Epicuticular Waxes On Greening Plants Leaves And Its Relationship With Air Pollution

The cuticular wax layer of plant is the outmost interface, which is sensitive to environmental stresses, and could regulate itself through physiological changes under environmental stresses. Therefore the changing of epicuticular wax content is result of adaptation for environment for a long time,also can be applied as indicator, as well as the relative content of wax composition. The Ligustrum lucidum, Euonymus japonicus, Photinia serrulata Lindl, Pittosporum tobira were researched in the study. the upper leaf surface wax of 4 plants were sdutied by crystal morphology and chemical composition levels using Scanning electron microscope（SEM） and gas chromatography-mass spectrometry（GC-MS） analysis. We explored the relationship between epicuticular wax content、relative content of wax composition and air pollution at the same time, thus expect to prove basis for a further understanding of the adaptability of greeing plants. The results were as follows:（1） Seasonal changes of leaf epicuticular wax content were 79.74 μg/cm2（May）to 100.99 μg/cm2（July）, 18.60 μg/cm2（April） to 51.00 μg/cm2（October）, 38.96 μg/cm2（April） to 71.95 μg/cm2（July）, 14.93 μg/cm2（May） to 31.52 μg/cm2（October）, respectively for Ligustrum lucidum, Euonymus japonicus, Photinia serrulata Lindl, Pittosporum tobira. Seasonal changes of leaf epicuticular wax content were similarity trend to same extent, the leaf epicuticular wax content of 4 plants in April, May were the lowest; the highest was in July for the Ligustrumlucidum, Euonymus japonicus, October for Photinia serrulata Lindl, Pittosporum tobira.（2） Relative content of Alkanes of Ligustrum lucidum leaf wax accounts for 61.24%, Acids, Alcohols, Triterpenoids account for 16.72%, 13.56%, 0.34% respectively; Relative content of Alkanes of Euonymus japonicus leaf wax accounts for 55.32%, Acids, Alcohols, Esters account for 17.45%, 13.87%, 19.90% respectively; Relative content of Alkanes of Photinia serrulata Lindl leaf wax accounts for 50.89%, Acids, Esters, Diketones and Triterpenoids account for 0.56%, 0.71%, 0.20%, 47.63%; Relative content of Alkanes of Pittosporum tobira leaf wax accounts for 58.13%, Alcohols, Esters account for 25.56%, 15.58% respectively.（3） The correlations of leaf epicuticular wax content with air contaminants show that the frequency of appering correlations of leaf epicuticular wax content in 4 plants were significant negative with CO, follow others.then found the frequency of appering correlations of leaf epicuticular wax content with SO₂, NO₂, CO and O₃8 in Photinia serrulata Lindl were highest.（4） The correlations of relative content of wax composition with air contaminants show that negative correlations of alkanes wax composition in Photinia serrulata Lindl with SO₂, NO₂, O₃8 are stronger; positive correlations of fatty acids wax composition in Photinia serrulata Lindl with air contaminants are highest; positive correlations of alcohols wax composition with NO₂ in Euonymus japonicus are highest; positive correlations of esters wax composition in Photinia serrulata Lindl with NO₂, CO, O₃8 were highest; leaf epicuticular wax of Photinia serrulata Lindl contained little ketone wax composition, which is weak positive correlation with SO₂, PM2.5; positive correlations of triterpenoids wax composition in Photinia serrulata Lindl with air contaminants is higher. In general, the research suggest that epicuticular wax on greening plants leaves of Photinia serrulata Lindl is more sensible to responese to air pollution.As a result of living in the natural environment, those changes are comprehensive response, therefore we should need furthure study on whether it can be used as the bio-indicator of environmental quality.