Decoding drought and growth regulator responses: Metabolic mastery and antioxidant gene expression in Poa pratensis L.

The aim of this study was to examine the physiological, biochemical, and gene expression responses of Poa pratensis L. to drought stress and the application of anti-gibberellin, trinexapac-ethyl (TE) and paclobutrazol (PBZ). The study was conducted in a greenhouse in which Poa pratensis L. 'GEISHA' seeds were planted in PVC containers. The experimental design included three irrigation regimes [100, 75 and 50% of field capacity (FC)], two plant growth regulators (TE and PBZ), and a control, with assessments conducted at various intervals. The present study demonstrated that reduced irrigation significantly decreased visual quality (VQ), relative water content (RWC) and clipping weight while increasing proline and malondialdehyde (MDA) levels. The application of TE and PBZ was instrumental in maintaining higher RWC, chlorophyll content, and antioxidant activity, with TE showing superior results overall. Water consumption peaked at 100% FC, with the TE-treated groups exhibiting more efficient water usage. The root weight increased to 75% FC but declined beyond this threshold. The soluble carbohydrate contents (SCC) significantly changed under stress conditions. TE and PBZ treatments differentially influenced amino acid concentrations, with TE maintaining better external quality and antioxidant gene expression under stress. Overall, the growth regulators TE and PBZ effectively mitigated the adverse effects of drought stress, enhancing water retention, chlorophyll content, and overall plant health. The findings of this study provide valuable insights into the molecular mechanisms that contribute to drought tolerance in Kentucky bluegrass. Additionally, these results provide valuable guidance for the genetic enhancement of drought tolerance in this turfgrass species.