f the roots of a plant always grow downwards due to geotropism, then the growth of pollen tubes towards ovules is due to _______.

Correct option is D

• Chemotropism is a type of tropism where growth is directed by a chemical stimulus. This is seen in processes like pollen tube growth, where chemicals released from the ovule guide the pollen tube.

• The pollen tube grows towards the ovule, ensuring successful fertilization by delivering the male gamete to the female gamete in the ovule.

• Common in plants, especially in the growth of roots towards nutrients or away from harmful substances like toxic chemicals.

• Example: Plant roots exhibit chemotropism when they grow toward areas with higher concentrations of water or essential nutrients like nitrogen or phosphorus.

• Chemotropism plays a role in pollination and reproduction in some plants, where pollen tubes grow toward the ovule under the influence of chemical signals.

Additional Information

• Geotropism refers to the response of plant growth to gravity.

• Phototropism refers to plant growth in response to light, where plants like stems grow towards the light source.

• Hydrotropism refers to the growth of plant roots in response to water, ensuring that roots grow towards areas of higher moisture.