Tropisms can be distinguished according to the orientation with respect to the direction of the stimulus. They can commonly be either
positive (towards the stimulus) or
negative (away from it). Both of these are
orthotropic, and can be contrasted with tropisms that are
diatropic (perpendicular to the stimulus) or
plagiotropic (at an oblique angle). According to the type of stimulus, tropisms can be: •
Aerotropism: the growth of plants towards or away from a source of
wind •
Chemotropism: the movement or growth in response to
chemicals •
Electrotropism, or galvanotropism: the movement or growth in response to an
electric field • Exotropism: continuation of growth "outward," i.e. in the previously established direction •
Gravitropism (sometimes referred to as geotropism): is movement or growth in response to
gravity • Prohydrotropism: positive hydrotropism •
Inotropism: muscular contraction in response to drugs •
Magnetotropism: movement or growth in response to magnetic fields •
Phototropism: movement or growth in response to
lights or
colors of light • Aphototropism: negative phototropism • Skototropism: negative phototropism of vines • Selenotropism: motion of plant parts in response to the direction of the Moon •
Thermotropism: movement or growth in response to
temperature •
Thigmotropism: movement or growth in response to
touch or contact • Traumatotropism: orientation deviation after suffering a wounding == See also ==