The Nature of Reaction Wood II. The Cell Wall Organization of Compression Wood Tracheids

Abstract

Optical and X-ray methQds have been used in the examinatiQn Qf the secQndarycell wall Qf cQmpressiQn WQQd tracheids from a number Qf species QfgymnDsperms.By these methQds it has been shQwn that the cell wall Qf CQmpressiQn WQQd tracheidscDnsists Qf two. layers. In the Quter layer the micelles are inclined at a large angle 'to. the lQngitudinal axis Qf the tracheid, while in the inner layer the micelles areinclined at a relatively smaller angle. In the inner Df the two. layers there exist radialdiscQntinuities in the spiral micellar structure, which are visible as IQngitudinal striatiQnsin the cell wall. These discQntinuities also. aCCQunt for the radial distributiQn Qflignin which is observed in transverse sectiQns Qf cQmpressiQn WQQd tracheids. Bydetermining the average tracheid length Qf the last-fDrmed late WQod in the variQusgrowth rings Df several eccentric stems Qf Pinus radiata D.DQn it has been shDwn thatthe tracheids Qf cQmpressiQn WQQd are appreciably shQrter than WQuld be the case ifno. cQmpressiQn WQQd were present. A study Qf the change in micellar QrientatiQn withchange in tracheid length has indicated that the angle Qf micellar QrientatiQn in CQmpressiQnWQQd tracheids dQes nQt differ signific(mtly frQm that existing in nQrmalWQQd tracheids Qf similar length. In so. far as the prQperties Qf WQQd are determinedby cell wall QrganizatiQn, it is cQncluded that cQmparisQns between cQmpressiQn WQDdand normal WQQd shQuld be made Qn material Qf the same tracheid length and spiralQrganizatiDn. It is suggested that bQth the reductiQn in tracheid length and eccentricradial growth in stems cQntaining cQmpressiQn WQQd are to. be attributed to. an increasein the number Df bDth transverse and tangential lQngitudinal divisiQns Qf thefusifQrm initials Qf the cambium.