Plant Growth Regulator and Soil Surfactants' Effects on Saline and Deficit Irrigated Warm-Season Grasses: II. Pigment Content and Superoxide Dismutase Activity

Drought conditions on turf areas are frequent in the Southwest due to limited rainfall and a shortage of potable irrigation water. A study was conducted at New Mexico State University in Las Cruces, NM during the summers of 2010 to 2012 to determine bermudagrass (Cynodon dactylon L.) cultivar Princess 77 and seashore paspalum (Paspalum vaginatum Swartz) cultivar Sea Spray treated with either a soil surfactant (Revolution [modified methyl capped block copolymer]) or a plant growth regulator (PGR) (Trinexapac-ethyl [TE]; 4-[cyclopropylhydroxymethylene]-3,5-dioxocyclohexanecarboxylic acid) response to drought stress. Plots were irrigated at 50% reference evapotranspiration with either saline (electrical conductivity [EC] = 02.3 dS m(-1)) or potable (0.6 dS m(-1)) water from either a sprinkler or subsurface drip irrigation (SDI) system. Chlorophyll a and b and carotenoids content and superoxide dismutase activity (SOD) in leaves and stolons were measured monthly to assess response to turf stress. Princess 77 plots treated with TE showed the highest chlorophyll and carotenoids content (15.7 and 6.0 mu g g(-1) fresh weight [FW], respectively) and greatest SOD activity in leaves (37.7 units mg(-1) proteins). Both grasses under SDI had higher pigment content at the end of the study than sprinkler-irrigated grasses, suggesting that SDI may be more effective than sprinkler under deficit evapotranspiration (ET) replacement conditions. Only a weak correlation was found between chlorophyll content and either Normalized Difference Vegetation Index (NDVI) or visual ratings.