Question

What is geotropism? Draw a labelled diagram of a potted plant showing positive geotropism and negative geotropism.

Answer 1

Gravitropism (also known as geotropism) 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. Charles Darwin was one of the first to scientifically document that roots show positive gravitropism and stems show negative gravitropism.[1] That is, roots grow in the direction of gravitational pull (i.e., downward) and stems grow in the opposite direction (i.e., upwards). This behavior can be easily demonstrated with any potted plant. When laid onto its side, the growing parts of the stem begin to display negative gravitropism, growing (biologists say, turning; see tropism) upwards. Hebaverns (non-woody) stems are capable of a small degree of actual bending, but most of the redirected movement occurs as a consequence of root or stem growth outside.

Positive geotropism: The tendency of roots to grow downwards is positive geotropism. It is seen in all kinds of plants except the ones that grow on marshy or swampy lands. Roots are an example of positive geotropism.

Negative geotropism: The negative geotropism is defined as the upward growth of the plant's part against gravity. The tendency of roots to grow upwards i.e. against the gravitational pull is also called negative geotropism. Stem or aerial roots called pneumatophores are examples of negative geotropism.