Effect of Polyamines on Salinity Stress Tolerance in Creeping Bentgrass.

Creeping bentgrass, an important golf course putting green species, is threatened by salinity stress. A common method in the turfgrass industry to improve turf performance and stress tolerance is through application of plant growth regulators (PGR). Polyamines (PA), such as putrescine (Put), spermidine (Spd), and spermine (Spm), have PGR function and protect from abiotic stress, but the effects of PAs are not well investigated in turf species. This project was designed to study the effect of exogenous PA application on salinity stress in creeping bentgrass with Put, Spd, and Spm each applied at level of 0 (control), 5, 10, and 25 mM·L^-1 by drenching. Salinity stress was given as a stepwise increase from 0 to 30 dS·m^-1 in increments of 5 dS·m^-1 for 70 days. Turfgrass quality rating (TQ), leaf chlorophyll content (Chl), leaf electrolyte leakage (EL), leaf osmotic pressure (Π_i, OP), relative water content (RWC), normalized difference vegetative index (NDVI), and phytohormone content were evaluated. Generally, the results showed that most levels of PA treated plants had significantly higher TQ, RWC, and OP than control. However, early phytotoxicity was seen in 25 mM·L^-1 Spm. Plant biomass and height were stimulated by 25 mM·L^-1 PA treatment. Generally, Put and Spd 25 mM·L^-1treatment induced higher amount of abscisic acid, gibberellic acid (GA20), and indole-3 acetic acid than control. PA treated samples had lower accumulation of jasmonic acid and salicylic acid than plants without PA treatment.