Movements, no matter of what kind, do always consume energy. If the supply of this gas is interrupted, then the inner movements that cause growth stop, the current of the protoplasm the most obvious expression of life ceases, the periodic movements of leaves and flower parts end, and the organs usually stimulated by vibration loose their sensitivity. Today exist different classifications of plant movements. The first type has no detectable extern cause while the latter are termed movements caused by stimulation. The reactions of each group can be either positive or negative.
Movements are, too, classified according to the cause of stimulation.
Tactic movements are oriented towards a certain direction. Classic examples are phototropism and geotropism . Nastic movements are independent of the direction of the controlling signal. An example is the seismonasty of the mimosa. The folding up of the leaflets and the leaves occurs not in the direction of the haptic stimulus.