The Effect Of Oust Stress On The Photosynthetic Physiology Of Pistacia Vera L. Leaf

This experiment was designed to study the adaptive photosynthetic mechanism and chlorophyllfluorescence characteristics of Pistacia vera L. under dust stresses. Plant material was grown in greenhouseand the stress treatment was performed by2mg·cm-2~18mg·cm-2on plant leaves the photosynthesis,chlorophyll and the chlorophyll a fluorescence characteristics were measured at short time dust treatment;in addition, covering2mg·cm-2and9mg·cm-2on plant leaves, the photosynthesis, chlorophyll and thechlorophyll a fluorescence characteristics and contents of SOD and CAT in leaves, and changes in proteincontents were measured at7d,14d,28d and42d after treatment.The results showed that:(1) For short time dust treatment, the net photosynthetic rate down regulated under2-18mg.cm-2ofdust, and the intercellular CO2concentration showed an upward trend, the change trend of stomatalconductance and transpiration rate similarly showed a decline current; dust coverage has a certain influenceto leaf temperature as well. The Fv/Fm values further reduced with increasing in the thickness of the dust.TheΦPSⅡ and ETR increased at first and then began to declined with gradually increasing in thethickness of dust between2~18mg cm-2.(2) The long time dust stress lead to decrease in net photosynthetic rate (Pn) and stomatal conductance(Gs), while the intercellular CO2concentration (Ci) increased at first and second stages, and later it declined.and later it was declined. Chlorophyll-a(Chla), chlorophyll-b(Chlb) and the total chlorophyll contents weredecreased with increasing in stress intensity, and the decreasing rate of Chla higher than Chlb, and it causedthe decrease in Chla/b ratio.The Fv/Fm gradually decreased under mild and severe stress conditions, whilethe quantum efficient of photo systemⅡ(ΦPSⅡ) and nonlinear electron transport rate (ETR) decreasedafter42d of mild dust treatment, however, it was rapidly decreased at14thday after treatment under severestress condition, and then it increased to the level of control plants at42ndday of treatment. Thenon-photochemical quenching (NPQ) decreased at first and then continually increased under mild stresscondition, and maintained at high level during treatment stage under severe stress. in Conclusion, the contribution of nonstomatal inhibition was bigger than stomata of photosynthetic rate, then the stomatalinhibition was main factor at later stage, due to the increased adaptive dissipation of absorbed photoenergyby photosynthetic machinery, and it caused to decrease in photosynthetic CO2assimilation rate in Pistaciavera L. leaves.(3) Under the conditions of covered dust thickness of2and9mg cm-2, during the7d to42d oftreatmen, the superoxide dismutase (SOD) and peroxide and catalase CAT activity tends to first increaseand then drop in the Pistacia leaves.