Particle Retention Ability And Physiological Responses Of Euonymus Japonicus Thunb.var.aurea-marginatus Hort.under Continuous Drought

To explore the effects of continuous drought on the particle retention ability of the typical urban greening broad-leaved plants and their physiological responses.Based on controlled experiments,using vehicle exhaust to simulate particulate matter pollution.Euonymus japonicus Thunb.var.aurea-marginatus Hort.was selected as the research material,and this paper analyzed the particle retention ability in different particle size fractions of E.japonicas var.aurea-marginatus with normal water supply and that with continuous drought,respectively,in the open-top gas chamber.The physiological and biochemical responses of E.japonicus var.aurea-marginatus to drought and vehicle exhaust exposure were also observed.And the changes of physiological and biochemical indexes of the plant within 21 days after the stress removal were analyzed.The results showed:（1）Continuous drought stress reduced the amount of particle on plant leaves by an average of 2³μg?cm^-2 in each particle size fractions.Drought advanced the saturation time of particle retention and reduced the amount of saturated particle retention.Drought significantly reduced the accumulation of particulate matter on the 35th day because many of mature leaves fall off.（2）The exhaust pollution alone had little effects on plant morphology,while the drought environment would aggravate and accelerate the negative effects of exhaust pollution on the plants,and the yellowing and shedding of old leaves appeared 9 days in advance.（3）With the synergy of drought and vehicle exhaust exposure,the pigment content and photosynthetic capacity of E.japonicus var.aurea-marginatus were significantly reduced.The pigment was more sensitive to vehicle exhaust.The drought would accelerate the degradation of the pigment by vehicle exhaust,and made the negative impact of exhaust pollution upon the leaf mass per area appearing one week earlier.（4）Soluble total sugar was more sensitive to drought,and vehicle exhaust would accelerate the response process of the soluble total sugar to drought.Drought would accelerate the response of antioxidant enzymes to vehicle exhaust,but there were little interactions of two stresses on antioxidant enzymes.The damage of vehicle exhaust to the cell membrane was more permanent compared with drought.（5）After the removal of stress,most potted plants could basically recover completely within 21 days.Soluble total sugar and antioxidant enzyme activities were basically returned to normal levels,and the malondialdehyde content and pigment content of plants that had experienced vehicle exhaust were still far from the initial level.In conclusion,the short-term mild to moderate drought has little effect on the particle retention ability of E.japonicus var.aurea-marginatus,while the extreme drought will significantly reduce its particle retention ability,and weaken the resistance of plants to particulate matter and change the plant morphology.