Morphogenesis And Adaptation Mechanism Comparative Study Of Fissurate Growth In Xermorphic Shrubs

There are abundance of shrubs in Inner Mongolia West Erods region,which develop respective ways to adapt to the abominable conditions:drought,high temperature,sandy wind etc.Some of them have the same character-fissurate growth.In the study,we selected typical fissurate growth species living in the regionjleaumuria trigyna Maxim ,studied cell characters of fissurate growth .At the same time,we selected both fissurate growth species- Reaumuria trigyna Maxim, Reaumuria soongorical(Pall) Maxim and unfissurate growth species-Helianthemum soongoricum Schrenk ,studied the changes of the endogenous phytohormones content and the enzyme activity of the antioxidation system and wanted to know the physiological mechanism and adaptation of fissurate growth.The results are as follows:1 .Cell characters of fissurate growth in Reaumuria trigyna Maxim is very similar with that in potaninia mongolica. Fissurate growth starts from the base of stem.During certain phases of growth,the cambium layer of the fissurate part is asymmetric, the vessel of secondary xylem becomes smaller and less,while the amount of xylem fiber increases.The constriction forms here.Then the cells gradually disintegrate at the front of the constrition,the constrition gradually becomes deeper and splits here.One constrition will connect with the next one when they extend to the center of fissurate part.The whole vascular bundle splits into many single vascular bundles and they separate from each other.2.There is unnormal cambium layer structure in the fissurate place of Reaumuria trigyna Maxim. Xylem are divided into several rings by the several layers of flat cells. We think it can play a role in fissurate growth.3.The contents of endogenous phytohormones in the cells of different parts are different,especially in the fissurate place,the contents of IAA ,ZR are more than that in the root,which probably adjust the split of the cells in the place and accelerate the fissurate growth.4. The endogenous phytohormones of fissurate growth species-Reaumuria trigyna Maxim, Reaumuria soongorical(Pall) Maxim and unfissurate growth species-Helianthemum soongoricum Schrenk living in the same place was studied.The contents of IAA, ZR are higher in the fissurate place of Reaumuria trigyna Maxim; The contents of GA3, ZR are higher in the fissurate place in Reaumuria soongorical(Pall.) but the content of endogenous phytohormones are higher in seedling of Helianthemum soongoricum Schrenk ,which illuminates endogenous phytohormones are higher in the actively growing parts and probably adjust the fissurate growth.5. The enzyme activity of the antioxidation system of xermorphic shrubs in Inner Mongolia West Erods region was studied. The extent of lipid peroxidation is not higher, but SOD POD CAT activity is different in different vegetation,which illuminates different vegetation has different adaptive mechanism to the droughty environment.