Physiological Response, Cell Wall Components, and Gene Expression of Switchgrass under Short-Term Drought Stress and Recovery

Switchgrass (Panicum virgatum L.) grown in marginal soils may frequently be subjected to water deficit conditions. The study was designed to determine physiological response, cell wall components, and expression of genes involved in cell wall biosynthesis of switchgrass under short-term drought stress and recovery. Grasses were exposed to drought for 4 d in 2007 (Exp. 1) and 7 d in 2008 (Exp. 2) in a greenhouse and then rewatered for 1 d in both experiments, respectively. Drought stress reduced tissue water content, leaf dry weight, and chlorophyll fluorescence and increased total carotenoid concentration and electrolyte leakage, and the values of these parameters returned to those of the control levels after rewatering. Reductions in leaf hemicellulose and total plant hemicellulose concentrations and increases in stem and total plant lignin concentrations were observed in Exp. 1; however, LH and TH were not recovered after rewatering. The concentration of leaf acid detergent fiber increased under drought stress and was back to the control level after recovery while leaf neutral detergent fiber remained unchanged under drought stress but decreased after recovery. The transcript levels of CesA1, CesA6, and CesA12 encoding cellulose synthesis and Cs/H1 encoding hemicellulose were suppressed by drought stress but the suppressions were reversed by rewatering. These candidate genes can be used for further studying the mechanisms that regulate cell wall biosynthesis in switchgrass.