Biology πŸƒ | Transport in plants | 8 Flashcards Preview

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Flashcards in Biology πŸƒ | Transport in plants | 8 Deck (40)
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1
Q

Vascular bundles consist of…

A

Xylem vessels and phloem tubes.

2
Q

What is the function of xylem?

A

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

3
Q

What is the function of phloem?

A

Transporting sucrose and amino acids made by the plant.

4
Q

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

A

In the center.

5
Q

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

A

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

6
Q

What is the cortex?

A

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

7
Q

Where is the cambium?

A

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

8
Q

What is the stele?

A

The central part of the root containing vascular tissue.

9
Q

How do water molecules get pushed up the xylem vessels?

A

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.

10
Q

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

A
  • A two-way flow
  • Cells have end walls
  • It is living
  • It transports food
11
Q

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

A
  • A thick cell wall with lignin
  • No cytoplasm inside
  • A one way flow
  • Transports water.
12
Q

Why do xylem vessels have thick walls with lignin?

A

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

13
Q

Why do xylem vessels have no cell contents?

A

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

14
Q

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

A

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

15
Q

From where do plants take in water?

A

Root hairs.

16
Q

What is the root cap?

A

A tough protective layer of cells over a root tip.

17
Q

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

A
  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
18
Q

What is the purpose of root hair cells?

A

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

19
Q

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

A

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

20
Q

Define transpiration.

A

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.

21
Q

What 4 factors affect transpiration?

A

Temperature, light intensity, air flow, and humidity

22
Q

What are the functions of transpiration?

A
  • Transporting mineral ions
  • Provides water for cell turgidity
  • Provides water to leaves for photosynthesis
  • Keeps leaves cool.
23
Q

How does transpiration keep leaves cool?

A

Conversion of liquid water to water vapour requires heat energy.

24
Q

How are root hair cells adapted for transpiration?

A

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

25
Q

How do interconnecting air spaces help with transpiration?

A

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.

26
Q

How do stomata help with transpiration?

A

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.

27
Q

How are water molecules in xylem vessels held together?

A

By cohesion (attraction of same molecule)

28
Q

How does wilting occur?

A

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

29
Q

What do we use to measure transpiration rate?

A

A potometer.

30
Q

How does temperature affect the transpiration rate?

A

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

31
Q

How does humidity affect transpiration rate?

A

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

32
Q

How does wind speed affect transpiration?

A

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

33
Q

How does light intensity affect rate of transpiration?

A

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

34
Q

What is translocation?

A

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

35
Q

What is the source?

A

The region of production in a plant.

36
Q

What is the sink?

A

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

37
Q

How do roots absorb mineral salts?

A

Through active transport against a concentration gradient.

38
Q

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

A

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.

39
Q

When is a plant dormant?

A

In the hottest driest season or the coldest winter season.

40
Q

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

A

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

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