Question

Explain in detail sigmoid growth curve.

Answer 1

The period during which the growth rate in any term plotted against time is always a s-shaped curve. This is called a sigmoid growth curve.

Complete answer:
The growth rate in plants is studied with respect to cells, a plant organ, a whole plant or whole plant or whole life-cycle of plants.

Initial stages, a little decrease in weight may occur due to utilization of reserved food, growth rate increases slowly during the phase of cell elongation or enlargement and again slows down during the phase of cell maturation till the time growth stops.

The period in which the growth rate in any term is plotted against time is always an S-shaped curve. It shows a slow start gradually attaining a rapid growth rate followed by a period of slow growth and ultimately a decline. The growth rate of a plant organ or a complete plant does not remain the same but varies. The variation in growth is due to irregular changes.

In initial stages during phase of cell formation growth rate is quite slow while it increases rapidly during g elongation phase and becomes maximum during the phase of cell maturation. Finally, at a stage, the growth stops. This total phase from initial to final stage of growth is called the grand period of growth.

Total period of growth can be divided into four stages
(a) Long period-slow growth and growth starts from this period.
(b Long period-period of maximum growth. In this stage, cell division and physiological growth. In this cell division and physiological process are fast.
(c) Decline growth period. Due to the decrease in metabolic process, the growth period slows down.
(d) Senescence period or steady period. Growth ultimately completes during phase and becomes static. Thus growth rate decreases to zero.
The graph plotted for growth rate and time is always a s-shaped are called sigmoid or growth period curve. Fundamental conditions do not alter this curve.

Note: There are two kinds of growth curves which are used in biology,
i) Exponential curve: It is also known as J-curve and is used when the population size is not limited.
ii) Logistic curve: It is also known as S-curve and it is used to show the effect of a limiting factor.