Meristems, Primary Growth Flashcards
What is a tissue?
A tissue is a group of one or more cell types, which carry out specialized functions
Describe meristems, locations and their role in plant growth in depth
- 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
What are the characteristics of meristematic cells?
- 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
What are the 3 types of meristems?
- Apical meristems
- Lateral meristems
- Intercalary meristems
Describe apical meristems
- 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.
Where are apical meristems found?
These meristems are located at root tips and shoot tips
What is the function of apical meristems?
They add new cells that enable increase in length. This process is known as primary growth.
Describe lateral meristems
- 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
What are the 2 main lateral meristems?
Vascular cambium
Cork cambium
Where are lateral meristems found?
In woody plants
What is the function of lateral meristems?
- 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
Describe intercalary meristems
- 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.
Where are intercalary meristems found?
At the bases of stems and leaves of some monocots
What is the function of intercalary meristems?
- They allow rapid regrowth in damaged leaves.
Define the primary growth of the root
Elongation of root due to the activity of primary meristems located on the root apex
What are the 3 processes that take place during primary growth?
Cell division - due to mitotic division
Cell elongation
Cell maturation - due to differentiation
Describe the process of primary growth of the root
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
What does the zone of cell division include?
The root apical meristem and its derivatives
What’s the function of the root cap?
It prevents damaging the root apical meristem from friction when growing through the soil.
Where do cells produced inward to meristem undergo elongation?
In the zone of cell elongation
How much do root cells elongate?
Sometimes to more than 10 times their original length
How is the root pushed forward through the soil?
By elongation of root cells
What occurs in the zone of maturation?
Cells begin specializing in structure and function
Cells complete their differentiation and become functionally mature
Define the primary growth of the shoot
Elongation of the shoot due to the activity of the primary meristem located in the shoot apex is called primary growth of shoot
What is a shoot apical meristem?
It is a dome shaped mass of dividing cells located at the shoot tip
Where do leaves develop from?
Leaf primordia
What are leaf primordia
Finger-like projections along the sides of the apical meristems.
Normally, these primordia cover the shoot apical meristem
Describe the primary growth of the shoot
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
What are the differences between root apex and shoot apex?
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
