B4 - Plan Structure, Transportation and Transpiration

Question 1

Define the terms tissue and organ

Answer 1

• Groups of similar cells work together as a tissue.
• Groups of different tissues work together as an organ.

Question 2

Describe different organs in a plant and their function

Answer 2

Stem - Supports the plant.
- Transports substances through the plant.
Leaf - Produces food by photosynthesis

Root- Anchors the plant
- Takes up water and minerals from the soil.

Flower (three organs: the petal, the stamen, and the carpel)
- Reproduction

Question 3

What do vascular bundles do?

Answer 3

They contain two major tissues : xylem and phloem .

The bundles form a continuous transport system from the roots, through the stem to the leaves. They carry out two major functions :

• transport
• support

Question 4

Describe the structure and function of xylem

Answer 4

These cells are dead and have a hollow cavity called the lumen. They are stacked on top of one another to form long hollow tube-like vessels. Xylem cells are involved in the transport of water and dissolved minerals from the roots to the shoots and leaves.

Question 5

Describe the structure and function of phloem

Answer 5

Phloem: these cells are living and are also stacked on top of one another in tubes. They transport the food substances made in the leaf to all other parts of the plant.

Question 6

Describe how the distribution of vascular bundles changes in the root, stem and leaf. Why?

Answer 6

• Root : in the centre of the root. Helps the root act like an anchor and allows it to bend as the plant moves in the breeze or is tugged from above.
• Stem : around the outer edge of the stem. Provides strength to resist bending of the stem in the breeze.
• Leaf : form a network which supports the softer leaf tissues.

Question 7

Define the terms transpiration stream and translocation

Answer 7

Transpiration stream - the movement of water up the xylem from the roots to the leaves

Translocation - the transportation of sugars to areas of the plant that need it by phloem

Question 8

What is one adaptation of roots for getting water?

Answer 8

They have tiny root hairs that reach between the soil particles, which greatly increases the surface area of the roots.

Question 9

Why do plants need water?

Answer 9

• photosynthesis
• to evaporate so it can cool the plant
• to enter the cells through osmosis and make it turgid - support
• to transport dissolved minerals

Question 10

What are guard cells and what do they do?

Answer 10

Two special cells on either side of the stomata. When there is a lot of light and water, they take up water by osmosis, swell and become turgid. This makes them bend and open the stoma.

If no water - then not turgid - and no open stomata

Question 11

How does the leaf reduce water loss?

Answer 11

• waxy cuticle doesn’t allow evaporation
• few stomata on upper and lower surfaces of leaf
• plants that live in dry areas have fewer stomata and are enclosed on the inner surface of a rolled leaf, protected from the sun.
• stomata can be opened or closed. Photosynthesis - open. Night - closed.

Question 12

What factors increase the rate of transpiration and why?

Answer 12

1. More light intensity = more stomata open = more evaporation
2. Increased temperature = particles in air will move faster = water molecules will move faster = evaporate faster
3. Increased air movement = moves evaporated water molecules away from leaf. Increases diffusion as conc. of water outside leaf is kept lower, so high conc gradient .
4. Decreased humidity = less water in air = higher conc. gradient = higher diffusion