Nutrition in Flowering Plants

Question 1

Describe the distribution of Chloroplasts in a leaf

Answer 1

Palisade Mesophyll:
Highest concentration of chloroplast -> Main site of photosynthesis

Spongy Mesophyll:
Lower concentration of chloroplast -> Some photosynthesis occurs here

Question 2

State the functions of the Vascular Tissues

Answer 2

Xylem:
Transports Water and dissolved Mineral Salts from the roots to the mesophyll cells

Phloem:
Transports Synthesised Sucrose and Amino Acids away from the leaf to the rest of the plant

Question 3

Describe the Upper and Lower Epidermis functions

Answer 3

Upper Epidermis:
-Covered by a Waxy and Transparent Cuticle to reduce water loss due to evaporation of water from the epidermal cells
-Transparent to allow light to pass through to the palisade layer

Lower Epidermis:
-Many Stomata present which allow for gaseous exchange between air spaces in the Spongy Mesophyll and the surrounding atmosphere
-Also has a Waxy and Transparent Cuticle

Question 4

State the 4 differences between Guard Cells and Epidermal Cells

Answer 4

Guard Cells:
-Bean-shaped
-Contain chloroplast
-Control size of the Stomata (Function)
-Cell wall near the Stoma is thicker than the rest of the cell wall

Epidermal Cells:
-Irregularly-shaped
-Do not contain chloroplast
-Protect the inner regions of the leaf (Function)
-Uniform thickness in the cell wall

Question 5

State the 4 step process on how the Stoma opens

Answer 5

1. Water potential of the cell sap of the guard cells is decreased by:
   -Increase in glucose concentration
   -The glucose is then metabolised to release chemical energy via respiration to pump potassium ions (K+) from neighbouring epidermal cells into the guard cells
2. Water from neighbouring epidermal cells enters the guard cells by osmosis so that they swell and become turgid
3. The guard cells have a thicker cellulose wall on the inner side of the cell around the stoma. Hence, the swollen guard cells curve around the stoma and the stoma opens

Question 6

State the 3 step process on how the Stoma closes

Answer 6

1.The potassium ions (K+) accumulated in the guard cells during the day diffuse out of the guard cells

2. This increases the water potential in the guard cells and water leaves them by osmosis
3. The guard cells become flaccid and the Stoma closes

Question 7

Explain why the Stoma remains closed on very hot days

Answer 7

On very hot days, there is excess evaporation of water. Hence, the stoma closes to prevent excessive water loss from the leaf by reducing the amount of water vapour escaping from the leaf

Question 8

State the Word and Chemical Equation of Photosynthesis

Answer 8

Word Equation:
Water + Carbon Dioxide ————> Glucose + Oxygen
(Light+ Chlorophyll)

Chemical Equation:
6H2O + 6CO2 ————> C6H12O6 + 6O2
(Light + Chlorophyll)

Question 9

State the Word and Chemical Equation of Respiration

Answer 9

Word Equation:
Glucose + Oxygen —> Water + Carbon Dioxide + Energy

Chemical Equation:
C6H12O6 + 6O2 —> 6H2) + 6CO2 + Energy (36 ATP)

Question 10

Describe the differences between Photosynthesis and Aerobic Respiration

Answer 10

Photosynthesis:
-Anabolic process — Synthesis of carbohydrate molecules from simple inorganic molecules
-Energy is accumulated and stored in glucose
-Results in an increase in dry mass

Aerobic Respiration:
-Catabolic process — Breakdown of carbohydrate molecules into simple inorganic molecules
-Energy is incorporated into ATP
-Results in a decrease in dry mass

Question 11

State the 5 outcomes of Glucose produced via Photosynthesis

Answer 11

1. Used immediately in leaf
   - For cellular respiration to provide energy for cellular activities
   -To form cellulose cell walls
2. a) In daylight, formation of glucose > depletion of glucose. Excess glucose is converted into Starch
3. b) In darkness, photosynthesis stops and starch is converted back to glucose to be used
4. Converted to Synthesised Sucrose
   -To be transported to other parts of the plant / storage organs
   -May be converted to other forms of storage compounds at storage organ
5. Converted to Amino Acids (Requires Nitrates from Mineral Salts)
   -Used to form proteins which are used for synthesis of new protoplasm in leaves
   -Excess amino acids is transported to other parts of the plant to be used or stored
6. Converted to Fats
   -For storage
   -To be used in cellular respiration
   -For synthesis of new protoplasm

Question 12

State the 4 factors affecting the Rate of Photosynthesis

Answer 12

1. Light Intensity
2. Light Colour
3. Concentration of Carbon Dioxide
4. Temperature