Tropism is the growth response that results in the curvature of the whole plant organs based on stimuli. There are many different types of tropism. Tropisms can include chemotropisms, gravitational tropisms, and phototropisms. The photo shows bish orchids (Orchidaceae Bish) reacting to positive phototropism. This means the orchid are elongated towards the direction of light so it can perform photosynthesis more efficiently.