Populus sp.

Caffeic acid phenethyl ester Populus sp. (Salicaceae), bee propolis (phenvlpropanoid)... 

Figure 1.2. The transverse and tangential-longitudinal faces of the hardwood poplar, Populus sp. The wood comprises vessels arranged in radial groups and fibres both in the axial system of cells, as well as uniseriate parenchyma in the ray system. Magnification x 210.

Figure 1.25. Inter-vessel bordered pits between two adjacent vessel elements in Populus sp. X 500.

Figure 1.26. Inter-vessel pit membranes exposed by a split wall in Populus sp. x 2500.

T igwre/.5/. Tyloses completely fining the Figure 1.32. Tyloses filling two vessels in vessels in Populus sp. x 85. Populus sp. x 350. 

Indeed in some parts of the world plantation-grown trees harvested for commercial uses are composed entirely of juvenile wood, examples being 10-15 yr-old Paulowania and Populus sp. in parts of China (Bao et al., 2001). Fortunately the differences between corewood and outerwood, and between the juvenile wood and mature are not nearly as obvious in hardwoods (or maybe they are less well categorized). 

For almost all softwoods and low-to-medium density hardwoods increasing wood density has been ranked above all other desirable objectives in traditional wood quality improvement programmes. Basic density provides an index of wood quality to which all end users are able to relate. To the sawmiller a high density indicates the timber will be stiff and strong to the pulpmill it indicates that a given volume of wood will yield more pulp than would a low-density timber. But too high a basic density (> 600 kg m ) - more a problem with some hardwoods - is as undesirable as too low a basic density (< 400 kg m ) - more a problem with softwoods (also Paulownia and Populus sp.). For woods above 600 kg m", furniture... 

VILLAR, M., LEFEVRE, F., BRADSHAW, H.D., DUCROS, E.T., Molecular genetics of rust resistance in poplars Melampsora larici-populina Kleb Populus sp) by bulked segregant analysis in a 2x2 factorial mating design. Genetics, 1996, 143, 531-536. 

Fig. 7-10. Leaf cross sections of Phaseolus vulgaris > hybrids of Populus sp., and Quercus palustris after one to several rainfalls of simulated acid rain of low pH. Fig. 7. Initial injury of epidermal cells near a trichome hydathode. Note injury is greatest at the anticlinal walls of epidermal cells at the base of a hydathode on P. vulgaris. Fig. 8. Initial injury of subsidiary cells near the guard cells of a stoma. The cells of the palisade parenchyma appear normal on P. vulgaris. Fig. 9. A large lesion with an injured adaxial epidermis, palisade parenchyma, and spongy parenchyma near vascular tissues in poplar. Fig. 10. A cross-section of a gall on a leaf of palustris. Note both collapsed epidermal and palisade cells. Hypertrophy and hyperplasia of spongy mesophyll cells are also evident.

While the contribution of extracellular nitrogenous compounds is uncertain, preparations of poplar (Populus) sp. leaves have been used as a high-energy feed supplement for livestock (e.g., 36). Some preparations may contain toxic extracellular compounds. Lectins from Robinia pseudoacacia are toxic to mammalian cells, and have been explored as therapeutic agents in cancer patients (cf., 81, 88). 

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