Question

Plants use statoliths to detect gravity (see Figure 39.22). How do plants and animals differ with regard to the type of compartment in which statoliths are found and the physiological mechanism for detecting their response to gravity?

Short answer

The statoliths in animals are extracellular, while those in plants are intracellular. In terms of function, statoliths in animals use ciliated cells with mechanoreceptors for detecting gravity. The statolith of plants uses calcium signaling for gravity detection.

Step-by-step solution

Sense of balance

The ears are mostly regarded as the organ of hearing, but it also plays another sensory role, which is the detection of body movement.This allows the animals to stabilize their structure and also adjust vision with the changing direction.

Plants, though immobile, also have some mechanisms for detecting gravitational force; this facilitates the proper development of their aerial and underground parts.

Statoliths

The term statolith is used to describe the structure responsible for detecting body movements in the case of animals and the force of gravity in the case of plants. This sensory structure has different methods of functioning in animals and plants, and their compartmentalization is also different.

Difference in plant and animal’s statoliths

The statoliths in the case of animals are extracellular structures; that is, they are present outside the cell. In terms of functioning, the animal body’s statoliths use mechanoreceptors present on the ciliated cell surface for detecting balance.

In contrast, the structure of the plant’s statoliths is intracellular; they are present inside some cellular organelle. The statolith of plants detects the gravitational force with the help of cell signaling that incorporates calcium ions as a messenger.