Drought and Salt Stress-Induced Senescence Is Associated with Hormonal Balance Alteration in Kentucky Bluegrass.

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 to investigate responses of hormones to salt stress and examine if salt stress- induced injury is associated hormonal alteration in Kentucky bluegrass (KBG, Poa pratensis L.). The grass was grown in a growth chamber for six weeks and then subjected to salt stress (250 mM NaCl) for 28 d. Salt stress caused cell membrane damage, resulting in photosynthetic rate (Pn), chlorophyll, visual 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 impact gibberellin A4 (GA4). On average, salt stress reduced ZR by 67.4%, IAA by 58.6%, while increased ABA by 398.5%. At the end of experiment (d28), turf quality, Pn, and gs were negatively correlated with ABA and ABA/CK ratio, but positively correlated with ZR, iPA, IAA. The 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 suggests salt stress-induced injury of cell membrane and photosynthetic function may be associated with hormonal alteration and imbalance in KBG.