Seasonal Changes in Morphology and Physiology of Roughstalk Bluegrass

Roughstalk bluegrass (Poa trivialis L.) (RBG) is a weed in many turf settings because it often thins, goes dormant, or dies with increasing summer temperatures. Morphology and physiology of RBG are not well understood. Our objective was to describe morphological differences and physiological changes in shoots and stolons of RBG and creeping bentgrass (Agrostis stolonifera L.) (CBG) during the growing season in Indiana. The study evaluated three grasses (‘L93’ CBG and ‘Laser’ and ‘Pulsar’ RBG) over nine harvests from field plots between April and October of 2008 and 2009. Turf quality and percent cover were consistently higher for CBG compared to RBG. However, mild summer temperatures in 2008 and 2009 likely resulted in minimal separation between RBG cultivars. Stolon production began in May for RBG and CBG after planting in August of the previous year. Specific stolon dry weights (mg cm−1) of RBG doubled compared to L93 during peak summer stress in August. Total nonstructural carbohydrate (TNC) concentration of RBG shoots decreased 26% while TNC in stolons remained unchanged. Additionally, protein and amino acid concentrations increased in stolons and decreased in shoots of RBG during summer stress, further supporting our hypothesis that stolons act as storage organs during high temperatures. Conserving protein and carbohydrates in stolons at the expense of shoots until high temperature stress subsides may be a stress tolerance mechanism of RBG.