Differential cellular growth in response to touch explains the coiling behavior of the tendrils of vines. General mechanical stimulation, such as motion in response to wind, stunts growth. A tree on a windy mountain will have a shorter, thicker trunk. This enables the plant to better maintain its attachment to the soil in windy conditions. These responses to touch and motion are examples of thigmotropism.
Plants are also capable of rapid and reversible changes in shape.
Turgor presssure is reduced by loss of water in plant tissues, and the leaf becomes temporarily flaccid. Stimulation somehow induces loss of potassium in the cell, which causes water to leave the cells by osmosis. A remarkable example of this behavior occurs in the Sensitive Plant, a variety of Mimosa . The plant clearly has the equivalent of a nervous system, whereby responses to stimuli are transmitted throughout the plant. Comment - My chinese wisteria exhibits odd behavior.