A Comprehensive Study on Plant Growth & Development for NEET

We have all learnt about plants and their classifications. But it is quite interesting if we focus on the orderly sequence of roots, stems, leaves, flowers, fruits and seeds, from where and how do they appear?

Till now, you must have learnt how trees increase in height and girth over a particular time. Therefore, the development of a plant is the sum of two combined process. These are growth and differentiation. Let’s start with, as it is also crucial to know that the development process of a matured plant occurs from the zygote. A zygote is a fertilized egg that follows a precise and ordered sequence of events. During this spell, a complex body organization takes place which helps in the production of roots, leaves, branches, flowers, fruits and seeds. After a specific period, they eventually die. 

What is Plant Growth?

Every plant and animal is composed of cells; hence they are living things. Growth is a fundamental and conspicuous characteristic of every living thing. Growth can be defined as a permanent increase that is irreversible. The size of an organ or even the parts of an individual cell cannot be transformed once it grows. The metabolic process (anabolic and catabolic) is responsible for the rate of growth. This occurs at the expense of energy. This means the expansion of a stem is growth.

The Difference in Growth when Compared with Animals

When it comes to growth, plant differs from an animal. When animal mature, the parts of the bodies stop the rate of growth after reaching a certain age. However, in the case of plants, they continue to grow throughout the life span. The growth is restricted only to specific meristematic tissue regions. This continued growth results in the formation of: 

  • Two general groups of tissues which are primary and secondary

  • Apical and lateral meristems.

Apical Meristems

Apical meristems are the zones of cell division that take place at the tip of roots and stems. It is responsible for increasing the overall length or the primary plant body, as the tissues differentiate from the meristems.

Lateral Meristems

Some plants grow in diameter with the production of new tissues in a lateral way. They laterally form tissues, in the cylindrical form, which is known as vascular cambium. It keeps extending throughout the length of a plant right from the tips of the shoots to the roots.

Phases of Growth

Plant growth and development can be divided into three phases. These are:

  • Meristematic

  • Elongation

  • Maturation

Meristematic: The meristematic phase of growth can be determined by the constant division of cells occurring at the apex of roots and shoot. 

Elongation: Elongation is the phase of enlargement where the cell elongates through a development process regulated by phytohormones and light. This has special significance to plant growth. 

Maturation: It is the phase of cell wall lignification and thickening. The cells become matured and come to maximum size. They further undergo protoplasmic modifications.  

The Growth Rates of Plants

The growth rate is the development process per unit time. Therefore, the rate of growth can be expressed in mathematical form. An organism or parts of it can produce a number of cells in various ways. The increase in growth rate can be expressed either in arithmetic or geometrical form.

When it comes to arithmetic growth, only one daughter cell can divide while others continue to mature and differentiate. The simplest arithmetical expression can be expressed by a root that elongates at a constant rate. 

Lₜ = L₀ + rt 

Lₜ = length at time ‘t’

L₀ = length at time ‘zero’

r = growth rate / elongation per unit time.

FAQ (Frequently Asked Questions)

Q. What is Plant Development?

Ans. The process of originating structures and maturing the parts of a plant is known as plant development. Plants continue to produce new structures and tissues throughout the life span with the help of undifferentiated cells known as meristems.

Q. Where does Cell Elongation Occur in a Plant?

Ans. Cell elongation is a process of cell division that takes place in the regions of meristems. Most of the higher plants grow through cell elongation. The meristems are found at the tips of shoots and roots.

Q. What is the Difference Between Plant Growth and Development?

Ans. The irreversible change of sizes in cells and organs of a plant is known as growth. It occurs due to cell enlargement and divisions. On the contrary, development is the progress of earlier to later stages during maturation.

Q. What are the Three Stages of Plant Growth?

Ans. Growth may be defined as irreversible, but it consists of three phases. These are meristematic, elongation and maturation. Each has its own characteristics and follows a specific process to promote an apt development of a plant.