Consider the following statements:

I.  The movement of a plant part in response to light is called Geotropism.

II. The movement of plant part in response to gravity is called Thigmotropism.

III. The movement of a plant part in response to a chemical stimulus is called Chemotropism.

IV. The movement of a plant part in response to water is called Hydrotropism.

Which of these is/are correct?