GABA (gamma-aminobutyric acid) and Polyamines Alleviate Drought Stress in Creeping Bentgrass.

GABA (a non-protein amino acid) and Polyamines (PA) such as spermidine (Spd), and spermine (Spm) are involved in abiotic stress response in plants. The objective of this study was to investigate whether exogenous application of these compounds play a role in mitigating drought stress response in creeping bentgrass. Two growth chamber experiments were conducted to evaluate the response of ‘penncross’ to physiological responses and hormonal content under drought stress and optimal water conditions. During the first study Spm was foliar sprayed at 1 mM while Spd was applied at 1 and 5 mM concentration levels. After 9 and 11 d of treatment (DAT), Spm and Spd (1 and 5 mM) treated plants maintained approximately 70 and 55% relative water content (RWC) respectively compared to 50 and 35% for the drought control.  Significantly higher turf quality (TQ), photosynthetic efficiency (Yield and Fv/Fm) and lower electrolyte leakage and malondialdehyde content were observed for PA treated plants compared to drought controls. Higher abscisic acid , and lower salicylic acid and indole-acetic acid was observed for PA treatment compared to drought control. During the second experiment GABA, Spm and Spd were applied at 50, 1 and 5 mM concentration levels. On 12 DAT, Spd applied plants maintained 51% RWC compared to 28% for the drought control. TQ, yield and Fv/Fm were significantly higher for GABA and PA treated plants compared to drought control. MDA content was significantly lower for GABA and Spd treated plants compared to control at 7 and 10 DAT. The results suggested that GABA and PA mitigation of drought stress damage in creeping bentgrass may be related to differential regulation of phytohormone responses.