Lacking roots or rootless, especially in botanical contexts describing plants that have no true root system.
From Greek 'a-' (without) + 'rhiza' (root). The prefix 'a-' meaning negation combined with the botanical term for roots created this specialized descriptor in 19th-century plant science.
Some aquatic plants like duckweed are arrhizal—they float freely without needing to anchor themselves, which is why they can spread so explosively across ponds and become invasive species.
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