It is evaluation of the effect of a substance on a living organism under controlled conditions. Two bioassays used to examine auxin activity in plants are:
1. The Avena Curvature Test
2. Root growth inhibition test

Yes, we can alter the rate of growth by making variations in the factors affecting growth, these are light and temperature. A plant grows quicker during the night then during the day. During the night retarding or inhibiting action of light is absent and rate of growth of a plant gradually increases until dawn while during the day the rate of growth gradually decreases until about sunset.

(i) Gibberellin.
(ü) Cytokinins.
(iüi)Gibberellin
(iv) Abscisic acid.

Relative growth rate of A\(=\frac { (10-5) }{ x\times 5 } =\frac { 5 }{ 5x } { cm }^{ 2 }\)
Relative growth rate of B\(=\frac { (55-50) }{ 50\times x } =\frac { 5 }{ 50x } { cm }^{ 2 }\)
Thus, A shows higher relative growth rate.

Abscisic acid (ABA) and cytokinin antagonistically regulate many developmental processes and environmental stress responses in plants.

Cut leaves in cytokinins stayzreen for longer duration because cytokinins retard ageng of plant organs by promoting protein synthesis aid mobilisation of nutrient resources.

The compound, which can be converted into auxin are called auxin precursors. The compounds, which inhibit the actions of auxins, are termed anti-auxins. The auxins, which can easily be extracted, are called free auxins. And auxins, which are hard to extract and need the use of organic solvents, are reffered to as bound auxins.

IBA and 2,4 are used to induce formation of roots on cutting of many ornamental, horticultural and forest trees. 2,4-D can also be used as a weedicide

Spraying of sugar plants with gibberellin can increases the length of internodes and increased or lengthy internodes will produce more sugar. Thus,gibberelins can increase sugar yield.

Meristematic cells are actively dividing cells which show mitotic divisions, ie.each chromosome is split lengthwise into two homologous chromatids, which pass equally into daughter cells. These possess thin cell wasll and a dense cytoplasm.
Mature cells are incapable of divisions becauses inthese cells differentiation has take place. Also mature cells do not possess thin cell wall in and a dense cytoplasm.