Study On The Leaf Chromogenic Mechanism Of Fraxinus Linn

In contrast to Fraxinus chinensis,the two-year-old Fraxinus Linn was used to studyseasonal change of physiological indices,including pigment contents,leafcolorparameters(L*、 a*、 b*),souble sugar content,protein content,amino content,mineralelements, photosynthetic characters and chlorophyll fluorescence parameters,in order toexplore the seasonal change rule of leafcolor and correlative physiological indices;Insummer,by foliage spraying phosphorus fertilizer and potassium fertilizer, Fraxinus Linnwas used to study the influence on the change of leafcolor and correlative physiologicalindices.The results indicated that:(1)As the season changed,pigment contents and pigment ratios changed.Chlorophyllcontents of Fraxinus Linn and Fraxinus chinensis were in an upward-downward trend.Tnautumn,carotenoid contents ascended gradually. Anthocyanin contents which were stableand kept low level in the year had not a significant effect on the changes of leafcolor.ForFraxinus chinensis,though all pigment contents were lower than Fraxinus chinensis,carotenoid relative content was higher than Fraxinus chinensis.From July to August,descending carotenoid content and ascending chlorophyll content reached extremelysignificant difference (P<0.01)with the contents in primary period, respectively.(2)Leafcolor parameters (L*、a*、b*) changed as the season changed.For FraxinusLinn,the b*-value was extremely significant positive correlation with carotenoid contentand extremely significant negative correlation with chlorophyll content,respectively.TheL*-value was significant positive correlations with carotenoid content and extremelysignificant negative correlation and chlorophyll content respectively.There were notsignificant correlations between anthocyanin content and all leafcolor parameter. Thechange process of its leafcolor was yellow-green-yellow.For Fraxinus chinensis,there wasextremely significant positive correlation between L*-value and chlorophyll content.Therewere not significant correlations between carotenoid content, anthocyanin content and allleafcolor parameters.The change process of its leafcolor was green-yellow.(3)The seasonal variations of the contents of flavanone and total phenol wereconsistent. The seasonal variations of the contents of souble sugar and protein wereconsistent. They were significant positive correlation with anthocyarin content and theyhad not a significant effect on the leafcolors of Fraxinus Linn and Fraxinus chinensis. The amino content was extremely significant negative correlation with chlorophyll content ofFraxinus Linn and extremely significant positive correlation with carotenoid content ofFraxinus Linn. The amino content was extremely significant positive correlation withchlorophyll content of Fraxinus chinensis.(4) The carotenoid content of Fraxinus chinensis was extremely significant positivecorrelation with phosphorus content and significant positive correlation with potassiumcontent.There were not significant correlations between the mineral elements and allpigment contents of Fraxinus chinensis.(5) The net photosynthetic rate and intercellar CO2concentration of Fraxinus Linnwere lower than those of Fraxinus chinensis. while the transpiration rate and stomatalconductance of Fraxinus Linn were all higher than those of Fraxinus chinensis.In August,photoinhibition of photosynthesis of Fraxinus Linn appeared.The photosynthetic ability,adaptation of environmental variation and the ability of drought resistance of FraxinusLinn were lower than Fraxinus chinensis.So its leaves began to fade earlier.The netphotosynthetic rate of Fraxinus Linn was significant positive correlation with chlorophyllcontent,but those of Fraxinus chinensis were not significant correlation.The netphotosynthetic rate of two species was extremely significant positive correlations withtranspiration rate and stomatal conductance.but it was extremely significant negativecorrelation and intercellar CO2concentration.(6)In May,potential photochemical efficiency (Fv/Fo) and ratio of variable tomaximum fluorescence (Fv/Fm) of Fraxinus Linn and Fraxinus chinensis began toincrease,and the peak appeared in July.Fv/Fo was consistent with Fv/Fm of two species.InAugust, Fv/Fo and Fv/Fm of Fraxinus Linn decreased obviously and photoinhibition ofphotosynthesis appeared.(7)In some concentration range(0.4%～1.2%potassium fertilizer and0.5%～1%phosphorus fertilizer), foliage spraying phosphorus and potassium fertilizer could improveCar/Chl and increase leafcolor parameters(L*,b*).With increasing concentration, theleafcolor had more remarkable improved effects.But1.5%of phosphorus fertilizer wentagainst the expression on leafcolor of Fraxinus Linn.The most appropriate potassium andphosphorus fertilizers concentrations were1.2%and1%.1%phosphorus fertilizer wasbetter than1.2%potassium fertilizer.(8)After foliage spraying phosphorus and potassium fertilizer,MDA contentincreased.Then the SOD activity and POD activity increased. With increasingconcentration, the changes were much bigger.The leaf of Fraxinus Linn was not beendamaged obviously.