Heteroanthy is always associated with ________.

Heteroanthy is the condition in which a plant produces flowers with stamens of different lengths. This phenomenon is characteristically associated with heterostyly, a condition where flowers have styles of different lengths.

In heterostylous plants (such as Primula), the variation in style length is always accompanied by a corresponding variation in stamen length (heteroanthy). For example, pin-eyed flowers have long styles and short stamens, while thrum-eyed flowers have short styles and long stamens. This structural adaptation facilitates cross-pollination by insects and prevents self-pollination.

Therefore, heteroanthy is always associated with heterostyly.

Answer: heterostyly