Effects of combined extreme cold and drought stress on growth, photosynthesis, and physiological characteristics of cool-season grasses

Abstract

Abstract Abiotic stress is an important factor affecting turf establishment and limiting the sustainability of the turf industry. To alleviate the combined effects of cold and drought prevalent in cold- and drought-prone regions, the selection and introduction of turfgrass germplasm suitable for these conditions are essential for successful turf establishment. Thus, we evaluated the effects of combined extreme cold and drought stress on morphological, photosynthetic, and physiological and biochemical traits in 16 wild annual bluegrass (Poa annua) seedlings. We found that there were significant differences (P < 0.05) among the provenance, combined cold and drought stress, and main interaction factors. The combined cold and drought stress altered the morphological characteristics of the 16 germplasm to varying degrees. Furthermore, The combined cold and drought stress significantly also reduced the net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), instantaneous water use efficiency (WUE), Chlorophyll content, chlorophyll fluorescence parameters, however, ac-cumulated Intercellular CO2 concentration (Ci), relative electrical conductivity (REC), the contents of malondialdehyde (MDA), proline (Pro), soluble protein ( SP), soluble sugar (SS), superoxide anion (O2·−), hydrogen peroxide (H2O2), hydroxyl radical (·OH), and increased the activities of superoxide dismutase activity (SOD), peroxidase activity (POD), catalase activity (CAT), ascorbate peroxidase activity (APX) and glutathione reductase (GR). Comprehensive evaluation using PCA (Principal Component Analysis), affiliation function analysis, and clustered heat maps indicated that ‘HZ’ germplasm had better combined cold and drought tolerance, whereas ‘ZQ’ germplasm was more sensitive to combined cold and drought, which was roughly consistent with the order of morphological damage symptoms. It is recommended that ‘HZ’ seeds be used in planting projects under cold-and drought-prone areas, while ‘ZQ’ seeds are more suitable for use under non-cold and water-deficit conditions.