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901.
Studies on reproductive biology are difficult but useful in species like Aegle marmelos (Linn.) Correa which is of considerable socio-economic importance and possess morphogenetic variation and qualities of wider
adaptability to different soils. Cytology, phenology, pollination, breeding system and natural regeneration of wild and cultivated
trees from India revealed the existence of diploid (2n = 18) and tetraploid trees (2n = 36) in Pachmarhi hills and only diploid
trees in Punjab plains and Shiwalik hills. The diploid and tetraploid trees showed normal meiosis and high pollen fertility.
Phenological events which included leaf fall, leaf emergence, floral bud break, flowering and fruiting are nearly the same
in wild and cultivated trees. Natural pollen transfer in the species was highly efficient. Levels of fruit set following open
pollination was quite high and is reduced considerably following hand pollination probably due to some injury caused to stigma
during experiments. Inspite of synchronous nature of anther dehiscence and stigmatic receptivity, selfing in a flower was
avoided due to herkogamy. Some selfing, however, occurred through geitonogamous mode as bagging of panicles yielded 12.21 ± 0.99
to 14.12 ± 0.91% fruit set. High pollen ovule ratio (9,250–10,600) indicated toward the obligate outbreeding nature. The species
suited to insect and wind mode of pollination. High amount of air borne pollen grains deposited on glycerine smeared glass
microscopic slides suggested towards the wind mode of pollination. Though flowers are dull coloured a variety of insects visited
the flowers due to sweet fragrance and stamen/pollen as food reward. Among insect pollinators, honey bee (Apis dorsata) was the major and legitimate pollinator while the rest were either minor pollinators or mere visitors. Inspite of high fruit/seed
set, natural regeneration through seeds was poor as fallen fruits were destroyed by fungal pathogens and white ants. The species
also propagated vegetatively through coppices and root suckers. It lacks agamospermy as bagging of emasculated flowers yielded
no fruit. It is inferred that ‘bael’ which lacks agamospermy reproduced successfully through gamospermy (xenogamy and geitonogamy)
and vegetative mode (coppices and root suckers). We also concluded that tetraploid trees growing in the Pachmarhi hills with
large sized fruits possessed better potentialities in horticulture if planted through root suckers or coppices. 相似文献
902.
Georg Avramidis Gunthard Scholz Evelyn Nothnick Holger Militz Wolfgang Viöl Arndt Wolkenhauer 《Wood Science and Technology》2011,45(2):359-368
In this study, the impact of a plasma treatment using dielectric barrier discharge at atmospheric pressure on wax-treated
beech was investigated by surface energy determination and adhesion tests. Measurements of the surface energy revealed a strong
increase in surface polarity along with increased surface energy as a result of the plasma treatment, pointing to increased
adhesion properties. To evaluate the adhesion properties of a polyvinyl acetate (PVAc) adhesive on beech treated with montan
ester wax and synthetic Fischer–Tropsch wax, a special peel test was applied. This peel test provided evidence of increased
adhesion of the PVAc after plasma treatment of both materials investigated. 相似文献
903.
Juan Valencia Chris Harwood Russell Washusen Andrew Morrow Matthew Wood Peter Volker 《Wood Science and Technology》2011,45(1):15-34
Peripheral longitudinal growth strain (LGS) was measured on a total of 81, 22-year-old pruned Eucalyptus nitens trees from five thinning treatments in a plantation thinning trial in Tasmania. Growth strain data were gathered at breast
height on each tree using the CIRAD-Forêt method. The effects of thinning treatment and tree diameter on LGS and its relationships
to solid-wood traits determined in a processing trial were examined. LGS was significantly higher in the direction of the
prevailing wind and was not significantly affected by either thinning treatment or tree diameter. An index of log end splitting
was positively related to tree diameter, sawlog position (upper/lower), and LGS, which explained up to an additional 20% of
the variance after tree diameter and log position were accounted for in a linear regression model. High LGS and log end splitting
were significant indicators of increased board end splitting. 相似文献
904.
R. S. Yadav B. L. Yadav B. R. Chhipa S. K. Dhyani Munna Ram 《Agroforestry Systems》2011,81(3):195-202
An investigation was carried out in an Entisol at farmers’ field in Jaipur district, Rajasthan, India during 2002–2004 to evaluate the effect of traditionally grown trees
on soil biological characteristics. Traditionally grown trees in farm lands for study consisted of Prosopis cineraria (L.), Dalbergia sissoo (Roxb.) ex DC, Acacia leucophloea (Roxb.) and Acacia nilotica (L.) Del. having a canopy diameter of 8 m. Results revealed significant and substantial improvement in soil biological activity
in terms of microbial biomass C, N and P, dehydrogenase and alkaline phosphatase activity under different tree based agroforestry
systems as compared to a no tree control (cropping alone). Soil microbial biomass C, N and P under agroforestry varied between
262–320, 32.1–42.4 and 11.6–15.6 μg g−1 soil, respectively, with corresponding microbial biomass C, N and P of 186, 23.2 and 8.4 μg g−1 soil under a no tree control. Fluxes of C, N and P through microbial biomass were also significantly higher in P. cineraria based land use system followed by D. sissoo, A. leucophloea and Acacia nilotica in comparison to a no tree control. Thus, it is concluded that agroforestry system at farmers’ field enhance soil biological
activity and amongst trees, P. cineraria based system brought maximum and significant improvement in soil biological activity. 相似文献
905.
906.
Anisotropy of wood vibrational properties: dependence on grain angle and review of literature data 总被引:1,自引:1,他引:0
The anisotropy of vibrational properties influences the acoustic behaviour of wooden pieces and their dependence on grain
angle (GA). As most pieces of wood include some GA, either for technological reasons or due to grain deviations inside trunks,
predicting its repercussions would be useful. This paper aims at evaluating the variability in the anisotropy of wood vibrational
properties and analysing resulting trends as a function of orientation. GA dependence is described by a model based on transformation
formulas applied to complex compliances, and literature data on anisotropic vibrational properties are reviewed. Ranges of
variability, as well as representative sets of viscoelastic anisotropic parameters, are defined for mean hardwoods and softwoods
and for contrasted wood types. GA-dependence calculations are in close agreement with published experimental results and allow
comparing the sensitivity of different woods to GA. Calculated trends in damping coefficient (tanδ) and in specific modulus
of elasticity (E′/ρ) allow reconstructing the general tanδ-E′/ρ statistical relationships previously reported. Trends for woods with different mechanical parameters merge into a single
curve if anisotropic ratios (both elastic and of damping) are correlated between them, and with axial properties, as is indicated
by the collected data. On the other hand, varying damping coefficient independently results in parallel curves, which coincide
with observations on chemically modified woods, either “artificially”, or by natural extractives. 相似文献
907.
908.
Elena N. Tokareva Andrey V. Pranovich Bjarne R. Holmbom 《Wood Science and Technology》2011,45(4):767-785
Different model compounds for lignin, hemicelluloses and pectins were studied by time-of-flight secondary-ion mass spectrometry
(ToF–SIMS). Mass spectra of Klason lignin from normal and compression spruce wood, aspen wood and wheat straw were compared.
Spectra of brominated spruce and aspen wood sections showed fragment ions attributed to brominated guaiacyl and syringyl units
in lignin at m/z 215, 217, 229 and 231, and m/z 245, 247, 249 and 261, respectively. Spectra of mono-, oligo- and polysaccharides
showed fragment ions at m/z 127 and 145 characteristic for hexose units, and ions at m/z 115 and 133 characteristic for pentose
units. The same ions were detected in spectra of delignified spruce and aspen wood sections. Labelling of anionic groups by
Sr2+ ions followed by ToF–SIMS analysis showed that pectins were present at specific locations on the surfaces of spruce and aspen
wood sections still after delignification with hydrogen peroxide in acetic acid. 相似文献
909.
Hamid Reza Taghiyari 《Wood Science and Technology》2011,45(2):399-404
The present study is aimed at investigating the effect of heat treatment of nano-silver-impregnated Populus nigra on weight loss, modulus of rupture (MOR), modulus of elasticity (MOE), and compression parallel to grain. Specimens were
impregnated with 200 PPM water-based solution of nano-silver particles at 2.5 bar in a pressure vessel. For heat treatment,
both nano-silver-impregnated and simple specimens were kept for 24 h at 45°C and then further for 24 h at 145°C and finally
for 4 h at 185°C. MOR decreased from 529 to 461 kg/cm2 in heat-treated specimens; MOE and compression parallel to grain were though improved. Also, comparison between heat-treated
and nano-silver-impregnated heat-treated specimens showed that there was a decrease in MOR and MOE in nano-silver-impregnated
heat-treated specimens. This shows that nano-silver impregnation facilitates transfer of heat in wood and it may increase
the process of degradation and pyrolysis of wood structures in deeper parts of specimens. 相似文献
910.
The wood–adhesive interface was analyzed using five methods with the objective of quantitatively assessing penetration of adhesive into the porous wood network. Methods included fluorescence microscopy, scanning electron microscopy, backscatter electron imaging, wavelength dispersive spectroscopy, and X-ray microtomography (XMT). Each method provided a visual inspection, and all of the analysis methods were applied to the same field of view. XMT was the primary technique of interest. Rubidium hydroxide was used in place of sodium hydroxide in the formulation of phenol–formaldehyde adhesive. Rubidium was found to increase the X-ray attenuation of the adhesive. However, rubidium migrated beyond the adhesive interphase during specimen preparation, thus reducing its effectiveness for image contrast enhancement. The wood species studied included red oak (Quercus rubra), Douglas-fir (Pseudotsuga menziesii), and hybrid poplar (Populus deltoides × Populus trichocarpa). All techniques used for this study were useful, but each presented some limitations for bondline analysis. Despite the problem with rubidium migration, XMT for this application was promising. 相似文献