Some botanical variations in Pinus halepensis and Pinus canariensis were
investigated during summer and autumn of growing season 2003 to compare some
morphological characters and anatomical structure of the needles and to evaluate
their systematic significance. The anatomical variations in the needles affected by
needle age and needle parts, shading and position of the needle from the soil surface
were also studied. The obtained results could be summarized as follows: 1- There are noticeable morphological differences between the two pine species. P.
canariensis is characterized by great number of needles per dwarf stem,
remarkable length of needle, large needle sheath and an extension of the female
cone dimension as compared to P. halepensis. Another remarkable morphological
difference between the two species is nature of the surface of the young branches.
It is smooth without decurrent needle sheath in P. halepensis, while it is rough with
decurrent needle sheath in P. canariensis. These morphological features are used
for identifying the two species. 2- Anatomically, the needle of P. halep < /em>ensis is characterized by thicker epidermis
and endodermal cell layer and wider mesophyll tissue and resin ducts, but thinner
transfusion tissue compared with P. canariensis. The most striking anatomical
differences between the two species occur, mainly in the hypodermal cell layers.
endodermis as well as number and size of resin ducts. The hypodermis occurs in
1-3 cell layers in P. halep < /em>ensis. but in distinct patches in P. canariensis. The resin
ducts also were wider in P. halepensis with more diposion of resin materials in the
epithelial cell layer compared with P. canariensis. 3- Anatomical examination of dwarf stem and basal portion of the needle Indicated
that there is correlation between the number of vascular bundles and cortical resin
ducts in the dwarf stem and both are correlated with the number of needles per
dwarf stem. 4- The needle dimension was increased with increasing the needle age. Two years-
old needles have higher number and large size of resin ducts compared with one
year-old-needle. 5- The middle portion of the needle is characterized by wider hypodermis and
mesophyll tissue as well as presence and wider endodermis. It had also greater
number and larger size of resin ducts in the two pine species compared with both
basal and terminal portions of the needle. The results indicate that the anatomical
changes which took place in the lower portion of the needle, are represented by
lower degree of a sclerified fibrous hypodermis, thinner mesophyll tissue without
developed internal ridges on the cell wall. The unicellular endodermis is still
recognizable. 6- Needle structure is largely influenced by light conditions. The needle developing
under shade conditions had weaker hypodermis, thinner and poorly developed
mesophyll tissue as well as the resin ducts are lesser in number and smaller in
size compared with sun-light grown needle. All the recorded anatomical characters of the needles increased with an
increase in height from the soil surface. On the other hand. it was found a positive
  relation between the number and size of resin ducts in the neddle and their contents of total phenolic compounds.