Nutrition and Gas Exchange in Plants

• What is the process of photosynthesis?


  Conversion of light energy from the sun into chemical energy by chlorophyll

  
• Why is photosynthesis important?

  It converts light energy to chemical energy, producing glucose stored as starch

  
• What is the word equation for photosynthesis?

  Carbon dioxide + Water → Glucose + Oxygen

  
• What is the balanced chemical symbol equation for photosynthesis?

  $6CO_2 +$$6H_2O \rightarrow C_6H_{12}O_6 +$$6O_2$
• How does carbon dioxide concentration affect the rate of photosynthesis?

  Higher carbon dioxide concentration increases the rate of photosynthesis until it becomes a limiting factor

  
• What is the effect of light intensity on photosynthesis?

  Higher light intensity increases the amount of light energy available for chlorophyll to absorb

  
• How does temperature affect the rate of photosynthesis?

  Increased temperature up to the optimum level increases enzyme activity and the rate of photosynthesis

  
• What are the main structures of a leaf adapted for photosynthesis?

  • Wax cuticle: Prevents water evaporation
  • Upper epidermis: Thin and transparent for light entry
  • Palisade mesophyll: Packed with chloroplasts for light absorption
  • Spongy mesophyll: Air spaces for gas diffusion
  • Lower epidermis: Contains guard cells and stomata

  
• What is the function of the wax cuticle in a leaf?

  It acts as a protective layer that prevents water from evaporating
• Why is the upper epidermis of a leaf thin and transparent?

  To allow light to enter the palisade mesophyll
• What is the role of the palisade mesophyll in photosynthesis?

  It is tightly packed with chloroplasts to absorb more light

  
• What is the function of the spongy mesophyll in a leaf?

  It contains air spaces that increase the surface area for gas diffusion

  
• What do guard cells do in a leaf?

  They absorb and lose water to open and close the stomata for gas exchange
• What is the function of stomata in a leaf?

  They are the sites where gas exchange takes place
• What are the adaptations of leaves for photosynthesis?

  • Large surface area for gas diffusion and light absorption
  • Thin structure for easy diffusion of carbon dioxide
  • Presence of chlorophyll for light energy absorption
  • Network of veins for transport of water and carbohydrates
  • Stomata for carbon dioxide diffusion
  • Thin and transparent epidermis for light penetration
  • Thin wax cuticle for protection without blocking sunlight

  
• Why do plants require mineral ions for growth?

  Mineral ions are essential for various functions, including the production of chlorophyll and amino acids
• What is the role of nitrate ions in plants?


  Nitrate ions contain nitrogen needed to make amino acids and proteins
• What happens if plants do not get enough nitrates?

  They exhibit stunted growth and yellow older leaves
• What is the role of magnesium ions in plants?

  Magnesium ions are needed to make chlorophyll
• What are the symptoms of magnesium deficiency in plants?

  Plants develop yellow leaves
• What are the steps to investigate photosynthesis using a water plant?


  1. Set up the apparatus and change variables.

  2. Leave for 5 minutes for adaptation.

  3. Count the number of bubbles produced.

  4. Vary the light intensity by changing the distance of the lamp.

  5. Control carbon dioxide levels using sodium hydroxide and sodium bicarbonate.

  6. Use a variegated plant to test for chlorophyll.

  
• What is the origin of carbon dioxide and oxygen as waste products in plants?

  Carbon dioxide is produced during respiration, while oxygen is a waste product of photosynthesis

  
• How do gases diffuse in and out of a leaf?

  Gases diffuse through the stomata when they are open during the day
• What happens to carbon dioxide and oxygen during photosynthesis and respiration?

  Photosynthesis uses carbon dioxide and produces oxygen, while respiration uses oxygen and produces carbon dioxide

  
• How does the intensity of light affect the net exchange of gases in plants?

  The net exchange of gases depends on the balance between photosynthesis and respiration, which is influenced by light intensity

  
• When does respiration occur in plants?


  Respiration occurs both during the day and night
• What is the role of stomata in gas exchange?

  Stomata open and close to allow for gas exchange
• What are the steps to investigate the effect of light on net gas exchange using hydrogen-carbonate indicator?

  1. Place hydrogen carbonate indicator in boiling tubes.

  2. Add healthy leaves to three tubes and seal with rubber bungs.

  3. Control one tube without a leaf as a control.

  4. Wrap one tube in aluminum foil, another in gauze, and leave one uncovered.

  5. Leave all tubes in bright light for one hour.