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Characteristics of Growth and Development

Growth and development in animals or plants are characterised by certain features. The main characteristics are:
  1. Growth Curve
    Growth, whether it is of a cell, an organism, or a population shows a characteristic S-shaped (sigmoid) growth curve. The growth rate increases exponentially up to a point and then it levels off. Several periods can be distinguished in the growth of an organism. During the initial period called the lag period, very little growth occurs. This is followed by the logarithmic or exponential period in which a major spurt in growth occurs, first slowly and then rapidly. 

Typical S-shaped Growth Curve

The exponential period does not last long but soon enters into a period of deceleration, in which growth occurs more slowly and finally stops altogether.

During the lag phase the developing organism prepares for later growth; a seed for example imbibes water, in preparation for germination, or a cell may synthesise the necessary enzymes needed for the metabolic activity attendant with the growth process later. During the exponential period, the organisms' anabolism is much more than its catabolism and actual synthesis and accumulation of protoplasmic materials occurs.


  1. Cellular Growth
    Cells grow as a result of biosynthesis of proteins, carbohydrates and lipid material. Plant cells convert inorganic constituents into carbohydrates and they are also capable of synthesising proteins and lipids. Thus with adequate supply of the basic inorganic nutrients and sufficient light, plant cells can go on synthesising protoplasmic materials. However, animal cells have to ultimately depend on plant cells for the supply of ingredients needed for their biosynthetic activities.
  2. Cell Division
    Cell division is the process by which the unicellular zygote becomes a multicellular organism. A human being or a large tree both consist of countless number of cells, all derived from a single unicellular zygote. It is the series of mitotic divisions that occur during development and growth which enables the transformation of the zygote into the multicellular organism.
  3. Cell Expansion
    Differential cell expansion, that is, more rapid or more extensive growth by some cells than by others, and a specific pattern of cell division are other features of growth and development. These features enable the overall changes in the form of the organism, especially in plants, where it is called morphogenesis.
  4. Cellular Differentiation
    Along with cell division and cell expansion there is another process occurring during growth and development of organisms called cell differentiation. Differentiation is the specialisation of cells in terms of their structure and function. If all the cells derived from the zygote were similar or identical in structure and function, the multicellular organisms will have only one type of cell. However, as we have already seen, the multicellular body of the plant is composed of many different types of tissues and cells, specialised to perform varied functions. These tissues are the result of the process of cell differentiation, in which certain groups of genes are made selectively non-functional in certain cells. However, all the cells derived from the zygote retain their genetic potential and are all identical to the zygote nucleus with respect to their genome.

Conditions for Growth

We know that growth is brought about by cell division and cell enlargement. The conditions necessary for growth are similar to that of synthesis of protoplasm and cell division. The supply of nutrients, water, oxygen, suitable temperature and light are necessary for proper growth. The force of gravity, and also light determines the direction of root and shoot growth. Nutrients provide essential materials for the synthesis of protoplasm and act as a source of energy. Water maintains the turgidity of growing cells and provides the medium for enzymatic reactions. You know that oxygen is indispensable for respiration and for release of energy. Temperature has a thermotonic effect on growth and 28 to 30oC is an optimum range for proper growth in most cases. Temperature above 45oC coagulates and damages the protoplasm and hinders growth. Light is not essential during the initial stages of the growth, but is required for further growth and photosynthesis. There is a stimulating effect of light on plant growth, and its absence results in etiolation. Salt, mineral deficiencies and stress factors also influence the rate of growth.

Phases of growth

We know that growth in plants is localized in the meristematic regions only i.e. apical, lateral and even intercalary regions. The growth in length is due to the enlargement and elongation of cells at the apical regions, and in thickness due to the activity of lateral and intercalary meristems.

The period of growth is generally divided into three phases, namely formative, elongation and maturation. The formative phase has constantly dividing cells and is restricted to the apical meristems, both at the root and shoot tips. The cells of these regions are rich in protoplasm, with large nucleus and thin cellulose wall. The phase of elongation lies just behind the formative phase and is aimed at the enlargement of cells. The phase of maturation is further behind, and here, the cells start maturing to obtain a permanent size. These phases are also known as regions. The time interval from the formative phase to maturation phase is called the grand period of growth.

Measurement of Growth

You know that growth is a natural phenomenon, and generally takes place at the apical regions of the plant. Thus, the growth in length can easily be measured with the help of ordinary measuring scale at an interval of time. For precise measurement, the equipment named auxanometer or auxograph can be used. An auxanometer is used to measure the rate of growth of a plant in terms of shoot length. A thread is tied to the growing tip of a potted plant and at the other end, a weight is tied after passing the thread over the pulley. The needle attached in the center of the pulley will show the deflection, which can be read on the graduated arc to find out the increase in length of the plant.


Growth can also be measured by an increase in weight, both fresh and dry, and volume of the plant. The increase in the number of cells, specially in algae, yeast and bacteria also gives an idea about the rate of growth. The measurement of area or volume of an organ of the plant will also provide information about the rate of growth.

Plant Growth and Development

The features of growth and development detailed above are more or less applicable to all organisms. However, there are certain features of development and growth which are unique to plant species. Of course, plant development also involves the three component processes namely cell division, cell expansion and cellular differentiation. Unlike animals, plants, especially trees, are constructed in a modular fashion. In other words their development and growth is never complete. In this continuous type of growth and development new organs are always formed as the old ones are replaced and the plant may grow in size and height for a long, long time. This is possible in plants because of the presence of special meristematic tissues which go on producing fresh tissues endlessly. 

In perennial plants growth continues throughout their life. However, there may be periods of active growth and periods of dormancy in a calendar year. Plant metabolism shows a decrease during colder months, and the plants become dormant, without exhibiting much growth. Under favourable conditions, growth resumes once again. The growing season of plants refers to the period when they show maximum vegetative activity. In plants not only the overall growth of the organisms but such activities as flowering and fruiting also are seasonal in nature.

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