Plant Growth and Development: Phases, Curve, Measurement, Factors

Here we are going to discuss Plant Growth and Development, Plant growth Phases, Plant growth Curve, Measurement of Plant growth, Factors affecting plant growth. Regions of growth such as Apical, Intercalary and Lateral Meristems.

Growth is a vital process which brings about Irreversible permanent changes in any plant or its part. These changes may be size, form, weight and volume. Growth is part of the development of any plant or species.

Regions of Growth in plants

Regions or site of growth in unicellular and multicellular plants is different from each other. There is overall growth and not confined to any specific region in unicellular plants but in the case of multicellular plants, growth is restricted to specific regions having meristematic tissues or cells. Meristem is the tissues containing undifferentiated cells where growth can take place. Meristematic cells give rise to various organs which are responsible for the growth of the plant.

On the basis of position in the plant, body meristems are divided into three categories

Apical Meristem

The apical meristems found within the root tips and the tips of the new shoots and leaves. meristems are the growth regions in plants Parts. Apical meristem is one of three types of meristem which are responsible for the growth of a plant, The apical meristems are types of tissue which can differentiate into different cell types.

Apical Meristems are found at the apex of root and shoot. The length of the plant increases as a result of the activity of apical Meristem. In bryophytes and pteridophytes, a single tetrahedral cell found at the shoot Apex as apical Meristem, but in angiosperms and gymnosperms, a group of meristematic cells found.

Intercalary Meristems

Intercalary Meristems are found above the nodes in the plants. The activity of intercalary Meristem increases the length of plants takes place. Bambusa increases very fast with the help of intercalary Meristems

Plant Growth and Development: Intercalary Meristem

Lateral Meristems

Lateral Meristems are made up of cells which can divide in radial direction only. Lateral Meristems form laterally placed new cells towards the centre and Periphery. The best examples of lateral Meristems are Cork cambium and vascular cambium. Lateral Meristems increases the girth of shoot and roots.

Plant Growth and Development: Lateral Meristem

Plant Growth and Development: Phases of Growth in plants

There are three important phases of growth

I) Cell Division

Mitotic cell division divides cells to create another same cell for growth of tissues. The mitotic division also called mitosis cell division.

II) Cell Enlargement

Cell enlargement is the process of growth of cell which is followed by cell division. In the process of cell enlargement the cell increases in size. The cell size increases due to absorption of water or vacuolation.

There are two different ways of explanation of the cell enlargement.

The first view says that the turgor pressure of the cell is responsible for the cell enlargement
According to another view of cell enlargement, growth of cell wall is responsible for the enlargement of the cell.

III) Cell Maturation

Cell maturation is the process of differentiation. This is the process of the conversion of a cell into special nature. Cell maturation or differentiation followed by the cell division and cell and enlargement. Cell enlargement leads to the development of specialised tissue cells to do special function.

Xylem tracheids, xylem trachea, xylem sieve tubes are examples of cell differentiation

Plant Growth and Development: Growth curve in plants

The growth curve is the way to show the growth of any plant, animal or organism as Mathematically from its birth to death. This is the way a bi which we can explain the rate and phases of growth in a very easy way.

Growth pattern in different species and different organs is different so that the curve of different species or organs will be different. The rate of growth also differs from time to time in the same organ or in the same species. For example, the young leaf sheath of Banana grows for a time at the rate of almost 3 inches per hour but growth begins slowly then enters A. of enlargement.
After sometime no further enlargement occurs in that sheath.

Plant Growth and Development: Sigmoid Growth Curve

The matter mathematical curve of this banana Leaf-sheath will be S-shaped or sigmoid curve. The time in which growth takes place is called the “Grand Period of growth”. The term “Grand Period” was coined by Sachs.

The analysis of growth curve can be differentiated into three phases.

1. Lag Phase-

In this phase, the rate of growth is very slow. Growth needed more Time in Lag Phase.

2. Log Phase

log Phase is also called exponential phase. The growth of rate becomes maximum and more Rapid as compared to the lag phase. All the physiological activities of the cells are at their maximum level in Log Phase. The Lok Phase is referred to as the Grand period of growth.

3. Final Steady State (Adult Pase)

Stationary phase- stationary phase is also referred to as an adult phase or final steady state of the growth. Growth slows down because of the limiting of nutrients. All the physiological activities of the cells get slows down. This is of growth indicates the maturity of the growth system.

Measurement of Plant Growth

Growth can be measured by an increase in size for the area of an organ of a plant. Plant organ maybe leaf, flower,r fruits etc. Rate of growth is called efficiency index. The following methods are designed to measure the growth of plants or its organ in length.

Direct Method- Direct method measurement is the method of measurement of length which is done between two marked Scale at regular intervals.

Horizontal Microscope – Travelling microscope

Auxanometer- Arch Auxanometer and automatic auxanometer are very popular tools to measure the growth in length of a plant. Automatic auxanometer is also called Pfeffer”s auxanometer. The rate of growth of root can be easily measured by the use of root Auxanometer

Bose’s Crescograph- This is invented by Sir Jagdish Chandra Bose. Crescograph is a more delicate instrument and gives magnification up to 10000 times.

Plant Growth and Development: Plant Growth Factors

The activity of Protoplasm of a cell is affected by the various types of factors. These factors are environmental and physiological. Physiological factors include absorption of water, minerals, photosynthesis, respiration etc and environmental factors including climatic and edaphic changes. The effect of these factors may be transferred to one region to another region of a plant.

Environmental and physiological factors are divided into to measure parts
i) External factors and ii) internal factors

External factors affecting plant growth

External factors are environmental factors which affect the growth of the plant. Following are some examples of external factors

Light
Temperature
Water
Oxygen (O2)
Carbon dioxide (CO2)

Internal factors affecting plant growth

Internal factors are those factors which affect the physiology of the plant. Following are some examples of internal factors

Nutrition
Growth Regulators

Important Points Related to Plant Growth

Behind the apex maximum growth in roots occurs.
Auxanometer is useful to measure of growth activity of a plant.
Light and temperature are two factors primarily affect the developmental phase of growth.
Due to leaves falling in small numbers at intervals evergreen trees remain green throughout the year.
Cell enlargement and cell maturation are the major steps of growth.
We can find active cell division at the tip of roots and shoots of a plant.
Plant growth in length is increased by apical Meristem.
Growth is always unidirectional.
Plants are grown in a controlled environment with the help of phytotron.
Water is absolutely necessary for germination of seed.
Etiolation in plants is caused when we grow a plant in a dark environment.
Auxanometer is a tool which is helpful to measure the growth in length of a plant.
The rate of growth of any organism follows the sigmoid curve.
Exponential Growth occurs in asexual reproduction.
Determination of age of a tree is called dendrochronology.
Light promotes differentiation in vascular plants.
The growth is slowest in the lag phase.
Scarification is the removal of seed dormancy by mechanical method.
The exponential phase is known for the highest growth.
The growth is unlimited in plants.
The horizontal microscope is used to measure the growth in along Nation.
Auxanometre is a very popular instrument by which we can measure the growth of stem accurately.
Boysen- Jennsen performed classical experiments on growth.
The sequence of cellular growth stages is- division, elongation and differentiation.
Growth is maximum in the zone of cell elongation.
Turgor pressure is responsible for the growth.
The usual shape of the growth curve is sigmoidal.
Causes that delay in the germination of seeds are mechanical resistance of testa, impermeability of seed coat, unavailability of water and oxygen.
Crescograph is used to record plant growth by seconds

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Plant Growth and Development: Phases, Curve, Measurement, Factors