Coordination and Control

Cytokininspromote cell division, cell growth and differentiation along with auxin. Ethylene is responsible for fruit ripening. Abscisic acid helps the plant to sustain in adverse conditions. Gibberellins enable the plants to grow taller.

Auxins are synthesized at the shoot tip and help the cells to grow longer. When light is coming from one side of the plant, auxin diffuses towards the shady side of the shoot. This concentration of auxin stimulates the cells to grow longer on the side of the shoot which is away from light. Thus, the plant appears to bend towards light.

Phototrophic movement is the growthof a plant in response tolight. If the plant part growstowards light, it is called positive phototropism, and if the plant part growsaway from light, it is called negative phototropism. The shoot of a plant shows positive phototropism and the root of a plant shows negative phototropism.

The Nodes of Ranvier, also known as myelin sheath gaps, are the gaps (approximately 1μm in length) formed between the myelin sheaths generated by Schwann cells. Electrical impulses jump from these nodes.

Gibberellins promote internodal growth. Auxin helps in apical dominance. Cytokinin brings about cell division and ethylene promotes ripening of fruits.

Nerve impulses are simply signals that are transmitted along nerve fibres (or neurons). It is the process by which neurons communicate with one another. The transmission of a nerve impulse along a neuron from one end to the other occurs as a result of difference in electrical charges across the membrane of the neuron. Nerve impulses can travel very quickly because they are electrical impulses.