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3.9 - Transport in plants > Transport systems in dicotyledonous plants > Flashcards

Transport systems in dicotyledonous plants Flashcards

1
Q

Why do transport systems in plants have much higher pressures than in animals?

A

They are confined to much smaller spaces

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2
Q

What are the three main reasons why plants need transport systems?

A

1) Metabolic demands
2) Size
3) Surface area : volume ratio (SA:V)

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3
Q

What are the three metabolic demands of a plant?

A

1) Oxygen and glucose need to be transported to them and waste products of cell metabolism removed
2) Hormones need to be transported to where they take effect
3) Mineral ions absorbed by roots need to be transported to all cells to make proteins for enzymes for cell structure

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4
Q

Why do plants have high metabolic demands?

A

They make their own glucose and oxygen by photosynthesis

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5
Q

Why does size increase the need for transport systems?

A

Large plants need to move substances up and down from the tip of the roots to the tops of leaves and stems, even against gravity

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6
Q

How does SA:V ratio vary in plants?

A

Leaves are adapted to have a large SA:V ratio for gas exchange but other parts (e.g. stems, roots, trunks) have a small SA:V ratio

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7
Q

Why does a small SA:V ratio increase the need for transport systems?

A

Plants can’t rely on diffusion alone to supply their cells with everything they need

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8
Q

What are dicotyledonous plants (dicots)?

A

Plants that make their own seeds containing two cotyledons

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9
Q

What are cotyledons?

A

Organs that act as food stores for the developing embryo plant and form the first leaves when the seed germinates

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10
Q

What are the two types of dicots?

A

Herbaceous and woody

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11
Q

What are herbaceous dicots?

A

Dicots with soft tissues and a short life cycle (leaves and stems die down at the end of the growing season)

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12
Q

What are woody dicots?

A

Dicots with hard, lignified tissues and long life cycles

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13
Q

What is the vascular system of herbaceous dicots?

A

A series of transport vessels running through the stem, roots, and leaves

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14
Q

What are the two main types of transport vessels in herbaceous dicots?

A

Xylem and phloem

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15
Q

How are transport tissues arranged?

A

In vascular bundles in the leaves, stems, and roots

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16
Q

How are vascular bundles arranged in the stem?

A

Around the edge

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17
Q

Why are vascular bundles around the edge in the stem?

A

To give strength and support

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18
Q

How are vascular bundles arranged in the roots?

A

In the middle

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19
Q

Why are vascular bundles in the middle in the roots?

A

To help the plant withstand the tugging strains that result as the stems and leaves are blown in the wind

20
Q

How are vascular bundles arranged in the leaves?

A

The midrib is the main vein carrying the vascular tissue through the organ

21
Q

Why are vascular bundles in the midrib in the leaves?

A

It helps to support the structure of the leaf

22
Q

What type of tissue is the xylem?

A

Non-living

23
Q

What are the two main functions of the xylem?

A

1) Transport of water and mineral ions
2) Support

24
Q

How does material flow in the xylem?

A

Up from the roots to the shoots and leaves

25
Q

What are the main structures in xylem?

A

Xylem vessels

26
Q

What are xylem vessels?

A

Long, hollow structures made by several columns of cells fusing together end to end

27
Q

What are the two other tissues associated with xylem?

A

Thick-walled xylem parenchyma packs and lignin

28
Q

What do xylem parenchyma packs do?

A

Store food and tannin deposits

29
Q

What is tannin?

A

A bitter, astringent-tasting chemical that protect plant tissues from attack by herbivores

30
Q

What are xylem fibres?

A

Long cells with lignified secondary walls that provide extra mechanical strength but don’t transport water

31
Q

What is laid in xylem walls to provide support?

A

Lignin

32
Q

How can lignin be laid?

A

It can form rings, spirals, or solid tubes with lots of unlignified areas called bordered pits

33
Q

Why are bordered pits important?

A

It is where water leaves the xylem and moves into other cells

34
Q

What is phloem?

A

A living tissue that transports food in the form of organic solutes around the plant from the leaves

35
Q

What does the phloem do?

A

Supplies the cells with the sugars and amino acids needed for cellular respiration and for synthesis of all other useful molecules

36
Q

How does material flow in the phloem?

A

Both up and down

37
Q

What are the main transporting vessels of the phloem?

A

Sieve tube elements

38
Q

What are sieve tubes made up of?

A

Many cells joined end to end to form a long, hollow structure

39
Q

How are phloem tubes different to xylem tissue?

A

The tubes aren’t lignified

40
Q

What happens in the areas between cells in phloem tubes?

A

The walls become perforated to form sieve plates which let phloem contents flow through

41
Q

Why do mature phloem cells have no nucleus?

A

As the large pores appear in phloem cell walls, the tonoplast, nucleus, and other organelles break down, leaving the phloem as a tube filled with phloem sap

42
Q

What forms with sieve tube elements?

A

Companion cells

43
Q

How are companion cells linked to sieve tube elements?

A

By many plasmodesmata

44
Q

What is plasmodesmata?

A

Microscopic channels through the cellulose cell walls linking the cytoplasm to adjacent cells

45
Q

Why are companion cells so important?

A

They have a nucleus and other organelles and function as a ‘life support system’ for sieve tube cells which have lost all their normal cell functions

46
Q

What are the two supporting tissues of phloem?

A

Fibres and sclereids

47
Q

What are sclereids?

A

Cells with extremely thick cell walls

3.9 - Transport in plants (2 decks)

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