Plant Nutrition Flashcards
Photosynthesis
the process by which plants manufacture carbohydrates from raw materials using energy from light
word equation and balanced chemical equation for photosynthesis:
- Carbon dioxide + water → glucose + oxygen, in the presence of light and chlorophyll
- 6CO +6HO -> C6H12O6 +6O2, in presence of light and chlorophyll
Chloroplasts
-Photosynthesis occurs in chloroplast of plants, chloroplast contains chlorophyll, Chlorophyll transfers light energy into chemical energy in molecules, for the synthesis of carbohydrates
subsequent use and storage of the carbohydrates made in photosynthesis
- Chloroplasts containing chlorophyll are responsible for trapping light energy.
- This energy is converted to chemical energy for the formation of carbohydrates (glucose);
- Glucose is usually changed to sucrose for transport around the plant, or to starch for storage;
- Oxygen is released as a waste product, or used by the plant for respiration.
the necessity of chlorophyll for photosynthesis, using appropriate controls
-A leaf is dropped in boiling water to kill the cells and break down the cell membranes
-left for 5-10 minutes in hot ethanol in a boiling tube, 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 occuring in all areas of the leaf
This method can also be used to test whether chlorophyll is needed for photosynthesis by using a variegated leaf (one that is partially green and partially white)
-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
-ethanol is extremely flammable, so at that stage of the experiment the Bunsen burner should be turned off. Safest way to heat the ethanol is in an electric water bath
the necessity of light for photosynthesis, using appropriate controls
- Before starting the experiment the plant needs to be destarched by placing in a dark cupboard for 24 hours, 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 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
- This proves that light is necessary for photosynthesis and the production of starch
the necessity of carbon dioxide for photosynthesis, using appropriate controls
- Destarch a plant
- Tie a clear bag containing sodium hydroxide, which will absorb carbon dioxide from the surrounding air, around one leaf
- Tie a clear bag containing water (control experiment), which will not absorb carbon dioxide from the surrounding air, around another leaf
- Place the plant in bright light for several hours.
- Test both leaves for starch using iodine
- The leaf from the bag containing sodium hydroxide will remain orange-brown as it could not photosynthesise due to lack of carbon dioxide
- The leaf from the control bag containing water should turn blue-black as it had all necessary requirements for photosynthesis
Investigate and describe the effects of varying light intensity, carbon dioxide concentration and temperature on the rate of photosynthesis, e.g. in submerged aquatic plants (inverted Funnel)
A. Set up the apparatus, Make sure that the test tube is completely full of water.
B. Vary the light intensity by changing the distance of light from the plant.
C. Count the number of bubbles produced per minute or the volume of gas (oxygen) collected after 10 minutes for each different intensity of light.
Control variables: Type of plant, size of plant, amount of water in the trough, amount of time to collect the volume of gas.
-As light intensity increases, so does the rate of photosynthesis.
-As the lamp is moved closer, the light intensity increases.
-The rate of photosynthesis is directly proportional to the light intensity.
-However the photosynthetic rate cannot be increased indefinitely, a point is reached where all the chloroplasts cannot trap anymore light.
Limiting factor
something present in the environment in such short supply that it restricts life processes
Identify and explain the limiting factors of photosynthesis in different environmental conditions
- CO2 Concentration: As CO2 concentration increases, rate of photosynthesis also increases.
- Temperature: Photosynthesis requires enzymes to carry out reaction, Enzymes as well as photosynthesis (25°C) has an optimum temperature. At low temperatures (winter) plants photosynthesis slowly, as enzymes has less kinetic energy, thus few enzyme-substrate complexes are made. At high temperatures, Enzymes denature, slowing rate of photosynthesis.
- Light intensity: As light intensity increases, rate of photosynthesis increases, high light intensity, lead plant heating above optimum temperature, thus temperature is limiting factor, rate of photosynthesis would not increase by further increase in light intensity.
use of carbon dioxide enrichment, optimum light and optimum temperatures in glasshouses in temperate and tropical countries
CO2:
- Growers can pump CO2 into glasshouses to increase conc.
- Can also burn BUTANE or NATURAL GAS which: provide CO2 and heat -> raise temp. in cold weather
Optimum light:
- Glass lets in sunlight
- ARTIFICAL LIGHTING for when light intensity is too low
- BLINDS keep out very strong light
- SHADING lowers temp. in tropical countries
Optimum Temperature:
- Sunlight heats up inside of glasshouse
- Glass stops heat escaping
- ELECTRIC HEATERS used in cold weather
- VENTILATOR FLAPS are opened to cool the glasshouse on hot days
- Allow plants to:
- Grow earlier in the year
- Grow in places where they would not normally grow well
- All these conditions are monitored by:
- Sensors which detect changes in limiting factors
- Computers which collect data from sensors and control all heating, ventilation, lighting, and shading
Describe the use of water in glasshouses in temperate and tropical countries
- AUTOMATIC WATERING SYSTEMS using SPRINKLERS and HUMIDIFIERS so plants always get enough water
Use hydrogen carbonate indicator solution to investigate the effect of gas exchange of an aquatic plant kept in the light and in the dark
- hydrogen carbonate indicator solution is RED
1. - 1st: Set up a test tube w/ 10 cm pondweed, TINFOIL (to prevent light passing) and hydrogen carbonate indicator - 2nd: Set up a test tube with 10 cm pondweed and hydrogen carbonate indicator
- 3rd: CONTROL Set up a test tube with hydrogen carbonate indicator solution ONLY
2. Leave the test tubes near a light for 2-3 hours - If carbon dioxide is added to the water by the plant the solution will turn YELLOW.
- If carbon dioxide is removed from the water by the plant the solution will turn PURPLE.
- 1st will turn yellow bc carbon dioxide was ADDED by PONDWEED bc of RESPIRATION (since there was no sunlight)
- 2nd will turn purple bc carbon dioxide was TAKEN IN by PONDWEED for PHOTOSYNTHESIS
- 3rd is red bc CONTROL
Identify chloroplasts, cuticle, guard cells and stomata, upper and lower epidermis, palisade mesophyll, spongy mesophyll, vascular bundles, xylem and phloem in leaves of a dicotyledonous plant
In textbook
Explain how the internal structure of a leaf is adapted for photosynthesis
Palisade mesophyll:
- Are packed TIGHTLY together, NEAR THE UPPER SURFACE of the leaf to maximise absorption of light where its intensity is highest
- Has MANY CHLOROPLASTS to absorb as much light as possible
Stomata:
- Open to allow carbon dioxide to diffuse into the leaf. Carbon dioxide is a raw material for photosynthesis
Leaves:
- Are THIN so that carbon dioxide does not have to diffuse FAR from the atmosphere to the cells of the palisade and spongy mesophyll
Spongy mesophyll:
- Spaces in spongy mesophyll allow easy diffusion of carbon dioxide. Diffusion through air is faster than diffusion from cell to cell
Xylem:
- Bring water and ions to mesophyll cells. Water is a raw material for photosynthesis and magnesium ions are needed to make chlorophyll
Phloem:
- Sugar from photosynthesis is converted to sucrose and is transported away by phloem
Stomata:
- Open and closed by GUARD CELLS
- Open during the DAY (bc sunlight present = photosynthesis); water passes in through OSMOSIS –> they swell, bend and open
- CO2 diffuses into leaf, O2 and water vapour out
- At NIGHT water passes OUT by OSMOSIS–> guard cells STRAIGTEN –> stomata closes
+ Stomata also closes during extreme conditions such as drought to prevent water loss, and wilting
