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Plant hormones play an important role in plant adaptation to abiotic stress, but hormonal responses of cool-season turfgrass species to salt stress are not well documented. This study was carried out to investigate the responses of hormones to salt stress and examine if salt stress-induced injury was associated with hormonal alteration in kentucky bluegrass (KBG, Poa pratensis L.). The grass was grown in a growth chamber for 6 weeks and then subjected to salt stress (170 mM NaCl) for 28 days. Salt stress caused cell membrane damage, resulting in photosynthetic rate (Pn), chlorophyll (Chl), and turf quality decline in KBG. Salt stress increased leaf abscisic acid (ABA) and ABA/cytokinin (CK) ratio; reduced trans-zeatin riboside (ZR), isopentenyl adenosine (iPA), and indole-3-acetic acid (IAA), but did not affect gibberellin A4 (GA4). On average, salt stress reduced ZR by 67.4% and IAA by 58.6%, whereas it increased ABA by 398.5%. At the end of the experiment (day 28), turf quality, Pn, and stomatal conductance (gs) were negatively correlated with ABA and ABA/CK ratio, but positively correlated with ZR, iPA, and IAA. Electrolyte leakage (EL) was positively correlated with ABA and ABA/CK and negatively correlated with ZR, iPA, IAA, and GA4. GA4 was also positively correlated with turf quality and gs. The results of this study suggest that salt stressinduced injury of the cell membrane and photosynthetic function may be associated with hormonal alteration and imbalance in KBG. [ABSTRACT FROM AUTHOR]

The presence of biologically active substances (BAS) in biosolids may enhance plant stress tolerance and growth, but the underlying mechanisms are not well understood. This greenhouse study investigated the effects of two biosolids: Alexandria (anaerobically digested; Class A product from the Alexandria Sanitation Authority Wastewater Treatment Facility in Alexandria, VA) and Blue Plains (lime-stabilized; Class B product from Washington, DC, Water and Sewer Authority) on tall fescue [Lolium arundinaceum (Schreb.) S.J. Darbyshire) antioxidant enzyme activity associated with drought resistance. Treatments included a fertilizer control, Alexandria (11.9 g-kg-1 soil) and Blue Plains (17.6 g-kg-1 soil) biosolids to match the nitrogen in the control. Tall fescue physiological responses were measured under well-watered or drought-stressed conditions. Drought stress reduced turfgrass quality, photochemical efficiency (PE), and catalase (CAT) activity while increasing superoxide dismutase (SOD), ascorbate peroxidase (APX), and peroxidase (POD) activities. The two biosolids improved turfgrass quality and root mass under both soil moisture regimes and delayed leaf wilting during moisture stress. The biosolids also improved PE, SOD, and APX activities relative to the control under both soil moisture regimes. The data suggest that biosolids application may improve antioxidant enzyme activity and subsequent drought resistance. [ABSTRACT FROM AUTHOR]