Physiological Responses Of Two Zoysia Species To Elevated O₃ Concentrations

The concentration of near-surface ozone?O₃?has rapidly developed along with urbanization and industrialization,especially in urban areas.The concentration of O₃precursors in the air has increased and O₃ pollution has intensified.High-concentration O₃ has a strong toxic effect on surface plants to a certain extent.This study compares the photosynthetic and adverse physiology of high ozone concentration by comparing two species of warm-season turfgrasses,and provided scientific basis for the urban greening and the selection and application of turf grass varieties in the area of climate change,especially in the area of ozone polluted areas.In this paper,two common warm season turfgrass Zoysia tenuifolia Willd.ex Trin.and Zoysia Sinica Hance were used as experimental materials.The Open top chamber?OTC?simulation method was used to study the changes in physiological and ecological indexes of leaves under the conditions of normal atmosphere O₃(CK,approximately40nmol·mol^-1)and high concentration O₃(80 and 120nmol·mol^-1).The main research works and achievements are summarized as follows.?1?Photosynthetic response.Compared with the control,the high concentration of O₃led to the decrease of the net photosynthetic rate of Z.japonica to 41%of the control,the stomatal conductance to 31%,and the intercellular carbon dioxide concentration to97.2%;the net photosynthetic rate of Z.Sinica Hance decreased to 41.2%,the stomatal conductance decreased to 98.8%,and the intercellular carbon dioxide concentration first rose to 98.8%,indicating that Z.japonica under high concentration of O₃ is a decrease in photosynthetic rate due to stomatal limitation,while that The decline of Zoysia Sinica Hance in photosynthetic rate is not directly related to the stomatal factor.?2?Stress physiological changes.Compared with the control,with the increase of O₃concentration,malondialdehyde?MDA?content in leaves of Z.japonica in two Z.japonica leaves increased significantly,and the activity of superoxide dismutase?SOD?did not change significantly.The activity of oxidase?CAT?increased significantly;the content of MDA in leaves of Z.sinica Hance was significantly increased and the activity of SOD was not significantly changed.While CAT activity was more active than Z.japonica,showing a significant upward trend at 80 nmol·mol^-1.The maximum value was reached in the treatment?up to 321.6%of the control?.?3?In summary,Z.tenuifolia is relatively sensitive to high concentrations of ozone stress,and Z.sinica Hance is more resistant to ozone.Z.sinica Hance has higher ozone-adaptive stomatal regulation and antioxidant capacity.