Primary growth:

Formation of primary permanent tissues and organs which is caused by activity of apical and intercalary meristems.

Secondary growth:

Initiated by cambium, which are essentially lateral meristem (vascular cambium and cork cambium) i.e., increase in girth.


Limited growth:

Growth which stops after some time e.g., leaves, flowers, fruits.

Unlimited growth:

Growth that continues throughout life as in case of root and stem.


Efficiency index:

Is the rate of growth which can be measured by an increase in size or area of an organ of the plant, like leaf, flower and fruit in a unit time.

The supply of nutrients, water, oxygen, suitable temperature and light are necessary for proper growth.

The force of gravity and light determines the direction of root and shoot growth.


Salt, mineral deficiencies and stress factors also influence the rate of growth.

Phases of Growth :

In plants, the growth in length is due to enlargement and elongation of cells at the apical regions and in thickness due to the activity of lateral and intercalary meristems.

In unicellular organisms growth consists of a single step while in higher plants, growth involves three steps or phases i.e., phase of cell division (formative phase), phase of cell enlargement (elongation phase) and phase of cell maturation (maturation phase). The phases are also known as regions.


Grand period of growth:

Time internal from the formative phase to maturation phase.

Growth curve:

The mathematical curve which represents the variation in growth rate, it is somewhat flattened S-shaped curve (sigmoid growth curve). It is differentiated into three phases:


(A) Lag phase (slow phase)

(B) Logphase (exponential phase)

(C) Stationary phase (steady state)

Measurement of Growth


Horizontal microscope:

Used to measure growth in length of a potted plant and herb/ seedling.


Devised to measure the growth in length of a plant.

Growth in plants can be measured in terms of

(i) Increase in the length of girth (in case of stem and root).

(ii) Increase in fresh or dry weight.

(iii) Increase in area or volume (in case of fruits and leaves) or

(iv) Increase in number of cells produced.

Growth regulators:

In all plant, minute quantities of some chemical substances (plant growth regulators or phytohormones) are present which regulate growth and differentiation. These are organic compounds and are capable of influencing physiological activities leading to promotion, inhibition and modification of growth.

Major types of Growth substances:

1. Auxins:

Related to cell enlargement and differentiation.

2. Gibberellins:

Related to cell enlargement and differentiation.

3. Cytokinins:

Related to cell division.

4. Ethylene:

Related with senescence.

5. Abscisic acid:

Related to resting states like lateral buds.

Other related growth regulators are Jasmenic acid, Salicylic acid and Brassinosteroids.