9.1 Transport systems in dicotyledonous plants

Question 1

How much pressure is in the phloem?

Answer 1

2000kPa

Question 2

What is the first reason for why multicellular plants need transport systems? Elaborate on it

Answer 2

Metabolic demands

• Internal and underground parts of plants can’t photosynthesise so need oxygen and glucose transported to them and waste products of cell metabolism to be removed
• Hormones made in one part of a plant need transporting to areas where they have an effect
• Mineral ions absorbed by roots need to be transported to all cells to make the proteins required for enzymes and the cell’s structure

Question 3

What are perennials?

Answer 3

Plants that live a long time and reproduce every year

Question 4

What are the two largest trees in the world?

Answer 4

USA: Coastal + giant redwood - 115m tall
Australia: Mountain ash - 114m tall

Question 5

What is the second reason for why multicellular plants need transport systems? Elaborate on it

Answer 5

Size

• Some plants are small but because plants grow throughout their lives, many perennials are very large
• This means plants need effective transport systems to move substances up and down from the tip of roots to the upper leaves and stems

Question 6

What is the third reason for why multicellular plants need transport systems? Elaborate on it

Answer 6

Surface area:volume ratio (SA:V)

• Leaves are adapted to have a large SA:V ratio for gas exchange
• When stems, trunks and roots are taken into account, they have a small SA:V ratio - this means they can’t rely on diffusion alone to supply the cells with everything they need

Question 7

What are dicotyledonous plants?

Answer 7

Make seeds that contain two cotyledons

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

Question 8

What are herbaceous dicots?

Answer 8

Have soft tissues and a short life cycle

Stems and leaves die down to the soil level at the end of the growing season

Question 9

What are woody dicots?

Answer 9

Have hard, lignified tissues and a long life cycle

Question 10

What is the vascular system? What are the 2 types?

Answer 10

1. A series of transport vessels running through the stem, roots and leaves
2. Xylem, Phloem

Question 11

How are transport tissues arranged?

Answer 11

In vascular bundles in leaves, stems and roots of herbaceous dicots

Question 12

*Page 195

Answer 12

*Refer to table 1

Question 13

What is the xylem?

Answer 13

Non-living tissue

Question 14

What are the 2 functions of the xylem?

Answer 14

1. Transport of water and mineral ions

2. Support for plant

Question 15

What direction is the flow of materials in the xylem?

Answer 15

Up from the roots to shoots and leaves

Question 16

What are xylem vessels?

Answer 16

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

Question 17

What are the 2 other tissues associated with the xylem?

Answer 17

1. Thick-walled xylem parenchyma

2. Xylem fibres

Question 18

What are thick-walled xylem parenchyma?

Answer 18

• Packs around xylem vessels, storing food and containing tannin deposits
• Tannin is a bitter, astringent-tasting chemical that protects plant tissues from attack by herbivores

Question 19

What are xylem fibres?

Answer 19

Long cells with lignified secondary walls that provide extra mechanical strength but don’t transport water
-Lignin can be laid down the walls of the xylem vessels in many ways

Question 20

How can lignin be laid down in the walls of the xylem vessels?

Answer 20

Can form rings, spirals or solid tubes with small, unlignified areas called bordered pits - this is where water leaves the xylem and moves into other cells of the plant