Transport in plants and transpiration Flashcards

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1
Q

What is the stele?

A

Vascular cylinder containing xylem and phloem (vascular tissue)

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2
Q

What does xylem transport?

A

Water and mineral salts

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3
Q

What does phloem transport?

A

Sugars e.g. sucrose

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4
Q

What are some characteristics of xylem vessels?

A

Highly specialised for transport of water and minerals
No end walls
No cell contents
Are dead
Secondary walls are thickened with lignin

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5
Q

What is the purpose of pits?

A

Allows movement of water between adjacent vessels and surrounding cells

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6
Q

What are 2 important properties of lignin?

A

Strength - prevents vessels from collapsing under the pressure of transpiration
Waterproof - prevents leakage of water

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7
Q

What is the definition of transpiration?

A

Evaporation of water from the mesophyll surface and subsequent diffusion of H2o vapour through the stomata and into the atmosphere.

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8
Q

What are the 3 main stages of transpiration?

A

Into and across the root
Up the root and stem into the xylem
Through the leaf and evaporation of water from the leaf

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9
Q

Explain the movement of water through roots:

A

Vast majority plants are terrestrial
Need to conserve water - waxy cuticle
Cannot absorb water over general surface

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10
Q

What helps root absorb water?

A

Root hairs

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11
Q

What does a root hair look like?

A

Long
thin
extension of a root epidermal cell

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12
Q

How long will a root hair be functional?

A

A few weeks

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13
Q

What is the main function of root hair cells?

A

Exchange surfaces in plants responsible for absorption of mineral ions and water

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14
Q

Why are root hairs efficient exchange surfaces?

A

A large surface area - occur in thousands of each root branch
Thin surface layer - substances can move easily

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15
Q

Does the soil have a low or high water potential and why?

A

High - soil solution is mostly water

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16
Q

Do root hair cells have a low or high water potential and why?

A

Low water potential - contain solutes such as sugars, amino acids and mineral ions

17
Q

What direction will the water move in relation to root hair cells?

A

From the soil solution into root hair cells -

from high water potential to low water potential

18
Q

What are the two pathways water moves once it has entered the root hair cells?

A

Apoplastic pathway

Symplastic pathway

19
Q

Where does water move in the apoplastic pathway?

A

Along the cellulose microfibrils of the cell wall

20
Q

What is special about microfibrils and what does this mean for the movement of water?

A

They are parallel

Water moves between the layers rather than through them

21
Q

What is the movement of water within the apoplastic pathway?

A

cell wall - cell wall

22
Q

What is meant by cohesive?

A

The water molecules stick to each other

23
Q

When water is drawn into the endodermal cells what happens?

A

More water is pulled along behind it

24
Q

How does water move in the Symplastic pathway?

A

From cytoplasm to cytoplasm

25
Q

Where does the water pass through?

A

Through tiny openings in the cell wall

26
Q

What are these tiny openings called?

A

Plasmodesmata

27
Q

What does each plasmodesmata contain?

A

filled with a thin strand of cytoplasm

28
Q

What does water entering by osmosis do within the symplastic pathway?

A

Increases the water potential in the root hair cell

29
Q

What does this therefore mean?

A

Has a higher water potential than the first cell in cortex

30
Q

In what way does water move in the symplastic pathway?

A

Water moves from root hair cell to first cell in cortex by osmosis

31
Q

What way will water move by osmosis?

A

Moves from cell to cell by osmosis along water potential gradient

32
Q

How do ions enter root hair cells?

A

By facilitated diffusion/ active transport

Either along or against the concentration gradient

33
Q

What is the first step of water moving into xylem?

A

When water reaches the endodermis by the apoplastic pathway - waterproof casparin strip prevents it from progressing along the cell wall

34
Q

Where is water forced during the symplastic pathway?

A

Into the living protoplast where it travels along the symplastic pathway

35
Q

What does the endodermal cells transport?

A

Actively transports salt in the xylem

36
Q

What does this process require?

A

Energy

37
Q

Where is the only place this process can occur?

A

In living tissue

38
Q

What must water enter first to get into the xylem?

A

Must enter the cytoplasm of endodermal cells