Báo cáo lâm nghiệp: Partitioning of assimilated nitrogen in beech (Fagus sylvatica)

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Báo cáo lâm nghiệp: "Partitioning of assimilated nitrogen in beech (Fagus sylvatica)"Partitioning of assimilated nitrogenin beech (Fagus sylvatica) M. Ben Driss AmraouiF. Martin Microbiologie Foresti6re, INRA, Centre de Recherches Forestieres de Nancy,Laboratoire de 54280 Seichamps, FranceChampenoux,introduction [in roots and patterns of with N]NH§ 15 transport, accumulation and utilization of assimilated nitrogen.The transport and incorporation of nitro-gen in trees involve many complex pro-cesses. Nitrogen ions taken up by the rootand its symbiotic associates may be Materials and Methodsretained in root cells for the synthesis oforganic compounds or may be trans-located directly to the aerial parts. The Growth and labeling of plantstypes of compounds transported, the Seeds of beech (F. sylvatica L.) were germinat-channels selected for transport and the ed in the dark on peat moistened with water atcharacteristics of the transport mechan- 20°C and 98% relative humidity. After 3 wk, uni- form seedlings were transferred to a modifiedisms, themselves are dependent upon the Ever’s solution containing 1 mM NH4 in sandnitrogen sources available, the charac- culture in a naturally lighted glasshouse. Label-teristics of the plant species, its stage of ing studies were performed on 100 d old plants.growth and the environment in which it is 5 d prior to the !5N-labeling experiment, the plants were transferred to a culture holdergrown. consisting of a polystyrene sheet punched with Nitrogen assimilation and translocation holes to accept the roots. The cultures werehave been extensively studied in orchard placed in aerated, fresh modified Evers’s solu-trees including apple (Hill-Cottingham and tion and returned to the glasshouse. At the start of an 1 experiment, the pump was 5N-labelingLloyd-Jones, 1977; Tromp and Ovaa, stopped, the container rapidly drained and1979) and Citrus (Kato, 1980). Data are refilled with culture solution containingalso available on conifers (Martin et al., [(50% 1 atom excess). Two cultures 5N 4 + 5N]NH 11981 a; Scheromm et al., 1988) but, so far, (4 plants each) were harvested at regular inter-no detailed information exists dealing with vals over a 4 d uptake period. The tissues of one culture were divided into roots, stem andhardwood species. This investigation ex- leaves, blotted, weighed, and frozen immediat-amines the importance of the roots in the ely. After being lyophilized, samples werenitrogen economy of beech (Fagus sylva- weighed separately and then combined prior totica L.) plants, describing labeling studies grinding. Xylem exudate was collected from the Labeling of soluble compounds in2nd culture, using a Scholander chamber, and rootsfrozen for later analysis. Plants were rinsed with and xylem sapdistilled water, weighed and frozen. 1 shows the pattern of 15 labeling of N Fig.Analyses intracellular NH+, soluble N in root tissuesSoluble and insoluble nitrogen compounds and xylem sap N. There are some indic- extracted in a methanol-water mixture aswere ations that multiple NHIpools ...