Ash Fraxinus excelsior

In some species, however, e.g. ash, Fraxinus excelsior, cells of the traumatic axial parenchyma of the compartmentalization wall 4 may show no evidence of cell wall alterations, yet appear to act normally as a functional barrier to decay (Pearce, R.B., unpublished data). It is to be presumed that the spread of decay fungi is arrested either by chemical defences or by environmental constraints (cf. 26-28) in such species. Clearly, a contribution may be made by these defences in suberizing species also phytoalexin-like antifungal compounds have been detected in association with a suberized wall 4 barrier in Acer saccharinum (42). More work will be required to elucidate the long-term effectiveness of the various mechanisms maintaining the function of these barrier walls. 

Subsequent studies show that iodoalkanes of 1-4 carbons (2388) and chloroacetic acids form abiotically in soil (413), in addition to their well-known biogenic enzymatic formation. An abiotic source of CH3Br is suggested for the emission of this gas from ash (Fraxinus excelsior) and saltwort (Batis maritima), plants having known bromine content (2389). The emissions are a function of both temperature increase and bromine concentration. The natural formation of chloroethyne (58) in soil is also proposed to involve a Fenton reaction (382), as is the production of dichloroacetic and trichloroacetic acids from phenols and soil humic acid (413). 

Several archaeological excavations provided samples of waterlogged European oak (Quercus sp.), European ash Fraxinus excelsior L.), Dutch elm Ulmus campestris L.), white-poplar Populus alba L.), and European spruce Picea abies (L.) Karst). The timbers were 400-2000 years old and had been covered by marine sediments. Cross sections were cut from timbers 10-20 cm in diameter and samples were taken from macroscopically discernible zones of different states of degradation, as well as from the border between these zones (Figure 1). 

Hayes, 1.1853. Therapeutic use of the bark, leaves, seeds, and root of the common Ash (Fraxinus excelsior). Quarterly Summaries of the Improvements and Discoveries in the Medical Sciences. Am. J. Med. Sci. 25 492-494. 

Heuertz, M. et al., Chloroplast DNA variation and postglacial recolonization of common ash (Fraxinus excelsior L.) in Europe, Molec. EcoL, 13, 3437, 2004. 

At the time of the release of the seed or fruit from the parent plant the embryos are still not fully developed. This development is made good during dormancy. An example taken from our indigenous flora is the seeds of the ash (Fraxinus excelsior, cf. Fig. 201), which exhibits a period of dormancy during which the embryo first fully develops. 

An example of the switching off of inhibitors in the embryo is provided by the embryo of the ash (Fraxinus excelsior) which, as we know, is at first incomplete. This development is made good in the summer of the next year. Only then, thus in the second winter, can the cold of winter be effective. It raises the gibberellin level in the embryo so that the inhibitors can be overcome and the seed can germinate the following spring. 

Oleuropein, a secoiridoid glycoside Fraxinus excelsior (ash tree), Olea europaea (olive tree) and Ligustrum obtusifolium from the family Oleaceae are the major sources of oleuropein. This compound has hypotensive. 

Fraxetin (7,8-Dihydroxy-6-methoxycoumarin) is obtained be heating fraxin with sulfuric acid. Fraxin occurs in the bark of the Com mon Ash tree (Fraxinus excelsior). 

Bark analysis (Gilbert, 1970a) has confirmed that nutrient streaks on ash trees (Fraxinus excelsior) contain more nutrients than adjacent parts of the trunk, but it has not been possible to link enhanced survival with any one or any particular combination of nutrients. As the best correlation was with pH, the role of nutrients could be chiefly their effect on this, but it may be significant that it has been reported from a number of sources that the resistance of many higher plants to SO2 injury can be increased by an application of nitrogen (Zahn, 1963). 

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