Secondary Growth

Question 1

Define secondary growth

Answer 1

Increase in the diameter of stems and roots in plants due to the new cells produced by lateral meristems is called secondary growth

Question 2

What are the plants that undergoes secondary growth

Answer 2

Woody perennial plants including all gymnosperms species and many dicot species

Question 3

What is the meristem that is involved in secondary growth

Answer 3

Lateral meristems

Question 4

What are the two types of lateral meristems that produces new cells for secondary growth

Answer 4

Vascular cambium and cork cambium

Question 5

What is the function of vascular cambium in secondary growth

Answer 5

Produces secondary xylem towards primary xylem and secondary phloem towards primary phloem increasing vascular flow and support for the shoot

Question 6

What is wood

Answer 6

Secondary xylem

Question 7

What type of cells are found in the tough thick covering produced by the cork cambium

Answer 7

Wax impregnated cells

Question 8

What is the function of the wax impregnated cells produced by the cork cambium

Answer 8

Protect the stem from water loss
Protect the stem from invasion of insects bacteria and fungi

Question 9

When does the second every growth of woody plants occur in relation to primary growth

Answer 9

Simultaneously

Question 10

How is the secondary vascular tissue produced

Answer 10

By the action of vascular cambium

Question 11

Describe the presence of the vascular cambium in a typical woody stem

Answer 11

The vascular cambium consists of a continuous cylinder of undifferentiated cells of often only a single cell layer in thickness located outside the pith and the primary xylem and to the inside of cortex and primary phloem

Question 12

Where does the vascular cambium add the secondary xylem and secondary phloem

Answer 12

Secondary xylem to the inside of the cambium secondary phloem to the outside

Question 13

How does the vascular cambium appear in a cross section

Answer 13

As a ring of initials

Question 14

How are the long initials oriented

Answer 14

They are oriented with their long axis parallels the axis of stem or root

Question 15

What is the function of long initials

Answer 15

They produce cells such as
Tracheids, vessel elements, fibres and parenchyma of xylem

Sieve tube elements, companion cells, phloem fibres and phloem parenchyma

Question 16

How are the short initials oriented

Answer 16

Perpendicular to the axis of the stem or root

Question 17

What is the function of short initials

Answer 17

Produce vascular rays

Question 18

What are vascular rays

Answer 18

Mostly parenchyma cells that connect secondary xylem and phloem

Question 19

What are the functions of vascular rays

Answer 19

Connect secondary xylem and phloem
Store carbohydrates
Aid in wound repairing

Question 20

What accounts for the hardness and strength of wood

Answer 20

The walls of secondary xylem cells being heavily lignified

Question 21

What happens to the epidermis during the early stages of secondary growth

Answer 21

The epidermis is pushhed outwards causing it to split dry and fall off

Question 22

What phones the cork cambium

Answer 22

A cylinder of dividing cells that arise in the outer layer of co tax in stems and in the pericycle in the roots become meristematic forming a cork cambium.

Question 23

To which directions do the cork cambium produce new cells

Answer 23

Both interior and exterior

Question 24

What happens to the cells that are formed to the exterior of cork cambium

Answer 24

They become cork

Question 25

What is known as periderm

Answer 25

Cork cambium and the tissues it produces

Question 26

How do cork cells become dead cells when they mature

Answer 26

As they mature they deposit a vaccine hydrophobic material called suverine in the walls

Question 27

What is the function of cork tissues

Answer 27

Act as a barrier that helps protect the stem or root from
water loss
physical damages and
pathogens

Question 28

True or false
Periderm is impermeable to water and gases

Answer 28

True

Question 29

What is the adaptation periderm have for gas exchange

Answer 29

Small pose known as lenticels are present

Question 30

How are the lenticels formed

Answer 30

By loosely arranged cork self

Question 31

Appearance of lenticels

Answer 31

Horizontal slits

Question 32

What are the small pores present in the periderm for gaseous exchange called?

Answer 32

Lenticels

Lenticels are formed by loosely arranged cork horizontal slits.

Question 33

What happens to the cork cambium as the stem or root grows?

Answer 33

It breaks and loses its meristematic activity, becoming cork cells

These cork cells together form the periderm.

Question 34

What is initiated inside the cork layer after the original cork cambium is broken?

Answer 34

A new cork cambium

This new cork cambium will produce a new layer of cork.

Question 35

What occurs as new cells are added to the cork?

Answer 35

The outer regions of cork crack and peel off

This process is common in many tree trunks.

Question 36

What contributes to the increase in girth of the stem or root during secondary growth?

Answer 36

Tissue layers produced by vascular cambium and cork cambium

This process is essential for the overall growth of the plant.

Question 37

What is commonly and incorrectly referred to as bark?

Answer 37

Cork

The main components of bark are secondary phloem and periderm.

Question 38

What are the main components of bark?

Answer 38

• Secondary phloem
• Periderm

Bark includes all tissues outside of the vascular cambium.

Question 39

True or False: The epidermis is a main component of bark.

Answer 39

False

Bark consists of secondary phloem and periderm, not the epidermis.