Effects of Plant Growth Regulators and Osmoregulants On Drought Tolerance and Post-Drought Recovery In Creeping Bentgrass (Agrostis stolonifera).

Drought is one of the most common environmental stresses limiting plant growth.  From a physiological perspective, there are various mechanisms involved in drought survival of plants, which can be categorized into three groups: low water usage prior to and during drought, tolerance to desiccation during water withholding, and rapid recovery of plants after drought conditions subside.  Some plant growth regulators may regulate these mechanisms and incorporating plant growth regulators into current management protocols can be greatly beneficial for maintaining high stand quality with limited water resources.  This study was designed to investigate effects of several PGRs and osmoregulants on water use, drought survival and post-drought recovery in creeping bentgrass, including 1) Trinexapac-ethyl (TE): growth inhibitor for gibberellic acid synthesis and vertical growth suppressant; 2) Glycine betaine (GB): osmotic regulator to facilitate water retention in leaves; 3) Cytokinins (CK: Kinetin): tiller and root growth promoter for stand re-establishment after drought stress; 4) Gibbrellic acid (GA): shoot growth promoter to help break dormancy for re-growth after drought stress has subsided.  Field plots were subjected to drought conditions and post-drought rewatering between June-July in 2010 and 2011. Physiological parameters, including leaf relative water content (RWC), osmotic adjustment (OA), evapotranspiration (ET), membrane stability, green leaf biomass (MSR), and visual rating of turf quality (TQ) were evaluated.  During the drought period, plants treated with TE+GB or GB-only displayed significantly better TQ compared to controls.  Enhanced turf performance was attributed to higher OA, lower ET rates, increased green leaf biomass, and higher TQ ratings.  During the re-watering period, plants treated with a combination of GA, CK, and nitrogen displayed better recovery compared to controls due to increased tiller density as well as an increased rate of tiller production and leaf elongation.