Plant Physiology (Sec C) Flashcards
What is rate of photosynthesis affected by (i.e. the limiting factors of photosynthesis)?
- Light intensity
- Carbon dioxide concentration
- Temperature
How can a plant be de-starched?
Keep it in the dark for 24 hours
What are the catalysts, reactants and products of photosynthesis?
- Catalysts: Light, chlorophyll
- Reactants: Carbon dioxide, water
- Products: Oxygen, glucose
What is glucose converted into after photosynthesis?
It is converted into sucrose and transported around the plant. It is converted into starch to be stored
How is the leaf adapted for gas exchange?
- Thin, so diffusion is fast
- Flat, to absorb as much light as possible
- Chlorophyll, to facilitate photosynthesis
- Stomata, to allow gases to enter
- Internal air spaces, for faster diffusion
What minerals are needed by plants?
- Magnesium: To produce chlorophyll
- Nitrogen (Nitrates): To produce proteins
- Phosphorus (Phosphates): For respiration & growth
- Potassium: Photosynthesis & growth
What are diffusion & osmosis?
- Diffusion: The random movement of particles from a region of lower concentration to a region of higher concentration
- Osmosis: The movement of water molecules through a semi-permeable membrane down the concentration gradient
What are the functions of the xylem & phloem?
- Xylem transports water & mineral ions from the roots to the rest of the plant (made of dead cells and parenchyma)
- Phloem: Transports sucrose & amino acids from leaves to the rest of the plant
Why is osmosis important in plants?
When water moves into a plant cell, it swells up and becomes firmer. The plant cell is turgid now. This helps it support the structure of the plant. Without sufficient water, the cell shrinks and becomes flaccid. This causes the plant to wilt (bad). Osmosis makes cells turgid/flaccid
How does a plant absorb water and mineral ions through its roots?
The roots have specialised root hair cells. They increase the surface are for water absorption greatly. Mineral ions are brought into the plant by active transport.
What is transpiration?
The loss of water in the form of vapour through the mesophyll cells in the leaves is called transpiration
What controls the rate of transpiration?
Stomata control transpiration. They are present on the underside of the cell to reduce water loss. Light intensity, wind speed, humidity and temperature affect the rate of transpiration
What are tropisms?
Tropisms are directional responses to environmental stimuli. Some examples are phototropism (growing because of light) and geotropism (growing because of gravity)
What is phototropism?
Phototropism is the phenomenon of plants growing in a direction because of the influence of light. Auxins (hormones) are released from the tip of the shoot which tell the stem which way to grow.
How can plants reproduce asexually?
Plants can use mitosis. Offspring are identical to the parent. This can be achieved by runners/cuttings
