Plant Growth and Development Test - 4

Exponential growth is dependent on initial size, rate of growth and time interval. L_t = L₀+ rt.

Growth phase consists of leg phase, exponential phase and stable phase. It do not consist of linear phase.

A growth curve is an empirical model of the evolution of a quantity over time or a graphical representation of how a particular quantity increases over time.
Growth curves are used in statistics to determine the type of growth pattern of the quantity - be it linear, exponential or cubic.
It is also known as Sigmoid curve.

Exponential growth is represented by initial size and growth rate and time. If W₁is the final size, W₀ is the initial size, r is growth rate and t is the time of growth than exponential growth is W₁= W₀.ert.

Natural cytokinins are synthesised in regions where rapid cell division occurs, for example, root apices.

They help to prevent fruit and leaf drop at early stages but promote the abscission of older mature leaves and fruits.

Abscistic acid encourages fruit to drop and leaves to fall. When the plant is low on water abscistic acid closes the stomata, pores in the leaves. It encourages both seeds and plants to go dormant.The hormone induces seeds to produce proteins to store when the seeds are dormant. 

Auxin was first collected by F.W. Went (1928) from coleoptile tip of Avena. He also developed Avena curvature test for bioassay of auxin.

Auxins are generally produced in growing apices of shoot and root. These two regions are the meristematic cells which are actively taken part in cell division.

Auxins like IAA and indole butyric acid (IBA) have been isolated from plants.(naturally) NAA (naphthalene acetic acid) and 2, 4-D (2, 4-dichlorophenoxyacetic)are synthetic auxins.