Flashcards in Topic 6 - Plant Structures and Their Functions Deck (34):
Movement of water molecules from a high concentration to a low concentration through a partially permeable membrane. Requires no energy.
Particles moving from a high concentration to a low concentration down a concentration gradient. Requires no energy.
Define active transport.
Movement of particles from low to high concentration up a concentration gradient, requiring energy.
What is the word equation for photosynthesis?
carbon dioxide + water → glucose + oxygen
What is the symbol equation for photosynthesis?
6CO2 + 6H2O → C6H1206 + 602
What are the limiting factors of photosynthesis?
- light intensity
- concentration of CO2
How are mineral ions absorbed by root hair cells?
Active transport - the concentration of mineral ions is usually higher in the root hair cells rather than the soil.
How is water absorbed by root hair cells?
How are root hair cells adapted to their function?
- They are covered in millions of microscopic hairs
- Large surface area
- Thin membrane
What does the phloem transport?
Food substances, mainly sucrose.
What is translocation?
It is where the phloem transports food substances made in the leaves to the rest of the plant, requiring energy from respiration.
What is the structure of the phloem?
It is made of columns of elongated living cells with small pores in the end walls to allow things to flow through.
What does the xylem transport?
Water and mineral ions.
What is the structure of the xylem?
It is made of dead cells joined end to end with no end walls between them and a hole down the middle. They are strengthened with lignin.
What is lignin?
A complex organic polymer deposited in the cell walls of plants to strengthen them.
What is transpiration?
The process where water and mineral ions are transported up the xylem against the force of gravity from the roots and out of the pores of leaves.
What factors affect transpiration rate?
How does light affect the rate of transpiration?
The stomata open wider, allowing more CO2 into the leaf for photosynthesis and increasing transpiration rate.
How does temperature affect the rate of transpiration?
Evaporation and diffusion are faster at higher temperatures.
How does humidity affect the rate of transpiration?
Diffusion of water vapour out of the leaf slows down if the leaf is already surrounded by moist air.
How does wind affect the rate of transpiration?
Water vapour is removed quickly by air movement, speeding up diffusion of more water vapour out of the leaf.
What are stomata?
Tiny pores on the surface of a plant.
How are stomata adapted to their function?
- They are surrounded by guard cells, which change shape to control the size of the pore. When turgid, the stomata are open. When flaccid, they are closed.
What is the function of stomata?
Allow carbon dioxide and oxygen to diffuse directly in and out of a leaf. They also allow water vapour to escape during transpiration.
How do you use a potometer to estimate transpiration rate?
1 - Set up the apparatus and record the starting position of the air bubble.
2 - Start a stopwatch and record the distance moved by the bubble per unit time.
3 - Calculating the speed of air bubble movement gives an estimate of the transpiration rate.
What does a potometer actually measure?
The water uptake of a plant.
What equation do you use to estimate the rate of transpiration?
distance moved ÷ time taken
How are leaves adapted for photosynthesis? (3)
- Leaves are broad so there's a large surface area exposed to light.
- The palisade layer has lots of chloroplasts near the top of the leaf so can get the most light.
- The upper epidermis is transparent.
- Xylem and phloem form a network of vascular bundles, providing the leaf with water for photosynthesis and taking away the glucose produced.
- The epidermal tissues are covered with a waxy cuticle, to reduce water loss by evaporation.
How are leaves adapted for gas exchange?
- Lots of stomata to let CO2 diffuse directly into the leaf.
- The spongy mesophyll tissue contains air spaces, which increase the rate of diffusion of gases into and out of the leaf's cells.
How are plants living in hot and dry places adapted to live in extreme environments? (3)
- Small leaves/spines to reduce surface area for water loss.
- Curled leaves/hairs to reduce air flow close to the leaf.
- Thick waxy cuticles to reduce water loss.
- Thick. fleshy stem to store water.
- Fewer stomata/stomata that only open at night/stomata in sunken pits to reduce water loss.
What is an auxin?
A plant hormone that controls growth at the tips of shoots and roots.
What do auxins do?
Stimulate cell elongation and promotes growth in the shoot but inhibits growth in the root.
What is positive phototropism?
Grow towards light. (shoots)