The phrases “growth” and “development” are sometimes used interchangeably. But, from a scientific standpoint, that is utterly inaccurate. Growth is described as any living organism’s growth in size and mass, whereas development is defined as the physical maturing of organisms. Plant growth regulators are a group of nutrients found in plants in the form of compounds that aid in the regulation of plant growth and development. We are all aware that plants rely on sunshine, air, and water, all of which are extrinsic factors that play a significant part in plant growth and development. Aside from these extrinsic factors, internal factors such as plant growth regulators or hormones play an important role in the plant’s life cycle.

What is Plant Growth?

Any live organism’s growth is defined as a gain in size and mass. It is an essential component of all living organisms. Organisms grow as a result of the proliferation of animal and plant cells in their bodies. Throughout its existence, a creature grows in some form or another. Most living things develop at their fastest until they reach adulthood. After then, the rate of development steadily slows until they reach the end of their lifetime. Growth is an ongoing process. It’s also unstoppable.

Types of Plant Growth

Plant growth can be classified into the following types.

Primary and Secondary Growth

A plant’s growth is said to as primary when it occurs as a result of the mitotic division of the meristematic cells found at the plant’s root and shoot. Secondary growth in a plant, on the other hand, occurs through the division of the secondary meristem, which increases the diameter of the plant’s body.

• Unlimited Growth: A plant’s growth is said to be unlimited if there is a continuous rise in its length from the stage of germination to the end of its life cycle.
• Limited Growth: This refers to a sort of plant growth that is naturally limited. Such plants can only grow to a specific height before ceasing to thrive.
• Vegetative Growth: This form of plant growth is not related with the growth of flowers, but rather with the growth and development of stems, leaves, and so on.
• Reproductive Growth: This sort of plant growth is primarily concerned with the development of a plant’s flowers.

Phases of Plant Growth

1. Meristematic Phase

Cells keep continually dividing in root and shoot apex of a plant. They symbolise the meristematic stage of development. These type of cells have bigger nuclei, that are also rich in protoplasm, and also have thin, cellulose-containing cell walls.

2. Elongation Phase

The cells in the zone immediately after the meristematic area reflect the elongation phase. Cells in this zone exhibit cell expansion, enhanced vacuole production, and new cell wall deposition.

3. Maturation Phase

The maturation phase is situated near the elongation phase but away from the apex. Cells in this area attain their largest size in terms of protoplasm and cell wall thickness.

Factors that Affects Growth

Plant growth is affected by both external and internal factors. Factors affecting growth in plants are listed below:

External 

• Light – It is essential for food synthesis. It also influences the development of the roots and shoots. Light intensity, quality, and duration all have an impact on seed germination and flowering in various plants.
• Temperature – For normal and suitable plant growth, an ideal temperature of 25–30°C is recommended. Plant development is affected by temperatures exceeding 45 degrees Celsius due to high transpiration, enzyme denaturation, and protoplasm coagulation.
• Water – The most crucial medium for all chemical reactions and physiological activities is water. It is required for photosynthesis, cell elongation, and the maintenance of increasing cell turgidity. Plant development comes to a standstill when there is a lack of water. 
• Oxygen – It is necessary for plant cellular respiration. This energy is used by the cell for a variety of functions and is directly involved in the development stages.
• Nutrients – Both macro and micronutrients are required for protoplasmic production and serve as a source of energy. When the nutrition supply runs out, growth stops.
• Soil – Soil is a growing medium for plants. Soil supplies the plant’s roots with support, nutrition, and a network of water and air.

Internal factors

• Genetic Factors – These are internal variables. These are responsible for the general upkeep of a plant.
• Plant Development Hormones or Regulators – Some chemical substances that are present in trace amounts affect plant growth. These substances are known as phytohormones or plant growth regulators. Auxins, gibberellins, and cytokinins are regarded as growth promoters because they are engaged in growth-promoting functions. Abscisic acid, as a growth inhibitor, is responsible for growth-inhibiting properties. Ethylene has mixed effects, in that it has both promoting and inhibiting properties.

Conclusion

Growth is described as any living organism’s growth in size and mass, whereas development is defined as the physical maturing of organisms. Plant growth regulators are a group of nutrients found in plants in the form of compounds that aid in the regulation of plant growth and development. We are all aware that plants rely on sunshine, air, and water, all of which are extrinsic factors that play a significant part in plant growth and development. A plant’s growth is said to as primary when it occurs as a result of the mitotic division of the meristematic cells found at the plant’s root and shoot. Secondary growth in a plant, on the other hand, occurs through the division of the secondary meristem, which increases the diameter of the plant’s body. A plant’s growth is said to be unlimited if there is a continuous rise in its length from the stage of germination to the end of its life cycle.