Here's why:
* Pollen is a substance: It's the powdery stuff produced by flowering plants to help in fertilization.
* Antonyms relate to opposites: You could consider an antonym something that prevents pollination or something that is produced by the female part of the flower.
Here are some possibilities depending on your intended meaning:
* Nectar: While not directly opposite, nectar is a sweet liquid produced by flowers, attracting pollinators and facilitating pollination.
* Anti-pollination agents: These substances are designed to prevent pollen from reaching its target, like in allergy medications.
* Ovule: This is the female reproductive cell of a flowering plant. It's fertilized by pollen.
Therefore, the best antonym for "pollen" depends on the specific context of your use.