What traits govern root sprouting in temperate herbs?

Root sprouting, which occurs when a plant grows clonally from adventitious buds on the roots, can be an important survival strategy for species living in disturbed environments, since it allows rapid regrowth and the buds are protected from aboveground damage. While regeneration from seeds is most common in habitats with either rare or very frequent disturbance, root sprouting is most common at an intermediate frequency. The phenomenon has not been well-studied in terms of its phylogenetic distribution or associated ecology and anatomy.

In a recent article published in Annals of Botany, lead author Alena Bartušková and colleagues investigated the anatomical features that allow root sprouting, and what the relationship is between root sprouting ability, its vigour, and a given species’ niche. The authors studied 183 Central European herbaceous species from 31 families under controlled experimental conditions, noting phylogenetic distribution.

Fully one-quarter of the herbs studied produced adventitious root buds. These plants tended to grow in dry, open habitats, and to produce secondary root thickening and sclerified root cortical cells. The vigour of root sprouting was not correlated with anatomical features, but with habitats that were both dry and disturbed. The most vigorous root sprouters tended to have the largest roots, however.

Phylogenetically, root sprouting is fairly flexible, being easily lost and gained. It is particularly common in the Asteraceae, the Rosaceae, and in families from the order Malpighiales. Herbs with root sprouting are largely absent from wetter environments. This may be due to the shorter lifetime of aquatic roots due to anoxia versus the long-lived roots of dry habitats that have time to undertake secondary thickening. This facet of root sprouting ecology, the authors note, may be why root sprouting is so rare in monocots, which “are likely to have evolved in wet or aquatic habitats.”

“Our results are based on analysis from a single temperate flora that has been under high selection pressure from human activities (e.g., agriculture) since the beginning of the Holocene,” write the authors. “Other biomes and floras with different evolutionary histories, disturbance regimes and environmental factors should be studied to understan