| Datura stramonium L. is an annual poisonous plant. In recent years, it isdiscovered that there are some Datura stramonium L. seeds were contained in the importedseeds of Glycine max (L.) Merrill, which threat the cultivation and operation of soybean.Earlier research showed that it will cause a decline of production and quality of soybeanwhen some D. stramonium L. associated with the soybeans in the field. In order to clear themechanism of D. stramonium L. effect on soybean growth, the allelopathic potential ofaqueous extracts of D. stramonium L. was assessed by using soybean as the receiver plantand studying the effects of extracts allelochemical stress of different concentrations on seedgermination, seedling growth, root tip morphology, anatomy, and cell division by the petridish with filter paper indoor and paraffin dissection. The results were as follow:(1) In the experiments concentrations scope, seed germination was inhibited by theextracts and the degree of inhibition increased with increasing extract concentrations.Primary root elongation and lateral root development were inhibited by the extracts, and thedistance from the top of root to the root hair zone was gradually decreased. The higherextract concentrations resulted in thickened and brownished root tips. In some treatments,brown spots of different sizes were observed on root tip; at higher extract concentrations,soybean seedling root appeared brown chasm, and root tips were twisted and seriously bent.The soybean hypocotyl growth was accelerated under the middle concentration ofallelochemical stress.(2) Morphology and anatomy of root tips were altered by the extracts. The root tip edgecells damaged seriously, and the root cap, meristem zone, elongation zone and root-hair zone were not well differentiated. The root cap became shorter, and meristem zone shortened andbroaden. The parenchyma cells were arranged in a disorderly manner and their sizes varied,primary meristem thickness increased, the development of elongation zone was notsymmetric. Some voids in between the vascular bundles and cortical at elongation zone androot hair zone under the high concentration allelochemical stress. The occurrence of root hairalso was not symmetric, the lager number of epidermal cells were decaied. At higherconcentrations, one side of soybean root tip has more dense and shorter root hairs, whichsuggested that the inhibition of allelochemical stress produced by D. stramonium L. is on theelongation stage of root hair development. In addition, the differentiation of vascular bundlewas accelerated, and vessel diameter and vascular bundle diameter added obviously. Therewere a few dark stripes in the cortical parenchyma under the high extract concentration. Thisis the reason that these structural abnormalities affected the normal physiological functionsof root tip, thereby inhibiting soybean growth and development.(3) Root hair development and meristematic cell division showed a response that theywere promoted when under lower concentration and inhibited when under the higher extractconcentration. To wit, the relative lower concentration significantly promoted root hairdevelopment and increased the mitotic index. At higher concentrations, the root hair lengthand density were decreased and the mitotic index was decreased significantly by the extracts.The allelochemical stress also induced chromosome aberrations, and produced a largenumber of micro-nuclear. All phases of root tip mitosis were inhibited by the aqueous extractof D. stramonium L., but the abnormal chromosomes were more at the anaphase. It isindicated that the interference of allelochamical stress produced by the aqueous extract of D.stramonium L. to meristematic cell division resulted in the abnormal anatomy structure ofroot tip.(4) The response of soybean seedling root to allelochemical stress is similar to otherstresses, but root tip also has its own unique response mechanisms to allelochemical stress. Itis indicated that the response diversity of plant to different stresses. |
PDF Full Text Request