Solution:

Gravitropism is a coordinated process of differential growth by a plant or fungus in response to gravity pulling on it. It is a general feature of all higher and many lower plants as well as other organisms.

Phototropism is the growth of an organism which responds to a light stimulus. It is most often observed in plants, but can also occur in other organisms such as fungi. The cells on the plant that are farthest from the light have a chemical called auxin that reacts when phototropism occurs.

The growth of a plant part due to chemical stimulus is known as chemotropism ‘Chemotropism is the growth of organisms such as bacteria and plants, navigated by chemical stimulus from outside of the organism or organism’s part.