Profiling of Water-Use Efficiency in Switchgrass (Panicum virgatum L.) and the Relationship with Cadmium Accumulation

Planting bioenergy crops with high water-use efficiency (WUE) on heavy metal-polluted land is a good practice for biomass production and phytoremediation. Switchgrass (Panicum virgatum L.), a C-4 perennial bioenergy grass, is native to the United States. The relationship between the WUE and Cd accumulation of switchgrass has seldom been studied. Here, the WUE and Cd accumulation characteristics of 14 high-biomass switchgrass cultivars were investigated under Cd stress by hydroponic culture. The main results showed that Cd inhibited the instantaneous WUE in switchgrass seedlings and that the inhibition rate was more significant in the upland types than in the lowland types of switchgrass. A positive correlation was found between relative WUE and Cd accumulation in roots and shoots. The relative expression level of stomatal control-related genes (ERECTA and EPF1) in lowland cultivars with high WUE was higher than in upland cultivars with low WUE, both in control and Cd treatment conditions. The results suggest that it would be possible to further select and cultivate switchgrass with high WUE and a high capacity for Cd accumulation for phytoremediation in Cd-contaminated land.