Differential physiological and metabolic responses to drought stress and post-stress recovery for annual bluegrass and creeping bentgrass

Annual bluegrass (Poa annua L.) and creeping bentgrass (Agrostis stolonifera L.) commonly coexist in turfgrass ecosystems but differ in drought tolerance, contributing to uneven turf quality. This study was conducted to examine the physiological and metabolic responses of P. annua and A. stolonifera to drought stress and rewatering and identify major metabolites associated with the interspecific variation in drought tolerance and recovery. Plants grown in controlled-environment chambers were well irrigated (non-stress control) or subjected to drought stress by withholding irrigation for 21 days. For the evaluation of post-stress recovery, drought-stressed plants were rewatered for an additional 21 days. Leaf relative water content, visual turf quality, green canopy cover, and leaf electrolyte leakage were measured weekly. Metabolomic analysis was performed with leaf tissue collected at 21 days of drought stress and 21 days of rewatering. Poa annua demonstrated lower drought tolerance and post-stress recovery compared to A. stolonifera when drought-stressed plants were compared to their respective control across physiological parameters. Metabolomic analysis identified a relatively greater upregulation of sugars and amino acids in A. stolonifera and downregulation of more carbon intermediates and nucleic acids in P. annua in response to drought stress. Upon rewatering, both species had declined sugar content and increased carbon intermediates and nucleic acids. The differential response to drought stress and recovery between A. stolonifera and P. annua could be attributed to a greater accumulation of sugars and amino acids involved in osmotic adjustment during drought stress and their utilization upon rewatering to stimulate post-stress recovery in A. stolonifera.