Meristems, Primary Growth

Question 1

What is a tissue?

Answer 1

A tissue is a group of one or more cell types, which carry out specialized functions

Question 2

Describe meristems, locations and their role in plant growth in depth

Answer 2

• Plants have undifferentiated tissues called meristems, consisting of cells which constantly divide under suitable conditions and produce new cells.
• Some of these cells then elongate and differentiate to produce new tissues of the plant body, and others remain as meristems.
• Meristems may have dormant periods
• Due to the action of meristems, new cells are added. Subsequently, these cells get differentiated. Therefore, plant growth occurs by making new plant tissues

Question 3

What are the characteristics of meristematic cells?

Answer 3

• They are living cells
• Are isodiametric (roughly spherical)
• Are structurally and functionally undifferentiated
• Have a central nucleus
• Have a dense cytoplasm
• Have the ability to multiply

Question 4

What are the 3 types of meristems?

Answer 4

1. Apical meristems
2. Lateral meristems
3. Intercalary meristems

Question 5

Describe apical meristems

Answer 5

• These meristems are located at root tips and shoot tips
• They add new cells that enable increase in length. This process is known as primary growth.

Question 6

Where are apical meristems found?

Answer 6

These meristems are located at root tips and shoot tips

Question 7

What is the function of apical meristems?

Answer 7

They add new cells that enable increase in length. This process is known as primary growth.

Question 8

Describe lateral meristems

Answer 8

• Vascular cambium and cork cambium are lateral meristems
• They’re found in woody plants and involve in secondary growth by increasing the circumference of roots and stems
• The vascular cambium produces secondary xylem and secondary phloem
• Cork cambium produces a thick and tough periderm, replacing epidermis

Question 9

What are the 2 main lateral meristems?

Answer 9

Vascular cambium
Cork cambium

Question 10

Where are lateral meristems found?

Answer 10

In woody plants

Question 11

What is the function of lateral meristems?

Answer 11

• Involve in secondary growth by increasing the circumference of roots and stems
• The vascular cambium produces secondary xylem and secondary phloem
• Cork cambium produces a thick and tough periderm, replacing epidermis

Question 12

Describe intercalary meristems

Answer 12

• Some monocots such as grasses show meristematic activity at the bases of stems and leaves. These are known as intercalary meristems.
• They allow rapid regrowth in damaged leaves.

Question 13

Where are intercalary meristems found?

Answer 13

At the bases of stems and leaves of some monocots

Question 14

What is the function of intercalary meristems?

Answer 14

• They allow rapid regrowth in damaged leaves.

Question 15

Define the primary growth of the root

Answer 15

Elongation of root due to the activity of primary meristems located on the root apex

Question 16

What are the 3 processes that take place during primary growth?

Answer 16

Cell division - due to mitotic division
Cell elongation
Cell maturation - due to differentiation

Question 17

Describe the process of primary growth of the root

Answer 17

Elongnation of root due to the activity of primary meristems located on the root apex is primary growth of the root.

During the growth, 3 processes take place:
Cell division - due to mitotic division
Cell elongnation
Cell maturation - due to differentiation

These stages are found in 3 overlapping regions starting from meristems

The zone of cell division includes the root apical meristem and its derivatives

In this region, new cells are produced to both sides.

Cells produced outward to the apical meristem are differentiated to form the root cap which prevents damage to root apical meristem from friction when growing through the soil

Cells produced inward to meristem undergo elongation, in the zone of cell elongation

Root cells elongate, sometimes to more than 10 times their original length. Hence the root is pushed forward through the soil.

In the zone of cell maturation, cells begin specializing in structure and function, and cells complete differentiattion and become functionally mature.

The primary structure of the root is formed as a result of primary growth

Question 18

What does the zone of cell division include?

Answer 18

The root apical meristem and its derivatives

Question 19

What’s the function of the root cap?

Answer 19

It prevents damaging the root apical meristem from friction when growing through the soil.

Question 20

Where do cells produced inward to meristem undergo elongation?

Answer 20

In the zone of cell elongation

Question 21

How much do root cells elongate?

Answer 21

Sometimes to more than 10 times their original length

Question 22

How is the root pushed forward through the soil?

Answer 22

By elongation of root cells

Question 23

What occurs in the zone of maturation?

Answer 23

Cells begin specializing in structure and function

Cells complete their differentiation and become functionally mature

Question 24

Define the primary growth of the shoot

Answer 24

Elongation of the shoot due to the activity of the primary meristem located in the shoot apex is called primary growth of shoot

Question 25

What is a shoot apical meristem?

Answer 25

It is a dome shaped mass of dividing cells located at the shoot tip

Question 26

Where do leaves develop from?

Answer 26

Leaf primordia

Question 27

What are leaf primordia

Answer 27

Finger-like projections along the sides of the apical meristems.

Normally, these primordia cover the shoot apical meristem

Question 28

Describe the primary growth of the shoot

Answer 28

Elongation of the shoot due to the activity of the primary meristem located in the shoot apex is called primary growth of shoot

A shoot apical meristem is a dome shaped mass of dividing cells located at the shoot tip

Leaves develop from leaf primordia, finger-like projections along the sides of the apical meristems

Normally, these primordia cover the shoot apical meristem

Shoot apical meristem only produces new cells towards the stem, due to mitosis.

After elongation, cell differentiation takes place

Then primary tissues of the stem are formed due to cell differentiation. Therefore, the stem’s height is increased due to primary growth

Question 29

What are the differences between root apex and shoot apex?

Answer 29

Shoot apex is found at tips of shoot.
Root apex is found at tips of root

Shoot apex is protected by leaf primordia
Root apex is protected by root cap

Shoot apex produces new cells only inwards
Root apex produces new cells on both sides, inwards and outwards