Action des facteurs écologiques sur la structure et les propriétés mécaniques du bois d'épicéa (Picea excelsaLink.)

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URI: http://hdl.handle.net/2042/33565
Title: Action des facteurs écologiques sur la structure et les propriétés mécaniques du bois d'épicéa (Picea excelsaLink.)
Author: IABLOKOFF, A.-Kh.
Abstract: SUMMARY. The width of the annual ring has an influence not only on theceli chapes but also on the submicroscopic structure of the cell-wall.The relation between the weight of buds and the weight of the woodprocluced during the annual vegetative period, arts directly upon theorganization of this very wall.The micrographie study of cross sections of Spruce wood (Piceaexcclsa Link.) shows that the larger is e (width of the annual ring)the larger are the variations of the radial and tangential sizes of theMis, and the shape of the cross section tends to turn hexagonal.f f we cali the relation between the springwood celi maximum andminimum tangential sizes t, and this same relation for radial sizes r,we obtain two curves t f (e) and r f (e), which are increasingf rom e = I mm, and which tend towards a level with inflexion pointand change in the orientation of the concavity at about e 2,5 mm.The curve V r/t is approximately a horizontal straight line, ther curve being also higher than the t one.The curve HUA i= f (e) representing the relation between thenumber of hexagonal section cells and of rectangular-section cellsof the springwood in ternis of e, is an inclined straight lire betweene 0,03 mm (in this case H = O) and e 2,5 mm ; starting fromthis value the straight lire is replaced by a fast rising exponential.nies(' morphological alteration are acompanied by a desorganizatienof the cellulose structure of the cell wall. The coefficient), = n/a which characterizes the gracie of organization of that structurein inverse ratio to the, spreading out (a) of the half-spots A4(002) of x-ray diagrams, decreases when e increases. This decreaseis faster and sharper in the spring wood than in the summer one,thus corresponding tu lewering of mechanical properties followingthe increase of e,The desor; anization of the structure of the summerwood of thelarge annual rings in high forest trees is yet less marked than shouldhe expected from the x-ray diagrams.The samples, after treatment with soda up to an 18 c/o. loss, provideclearer x-ray diagrams, indicating an excess of hemicellulosesin the summerwood of fast growth.As to the disorganization of the springwood structure, it is especiallymarked in thick rings. When e= 6 mm, the x-ray study shows that this disorganization varies throughout of the springwood andthat it increases as the vegetative period proceeds. The opening anglea of the x-ray diagram half-spots A4 increases f rom 35° againstthe preceding year summerwood to 55° against the present year summerwood.This variation is roughly expressed by a straight line.On the other hand, in the Picea having grown isolated, the inclinedtraight line which representes the variations of A4 half-spots openingangle of the x-ray diagrams in the thickness of the high forest treespringwood, is replaced by a horizontal line corresponding to an ordinateof 33°.There is an difference between the high forest tree and the isolatedtree in the development of the foliage and the mass of buds. Thiscircumstance seems to interf ere not only in the quantity of woodproduced but also in the celi wall organization.These results are perhaps to be compared to those obtained in thein vitro cultures of cambial meristem lamella which underline thepart played by growth hormones discharged by the buds.
Publisher: ENEF, Ecole nationale des eaux et forêts, Nancy (FRA)
Date: 1955

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