Plant Growth and Development is an essential chapter of NCERT class 11. 

Growth is a permanent and irreversible process in living organisms. In plants, seeds grow to a new seedling before it becomes an adult plant. The process in which the cells specialize into morphologically and physiologically different cells is called differentiation. Development is the sum of differentiation and growth. Both extrinsic and intrinsic factors regulate development. If the cells do not grow and differentiate, a plant cannot be developed. In this chapter, we will discuss plant growth and development in more detail.

All living organisms increase in size. But did you ever think about how they increase in size? Cell division increases the number of cells in our body continually. Due to this, we observe changes in weight, size, and volume of organisms, including plants. This is called growth in plants.

Growth is a permanent and irreversible process. It is not uniform throughout the life span in all organisms. The size of tissues, organs, cells become large during this stage due to protoplasm formation, vacuoles, cell walls, etc. Many factors affect the growth of the plant, such as temperature, water, soil nutrients, light, and plant growth regulators.

• Differentiation

It is the process when cells specialize into the physiologically and morphologically different cells. The cells undergo few to major structural changes in both their cell walls and protoplasm during the differentiation.

• Dedifferentiation

In the process of dedifferentiation, there is a possibility of dividing and differentiating mature cells again. For example, in the interfascicular cambium, the formation of meristems and cork cambium. Dedifferentiation usually happens in the wounded tissues. The wound is repaired during the dedifferentiation of parenchyma cells.

• Redifferentiation

Redifferentiation is when the dedifferentiated cells become mature and lose cell division capacity again to serve the specific functions.

The sum of growth and differentiation is development. Development, like growth, is also governed by both extrinsic and intrinsic factors.

The development includes many changes during the whole life cycle of a plant following many different pathways. We can see the leaves of mature plants have slightly different structures than young plants. If the cells do not grow or differentiate, plant development is impossible.

Plants require sunlight, oxygen, nutrition, and water to develop and grow. They also require certain chemical substances to manage their growth and development. These chemical substances are naturally produced by the plants themselves, known as ‘Plant Growth Regulators’. These are simple organic molecules that have several chemical compositions. They are also described as plant growth hormones, phytohormones, or plant growth substances.

Plant growth substances or plant growth regulators have many functions, some of which are as follows:

1. Differentiation of cells

2. Formation of flowers, leaves, and stems

3. Ripening of fruit

4. Wilting of leaves

5. Seed dormancy

Generally, there are five types of plant hormones: Gibberellins (GAs), Auxin, Cytokinin, Ethylene, and Abscisic acid (ABA).

Photoperiodism refers to the response seen in plants due to seasonal changes in the length of day and night. The effect of photoperiods on the growth and development of plants is known as photoperiodism, especially flowering. The flowering plants have been divided into the following categories based on photoperiodic response:

1. Short Day Plants (SDP) - Some plants produce flowers when exposed to a shorter duration of light than the critical                      duration (8-10hours). These are called Short-day Plants—for example - Sugarcane, Dahlia, Soyabean Xanthium, Potato, Rice.

2. Long Day Plants (LDP) - Some plants produce flowers when exposed to a light period more extended than the fixed period.        Examples include - Lettuce, Gulmohar, Radish, Spinach, Barley are long-day plants.

3. Day Neutral Plants (DNP) - This type of plant can blossom throughout the year. The length of the light period does not              affect these plants. They produce flowers in almost all photoperiods: Tomato, Cucumber, Wild Kidney, Sunflower, and Bean.

A particular temperature is required for flowering in some plants. Studies show that flowering can occur early if the temperature is reduced to a specific point. For example, suppose we apply a temperature ranging between 1-10° C to a certain variety of rice, cotton, and wheat, the flowering occurs earlier, and the growth of seedlings is accelerated. This method is called vernalisation. Vernalisation is the process of accelerating plant growth and flowering by exposing the plant to a low temperature.

1. Define different terms like separation, development, improvement, redifferentiation, dedifferentiation, meristem, and determinate development

Separation - It is a subjective limited change in natural chemistry size, the capacity of cells and structure, organs, or tissues. 

Development - Development includes many changes that an organism goes through during its life cycle. Germination of seeds, growth, differentiation, maturation, flowering, seed formation, and senescence are all events that come under development. These are all the series of events that occur in the life history of a plant.

Improvement - It might be categorized as the cycle that includes separation, development, and development in the lifecycle of an organ, tissue, or creature.

Dedifferentiation - The plants that lose the capacity to divide can regain the capacity under certain conditions by a phenomenon called dedifferentiation. It usually happens in wounded tissues.

Redifferentiation - Redifferentiation is the process by which dedifferentiated cells lose their ability to divide and become mature.

Determinate development - Some plants grow to a certain stage and then stop growing after that. This is called determinate development.

Meristem - The specialized regions in the plants where active cell division takes place. Plant tissue containing meristematic cells (undifferentiated cells) is called meristems.

2. Is there any reason why there is no boundary to exhibit plan development during its blooming life cycle?

A blooming plant consists of various organs, viz., stem, blossoms, roots, leaves, natural products, and so on. All these plant organs require various types of boundaries to exhibit their development. The development of plants is estimated by weighing the new weight of the organs of plants such as bulbs, natural products, corms, and so on. When a change in the organic products arises, such as an increase in width, volume, and so on, they are additionally utilized as the different boundaries for estimating development. Increment in the surface zone is utilized as the boundary for organs like leaves. Root and stems fundamentally fill long and afterwards in circumference. Subsequently, increment length and breadth are used for calculating their development.

3. What is Vernalisation?

Vernalisation is the process of accelerating the growth of flowering by exposing the plant to a low temperature. Flowering in specific plants is dependent on low-temperature exposure. This process is referred to as vernalisation. Vernalisation focuses explicitly on promoting flowering. It provides the plant with enough time to mature and prevents premature reproductive development.