Excessive heat or cold usually reduces the growth and quality of turfgrass. Genetic variations along with efficient biochemical and physiological mechanisms can diversify the tolerance to heat and cold. This study examined the effects of heat and cold stress on several biochemical and physiological parameters in Iranian tall fescue ecotypes (Festuca arundinacea L.). The control group of plants was maintained under optimal temperatures, whereas other groups were exposed to heat or cold in a growth chamber. The experiment was designed as a split plot, with stress treatments as the main plots and ecotypes as subplots. Physiologically and biochemically, the results revealed that three ecotypes (‘FA1’, ‘FA3’, and ‘FA5’) of the eight ecotypes examined in this study had better abilities to survive the simulated heat and cold stress. Better tolerance to heat and cold in the ‘FA1’, ‘FA3’, and ‘FA5’ ecotypes were probably due to higher levels of enzymatic and nonenzymatic antioxidant activities, maintenance of lower levels of malondialdehyde (MDA) and hydrogen peroxide (H2O2), higher levels of proline and total nonstructural carbohydrates (TNC), along with a more efficient osmotic adjustment. Diamine oxidase (DAO) and polyamine oxidase (PAO) activities increased significantly in ‘FA1’, ‘FA3’, and ‘FA5’ ecotypes. In summary, the strength of tolerance among ecotypes can be ranked as ‘FA1’ > ‘FA3’ > ‘FA5’ > ‘FA2’ > ‘FA6’ > ‘FA4’ > ‘FA7’ > ‘FA8’ under heat stress and ‘FA5’> ‘FA1’ > ‘FA3’ > ‘FA2’ > ‘FA4’ > ‘FA6’ > ‘FA7’ > ‘FA8’ under cold stress.
Traffic stress is one of the major abiotic stresses that limits grass growth in lawn fields. The severity of losses depends on several factors, including the number of events per season, the athletic field size, and the soil moisture content during the traffic incident. Trinexapac-ethyl (TE) is considered to influence plant tolerance to traffic stress. Therefore, the physiological responses of the wheatgrass (Agropyron desertorum L.) and tall fescue (Festuca arundinacea L. cv. Rebel) species to different levels of TE and traffic stress were investigated. A factorial experiment including combination of TE application and traffic stress treatments was performed based on a randomized complete block design (RCBD) with three replications in 2014 and 2015. The treatments, including traffic stress (traffic and nontraffic stress) and TE at three levels (0, 0.25, and 0.5 kg·ha−1), were applied once every 3 weeks. The simulated traffic stress was imposed using a Brinkman traffic simulator (BTS). The results showed that traffic stress reduced the turf quality, relative water content (RWC), total chlorophyll content, and antioxidant activity and increased electrolyte leakage (EL), soluble sugar content (SSC), and malondialdehyde (MDA) in both species. Conversely, TE increased the turf quality, RWC, SSC, and total chlorophyll and resulted in less EL and MDA in both species. Furthermore, TE application increased the superoxide dismutase (SOD) (EC 22.214.171.124), ascorbate peroxidase (APX) (EC 126.96.36.199), and peroxidase (POD) (EC 188.8.131.52) activities, especially under traffic stress conditions. TE application enhanced the resistance to traffic stress in both species by improving the osmotic adjustment and antioxidant activity.
Desert wheatgrass (Agropyron desertorum L.), tall wheatgrass (Agropyron elongatum L.), and crested wheatgrass (Agropyron cristatum L.) are native cool-season grass species that exhibit potential as a low-input turfgrass. An increased understanding of the biochemical and physiological responses of wheatgrass species and genotypes to salt stress conditions is important for developing genotypes with enhanced tolerance to salinity. The objective of this study was to characterize the physiological and antioxidative properties in 20 Iranian wheatgrass genotypes and to observe their responses to salinity stress during seed germination and seedling growth stage. A completely randomized factorial design was used with two types of factors, four levels of salinity (0, 50, 100, and 150 mm of NaCl), wheatgrass genotypes, and three replicates. In this experiment, the results demonstrated that salinity limits the germination of Iranian wheatgrass genotype seeds. The result of this study showed that among the wheatgrass genotypes, ‘AD1’, ‘AD3,’ ‘AC6’, and ‘FA’ took the shortest average time to germinate. Higher levels of final germination percentage (FGP) were observed in ‘AD2’, ‘AD3’, and ‘AE5’ under salinity stress than other genotypes throughout the experiment. During a prolonged period of study, ‘AD1’ had greater rate of germination (GR) than other genotypes. Out of the 21 genotypes, five genotypes (‘AD1’, ‘AD2’, ‘AD3’, ‘AE5’, and ‘FA’ genotypes) were in the range of “salinity tolerant genotypes” cluster. The ‘AD1’, ‘AD2’, ‘AD3’, ‘AE5’, and ‘FA’ genotypes generally performed better than other genotypes under salinity conditions, mainly through maintaining higher enzymatic activities such as superoxide dismutase (SOD) (EC 184.108.40.206), catalase (CAT) (EC 220.127.116.11), ascorbate peroxidase (APX) (EC 18.104.22.168) and peroxidase (POD) (EC 22.214.171.124), and nonenzymatic antioxidant activities by glutathione (GSH). The ‘AD1’, ‘AD2’, ‘AD3’, ‘AE5’, and ‘FA’ genotypes also had higher proline levels and more of total nonstructural carbohydrates (TNC) content, lower malondialdehyde (MDA) content, and lower hydrogen peroxide content (H2O2).