Photosynthesis, antioxidant system and gene expression of bermudagrass in response to low temperature and salt stress

There is widespread distribution of salinized lands in northern China. Harnessing such land is essential to environmental health. Bermudagrass [Cynodon dactylon (L.) Pers.] has the potential to improve the salinized lands. However, low temperature remarkably limits the growth of bermudagrass in winter. Currently, there is no information about the interaction of cold and salt in this plant. Hence, the objectives of this study were to figure out the effects of combined cold and salinity stress on bermudagrass. In this study, 4 °C and 200 mM salt solution was used as cold and salt treatments respectively while 4 °C along with 200 mM salt solution were applied as combined stress. After 5 days treatment, bermudagrass displayed a dramatic decline in the turf quality and chlorophyll content, but higher malonaldehyde, electrolyte leakage, hydrogen peroxide content, antioxidant enzyme activity in the combined stress regime as compared to cold or salt treated alone. Analysis of chlorophyll a revealed that the combined stress aggravated stress-induced inhibition of photosystem II. In addition, the expressions of stress-related genes were up-regulated with a lower expression level when cold and salt applied together. In summary, the grass exposed to combined stress presented a relatively lower stress tolerance and suffered a more severe damage than grass grown in the other regimes. These findings are crucial for elucidating the molecular mechanisms of cold and salt combined stress in bermudagrass, and provide information for breeding programs to select and develop bermudagrass cultivars that are suitable for improvement of the northern China salinized land.