Responses Of Flavonoid Synthesis In Ginkgo Leaves To Temperature And Soil Moisture

Temperature and soil moisture are two important environmental factors that influenceflavonoid synthesis in ginkgo (Ginkgo biloba). Here I studied the effect of three temperatures (T1,15℃;T2,25℃;and T335℃, respectively) and three soil water content levels (30-35%,40-45%,and55-60%, of field water capacity, respectively) on ginkgo plant growth, primary metabolitecontent, flavonoid content, and the activity of key enzymes during flavonoid metabolism. Resultswere as follows：(1) Soil water deficit was limiting to plant growth. Dry matter accumulation decreased withsoil water content, while the root shoot ratio was increased. The latter was also higher in the lowtemperature treatment.(2) The accumulation of soluble sugar and protein was related to soil water deficit. Lowertemperatures also promoted the accumulation of soluble sugar.(3) Reduced soil water stimulated activities of PAL, C4H and4CL in a short period of time,which are key enzymes of flavonoid biosynthetic pathways. Activities of PAL and C4H increasedunder the low temperature treatment.(4) The accumulation of flavonoid and its three components was reduced under soil waterdeficit. The conent of flavonoid and its components increased in the low temperature treatmentand decreased in the high temperature treatment.(5) Correlation analysis indicated a significant negative correlation between soluble proteinand flavonoid content. There were positive correlations between PAL activity, and flavonoid,Quercetin and Keampferol content. PAL activity was negatively correlated with Isorhamnetin.There were positive correlations between C4H activity, and flavonoid content and its threecomponents during the last56days of the experiment but not earlier. Positive correlations wereobserved between4CL activity and flavonoid and its three components during the last42days ofthe experiment but correlations were negative earlier.(6) Soil water deficit promoted the accumulation of flavonoid precursor, and stimulatedactivities of PAL, C4H and4CL, catalyzing the accumulation of flavonoid in a short period oftime. Suggestions were that in short-term manufacture, increasing content of flavonoid byreducing soil water content or reducing temperature, without less leaves. Soil water deficitdecreased dry matter accumulation, and restrained activities of PAL, C4H and4CL, slowingdown the accumulation of flavonoid in a long period of time. Lower temperatures also resulted inless dry matter of leaves. Advices were that in long-term manufacture, management of sufficientsoil water and25℃was the best for the output and quality of ginkgo leaves.