Effects Of Different Shading Intensities On Branch And Leaf Biomass And Cumulative Active Ingredients Of Taxus Yunnanensis Seedlings

Taxol is a unique secondary metabolite of Taxus,which has unique anticancer mechanism,broad-spectrum,high-efficiency anticancer activity,is known as "the last defense line of advanced cancer".However,due to the limited resources of Taxus,the low content of effective components of taxol,and the increasing demand of anticancer drugs taxol,its derivatives in the market,the contradiction between supply and demand in the market has been prominent.As another important taxane compound in yew,10-DAB is the main raw material for the synthesis of taxol and its derivatives.Therefore,artificially synthesizing taxol using 10-DAB as raw material has become the principal way of taxol production in China and even in the world.Taxus yunnanensis is a precious tree species unique to China.The active components of Chinese herbal medicine in branches and leaves of Taxus yunnanensis were higher than those in seedlings,decreased with the growth of tree age,but decreased rapidly after the fourth year.In addition,Taxus yunnanensis liked wet and warm environment,so it was feasible to build a high-quality Taxus medical raw material forest under the forest.Taking 2-year-old Taxus yunnanensis seedlings as the research object,through setting4 different shading treatments(0%,50% and 90% shading),the ground diameter,plant height growth,biomass of branches,leaves,the content,accumulation of taxol,10-DAB in the branches and leaves of the seedlings under different shading intensities were measured,the effects of different lighting conditions on the growth and medicinal components of Taxus yunnanensis were discussed To provide scientific basis for the cultivation of Chinese fir medicinal plantation.The main results are as follows:(1)Different shading intensity had significant effects on the ground diameter,height and biomass accumulation of 2-year-old Taxus yunnanensis seedlings.The highest ground diameter,height and biomass of 2-year-old Taxus yunnanensis seedlings in different months appeared under the condition of 70% shading,and the growth was the largest;the ground diameter,height and biomass of 2-year-old Taxus yunnanensis seedlings increased with the growth time,and the growth period was from June to September,which accounted for more than 40% of the annual growth,the growth trend in autumn and winter weaken.(2)There was no significant difference of taxol content in the leaves and branches of2-year-old Taxus yunnanensis seedlings under different shading intensity.However,under different shading intensity,the accumulation of taxol in a single plant of 2-year-old Taxus yunnanensis seedlings was significantly different.Under 70% shading in September,the accumulation of taxol in a single plant of two-year-old Taxus yunnanensis seedlings reached the highest value in the whole test cycle,reaching 2.217mg/plant,which was 2.5times of the lowest value(under 70% shading in March).Therefore,in a one-year experiment period,70% shading is the best condition for the increase of taxol accumulation in a single plant of Taxus yunnanensis seedlings,and September is the peak of taxol accumulation in a single plant of a 2-year-old Taxus yunnanensis seedlings.(3)Under different shading intensity,the 10-DAB content of branches,leaves and the accumulation of 10-DAB in a single plant of 2-year-old Taxus yunnanensis seedlings were significantly different: full-light conditions were more conducive to the synthesis of10-DAB in the branches and leaves of 2-year-old Taxus yunnanensis seedlings,but not conducive to the increase of 10-DAB accumulation in a single plant;although the 10-DAB content of branches and leaves was slightly lower under 70% shading,the accumulation of10-DAB in a single plant was the highest due to its large biomass,the accumulation of10-DAB per plant of 2-year-old Taxus yunnanensis seedlings reached the highest value of0.161g/plant under 70% shading in September,which was 5.6 times of the lowest value(90% shading in March);the accumulation of 10-DAB per plant of 2-year-old Taxus yunnanensis seedlings was 70% in September,which was consistent with the accumulation of taxol.In the management of the local(Yibin)Taxus yunnanensis medicinal forest,it is suggested to use 70% shading net for shading treatment,and pick the branches and leaves in September,so as to obtain the most taxol and 10-DAB raw materials and obtain the maximum profit.At the same time,the Taxus yunnanensis can still grow normally under70% shading,which indicates that it is possible to plant Taxus yunnanensis under forest.