Wood density, latewood percentage, ring width and the cross sectional dimensions of tracheids (wall thickness, lumen area, radial and tangential lumen diameters) were evaluated from ten-year-old trees of Pinus maximinoi H.E. Moore, P. pseudostrobus Lindley and P. patula Schiede ' Deppe grown in South Africa. The species were almost equal in terms of average volume per tree. The wood of P. patula differed from the other species in latewood percentage, tracheid wall thickness, lumen area, radial and tangential lumen diameters. Apart from ring widths, significant differences within species were found for all of the wood and tracheid properties studied. The wood of P. patula has a higher latewood percentage especially in the outer parts of the stem and smaller tracheids than the other two species. The wood densities of P. patula and P. maximinoi were similar. The tracheids of P. pseudostrobus had thinner cell walls than the other two species and wood density was also lower for this species possibly as a result of reduced volume of cell wall material. The differences between and within species for wood and tracheid properties suggest that end use products will vary according to the seed source used.
The variation of specific gravity, ring width, tracheid length and tracheid crosssectional dimensions was studied among the remote natural forests of Cupressus sempervirens var. horizontalis Gord. of the Greek islands Crete, Rhodes and Samos.
The increasing concern about the health conditions of forests in the United States and Europe 1ed to a comparative study of wood characteristics of Abies balsamea (L.) Mill. in the New England states, and Abies alba Mi1!. in the Federal Republic ofGermany. The advanced visible disease in Abies alba at several sites can be documented by means of many structural and physiological alterations. In diseased trees a suppression of the annual growth increment is obvious, and the individual transverse area of early and latewood cells decreases. The moisture content diminishes in the sapwood significantly and at the same time, wetwood deve10ps and expands into the sapwood. The element content per gram of wood does not significantly differ between healthy and diseased trees of the same stand. The content of soluble sugars increases in diseased trees, while the starch content is drastically reduced. However, parallel to the growth suppression the total amount per year of elements, soluble sugars and starch is significantly less in diseased trees than in healthy ones. In addition, accessory compounds appear to increase with the progress of disease. Cambial electrical resistance is strongly related to damage c1assification, and thereby to cambial growth.
the rings without IADFs, tracheidsize varied along the ring following the usual trend, narrowing lumen and thickening cell walls moving from earlywood to latewood. IADFs were classified as: 1) L -IADFs, consisting in earlywood-like cells in the latewood ( Fig. 2b ), and 2) L + −IADFs or transition
Annual ring width and characteristics of latewood tracheids were characterized for the past 100 years for old trees of Abies religiosa growing in the Desierto de Los Leones within the air-polluted Mexico City basin. Sampled trees had lost nearly 50% of their branches and leaves. Radial variation in most measured characteristics followed typical trends for maturation until the 1970s, when trees were about 70 years old. From that decade onward, there was a continued reduction in annual ring width as well as a reduction in cell wall thickening and tracheid length, but an increase in lumen diameter. These xylem modifications started before the first visual symptoms of leaf damage were detected. We suggest that changes in annual ring width and tracheid size are caused by air pollution rather than by tree age.
Flooding of soil for 66 days decreased the rate of dry weight increment and induced stem hypertrophy and abnormal cambial growth in 3-year-old Thuja orientalis seedlings. The rate of dry weight increase of seedlings was reduced largely because of root decay and a decrease in root growth and in initiation of new roots. Diameters of the submerged portions of stems increased as a result of accelerated growth of bark as weil as xylem increment. stem diameters also increased above the water level but alm ost en tirely because of an increase in tracheid production. The xylem of submerged portions of stems was characterised by wide variations in tracheid size (with many largediameter tracheids), lack of arrangement of tracheids in orderly radial rows, and an increased number of xylem rays and large ray cells. Flooding also stimulated ethylene production in stems but did not affect formation of resin ducts in the bark and did not induce formation of compression wood. Ethylene appeared to play a role in regulating cambial growth of flooded plants.
One of the key functions of wood is hydraulic conductivity, and the general physical properties controlling this are well characterized in living plants. Modern species capture only a fraction of the known diversity of wood, which is well preserved in a fossil record that extends back over 400 million years to the origin of the vascular plants. Early fossil woods are known to differ in many key respects from woods of modern gymnosperms (e.g., tracheid size, secondary wall thickenings, lignin chemistry, cambium development) and recent discoveries are shedding new light on the earliest stages of wood evolution, raising questions about the performance of these systems and their functions. We provide an overview of the early fossil record focusing on tracheid morphology in the earliest primary and secondary xylem and on cambial development. The fossil record clearly shows that wood evolved in small stature plants prior to the evolution of a distinctive leaf-stem-root organography. The hydraulic properties of fossil woods cannot be measured directly, but with the development of mathematical models it is becoming increasingly feasible to make inferences and quantify performance, enabling comparison with modern woods. Perhaps the most difficult aspect of hydraulic conductance to quantify is the resistance of pits and other highly distinctive and unique secondary wall features in the earliest tracheids. New analytical methods, in particular X-ray synchrotron microtomography (PPC-SRμCT), open up the possibility of creating dynamic, three-dimensional models of permineralized woods facilitating the analysis of hydraulic and biomechanical properties.
Tree rings provide information about environmental change through recording stress events, such as fires, that can affect their growth. The aim of this study was to investigate wood growth reactions in Pinus halepensis Mill. trees subjected to wildfires, by analysing anatomical traits and carbon and oxygen isotope composition. The study area was Southern France where two sites were selected: one subjected to fires in the last 50 years, the other characterised by comparable environmental conditions although not affected by fire events (control site). We analysed whether wood growth depends on the tangential distance between developing xylem cells and the limit where the cambium was directly damaged by fire. In the burnt site, thick wood sections, including fire-scar, were taken from surviving plants. Digital photo-micrographs were analysed to measure early- and latewood width, wood density, and tracheid size. Anatomical and isotopic traits were analysed in two series of tree rings (5 rings before and 5 after the fire) selected at different positions along the circumference (close or far from the scar). Anatomical and isotopic traits were quantified also on tree rings of the same years from cored trees growing at the control site. Results showed different wood reaction tendencies depending on the distance from the scar. The comparison between plants from the two sites allowed to exclude possible climate interference.
Our results are discussed in terms of two kinds of growth reactions: the local need to promptly compartmentalise the scarred cambial zone and sapwood after fire, and the general growth perturbations due to tree reaction to crown scorch during fire. Anatomical results, combined with dendrochronological and isotopic analysis, could provide an efficient way to distinguish between direct growth reactions due to heat-related damage on cambium and indirect outcomes related to defoliation.
). The specimens, which may have corresponded to two successive orders of axes, differ in their tracheidsize, ray density and ray dimensions ( Fig. 1 ). We assigned them both to the same new species because they show sclerotic nests in the central pith, a character never recorded in the genus before
) the lack of tracheidsize patterning that would fit a vascular trace to a lateral, i.e. , the detached xylem segment ending abruptly with the largest tracheids on one side, whereas a vascular trace would show more equal-sized tracheids around the periphery; and (3) the matching anatomical distortion