tailieunhanh - Báo cáo lâm nghiệp: "Experimental study of pine ectomycorrhizae: ectomycorrhizal organization after girdling of the hypocoty"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: Experimental study of pine ectomycorrhizae: ectomycorrhizal organization after girdling of the hypocoty. | 741s Ann. Sci. For. 1989 46 suppl. 741s-744s Forest Tree Physiology E. Dreyer etal. eds. Elsevier INRA Experimental study of pine ectomycorrhizae ectomycorrhizal organization after girdling of the hypocotyl J. Lei and J. Dexheimer Laboratoire de Biologie des Ligneux . CNRS 034613 Université de Nancy I BP 239 54506 Vandceuvre Cedex France Numerous authors have already described the ultrastructural organization of ectotrophic mycorrhizas in various species. In the present work we studied how the ectomy-corrhizal architecture is modified when the host plant-fungus equilibrium is disturbed by girdling the hypocotyl of Pinus sylves-tris plantlets mycorrhized by Hebeloma crustuliniforme or Paxillus involutes. This stops the flow of sugars to the roots. We examined the changes in mycorrhizal structure and function at different time intervals. Girdling of the host plant causes extensive changes in both partners leading morphologically in the pine to the swelling of the stem above the ablation Fig. 1 and in the fungal partner to the more or less complete disappearance of the intramatri-cal mycelium Figs. 2 and 3 . The swelling of the stem is characteristic of plants that have undergone girdling. The products of photosynthesis in the aerial part are blocked by girdling and can no longer migrate into the root system Zimmermann 1969 . This operation also induces a profound transformation of mycorrhizal structure Figs. 4 and 5 . In about 10 days the thickness of the mantle is reduced and its structure becomes increasingly loose. Twenty days after girdling the mantle is replaced by a loose network which is very different from the usual mycelial sleeve Fig. 5 . The Hartig net also has an abnormal structure Figs. 6 and 7 . Like the mantle it becomes less dense and in most cases the hyphae are bordered by dead cortical cells which are often filled with tannins. Moreover the component hyphae have an unusual behavior as they give off branches which penetrate into the host cells. .