Growth and Development: Types, Phases & Characteristics

Ans. Flowering plants have various organs such as leaves, stems, roots, flowers, fruits, etc. All these organs grow at different rates. Each organ has its own specification that can be accounted for as growth. For example, fruits can be weighed to determine their growth, the surface area of leaves can be calculated to determine their growth, length, and diameter of stems can be measured to determine their growth. A single parameter cannot encompass all these variables. That is why different parameters are used to determine the growth and development of flowering plants rather than a single method.

Ans. Growth is defined as the increase in size and mass in any living organism. Growth occurs in organisms due to the multiplication of animal cells and plant cells in their bodies. The types of growth in plants are primary growth, secondary growth, vegetative growth, and reproductive growth.

Ans. Development is defined as the overall maturation of organisms physically as well as emotionally and psychologically. And growth is defined as the increase in size and mass in any living organism. It is evident from these definitions that growth is only physical but development is physical, emotional, and psychological.

Ans. Everything in the universe is affected by some factors. Growth receptors in plants and hormones in animals and humans aid the growth of organisms. But there are other factors that affect the growth of living organisms. These factors can be broadly classified into two categories namely,

• Internal factors 
• External factors

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Ans. 

Phase I: Phase I is commonly known as the formative phase. In this phase, the division of cells starts taking place. The process of division of parent cells into daughter cells which further divide into more daughter cells is called mitosis. During mitosis, cells not only divide quantitatively but also qualitatively.

This division of cells has two significant steps. In the first step, the parent nucleus gets divided into two nuclei. The division of the nucleus is termed karyokinesis. The next step is the division of the cytoplasm around the newly formed nuclei. The cytoplasm is divided to gather around each nucleus and form two individual cells. The division of cytoplasm is termed cytokinesis.

Phase II: Phase II is known for cell enlargement and cell differentiation. The formation of cytoplasm around the nucleus leads them to the next phase of growth. In this phase, the size of tissues and organs starts to increase. Vacuoles start developing and the cell wall starts building up. Due to this, the cell is now able to hold water for hydration. In this phase, the size of cells gets enlarged.

Phase III: Phase III is known for cell maturation. After the cell is completely built, it starts gaining its identity. Every cell has a specific function. This is the phase of growth where the cells are assigned their functions. Based on the location of the cells, different cells acquire specific forms to carry out their functions. These cells can form simple and complex tissues.

Ans. 

• Growth, in plants, takes place due to meristems and an increase in protoplasm. The meristems are located at different locations on the plant. They enable the overall growth of plants.
• Since meristems do not die they ensure that a plant grows throughout its lifespan.
• Growth is not easily measurable in plants since it is minute when observed over shorter periods of time. 
• The growth of plants can be measured in terms of the number of plant cells, dry weight, fresh weight, volume, etc.

Ans. There are four types of growth in plants. They are primary growth, secondary growth, vegetative growth, and reproductive growth.

Primary Growth: The increase in length of a plant is termed as primary growth. Primary growth is a result of mitotic divisions in meristematic cells. These divisions increase the length of the roots and apex of the shoot of the plants.

Secondary Growth: The increase in diameter of a plant is termed secondary growth. Secondary growth is a result of the division of secondary meristematic cells.

Vegetative Growth: Vegetative growth is the growth that takes place before a plant starts bearing flowers. During vegetative growth, the formation of parts of plants such as roots, stems, branches, and leaves takes place.

Reproductive Growth: Reproductive growth is the growth of reproductive parts. In plants, flowers are the reproductive part. Thus, during reproductive growth, a plant starts bearing flowers.

Ans. Morphogenesis is defined as the process in which an organism undergoes a change in shape due to embryological factors.

Differentiation is defined as the process in which a plant's cells, tissues, and organs undergo considerable and significant changes, both internally as well as externally.

• Cytoplasm

• Nucleus of a cell

Ans.

1. The cytoplasm is the fluid present between the cell membrane and the nucleus. Organelles of cells are present in the cytoplasm. These are mitochondria, Golgi bodies, ribosomes, etc. The cytoplasm is made up of basic elements like C, H, O, and N. They are found in the form of carbohydrates, proteins and water.
2. Nucleus of a cell is generally spherical and located in the centre of the cell. It is separated from the cytoplasm by a membrane called the nuclear membrane. It also contains nucleolus and chromosomes. It helps in inheritance and acts as the control centre of the activities of the cell.

Ans. Cell size. Some cells are very small and visible only with a microscope. The smallest cell is of bacterium, PPLO. An ostrich egg is the largest animal cell. In plants, an algae, Acetabularia has a single cell of about 10 cm in length. Cell shapes are very diverse. Some cells like those of Amoeba and white blood cells continuously change their shape. Most cells, however, maintain their constant shape. The shape of the cell is related to its function.