Root growth dynamics of Deyeuxia angustifolia seedlings in response to water level

A greenhouse experiment was performed to investigate root growth dynamics, plant growth, root porosity and root morphology of a marsh plant Deyeuxia angustifolia, one of the dominant species in the Sanjiang Plain, China. The aim of this study was to elucidate how this plant adjusts its root system to acclimate to different hydrological environments. Experimental treatments included three water depths: −5, 0 and 5 cm (relative to the soil surface). Biomass accumulation was higher in the −5 cm (0.90 g per plant) and 0 cm water-depth (1.18 g per plant) than that in the 5 cm water-depth treatments (0.66 g per plant), indicating that plant growth was inhibited in the high water level. Root:shoot ratio (0.67 versus 0.42-0.43), the length (16 cm versus 12-13 cm) and diameter of adventitious roots (0.47 mm versus 0.41 mm), and root number (167 versus 81-119 number of roots per plant) were higher in the 0 cm water-depth than those in the high and low water-depth treatments. Enhanced water level led to slightly increased porosity of main roots, but porosity was about 7% in all treatments. After 8 weeks, roots had been distributed into 14, 11 and 7 cm soil depth in the 0, −5 and 5 cm water-depth treatments, respectively, indicating that both high and low water levels led to shallow root systems. Our data suggest that D. angustifolia can adjust root morphology and root growth pattern according to water level, and that this plant has limited oxygen diffusion potential to the roots due to the reduced biomass in the high water level.