Salicylic Acid, Auxin and Tryptophan Impact on Salt Tolerance of Creeping Bentgrass.

Plant growth regulators have been used to improve turf quality and salt stress tolerance in turfgrass management. This study was designed to investigate if foliar application of auxin indole-3-butyric acid (IBA, 2 µM), salicylic acid (SA, 10 µM)), or tryptophan (TRYP, 100 µM) improves creeping bentgrass (Agrostis stoloniferia) root growth and antioxidant metabolism under salt stress conditions. The treated plants were subjected to control (non-salt) or salt water (170 mM NaCl) irrigation conditions for up to 42 d in a growth chamber. Salt stress reduced turf quality and net photosynthetic rate (Pn), leaf superoxide dismutase (SOD), and ascorbate peroxidase (APX) activity. Exogenous application of IBA, SA, or TRYP improved turf quality and Pn under salt stress conditions. Foliar application of SA increased leaf SOD and APX activity relative to the control under salt stress. IBA treatment also increased root biomass under salt stress conditions.  The results of this study suggest that foliar application of IBA and SA may promote root growth and antioxidant metabolism and improve creeping bentgrass tolerance to salt stress.