Gravity primarily affects the development of a plant by influencing the direction of the growth of its roots in relation to Earth. A plant's root system generally responds to gravitational pull by growing earthward. The opposite effect occurs in the stems of most plants, which grow upward in response to sunlight.
The environment provides various stimuli, such as sunlight and gravity, that elicit a growth response from the flora that inhabit it. These natural reactions are referred to as tropisms. Gravitropism pertains to a living thing's response to gravity, while phototropism is an organism's reaction to light.
Gravity serves as a key determinant for root growth orientation. Plant roots sense the pull of gravity through specialized cells known as statocytes. These functional units house tiny structures called statoliths that descend to the base of the cells as gravity exerts its downward force. Based on the position of the statoliths, the statocytes can identify which way is towards the center of Earth. The statocytes then convey this piece of information to other parts of the root system via signal transduction. This process involves the transformation of the message into a chemical signal before it is transmitted. The information is eventually received by the root tips, which grow in the appropriate direction.