Effects Of UV-B Radiation On The Photosynthetic And Aromatic Characteristic Of Dendranthema Indicum Var.aromaticum

Through simulation ultraviolet UV-B radiation treatment on Chrysanthemum indicum var.aromaticum leaves introducted from Hubei Shennongjia region and observation in different UV-B radiation intensity and radiation time of plants,the effects of morphological structure,density,photosynthetic characteristics,chlorophyll fluorescence characteristics and chlorophyll content,expression of aroma secretions and related genes were studied.The results show that:(1)Different UV-B radiation intensity and radiation time had an important effect on the morphology and density of head glandular hairs and T-shaped non-glandular hairs.Under high intensity of UV-B radiation,there were serious injury and even the phenomenon of loss on head glandular hairs and T-shaped non-glandular hairs.Density of head glandular hairs and Tshape non-glandular hairs varied with the increase of the radiation intensity within a certain time range and intensity range and when radiated more than 3ds and 1d,the density began to reduce significantly.(2)With the increase of radiation time and the increase of radiation intensity,each photosynthetic parameter changed.the net photosynthetic rate showed a decreasing trend.The transpiration rate and stomatal conductance tend to be consistent,and it increased first and then decreased,and tend to decrease totally.But the intercellular CO2 concentration showed an increasing trend,indicating that the photosynthesis of Chrysanthemum indicum var.aromaticum leaves were not restricted by the stomatal activity during UV-B radiation,and UVB radiation affected plant leaf photosynthesis by non-stomatal factors.UV-B radiation could significantly affect chlorophyll fluorescence parameters of Chrysanthemum indicum var.aromaticum leaves.On the 7th day of radiation,the maximum photochemical efficiency and photochemical quenching coefficient of Fv / Fm,Fv / F0,?PS?,PS? were significantly decreased with the increase of radiation intensity,the original reaction of photosynthesis was inhibited,and the process of photosynthetic electron transfer was hindered.Too much light could be lost in the form of heat through its own compensation mechanism of Chrythanthemum indicum var.aromaticum leaves thereby reducing the UV-B radiation damage to plant leaves to complete the self-protection mechanism.The content of chlorophyll-a and chlorophyll-b were totally decreased with the increase of radiation time and radiation intensity,and the variation of carotenoids content was not obvious.The degradation rate of chlorophyll-a was significantly higher than that of chlorophyll-b and carotenoids,and chlorophyll-a showed more sensitive to UV-B radiation than that of chlorophyll-b and carotenoids.(3)Through extracting and analyzing the leaf surface extracts of Chrysanthemum indicum var.aromaticum from the control group which were not radiated from UV-B,there were 35 kinds of leaf surface secretions,which were mainly divided into terpenes,camphors and alcohol ketones.UV-B radiation had a great effect on the relative content of 1-carbitone,dihydrocene-diene,camphor eucalyptus brain and levorotatory camphors and cliff ketone of alcohol ketones in the terpenes of leaf aromatic secretions,and its content showed related changes.The internal genes was Dendranthema indicum var.aromaticum CmEF1?,and the results showed that the expression of HMGR,DXR,LIS,GPS,FDS and DXS were studied by qRT-PCR,and the genes HMGR,DXR,LIS,The relative expression of FDS and DXS reached the highest level at 2h,and the relative expression of FDS and DXS increased with time increasing.