Plant Nutrition. Flashcards
What is photosynthesis?
The process by which plants synthesise carbohydrates from raw materials using energy from light.
What is the word equation for photosynthesis?
Carbon dioxide + water → glucose + oxygen.
in the presence of light and chlorophyll.
In the presence of light and chlorophyll.
What does the photosynthesis reaction require and what is it obtained from?
The reaction requires light energy which is obtained by the green pigment chlorophyll in the chloroplasts that traps light energy and transfers it to chemical energy for the synthesis of carbohydrates.
What is the chemical equation for photosyntheis?
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Give 5 uses for the carbohydrates made in photosynthesis.
- starch as an energy store.
- cellulose to build cell walls.
- glucose used in respiration to provide energy.
- sucrose for transport in the phloem.
- nectar to attract insects for pollination.
Minerals are taken up actively by root hair cells and have a variety of important roles in the plant.
Name the two most important minerals and their functions.
Nitrate ions for making amino acids and magnesium ions for making chlorophyll.
- Magnesium ions.
What is the use of nitrate ions in plants?
Nitrate ions are used in the plant to build amino acids, and thus proteins and enzymes.
Describe the test for starch production (5).
A leaf is dropped in boiling water.
The leaf is left in hot ethanol in a boiling tube.
The leaf is dipped in boiling water to soften it.
The leaf is spread out on a white tile and covered with iodine solution.
RESULT: In a green leaf, the entire leaf will turn blue-black as photosynthesis is occurring in all areas of the leaf.
Describe the test that shows leaves need for chlorophyll for photosynthesis.
A destarched variegated leaf is dropped in boiling water.
The leaf is left in hot ethanol in a boiling tube.
The leaf is dipped in boiling water to soften it.
The leaf is spread out on a white tile and covered with iodine solution.
RESULTS: The white parts of the leaf contain no chlorophyll so no photosynthesis takes place and the iodine solution remains orange. The green part of the leaf contains chlorophyll which is needed for photosynthesis to make starch and the iodine solution turns blue-black.
Describe the test that shows leaves need for light in photosynthesis (4).
- Before starting the experiment the plant needs to be destarched by placing in a dark cupboard for 24 hours.
- A leaf of the plant can be partially covered with aluminum foil and the plant placed in sunlight for a day.
- The leaf can then be removed and tested for starch using iodine.
RESULT: 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.
Describe the test that shows leaves need for carbon dioxide in photosynthesis.
Destarch a plant.
Tie a clear bag containing soda lime, which will absorb carbon dioxide from the surrounding air.
Place the plant in bright light for several hours.
Test both leaves for starch using iodine.
RESULT: 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.
Describe the test for oxygen.
- The plants used are aquatic plants.
- 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 aquatic plant into the inverted test tube.
- To test if the gas released is oxygen, place a glowing splint in the test tube and if it relights, oxygen is the gas present.
CORE INFORMATION FOR RESULTS - 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.
A leaf is dropped in boiling water for the starch experiment. Why?
To kill the cells and break down the cell membranes.
The leaf is left in hot ethanol in a boiling tube for the starch experiment. Why?
This removes the chlorophyll so colour changes from iodine can be seen more clearly.
Why is the Bunsen burner be turned off after boiling the leaf?
Ethanol is extremely flammable, so at that stage of the experiment, the Bunsen burner should be turned off.
