Therofyytit

Therofyytit, or therophytes, are a life-form category in plant ecology used in Raunkiaer’s system to describe plants that survive unfavorable seasons as seeds rather than as perennating organs. They are typically annuals or ephemeral herbaceous plants that complete their life cycle in a single growing season.

In therophytes, the above-ground portion of the plant dies back after seed production, and only seeds persist through the adverse period. Germination, flowering, and seed set occur rapidly when conditions are favorable, often in response to moisture and warmth. Because they do not invest in structures to survive winter or drought, their success depends on high seed output and rapid turnover.

Habitats with pronounced seasonality or unpredictable moisture regimes favor therophytes. They are common in deserts, arid and semi-arid regions, steppe zones, and Mediterranean-type climates. They also appear in disturbed or ruderal habitats, where opportunistic annuals can quickly colonize after disturbances such as fire or cultivation.

Adaptations of therophytes include short life cycles, high fecundity, and seeds with dormancy or other germination cues that align with favorable conditions. Seed banks in the soil help maintain their presence in ecosystems across years, enabling rapid rebound after favorable rains.

In ecological terms, therophytes contribute to species turnover and early-successional dynamics. They often dominate annual weed communities and play a role in nutrient cycling and habitat succession. The concept is one of several Raunkiaer life-forms, alongside geophytes, hemicryptophytes, chamaephytes, and phanerophytes.