Effects Of Exocarp Development And Hormones On Ginkgolic Acid Accumulation In Ginkgo Biloba L.

Ginkgo biloba is the oldest existing tree species,it has extremely high ecological,economic,ornamental and scientific research value.In the past,due to the large use of ginkgo seed,the Ginkgo biloba exocarp,which is a by-product of Ginkgo biloba,has been abandoned for a long time.In recent years,it has been found that ginkgolic acid has various medical efficacy like anti-inflammatory,anti-allergic,anti-tumor,insecticidal and bacteriostatic while ginkgolic acid has the highest content in the Ginkgo biloba exocarp.The commercial cultivation of Ginkgo biloba in China is mainly for obtaining ginkgo leaves and ginkgo seed,but the usage of Ginkgo biloba exocarp is rarely reported.To realize the relationship between hormone and the development of Ginkgo biloba exocarp and the accumulation of ginkgolic acid,and to find methods to promote the growth and ginkgolic acid accumulation of Ginkgo biloba exocarps,it is of great significance for the mass planting of ginkgo forest with high yield of Ginkgo biloba exocarp.In this paper,10 clones of Ginkgo biloba in China were selected as research objects,and selection of clones suitable for exocarp of Ginkgo biloba.The development of exocarp of Ginkgo biloba was further observed and paraffin sections were made to divide the main stages of exocarp development of Ginkgo biloba.The changes of 15 endogenous hormones during the development of exocarp of Ginkgo biloba were analyzed by HPLC-MS/MS.The effects of exogenous hormones on the development of exocarp and accumulation of ginkgolic acid were studied by orthogonal design in Ginkgo biloba.The results are as follows:(1)By comparing the seed yield,exocarp yield and ginkgolic acid content of 10 clones of Ginkgo biloba,we selected three good varieties:Zhongnanlin-2,Zhengan-1 and Shao 2-3.(2)Through the observation of the development process of Ginkgo biloba seed and exocarp,it was found that the growth curve type of Ginkgo biloba seed belongs to type S,and the growth process of Ginkgo biloba seed can be divided into four stages:the early stage,the vigorous stage,the late stage and the mature stage.(3)The content of inclusions in the development of Ginkgo biloba exocarp has regular changes.It was found that the content of soluble protein increased rapidly in the stage of seed coat differentiation,and reached the highest in the lignification stage of the mesosperm;the content of soluble sugar had two peaks on June 1 and August 15 respectively;The content of starch in the mesosperm was higher in the lignification stage,reached the highest point on June 15th;the content of fat increased continuously between pollination and the vigorous stage,decreased slowly after July 1st and slightly increased in the mature stage.During the development of Ginkgo biloba exocarp,the content of ginkgolic acid decreased first,then increased,and decreased last.The content of ginkgolic acid was high and fluctuated in the early stage.The content of ginkgolic acid decreased continuously during the differentiation.stage of seed coat,reached the lowest point on June 1st.The content of ginkgolic acid increased continuously in the lignification stage of mesosperm and decreased gradually in the mature stage.(4)HPLC-MS/MS analysis showed that endogenous hormones had obvious changes in the development of Ginkgo biloba exocarp.The content of IAA increased rapidly during the differentiation stage of seed coat,and continuously decreased during the lignification stage of mesosperm.The content of ABA had been decreasing in the differentiation stage of seed coat and the lignification stage of mesosperm.The content of CTK decreased and rebounded during the differentiation stage of seed coat,decreased during the lignification stage of mesosperm.The content of GA had been decreasing in the differentiation stage of seed coat and the lignification stage of mesosperm,in the countrary,was at a higher level in the maturation stage of exocarp.The content of SA reached the highest value on May 1st,decreased and rebounded during the differentiation stage of seed coat and the lignification stage of mesosperm.The content of Jasmin had the highest point in the pollination of Ginkgo biloba,then decreased continuously and was at a higher level in the maturation stage of exocarp.During the development of Ginkgo biloba exocarp,the(IAA+GA+CTK)/ABA ratio decreased rapidly within a month after pollination.During the rapidly growth stage of exocarp,it increased first and then decreased,and remained stable in the maturation stage of exocarp.The overall trend of(IAA+CTK+GA)/ABA)is downward.(5)The effects of exogenous hormone treatment on the yield of Ginkgo biloba exocarpand the content of ginkgolic acid were detected by orthogonal test.The degree of effects between different factors on the yield of exocarp’s dry weight were:NAA>6-BA>SA,NAA and 6-BA had a significant effect on the yield of exocarp’s dry weight while SA had no significant effect.The best orthogonal combination for promoting the growth of Ginkgo biloba exocarp was A2B3C1.The degree of effects between different factors on the content of ginkgolic acid was:SA>NAA>6-BA.Those three factors all significantly affected the content of ginkgolic acid.The best orthogonal combination of ginkgolic acid’s accumulation in Ginkgo biloba exocarp was A2B2C2.The degree of effects between different factors on the economic yield of Ginkgo biloba exocarp was:NAA>SA>6-BA,NAA and SA had significant effects while 6-BA had no significant effect.The best orthogonal combination which promoted the growth of Ginkgo biloba exocarp and the accumulation of ginkgolic acid was A2B2C2.Finally,the best orthogonal combination for promoting the growth of Ginkgo biloba exocarp and the accumulation of ginkgolic acid was A2B2C2:300 mg/L NAA+100 mg/L 6-BA+200 mg/L SA.