Effect Of Ethephon On The Formation Of Traumatic Gum Ducts In Liquidambar Formosana

Nine Chinese sweetgum (Liquidambar formosana) trees of15years old with almostsimilar diameter were selected in natural forest of Purple mountain. All trees were dividedinto2groups. One group was used for studying the development of traumatic gum ducts(TDs) by observation of TD shape, size and TD Area/Tangential width after treatment ofethephon(Et) with different concentration. The other was used to study the influence ofethephon in both vertical and horizontal directions. The flow channel was also investigatedby microscopy after comparing with the control group without ethephon treatment. Thefollowing conclusions were obtained:1.TD shape was divided into3types for the analysis of the results, depending on theirdifferentiating states; that is, mature, differentiated and immature TDs. Based on the lightmicroscopic observation, the TDs in Chinese sweetgum were usually observed as acontinuous row; however, a discontinuous row of TDs was often observed in thisexperiment. Based on the number of TD rows, it can be divided into2types: single row ofTDs and multiple rows of TDs. These characters were also used for the analysis of theresults.2.It took about2months for the induction of TDs and totally it took about3months forthe maturation of TDs after1%Et treatment in Jun.2nd. In the case of5%Et treatment, ittook about0.5months for the induction of TDs and totally it took about2months for thematuration of TDs.3.The trees treated with1%Et showed an increase of the area of traumatic gum ducts pertangential width (TD area/width) for the first2month, followed by its constant level fromAugust to November.4.The trees treated with5%Et showed an increase of TD area/width successively fromJune to November.5.High concentration of ethephon gave successive stimulus to the cambium, resulting inthe induction of multiple rows of TD.6.The sphere of influence of Et with different concentration in different direction isdifferent(1%: upside0~6cm, lower side0~13cm, left side0~3cm, right side0~1cm;5%upside5~19cm, lower side6~20cm, left side1~7cm, right side1~7cm). The sphere ofinfluence in vertical direction is larger than in horizontal direction. The sphere of influencein lower side is larger than up side, while the left side and right side don’t show bigdifference.7.5%ethephon was more effective than1%for the induction of TD in Liquidambar formosana.8.Flow channel of the resin was observed as xylem rays and phloem rays.