What term refers to pollen that is very flattened with a P/E diameter less than 0.5?

The term that describes pollen that is very flattened and has a polar to equatorial diameter ratio (P/E ratio) of less than 0.5 is "peroblate." In the context of pollen morphology, peroblate grains are characterized by their flattened shape, indicative of a broad, wide appearance relative to their thickness.

This classification is important in palynology, the study of pollen and spores, as it helps in identifying and differentiating between different types of pollen based on their geometric characteristics. Understanding these shapes is crucial for allergists and botanists alike, as they can influence how allergens are dispersed in the environment and affect respiratory conditions.

Perprolate, globular, and elongated do not accurately capture the definition of pollen with a P/E diameter of less than 0.5. Each of those terms describes different shapes and ratios, highlighting the importance of specific terminology in accurately communicating about pollen characteristics.