6. Plant nutrition Flashcards
Photosynthesis
The chemical process by which plants manufacture carbohydrates from raw materials using energy from light.
Carbon dioxide + Water –> Glucose + Oxygen
Products needed for photosynthesis
- Carbon dioxide
- Water
- Chlorophyll
- Chloroplasts
- Sunlight
Balanced equation for photosynthesis
6CO² + 6H²O —> C⁶H¹²O⁶ + 6O²
Chlorophyll
Green pigment found in plants, which absorbs energy from sunlight for photosynthesis.
Chloroplasts
Sub-cellular structures found in some plant cells; the site of photosynthesis.
Use of glucose in plants
Glucose is a source of chemical energy.
Some of the glucose produced by photosynthesis is broken down during respiration to release energy.
Photosynthesis - Use of carbohydrates as storage
Glucose = highly reactive molecule –> unwanted chemical reactions may happen.
- Glucose converted into sucrose (more stable molecule) before being transported in the phloem to the different parts of the plant
- Sucrose can easily be changed back to glucose when needed by the plant.
- Convert glucose to starch (stored in granules in the chloroplasts + cytoplasm and acts as an energy store) (stored in leaves) –> starch used bc it is insoluble (won’t be affected by movement of water) –> used as longterm energy source
- Starch can be converted back into glucose for respiration.
Use of carbohydrates for structural support
Some glucose is converted to cellulose. Cellulose is an important component of the plant cell walls.
Cellulose
A complex carbohydrate that forms tough fibres, which are the main constituent of plant cell walls.
Photosynthesis - Use of carbohydrates in pollination
- Glucose is also used to make nectar.
- Nectar is a sweet, sugary liquid that attracts animals like insects and birds.
- These animals in turn help with pollination.
Use of sucrose in plants
- Sucrose is transported through the phloem.
- Sucrose is used for the growth of shoots and young leaves.
- Sucrose is used for the growth of the roots or converted to starch and stored.
- Sucrose is used for the growth of the fruit or stored in the fruit.
Minerals
A group of substances that are essential to organisms in low concentrations to allow them to carry out various functions.
- Inorganic substances such as magnesium nitrate
- Formed in the soil by natural breakdown of rocks.
- Many minerals are insoluble in water. But those that are soluble can be used by plants.
- Theres minerals break down into their ions (mineral ions) and can be absorbed by root hair cells in plant roots.
Use of mineral ions
- Plants use magnesium ions for making chlorophyll.
- There is a magnesium ion at the centre of each chlorophyll molecule, and this is vital for the correct function of chlorophyll.
- Plants use nitrate ions for making amino acids.
- Amino acids are used by the plant to make the proteins it needs.
Limiting factor
The variable in the environment that controls the rate, growth or abundance of a biological processes. For instance, temperature can be the limiting factor in the growth of a plant.
When a process depends on two or more factors, the rate of that process is limited by the factor which is in shortest supply.
Examples of limiting factors of growth of plants
Light intensity, availability of carbon dioxide, temperature (bc enzymes breaking down carbon dioxide + water need optimum temp)
Water/ions + chlorophylls → they are limiting factors just more difficult to measure.
