Topic 7 Transport in Plants.1

Question 1

7.1 Structure of transport tissues.

Answer 1

Point 1, 2 and 3.
Phloem and Xylem sap.

Question 2

What are the two vessels/tissues of the vascular system: Name them.

Answer 2

• Xylem vessels.
• Phloem vessels.

Question 3

What is vascular tissue?

Answer 3

A tissue in plants consisting of mainly xylem and phloem but also containing scelerenchyma and parenchyma cells.

Question 4

What is xylem?

Answer 4

Xylem is lignified plant vascular tissue containing tubes called vessels that transports water and dissolved mineral salts (inorganic compounds) from the roots to the rest of the plant in a transport process called transpiration while providing physical support to the plant.

Answer 5

SCELERENCHYMA AND PARENCHYMA CELLS.

Question 6

What is phloem?

Answer 6

Phloem is the living tissue in vascular plants containing tubes called sieve tubes that transports the soluble organic compounds called assimilates made during photosynthesis, particularly sugars like sucrose, to the rest of the plant. This transport process is called translocation.

Question 7

What is the direction of movement in the xylem and phloem?

Answer 7

Movement in the xylem only takes place in one direction (from roots to leaves) unlike phloem where movement takes place in different directions.

Question 8

What are the four adaptations of the xylem?

Difference between xylem and phloem.

Answer 8

• Cells are joined end to end with no cross walls to form a long continuous tube to allow free passage of water.
• Cells are dead, without cell contents, to allow free passage of water.
• Outer walls are thickened with a substance called lignin, strengthening the tubes, which help support the plant.
• Pits in the walls allow water in and out of the tubes.

https://cdn1.byjus.com/wp-content/uploads/2018/06/Difference-Between-Xylem-And-Phloem-2.png

Question 9

What are the two adaptations of phloem vessels?

Difference between xylem and phloem.

Answer 9

• The cells are joined end to end and contain holes in the end cell walls (called sieve plates) which allow easy flow of substances from one cell to the next.
• Phloem tubes are made of living cells that transport sap containing sugars produced during photosynthesis to non-photosynthetic parts of the plant or storage structures.

https://cdn1.byjus.com/wp-content/uploads/2018/06/Difference-Between-Xylem-And-Phloem-2.png

Question 10

Describe the movement of water.

Answer 10

Water molecules move from a region of higher water potential to a region of lower water potential down the water potential gradient.

Question 11

What is transpiration?

What energy source causes water to evaporate from leaves, transpiration?

Location of the stomata.

Answer 11

Transpiration is defined as the loss of water from plants, where water vapor escapes from the plant through stomata, which are tiny pores located on the underside of leaves.

The energy of the Sun causes water to evaporate from the leaves.

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Question 12

What is a stoma (plural: stomata)?

Answer 12

A tiny pore located in the epidermis of a leaf, bounded by two guard cells and needed for efficient gas exchange.

Question 13

Why are stomata located on the underside of the leaf?

Answer 13

Stomata are located on the underside of the leaf to reduce water loss. The lower epidermis of the leaf is cooler and less exposed to direct sunlight, which helps in minimizing water loss through transpiration.

Question 14

Explain the water potential gradient that allows for transipiration to take place?

Answer 14

There is a water potential gradient between the air inside the leaf (higher water potential) and the air outside the leaf (lower water potential). Water vapour will then diffuse out of the leaf through the stomata down this water potential gradient. This allows for transpiration to take place.

Question 15

What are the four functions of transpiration in plants?

Answer 15

• Transporting mineral ions.
• Providing water to keep cells turgid in order to support the structure of the plant.
• Providing water to leaf cells for photosynthesis.
• Respiration.

Question 16

What are four factors that affect the rate of transpiration?

Answer 16

• Temperature.
• Humidity.
• Light intensity.
• Wind speeds.

Question 17

What is the effect of temperature on transpiration rates?

Answer 17

The higher the temperature, the greater the kinetic energy of water molecules. This means that water evaporates faster from the surface of the mesophyll cells, and the water vapour diffuses out of the leaf into the air more quickly.

Question 18

What is the effect of humidity on transpiration rates?

Humidity means the moisture content of the air.

Answer 18

The higher the humidity of the air outside the leaf the lower the transpiration rate because water usually diffuses down a water potential gradient, but if the air outside is already saturated with water, there is more likely to be a net movement of water into the leaf (providing the stomata are open) rather than out.

Question 19

What is the effect of wind speed on transpiration rates?

Answer 19

The faster the wind speed, the faster the water is moved away from the plant, creating a steeper gradient and increasing the transpiration rate.

Question 20

What is the effect of light on transpiration rates?

Answer 20

The direct relationship between light intensity and transpiration rate means that as light intensity increases, so does the rate of transpiration in plants. This is because as more light is available, the plant requires more carbon dioxide for photosynthesis, leading to an increased opening of stomata, resulting in more water being lost through transpiration.

Question 21

Describe fully the movement of water through a plant.

Answer 21

1. Water uptake by roots .
   2.Transport through the xyelm vessels which transport water from the roots up through the stem and into the leaves.
2. Water moves from xylem into leaf cells.
3. Evaporation of water from mesophyll cell walls into leaf air spaces.
4. Diffusion of evaporated water into air spaces.
5. Transpiration of water vapour through open stomata on the underside of the leaf into air.

Roots have a higher water potential → Leaves have a lower water potential.

Question 22

What are xerophytes?

Answer 22

Xerophytes or xerophytic plants are plants that live in places where water is in short supply.