The growth of a pollen tube towards the ovule is caused by

• (a) Phototropism
• (b) Hydrotropism
• (c) Gravitropism
• (d) Chemotropism

The growth of a pollen tube towards the ovule is primarily influenced by chemotropism. This process involves the pollen tube responding to chemical signals released by the ovule, guiding its growth direction.

Understanding Chemotropism

Chemotropism is the movement of an organism or part of an organism in response to a chemical stimulus. In the case of pollen tubes, they detect specific chemicals emitted by the ovule, which directs their growth towards it.

Other Tropisms Explained

• Phototropism: Growth in response to light.
• Hydrotropism: Movement towards moisture.
• Gravitropism: Growth in response to gravity.

While all these tropisms play essential roles in plant growth and development, chemotropism is the key factor for pollen tube guidance towards the ovule.