6.1.4Plant Nutrition
Minerals in Plants — Cambridge IGCSE Co-ordinated Sciences 0654 - Biology Revision Notes & Topical Questions
5 min read 9 parts Lesson 5 of 11
Part 1 of 7Why plants need minerals
Other molecules
- Plants contain proteins, lipids and nucleic acid (DNA) as well as carbohydrates, and they must make these themselves.
Elements
- Carbohydrates contain carbon, hydrogen and oxygen, but proteins also contain nitrogen.
Chlorophyll
- It contains magnesium and nitrogen.
No source
- Without a source of these elements plants cannot photosynthesise or grow properly.
Part 2 of 7How minerals are obtained
Mineral ions
- Plants obtain these elements as mineral ions absorbed from the soil.
Root hair cells
- They absorb the ions by active transport.
Mineral
- Any naturally occurring inorganic substance.
Part 3 of 7Nitrate ions
Nitrate ions
Function
- Nitrate is a source of nitrogen needed to make amino acids.
- Amino acids are used to build proteins.
Deficiency
- Causes stunted growth and yellowing of leaves.
- Older leaves yellow first because nitrogen is moved to young growth.
- Fewer proteins means less growth of new cells.
Part 4 of 7Magnesium ions
Magnesium ions
Function
- Magnesium is needed to make chlorophyll.
Deficiency
- Causes yellowing between the veins of leaves, called chlorosis.
- Less chlorophyll means less light is absorbed.
- Less photosynthesis means less glucose and reduced growth.
Part 5 of 7Deficiencies compared
| Ion | Needed for | Deficiency symptom |
|---|---|---|
| Nitrate | Amino acids and proteins | Stunted growth and yellowing of leaves |
| Magnesium | Chlorophyll | Yellowing between the veins (chlorosis) |
Part 6 of 7Replacing minerals
Crops
- Farmers remove minerals from the soil when crops are harvested.
Fertilisers
- Fertilisers containing nitrogen, phosphorus and potassium replace the ions.
Part 7 of 7More from the specification
More from the specification
Photosynthesis Biochemical Equation
- Light energy trapped by chlorophyll drives the endothermic reaction between carbon dioxide and water to produce glucose and oxygen: 6CO2 + 6H2O → C6H12O6 + 6O2.
Essential Mineral Requirements in Plants
- Nitrate ions provide nitrogen necessary for synthesising amino acids and proteins,
- whereas magnesium ions form the coordination centre of the chlorophyll ring required for photon capture.
Limiting Factors of Plant Growth
- When investigating photosynthetic rate under varying light intensity, temperature,
- or carbon dioxide concentration, the factor present at the least favourable level limits overall reaction rate.
Starch Synthesis and Accumulation
- Excess glucose produced by mesophyll cells is polymerised into insoluble starch granules, preventing adverse osmotic effects within plant tissues.
Chloroplast
- The organelle of photosynthesis.
Indicator
- A chemical that changes colour depending on pH.
Light intensity
- Amount of light energy falling on a unit area.
Limiting factor
- Something in such short supply that it restricts a life process.
Palisade mesophyll
- A layer of tall, tightly packed cells with many chloroplasts; the main site of photosynthesis.
Starch
- An insoluble polysaccharide of glucose used by plants for energy storage.
Mesophyll
- The tissue in the middle of a leaf where photosynthesis takes place.
Key terms
| Term | Meaning |
|---|---|
| Mineral ion | A dissolved inorganic ion absorbed from the soil. |
| Nitrate | An ion providing nitrogen for amino acids. |
| Magnesium | An ion needed to make chlorophyll. |
| Chlorosis | Yellowing between the veins of leaves. |
| Deficiency | A shortage of a required substance. |
| Fertiliser | A substance added to soil to supply mineral ions. |
Avoid these mistakes
1
Swapping the two ions — nitrate is for proteins and magnesium is for chlorophyll.
2
Saying plants eat minerals — they absorb mineral ions through root hair cells.
3
Saying yellowing is always magnesium — yellowing between the veins is magnesium, stunted growth with yellow leaves is nitrate.
4
Saying minerals pass into roots by diffusion alone — root hair cells absorb them by active transport.
Last updated: