turions

Turions are specialized asexual propagules formed by some aquatic plants and algae to survive unfavorable conditions, particularly winter, and to resume growth when conditions improve. They arise from vegetative tissue rather than through sexual reproduction and can give rise to new shoots or plants once germinated.

Formation and morphology of turions are diverse. They are typically produced in late-season as day length shortens and temperatures drop, or in response to nutrient depletion. Turions often contain concentrated reserves such as starch and lipids and may have thickened walls to withstand desiccation, freezing, or physical stress. Morphologies range from compact, spherical bodies to elongated, bud-like structures; some turions are buoyant and float, while others are denser and sink to the sediment.

Function and life cycle are oriented toward persistence and rapid reestablishment. Under favorable conditions, a turion germinates to produce new shoots or a new plant, enabling quick colonization once growth resumes. Turions thus act as resting propagules that bridge unfavorable periods without reliance on seeds.

Examples and distribution vary among aquatic taxa. Turions are known in several freshwater plants, including duckweeds (Lemna and related genera) and pondweeds (Potamogeton spp.), and they also occur in some freshwater algae and other aquatic groups. They are distinct from true tubers, as they are vegetative propagules produced without fertilization and are not specialized storage organs in the same sense as tubers.

In summary, turions are adaptive, asexual overwintering or propagative structures in aquatic ecosystems, enabling survival through adverse conditions and rapid rebound when growth conditions improve.