Chapter 10:Plant Nutrition

Question 1

Question: What is the function of the upper epidermis in a leaf?

Answer 1

Answer: The upper epidermis is a layer of transparent cells that allows light to pass through to the mesophyll cells and protects the inner cells of the leaf. It also produces the cuticle to reduce water loss.

Question 2

Question: How does the cuticle benefit a leaf?

Answer 2

Answer: The cuticle is a waxy, waterproof layer covering the epidermis, reducing water loss from the leaf by evaporation.

Question 3

Question: What is the significance of palisade mesophyll cells?

Answer 3

Answer: Palisade mesophyll cells, located just below the upper epidermis, contain many chloroplasts and are the primary site for photosynthesis.

Question 4

Question: What role do spongy mesophyll cells play in a leaf?

Answer 4

Answer: Spongy mesophyll cells are loosely arranged with large air spaces, facilitating gaseous exchange by diffusion between cells and the air.

Question 5

Question: Describe the function of stomata in a leaf.

Answer 5

Answer: Stomata are small pores in the lower epidermis, controlled by guard cells. They allow gaseous exchange (CO₂ and O₂) and transpiration to occur.

Question 6

Question: What do xylem and phloem do in a leaf?

Answer 6

Answer: Xylem transports water and mineral ions, while phloem transports organic substances like sucrose and amino acids by translocation.

Question 7

Question: What is the importance of iron for plants?

Answer 7

Answer: Iron is a micronutrient needed for chlorophyll synthesis, formation of electron carriers, and some enzymes.

Question 8

Question: What are the effects of iron deficiency in plants?

Answer 8

Answer: Iron deficiency causes chlorosis (yellowing of new leaves), stunted growth, and leaves becoming whitish and dying.

Question 9

Question: Why is magnesium important for plant growth?

Answer 9

Answer: Magnesium is needed for chlorophyll synthesis, acts as an enzyme activator, and forms part of the middle lamella in plant cells.

Question 10

Question: What symptoms indicate magnesium deficiency in plants?

Answer 10

Answer: Magnesium deficiency leads to yellowing of older leaves (chlorosis), especially between veins and around the edges, and eventual plant death.

Question 11

Question: What role does phosphorus play in plant growth?

Answer 11

Answer: Phosphorus is needed for synthesizing nucleotides (DNA and RNA), forming ATP, and as a component of cell membranes (phospholipids). It also enhances early growth, root formation, and flower/fruit production.

Question 12

Question: What are the signs of phosphorus deficiency in plants?

Answer 12

Answer: Phosphorus deficiency causes stunted growth, brown areas on leaves and petioles, and poor flower production.

Question 13

Question: Explain the importance of nitrates for plants.

Answer 13

Answer: Nitrates are essential for amino acid synthesis (protein formation), chlorophyll synthesis, nucleotide synthesis, and the production of plant hormones like auxin.

Question 14

Question: What happens to plants when they lack nitrates?

Answer 14

Answer: Nitrate deficiency results in yellowing of leaves, stunted growth, and weak, pale stems and leaves.

Question 15

Question: What is the word equation for photosynthesis?

Answer 15

Answer: Carbon dioxide + water + (chlorophyll & light energy) → glucose + oxygen

Question 16

Question: What is the balanced chemical equation for photosynthesis?

Answer 16

Answer: 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂

Question 17

Question: How can you test for the presence of starch in leaves?

Answer 17

Answer: Boil the leaf, decolorize it with ethanol, rinse in hot water, and cover with iodine solution. If it turns blue-black, starch is present.

Question 18

Question: Why is starch presence used to indicate photosynthesis?

Answer 18

Answer: Starch is the first visible product of photosynthesis, indicating that glucose was produced and converted to starch.

Question 19

Question: How does light intensity affect the rate of photosynthesis?

Answer 19

Answer: At low light intensity, the rate of photosynthesis is slower due to less energy available. Higher light intensity increases the rate.

Question 20

Question: What effect does carbon dioxide concentration have on photosynthesis?

Answer 20

Answer: Insufficient CO₂ limits photosynthesis, while higher CO₂ concentrations increase the rate of photosynthesis.

Question 21

Question: Describe the impact of temperature on photosynthesis.

Answer 21

Answer: Low temperatures slow down photosynthesis. Optimum temperatures (20°C-35°C) increase the rate. High temperatures can stop photosynthesis by denaturing enzymes.

Question 22

Question: How can CO₂ concentration be controlled in a greenhouse?

Answer 22

Answer: By burning fuels, using CO₂ bottles, or ventilating with fresh air to increase CO₂ concentration, enhancing photosynthesis.

Question 23

Question: What methods are used to control light intensity in greenhouses?

Answer 23

Answer: Positioning for maximum natural light, using artificial lights, reducing brightness with blinds, and using reflectors to direct light.

Question 24

Question: How is temperature regulated in greenhouses?

Answer 24

Answer: Using heaters to increase temperature and fans or ventilators to decrease it, maintaining an optimum range for photosynthesis.

Question 25

Question: What is the role of humidity control in greenhouses?

Answer 25

Answer: Sprinkler irrigation systems or hydroponics provide a continuous water supply, maintaining optimum humidity for plant growth.