Biology Reference
In-Depth Information
Fig. 1. Confocal image depicting lignin auto-fluorescence in P. radiata normal
wood (top panel) and compression wood (bottom panel). Differences in tracheid
anatomy and lignin distribution between normal and compression wood tracheids
are evident. Scalebar
20
m
m.
ΒΌ
the S2 layer has deep grooves known as helical checks, whereas an S3 layer
is absent (
Fig. 1
).
Conifer xylem also contains parenchymatous tissue in the form of rays
and, in pine species, resin canals may also be present. Rays are uniseriate
columns of cells extending radially over a number of growth rings. Rays and
resin canal parenchyma cells may have thin unlignified primary walls or thick
lignified secondary walls (
Bamber, 1972; Bamber and Davies, 1969
). Conifers
other than pines may also contain axial parenchyma, usually single cells with
thin unlignified walls containing resin (
Core et al., 1979
).
