[Biology Class Notes] on Plant Differentiation and Development Process Pdf for Exam

The process wherein the cells of the root, cambium, apical meristems, and the shoot are matured in order to perform certain functions is known as plant differentiation. A lot of structural changes happen in this process within the plant cell. For example- While the tracheary elements in a plant are formed, there is a loss of protoplasm. 

Under biological terms differentiation is the process in which a cell changes from one cell type to another, usually cell changes to a more specialized type. Differentiation occurs several times during development of a multicellular organism as it changes from simple Zygote to a complex system of tissue and cell type. 

Differentiation Process in Plants

Plants belong to a different kingdom and their process of differentiation and development is also different from other kingdoms. In plants differentiation and development occurs in different ways from Animals. Plant differentiation is the process in which cells of the root system shoot apical meristem and the Cambium mature to perform specific functions.

In a more easy way we can say that cellular differentiation is the process in which a cell changes from one cell type to another.This Change mainly happens to form a more specialized type of cell.

During differentiation processes cells undergo different structural changes both in their cell wall and protoplasm. For example, to form a tracheary element, the cell would lose its protoplasm. Apart from this, they also develop a very strong, elastic and lignocellulosic cell wall, to transport water and minerals under extreme conditions.

It can also be termed as a process in which the different types of cells separate from their precursor cell and become different from each other. There are different types of fundamental cells in plants and all these types of cells are responsible for basic functioning in plants.

Under suitable conditions one kind of cell is transformed into another kind of cell depending on functions.

Advantages of Cell Differentiation

The main advantage of cell differentiation is that cells become more efficient at a particular task, conserve energy because they have to do that one task, and improve that task faster.

Differentiation Illustration 

Hormonal Influence in Differentiation Process

Many functions of differentiation are controlled by hormones like Auxin, which plays an important role in the differentiation of vessel elements.Auxin produced by the apical meristem and young leaves above the wound induces Parenchyma cells to regenerate the damaged Vascular tissue.

Dedifferentiation

Meaning: Cells which lose the capacity to divide can regain the capacity of division under different conditions, this phenomenon is termed as dedifferentiation.

Example: Formation of interfascicular and cork cambium from fully differentiated Parenchyma cells.

The given figure tells us how the protoplast system used to study cellular Dedifferentiation. Differentiated Mesophyll cells respond to the removal of cell walls (cellulose) by undergoing Dedifferentiation, thus becoming pluripotent. At this stage, additional signals determine cell fate:Auxin and Cytokinin induce their reentry into S phase, and Auxin by itself induce Redifferentiation, whereas in the absence of hormone presence cells die.  

Redifferentiation Process

Under this process, the cells divide and produce cells which one again lose their dividing capacity but get mature to perform specific functions.

Development Process in Plants

Most plants continue to grow throughout their life, they grow through a combination of cell growth and cell division(mitosis). Development process includes changes that an organism goes through during its life cycle. In plants, it starts with germination of seed and ends by senescence. This process includes steps like:

1. Cell division

2. Elongation of cell

3. Differentiation cell

4. Maturation

Cell division occurs in the meristematic tissue of plants due to which the elongation process occurs. This cell undergoes differentiation and forms a mature cell which undergoes aging and finally dies. Development process is the sum total of both extrinsic and intrinsic processes, intrinsic factors are genetic and chemical factors and extrinsic factors are sunlight, water, minerals, nutrients, etc.

Types of Plants Growth

1. Primary and Secondary Growth: The mitotic division of meristematic cells present at the root and shoot apex increases the length of the plant body. This is called the primary growth. The secondary meristem increases the diameter of the plant body and  it is called secondary growth.

2. Unlimited Growth: The root and the shoot system of plants grow continuously from germination stage to the death or throughout the lifespan of the plant. It is called the ‘Unlimited’ or ‘indeterminate’ type of growth. 

3. Limited Growth:  The leaves, fruits and flowers stop growing after attaining a certain size. This is called a ‘limited’ or ‘determinate’ type of growth. 

4. Vegetative Growth: The earlier growth of plants producing leaves, stems and branches without flowers is called ‘vegetative growth.

5. Reproductive Growth: After the vegetative growth, plants produce flowers which are the reproductive part of the plant. This is called reproductive growth.

Plant Differentiation – Types

1. Dedifferentiation Process

When in a process the cells lose their capability to divide and then under certain conditions regain this property of dividing, it is known as the dedifferentiation process. For example- 

1. When the normal cells present in the body are dedifferentiated, it leads to the formation of tumor cells. 

2. When fully differentiated, parenchymal cells lead to the formation of meristems.

 

2. Redifferentiation Process

When in a process, a
dedifferentiated plant cell loses again its capacity to divide one more time and evolves mature, it is known as the dedifferentiation process. In this process, the cells are matured in order to perform distinctive functions. Examples of redifferentiation may include formations of cork, secondary cortex, secondary phloem, secondary xylem, and so on.

Plant Differentiation- Developmental Process

The developmental processes in plants consist of all the life changes an organism goes through while completing its life cycle. The life cycle, in the case of seed, starts and ends with germination and senescence respectively. All the steps including cell division, cell elongation, differentiation of cells, and maturation of cells are there in this developmental process.

In the meristematic tissues, cell division occurs which may lead to the elongation or expansion of the cell. Then the process of differentiation occurs wherein the cells get matured and undergo senescence and eventually pass away. This whole process is the developmental process in the case of a plant.

The sum of total growth and differentiation is included in the developmental process and it is controlled by many factors which may include extrinsic factors such as temperature, light, oxygen, water, nutrients, etc, or intrinsic factors such as chemical and genetic factors, etc.

In order to respond to their environments, plants follow different pathways in different phases of life, and along with this plants also show different kinds of structure, and this phenomenon is referred to as plasticity. For example- heterophily is a condition in plants when the leaves in young plants and the leaves in mature plants are different. This condition can be found in plants such as coriander, cotton, etc.

Do You Know???

1. Long day plants produce flowers only when they are exposed to sunlight more than critical periods. 

Eg: Oat and Rye plant.

2. Short day plants produce flowers when they are exposed to sunlight less than critical periods. 

Eg: Coffee and Tobacco.