Tropism is well known by every one that it is the growth movement of plant part in response to some external stimuli it means when a plant part shows some external growth

now the question arises that when it could show tropism
chemo means chemical it is seen generally in flowers when pollentube is formed
photo means light it means growth towards light positive photropism or away from light negative phototropism generally seen in sunflower
Geo means Earth the growth of root part towards the earth

Phototropism is the growth movement of plants in response to light. The plant's response to light is due to the presence of a pigment called phototropin. When light is detected on one side of the plant, the phototropin pigment moves to the shaded side of the plant. This causes the cells on the shaded side to elongate, causing the plant to bend towards the light source. Phototropism is important for plant survival, as it enables plants to grow towards light, which is necessary for photosynthesis.


Chemotropism is the growth movement of plants in response to chemical signals. Plants use chemotropism to locate nutrients, water, and pollinators. When a plant detects a chemical signal, the plant's cells on the side of the source of the signal elongate, causing the plant to grow towards the source of the chemical. For example, the roots of plants can use chemotropism to grow towards nutrients in the soil.


Geotropism is the growth movement of plants in response to gravity. Geotropism is also known as gravitropism. When a plant is growing, the cells on the upper side of the plant elongate faster than the cells on the lower side. This causes the plant to grow upwards. However, when the plant is turned upside down, the cells on the lower side of the plant elongate faster, causing the plant to grow downwards. Geotropism is important for plant survival because it enables the roots to grow downwards towards nutrients in the soil, while the stems and leaves grow upwards towards sunlight.