate of photosynthesis (light)
Use a type of aquatic plant:
- put into a boiling tube or an into an inverted funnel in a cylinder with a rotated measuring tube above it
- cut the stem of the pondweed
- move the tube/cylinder near the light source (10cm) and leave it over time to adjust
CASE 1: bubbles
- As photosynthesis occurs, oxygen gas produced is released
- As the plant is in water, the oxygen released can be seen as bubbles leaving the cut end of the pondweed
- The number of bubbles produced over a minute can be counted to record the rate
- the more bubbles produced per minute, the faster the rate of photosynthesis
- Repeat process over larger distances from light source
CASE 2: volume of bubbles
- The bubbles produced will move up the funnel and collect in measuring tube
- this will take longer time
- give the volume of oxygen
CONCLUSION:
- the further the light source (lower the light intensity) the slower the rate of photosynthesis
Investigating the rate of photosynthesis (carbon dioxide)
Use a type of aquatic plant:
- put into an inverted funnel in a cylinder with a rotated measuring tube above it
- cut the stem of the pondweed
- Dissolve starting amount of sodium hydrogen carbonate in water (creates CO2)
- change amount over time and record change
Investigating the rate of photosynthesis (temperature)
Use a type of aquatic plant:
- put into an inverted funnel in a cylinder with a rotated measuring tube above it
- cut the stem of the pondweed
- Put a hot plate beneath the cylinder and begin to heat up the water within it (make sure a thermometer is used and all other factors are kept the same)
- change temperature and assess
Graph description of limiting factors of photosynthesis
1. Temperature: As temperature increases the rate of photosynthesis increases; as the reaction is controlled by enzymes, this trend only continues up to a certain temperature beyond which the enzymes begin to denature and the rate of reaction decreases
2. Light intensity: The more light a plant receives, the faster the rate of photosynthesis; this trend will continue until some other factor required for photosynthesis prevents the rate from increasing further because it is now in short supply (e.g temp.)
3. Carbon dioxide: the more carbon dioxide that is present, the faster the reaction can occur; this trend will continue until some other factor required for photosynthesis prevents the rate from increasing further because it is now in short supply
Waxy cuticle function and adaptation
Function: protective layer on top of the leaf, prevent water from evaporating
Adaptation: thin and transparent to allow light to pass through it but has a waxy surface to resist osmosis
Upper epidermis function and adaptation
Function: the part of the leaf above the palisades layer that prevents the loss of water found above palisade mesophyll
Adaptation: thin and transparent to allow light to pass to palisade layer beneath it
Palisade mesophyll function and adaptation
Function: Layer of tall, column-shaped mesophyll cells just under the upper epidermis of a leaf; full of chloroplasts used for photosynthesis
Adaptation: tightly-packed together and full of chloroplasts to maximise light absorption; rectangular shape increases surface area; large vacuole for water storage
Spongy mesophyll function and adaptation
Function: layer of loose tissue found beneath the palisade mesophyll in a leaf, widely spaced to allow gas exchange and also acts for photosynthesis
**Adaptation: **contains internal air spaces that increase the surface area to volume ratio for the diffusion of gases
Lower epidermis function
Protective layer on the bottom of leaf which contains stomata & guard cells
Guard cells function and adaptation
Function: absorbs and loses water to open and close the stomata to allow carbon dioxide to diffuse in and oxygen to diffuse in
Adaptation: wall of the guard cell is differentially thickened with the inner membrane to open the stoma when turgid; opens in an oval shape to aid diffusion and flattens when closed
Stomata function and adaptation
Function: where gas exchange takes place; opens during the day and closes during the night; evaporation of water also takes place
Adaptations: allows different gases to diffuse into separate areas
Vascular bundle function and adaptation
Function: contains xylem and phloem to transport substances to and from the leaf
Adaptation: thick cell walls of tissues help to support stem and leaf
Xylem function
Transports water into the leaf for mesophyll cells to use in photosynthesis and for transpiration through stomata
Phloem function
Transport minerals (sucrose and amino acids) around the plant
