Growth And Physiological Characteristics Responses Of Xanthium Italicum And Xanthium Sibiricum To O₃ Stress

In the context of global change,the increase in above-ground ozone?O₃?concentrations have become an indisputable fact.Plant invasion is one of the components of global change,invasive plants grow wildly,multiply,threaten local ecosystems and biodiversity,and even harm to human health.There are currently few studies on the correlation between invasive plants and above-ground O₃concentrations.Invasive plant Xanthium italicum and native species Xanthium sibiricum were used as test materials,the O₃ concentration was set to CK?40?,80,120,160nmol·mol^-1,studied the effects of O₃ stress on the growth,physiological and biochemical,photosynthetic characteristics of X.italicum and X.sibiricum,in order to explore the response mechanism of the invasive plant X.italicum to O₃ stress,the prevention,control and early warning of invasive plants provide a scientific basis for areas where above-ground O₃ concentrations and other factors may spread.The main results are as follows:?1?The growth status of X.italicum and X.sibiricum were subjected to different degrees of oxidation inhibition in different growth periods under different concentrations of O₃ stress.When the O₃ stress concentration in the breeding period is160nmol·mol^-1,the inhibition on plant height and base diameter is as follows:X.italicum>X.sibiricum,The inhibitory effect of O₃ stress on the single leaf area is:X.sibiricum>X.italicum,The plant height,base diameter and single leaf area of X.italicum appeared at the sensitive period of O₃ stress concentration 160 nmol·mol^-1earlier than X.sibiricum.?2?The same ecological strategy was adopted during the breeding season in different O₃ concentrations of X.italicum and X.sibiricum.By reduced plant height,biomass transfer from propagule to stem and leaf with increasing O₃concentration,strengthened photosynthesis ability of plants against O₃ stress,reduced investment in propagules,delayed maturity of involucre?with fruit?.?3?The physiological responses of X.italicum and X.sibiricum were different under different O₃ stress concentrations with the prolonged treatment time.X.italicum seedling and breeding seasons to remove active oxygen by increasing POD activity,the vegetative period mainly removed active oxygen by increasing the activities of SOD and POD.X.sibiricum can remove active oxygen by increasing POD activity in three growth periods,so the ability of X.italicum to scavenge reactive oxygen species is stronger than X.sibiricum;When subjected to O₃ stress,X.italicum and X.sibiricum can maintain cell homeostasis by accumulating soluble protein and free proline.The accumulation of soluble protein and free proline in X.italicum is higher than that of X.sibiricum.Therefore,the ability of X.italicum to regulate cell homeostasis is stronger than that of X.sibiricum.?4?The photosynthetic responses were different under different O₃ stress concentrations and different growth periods of X.italicum and X.sibiricum.The factors affecting the decrease of P_n in three growth period of X.italicum at O₃ concentration of160 nmol·mol^-11 were non-stomatal limitation.The factors affecting the decrease of P_n at the O₃ concentration of 80 and 120 nmol·mol^-1changed from stomatal limitation to non-stomatal limitation during the breeding period of X.italicum,The factors affecting the decrease of P_n in the three growing seasons with O₃ concentration of 160 nmol·mol^-1were non-stomatal limitation of X.sibiricum.The factors affecting the decrease of P_n at the O₃ concentration of 80 nmol·mol^-1changed from stomatal limitation to non-stomatal limitation during the breeding period of X.sibiricum.When the concentration of O₃ was120 nmol·mol^-1,the factors affecting the decrease of P_n were non-stomatal limitation at seedling period and vegetative period.?5?The chlorophyll fluorescence responses were different,under different O₃concentrations in different growth periods of X.italicum and X.sibiricum.With the increase of O₃ concentration and the prolongation of stress time,X.sibiricum's oxidative decomposition rate of chlorophyll was faster than X.italicum;The?PS?of X.italicum was significantly decreased in the vegetative O₃ concentration of 160nmol·mol^-11 and the O₃ stress in the breeding period.F_v/F_m decreased significantly at O₃ concentration of120 and 160 nmol·mol^-11 of X.italicum,the chlorophyll fluorescence system was subject to severe oxidative damage,?PS?decreased significantly under O₃ stress at different concentrations during the breeding period of X.sibiricum,F_v/F_m is significantly reduced at O₃ concentration of 160 nmol·mol^-1of X.sibiricum,the chlorophyll fluorescence system was subject to severe oxidative damage,inhibition of Chlorophyll Fluorescence System by O₃ Stress:X.italicum>X.sibiricum.?6?X.italicum and X.sibiricum have strong O₃ tolerance.Under the O₃ stress,the invasive plant of X.italicum has the ability to scavenge reactive oxygen species,maintain cell homeostasis,photosynthetic capacity is stronger than native species X.sibiricum.