Here's a breakdown:

* Tropism: A growth response of a plant in a specific direction in response to an external stimulus.

* Stimulus: An external factor that causes a response in an organism.

Some common examples of tropisms include:

* Phototropism: Growth towards light.

* Gravitropism: Growth in response to gravity (roots grow down, shoots grow up).

* Thigmotropism: Growth in response to touch (vines wrapping around a support).

* Hydrotropism: Growth towards water.

* Chemotropism: Growth in response to chemicals (e.g., pollen tubes growing towards the ovule).