9.1 Transport Systems in Dicotyledonous Plants

Question 1

Why do plants need transport systems?

Answer 1

-Plants have metabolic demand, because hormones, mineral ions, waste products, oxygen and glucose need to constantly be transported
-Plants can be incredibly large, so they need effective transport mediums to move substances both up and down
-Plants overall have a small surface area : volume ratio, so cannot rely on diffusion alone to supply their cells with everything they need

Question 2

What is a dicotyledonous plant?

Answer 2

A plant that makes seeds containing two cotyledons

Question 3

What makes a monocot’s vascular bundles different from a dicot’s?

Answer 3

Monocot vascular bundles are random, dicot vascular bundles are in a ring

Question 4

What are the two types of dicot plants?

Answer 4

Herbaceous and woody

Question 5

What is a vascular system?

Answer 5

Series of transport vessels running through the stem, roots, and leaves. Made up of xylem and phloem

Question 6

What is a vascular bundle?

Answer 6

A bundle of transport tissues arranged together.

Question 7

Describe the patterns of vascular tissue in a dicot leaf.

Answer 7

-The midrib of a leaf is the main vein carrying vascular tissue
-Many small, branching veins spread through the leaf.

Question 8

Describe the patterns of vascular tissue in a dicot stem.

Answer 8

The vascular bundles are around the edge to give strength and support

Question 9

Describe the patterns of vascular tissue in a dicot root.

Answer 9

The vascular bundles are in the middle, to help the plant withstand tugging strains.

Question 10

When viewing a transverse section of a vascular bundle, what is the name of the small tissue between xylem and phloem?

Answer 10

Cambium

Question 11

What type of cell makes up cambium tissue?

Answer 11

Meristem

Question 12

Is xylem largely living or non-living tissue?

Answer 12

Non-living

Question 13

What are the two key functions of xylem?

Answer 13

-Transport of water and mineral ions
-Supporting the plant

Question 14

Describe the flow of material in xylem.

Answer 14

Up from the roots, to the shoots and leaves. One way system

Question 15

What are the 3 key components of xylem?

Answer 15

Xylem vessels, xylem parenchyma, xylem fibres

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 is the purpose of xylem parenchyma?

Answer 17

Packs around the xylem vessels, storing food and tannin deposits

Question 18

What is tannin?

Answer 18

A bitter 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 do not transport water

Question 20

What is the importance of lignified walls?

Answer 20

-Prevents the wall from collapsing inwards
-Waterproofs the vessels
-Improves adhesion of water molecules

Question 21

What is the name for the holes in the xylem?

Answer 21

Unlignified/bordered pits

Question 22

What is the function of unlignified pits?

Answer 22

-Present to allow lateral movement of water (and dissolved minerals) between xylem vessels and living cells in the stem
-Also allows water to bypass blockages

Question 23

Is phloem tissue living or non-living?

Answer 23

Living

Question 24

Why are phloem cells alive?

Answer 24

Because the active loading of sucrose requires energy from cells

Question 25

What are the key roles of phloem tissue?

Answer 25

-Transports glucose in the form of sucrose throughout the plant -Supplies the cells with sugars and amino acids needed for cellular respiration, and for synthesis of all other useful molecules

Question 26

Describe the flow of materials in phloem tissue.

Answer 26

Flow of materials in the phloem can go BOTH up and down the plant. Two-way flow.

Question 27

What are the main transporting vessels of phloem?

Answer 27

Sieve tube elements

Question 28

What are sieve tube elements made up of?

Answer 28

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

Question 29

Are sieve tubes lignified or unlignified?

Answer 29

Unlignified

Question 30

How does content flow between sieve tube elements?

Answer 30

In the areas between the cells, the walls become perforated to form sieve plates. These let the phloem contents flow between cells.

Question 31

How do phloem cells lose their nucleus?

Answer 31

-As the large pores appear in sieve tube cell walls, the vacuole membrane, the nucleus and some of the other organelles break down -The phloem becomes a tube filled with phloem sap

Question 32

Why is it important for phloem cells to have no nucleus?

Answer 32

So there is more room for dissolved substances to be transported through the sieve tube elements

Question 33

What is the name of the type of cell that forms next to phloem?

Answer 33

Companion cells

Question 34

How are companion cells linked to sieve tube elements?

Answer 34

Through the plasmodesmata (microscopic channels through the cellulose cell walls, linking to the cytoplasm of adjacent cells)

Question 35

What is the function of the companion cells?

Answer 35

To act as a "life support system" for sieve tube cells, which have lost most of their normal cell functions. They are very active.

Question 36

What does phloem tissue contain?

Answer 36

Supporting tissues, including fibres and sclereids.

Question 37

What are sclereids?

Answer 37

Cells with extremely thick cell walls

Question 38

What is tree girdling?

Answer 38

Removal of the bark from a section of a tree

Question 39

What might you see when a tree is girdled?

Answer 39

Bulge above the ring, translocation past ring prevented, sucrose accumulates, water moves into area by osmosis

Question 40

Where is the cambium located?

Answer 40

In the stem, between the xylem and phloem tissue