Can Carolina buckthorn withstand both drought and flooding?

Details

Carolina buckthorn (Rhamnus caroliniana Walt.), also called Indian cherry, is an attractive small tree or shrub found in diverse habitats in the United States. Because it occurs in both moderately moist and dry soils, researchers asked whether selections could be marketed as new nursery crops resistant to both drought and flooding.

Their first objective was to characterize how soil water affects Carolina buckthorn growth and gas exchange. They studied potted plants under soil moisture conditions ranging from complete submersion of the root zone to severe drought, at 7% soil water by volume. The maximum photosynthetic rate occurred at 27% soil water content, while complete submersion killed plants.

Their second objective was to compare Carolina buckthorn with invasive common buckthorn (Rhamnus cathartica L.), using potted plants subjected to partial root-zone flooding and drought. Carolina buckthorn resisted the harmful effects of partial flooding. In contrast, after 17 days of treatment, common buckthorn leaves became epinastic, bending downward, and its photosynthetic rate was low at 2.14 μmol CO₂/m²/s. After 55 days of treatment, mean photosynthesis in common buckthorn had increased to 5.52 μmol CO₂/m²/s, a rate similar to that of Carolina buckthorn. Compared with control plants, drought reduced net photosynthesis by 52% in Carolina buckthorn and 68% in common buckthorn.

The researchers concluded that Carolina buckthorn can maintain carbon fixation and growth across a wide range of soil water contents and, unlike common buckthorn, does not depend on morphological, anatomical, or physiological adjustments to optimize growth and net photosynthesis in extremely wet soil. They said its use as an ornamental is warranted if invasiveness and other potential problems with the species are not identified.