Biology 🍃 | Transport in plants | 8

Question 1

Vascular bundles consist of…

Answer 1

Xylem vessels and phloem tubes.

Question 2

What is the function of xylem?

Answer 2

Transporting water and minerals from the roots to the stem and leaf

Question 3

What is the function of phloem?

Answer 3

Transporting sucrose and amino acids made by the plant.

Question 4

In the cross-section of a root or stem, where is xylem tissue found?

Answer 4

In the center.

Question 5

How is xylem and phloem arranged in the stem and how does this help the plant?

Answer 5

In a more spread out out way, which thanks to the lignin keeps it stable.

Question 6

What is the cortex?

Answer 6

The cells lying between the epidermis and vascular tissue of a stem or root.

Question 7

Where is the cambium?

Answer 7

It is a thin layer of cells between the xylem and phloem

Question 8

What is the stele?

Answer 8

The central part of the root containing vascular tissue.

Question 9

How do water molecules get pushed up the xylem vessels?

Answer 9

Water molecules attract each other. Pressure at the top of the vessels is removed from transpiration or photosynthesis and the pressure at the bottom stays high, forcing it upwards.

Question 10

What are the characteristics of Phloem that differs from the xylem?

Answer 10

• A two-way flow
• Cells have end walls
• It is living
• It transports food

Question 11

What are the characteristics of xylem that differentiate it from phloem?

Answer 11

• A thick cell wall with lignin
• No cytoplasm inside
• A one way flow
• Transports water.

Question 12

Why do xylem vessels have thick walls with lignin?

Answer 12

It makes the vessels waterproof from leaks and keeps the plant strong.

Question 13

Why do xylem vessels have no cell contents?

Answer 13

This maximises the water volume transported and leads to less resistance.

Question 14

Why are cells joined end to end with no cross walls in xylem vessels?

Answer 14

This allows the continuous transport of water as cell walls are removed.

Question 15

From where do plants take in water?

Answer 15

Root hairs.

Question 16

What is the root cap?

Answer 16

A tough protective layer of cells over a root tip.

Question 17

How does water go from the soil to the xylem vessels?

Answer 17

1. It moves into the root hair through osmosis as the cytoplasm and cell sap inside is concentrated
2. Water travels by osmosis to root cortex from cell to cell
3. Reaches xylem vessels

Question 18

What is the purpose of root hair cells?

Answer 18

It increases the surface area of the cell for osmosis to happen.

Question 19

How does water at the bottom of xylem vessels reach the top?

Answer 19

The pressure at the bottom is high and as water transpires out and loses pressure at the top water flows up the vessels.

Question 20

Define transpiration.

Answer 20

The loss of water vapour from leaves by evaporation of water at the surface of mesophyll cells followed by the diffusion of water through the stomata.

Question 21

What 4 factors affect transpiration?

Answer 21

Temperature, light intensity, air flow, and humidity

Question 22

What are the functions of transpiration?

Answer 22

• Transporting mineral ions
• Provides water for cell turgidity
• Provides water to leaves for photosynthesis
• Keeps leaves cool.

Question 23

How does transpiration keep leaves cool?

Answer 23

Conversion of liquid water to water vapour requires heat energy.

Question 24

How are root hair cells adapted for transpiration?

Answer 24

They provide a huge surface area that water can be absorbed through, increasing quantity of water that moves through the plant.

Question 25

How do interconnecting air spaces help with transpiration?

Answer 25

The air spaces in a leaf mean a large surface of wet cells that water can evaporate into the air from. This increases rate of evaporation, drawing more water out of the xylem and speeding up water flow up the plant.

Question 26

How do stomata help with transpiration?

Answer 26

Open stomata makes it easier for water vapour to diffuse out of the leaf. This reduces the leaf’s water potential and encourages evaporation from the surface of the mesophyll cells.

Question 27

How are water molecules in xylem vessels held together?

Answer 27

By cohesion (attraction of same molecule)

Question 28

How does wilting occur?

Answer 28

When, possibly due to a factor that increases the rate of transpiration, more water leaves the plant than enters it and turgidity is lost.

Question 29

What do we use to measure transpiration rate?

Answer 29

A potometer.

Question 30

How does temperature affect the transpiration rate?

Answer 30

With higher heat, water evaporates from the surface of a leaf faster and pressure is lost at the top of xylem vessels faster.

Question 31

How does humidity affect transpiration rate?

Answer 31

The higher the humidity, the less of a diffusion gradient for the water between the leaf’s air spaces and the wet air outside.

Question 32

How does wind speed affect transpiration?

Answer 32

Water vapour is removed which increases the concentration gradient for water to diffuse into the air.

Question 33

How does light intensity affect rate of transpiration?

Answer 33

A plant may open its stomata to supply CO2 for photosynthesis. More water can evaporate.

Question 34

What is translocation?

Answer 34

The transport of sucrose and amino acids from source to sink.

Question 35

What is the source?

Answer 35

The region of production in a plant.

Question 36

What is the sink?

Answer 36

The region of storage or where sucrose and amino acids are used for respiration or growth.

Question 37

How do roots absorb mineral salts?

Answer 37

Through active transport against a concentration gradient.

Question 38

When a plant is actively photosynthesizing, what is the source and sink?

Answer 38

The leaves are the sources, constantly producing sucrose. The sink is the roots and flowers. The flowers use it for fructose and the roots stores some as starch.

Question 39

When is a plant dormant?

Answer 39

In the hottest driest season or the coldest winter season.

Question 40

When a plant is dormant, what is the source and sink?

Answer 40

The source is the storage organs, often at the roots where starch has been source, the sink being the leaves.