Plant Growth and Development

Notes for NCERT Class 11 Plant Growth and Development: Plants have the capacity to develop all through their life. This is due to the presence of meristems in certain areas of their body, and these meristems are able to resolve and reproduce on their own. Growth is quantifiable. At the cellular level, growth is the result of the expansion of cellular material and this growth is difficult to quantify. Plant development is evaluated using various techniques such as dry weight, volume, cell count, mass, or new weight expansion.

NCERT Class 11 Biology Chapter 13 Plant Growth and Development: The attached graph shows the area of ​​the root apical meristem, shoot apical meristem, and vascular cambium. Bolts show placenta of cell and organ development. Growth is a permanent and irreversible increase in the size of a cell and hence, an organism. The basis of growth involves three main phases, i.e. cell division (mitosis), cell enlargement, and cell differentiation. Plant hormones play a crucial role in growth and development. Plant hormones or phytohormones are chemical compounds found in plants at very low concentrations.

Plant Growth is Generally Indeterminant

Plants show different stages of growth and development at any point in time. This is due to the unique capability for their unlimited growth which, occurs due to the presence of special actively dividing cells, called meristems.

 

Growth is Measurable

Some parameters can be considered to measure growth. Those parameters are:

• Increase in fresh weight
• Dry weight
• Length
• Area
• Volume
• Cell Number

Phases of Growth

Developmental/Meristematic Phase 

Cell division is an important possibility in plant development. All cells are the result of dividing the previous cells. Mitosis is a type of cell division that occurs during development and includes both quantitative and subjective cell division. This division occurs in two phases: the division of the nucleus, called karyokinesis, and the division of the cytoplasm, called cytokinesis. In higher plants, cell growth terminates at the meristematic site, so some small daughter cells maintain this meristematic motion while others enter the next developmental phase, such as the cell amplification phase.

Cell Enlargement/Elongation and Cell Differentiation

At this stage, the tissues and organs enlarge. This expansion occurs through the shaping of the protoplasm, hydration (water retention), the formation of vacuoles, and the subsequent addition of new cell divisions to make it permanent and thicker.

Cell Maturation

At this stage, the expanded cells acquire different sizes and structures depending on the area and task. In this way, different cells are separated from basic and complex tissues that have different roles.

Growth Rates

The increased growth per unit of time is called the growth rate.

 

Conditions for Growth

• Water
• Oxygen
• Appropriate temperature
• Light
• Gravity

Example of Plant Growth and Development

Stem growth can be easily observed. Plant development occurs when stems and roots are stretched. Some plants, especially woody plants, also increase in thickness over the course of their lives. The expansion of the shoot and root is called essential development and is a consequence of cell division in the shoot apex meristem.

Development

After seed germination, seedling development, plant development, flowering, and fruiting, there are several changes. Progress is systematic, from the basic structure of the undeveloped organism in the seed to the profoundly amazing association of the familiar plant. This is called improvement. Plant development involves both growth and separation. After a period of time and space, growth and separation lead to the establishment of a living being of metabolic and latent complexity. When the plant is grafted, there is a precise movement of change that gives the plant organism a distinct structure.

Differentiation, Dedifferentiation, and Redifferentiation

For more information read: Differentiation, Dedifferentiation, and Redifferentiation

DEVELOPMENT

 

Plasticity

The plant leaves in the juvenile phase are different in shape from those in the mature plants. This is known as heterophylly. It is an example of plasticity. Some examples of the plants which show such phenomenon are:

• Cotton
• Coriander
• Larkspur

 

Plant Growth Regulators

Plant growth regulators, also known as plant hormones or phytohormones, are naturally occurring chemical compounds that regulate various aspects of plant growth and development. These substances play a crucial role in controlling processes such as cell division, elongation, differentiation, and responses to environmental stimuli.

 

Plant Hormones/ Plant Growth Regulators and Their Effects

FAQs on Plant Growth and Development

Q1: Write the Physiological Effects of Cytokinins.

Answer:

It promotes cell division and leaf expansion. It also stimulates leaf expansion.

Q2: Define Differentiation.

Answer:

In this phase, the cells originated from the root and shoot apical meristems and cambium mature to play some specific functions. Cells also, undergo structural changes in terms of their cell wall and protoplasms.

Q3: Write Some Examples of Plasticity.

Answers:

Some examples of plasticity are:

• Cotton
• Coriander
• Larkspur