mineral nutrition

Question 1

What is the difference between autotrophy and heterotrophy in plants?

Answer 1

• Autotrophy: The ability to use light energy to produce organic compounds from carbon and minerals (e.g., plants, green algae, and green bacteria).
• Heterotrophy: The dependence on organic compounds supplied by other organisms for nutrition.

Question 2

What is the difference between organic and inorganic nutrition in plants?

Answer 2

• Organic nutrition: Involves the uptake of carbon, oxygen, and hydrogen to produce carbohydrates, proteins, lipids, and nucleic acids.
• Inorganic nutrition (also called mineral nutrition): Involves the uptake of mineral nutrients from the soil.

Question 3

What are the key components of soil?

Answer 3

• Soil is a dynamic and heterogeneous substrate containing solid, liquid, and gaseous phases.
• Nutrients are contained in colloids, forming micelles.
• Soil colloids are generally negatively charged, so they retain positively charged ions and leach negatively charged ions like nitrate.

Question 4

How do roots adapt to nutrient uptake in the soil?

Answer 4

• Roots develop length, density, and complexity based on soil properties and nutrient availability.
• Nutrient transport occurs by passive diffusion or facilitated transport, which may require energy.

Question 5

How are nutrients transported inside plants?

Answer 5

• Symplastic transport: Nutrients move through plasmodesmata from one cell to another until reaching the xylem.
• Apoplastic transport: Nutrients travel through the apoplast until the Casparian band, then are transported into the root cells to enter the xylem.

Question 6

What are the main types of nutrient transport in plants?

Answer 6

• Simple diffusion: Movement of ions down their concentration gradient without energy (e.g., CO₂, O₂, NH₃).
• Facilitated transport: No energy required, but relies on channel and carrier proteins to assist ion movement.
• Active transport: Requires ATP to move ions against their concentration gradient (e.g., ATPase-proton pumps).

Question 7

What happens when plants experience nutrient deficiencies or toxicity?

Answer 7

• Deficiencies: Lead to symptoms like yellowing leaves (chlorosis) due to lack of nitrogen, potassium, iron, or phosphorus.
• Toxicity: Can occur from excessive uptake of minerals, disrupting plant growth.
• Fertilization is a common solution to correct deficiencies.

Question 8

How do plants optimize nutrient uptake through relationships with other organisms?

Answer 8

• Mutualism: Both partners benefit (e.g., plants and nitrogen-fixing bacteria).
• Symbiosis: One partner benefits, and the other may be neutral or also benefit.
• Soil is a complex ecosystem with bacteria and fungi that affect plant health.

Question 9

What are mycorrhizae, and how do they benefit plants?

Answer 9

• Mycorrhizae are fungal associations with plant roots that improve nutrient uptake, especially phosphorus.
• Types of mycorrhizae:
  Ectomycorrhizae: Fungal sheaths around roots but no cell penetration.
  Endomycorrhizae: Fungi penetrate root cortical cells.
  Ectendomycorrhizae: Features of both ecto- and endo-mycorrhizae.

Question 10

How do plants benefit from their association with bacteria?

Answer 10

• Plants provide carbohydrates to bacteria, and in return, bacteria supply mineral nutrients (e.g., nitrogen fixation).
• Rhizobium bacteria form a symbiotic relationship with legume roots, creating root nodules where nitrogen fixation occurs.

Question 11

How does nitrogen fixation occur in plants?

Answer 11

• Rhizobium bacteria in legumes use ATP to reduce N₂ to NH₃, which is then processed into glutamine by glutamine synthetase.
• Cyanobacteria (e.g., Anabaena) also fix nitrogen in specialized cells called heterocysts, often in ferns or rice fields.