Evaluation of different woods against fungus-growing termite Odontotermes obesus (Rambur) (Blattodea: Termitidae: Macrotermitinae) for use in bait stations

Fungus-growing termites are important pests in buildings and agriculture in Pakistan and are difficult to control with existing bait systems. Development of bait systems requires the knowledge of foraging behavior of termite species. Behavior of foraging workers depends upon the quality and quantity of the food placed in the bait stations. In the current study, we tested 16 different woods (of varying density) for their susceptibility to an important fungus-growing termite, Odontotermes obesus (Rambur). The aim was to find a highly susceptible wood for use in bait stations. The woods were evaluated in no-choice and choice feeding experiments in the field by mass loss and visual ratings to the termites. Statistically significant differences were recorded (P?<?.001). Woods having low density were preferred to high density woods. Highest mass losses (%) were recorded from Ficus religiosa (86.49–87.8%), Bombax malabaricum (86.53–88.43%) and Populus euramericana (75.62–76.31%) in both no-choice and choice tests under “very heavy attack (almost collapsed) to completely consumed” visual rating category. The woods having least mass losses were Albizia lebbeck heartwood (7.03–9.91%), Syzygium cumini (14.25–19.89%) and Dalbergia sissoo heartwood (14.35–24.88%) and had “slightly to superficial attack” with minimum rating values. Ficus religiosa, B. malabaricum and P. euramericana appear suitable woods for use in bait stations for fungus-growing termites.     

How cellulose-based leaf toughness and lamina density contribute to long leaf lifespans of shade-tolerant species

Cell wall fibre and lamina density may interactively affect leaf toughness and leaf lifespan. Here, we tested this with seedlings of 24 neotropical tree species differing in shade tolerance and leaf lifespan under standardized field conditions (140-867 d in gaps; longer in shade). We quantified toughness with a cutting test, explicitly seeking a mechanistic linkage to fibre. Lamina density, but not fracture toughness, exhibited a plastic response to gaps vs shade, while neither trait was affected by leaf age. Toughness corrected for lamina density, a recently recognized indicator of material strength per unit mass, was linearly correlated with cellulose content per unit dry mass. Leaf lifespan was positively correlated with cellulose and toughness in shade-tolerant species but only weakly in gap-dependent species. Leaf lifespan was uncorrelated with lamina thickness, phenolics and tannin concentrations. In path analysis including all species, leaf lifespan was directly enhanced by density and toughness, and indirectly by cellulose via its effect on toughness. Different suites of leaf traits were correlated with early seedling survival in gaps vs shade. In conclusion, cellulose and lamina density jointly enhance leaf fracture toughness, and these carbon-based physical traits, rather than phenolic-based defence, explain species differences in herbivory, leaf lifespan and shade survival.     

Mechanical Defences to Herbivory

The two major mechanical defences of plants are toughness andhardness. These have different material causes and ecologicalfunctions. In any non-metal, high toughness is achieved by compositeconstruction (i.e. by an organized mixture of components). Theprimary source of toughening in plants is the composite cellwall (cellulosic microfibrils set in a hemicellulose and, sometimes,lignin matrix), with a toughness of 3.45 kJ m^-2, which is ten-timesthe probable toughness of its individual components if theycould be isolated. The toughness of most plant tissues is roughlyproportional to the volume fraction of tissue occupied by cellwall (V_c) and, compared to animal tissues and non-biologicalcomposites, is very low. High toughness in plant cells is notproduced by the walls themselves, but by their plastic intracellularcollapse. This is a truly cellular toughening mechanism, oneof the most potent ever discovered by materials scientists,depending on an elongate cell shape with microfibrils directeduniformly at a small angle to the cellular axis. Only ‘woody’cells, tracheids and fibres, have this framework and only inthe S2 layer of their secondary wall. Despite this non-optimumconfiguration, toughness is elevated by this mechanism ten-timesabove that due to cell wall resistance alone. The effectivenessof toughness in preventing herbivory is indisputable, but largelyindirect due to confusion over a false equivalence between nutritional‘fibre content’ and toughness. In contrast, generalizedhardness requires high density. If hardness is due to high V_c, this conflicts with ‘woody’ toughness becausethere is then no lumen for cell walls to collapse into. Thus,dense seed shells may be brittle (i.e. low toughness) even ifbuilt from fibres. However, solid cell wall is not very hard.Instead, high hardness in plants is associated with amorphoussilica and is always localized. The efficacy of hardness ismore difficult to evaluate than toughness because some animalsspecialize in coping with it. Copyright 2000 Annals of BotanyCompany Review, hardness, toughness, mechanical defence, herbivory, cell wall, plastic buckling, silica     

Effects of fish density on planktonic communities and water quality in a manipulated forest pond

We examined the effects of fish on lower trophic levels in a small pond in eastern Finland. The pond was divided into four sections with plastic curtains and stocked with crucian carp (Carassius carassius); two sections had low (4.4–5.5 g m^–3) and two high (10.4–13.7 g m^–3) densities of fish. In the summer of 1987, the pond was sampled weekly for phyto- and zooplankton until the fish were removed by rotenone in September after a three month experiment. Fish density as well as the extent of macrophyte cover had a considerable impact on planktonic communities and water quality. Mean zooplankton biomass was significantly lower and phytoplankton biomass higher, at high fish density. Water transparency was correlated negatively with chlorophyll-a at low fish density but turbidity appeared to reduce transparency at high fish density. The composition and dynamics of the plankton also differed at different fish densities. The mechanisms behind these effects, and the influences of habitat and fish behaviour on the results, are discussed.     

The measurement of water relations of plant cell culture. I. Water release in response to centrifuge-induced water potentials

Water loss by cell suspensions during centrifugation is well defined by simple physical principles. The major factors affecting water release during centrifugation are: duration of centrifogation, depth of the cell mass, density of cells, relative centripetal acceleration and centripetal force. Water release during centrifugation was best described by an exponential decay process with a decay constant that increases with acceleration from 0.31 ± 0.01 to 0.66 ± 0.12 min^?1 (mean ± SE) between 4 825 and 19 300 m s^?2, respectively. The cell mass relative water content (RWC) at equilibrium was not a function of rate of water loss and was constant for each acceleration. A centripetal force was generated by the mass of the cells being accelerated away from the axis of rotation. This force generated a pressure that removed some of the cell wall and symplast water, by compression at contact points between the cells and by compression of the cytoplasm. Pressure induced by centripetal forces ranging from ?0.02 to ?0.23 MPa gave a linear relationship (r² > 0.99) between force and RWC. The slope (0.900 MPa) was proportional to the cell wall modulus of elasticity (±). and the intercept was interpreted to give the mass of the cells at full turgor without interstitial water (RWC=1). This interpretation is supported by the findings, of two independent experiments. Centrifuged cells suspended at 100% relative humidity for over 48 h reached the same water content as predicted by the intercept. Interstitial water was labelled with solutions of polyethylene glycol (PEG. M_r 8 000), the diameter of which was too large to enter the pores of plant cell walls. Centripetal accelerations greater than 10 900 m s^?2 removed PEG-labelled water to levels below 0.9% of cell water content. Removal of interstitial water and other loosely bound water provided a convenient method for determination of growth, RWC and ±. The centrifugal methods provide the foundation for new quantitative methods for cell culture water relations analyses.     

Influence of nest box design on internal microclimate: Comparisons of plastic prototypes

Hollow-dependent fauna are declining worldwide, due primarily to the widespread clearing of hollow-bearing trees. Artificial cavities such as timber and plywood boxes are commonly used to increase hollow availability, yet there is increasing evidence that they are poor facsimiles of natural cavities, characterized by lower insulative properties and a shorter field life. We evaluated whether plastic materials could create a nest box with a stable thermal profile that more closely resembles the complex shapes and textures of natural tree hollows while containing fewer mechanical joins that represent potential failure points when installed. We developed three sets of prototype nest boxes comprising various combinations of plastic density (10%, 25% and 50%), insulation (single vs. double wall with or without sawdust between them), nesting chamber (with or without timber inserts) and bedding (with or without decomposed heartwood) and compared their thermal performance in a temperature-controlled laboratory to compare internal temperature and relative humidity. We found double-walled plastic nest box with an internal timber-lined chamber was best able to buffer ambient temperature fluctuations, consistently recording internal temperatures of 6⁺°C below maximum ambient temperature, maintaining high levels of relative humidity (76%–92%) when furnished with decomposed timber heartwood. This design also performed better during a simulated hot day; internal temperatures exhibiting twice the lag time of single-walled designs, noting that plastic density had little influence on internal conditions. While the recruitment and protection of hollow-bearing trees must be a priority, this work shows significant potential in improving the design and functionality of artificial hollows that are critical to the conservation of hollow-dependent species.     

Quantitative analysis of sugars in wood hydrolyzates with H NMR during the autohydrolysis of hardwoods

The focus of this work was to determine the utility of ¹H NMR spectroscopy in the quantification of sugars resulting from the solubilization of hemicelluloses during the autohydrolysis of hardwoods and the use of this technique to evaluate the kinetics of this process over a range of temperatures and times. Yields of residual xylan, xylooligomers, xylose, glucose, and the degraded products of sugars, i.e., furfural and HMF (5-hydroxymethyl furfural), were determined. The monosaccharide and oligomer contents were quantified with a recently developed high resolution ¹H NMR spectroscopic analysis. This method provided precise measurement of the residual xylan and cellulose remaining in the extracted wood samples and xylose and glucose in the hydrolyzates. NMR was found to exhibit good repeatability and provided carbohydrate compositional results comparable to published methods for sugar maple and aspen woods.     

Fungal diversity and deterioration in mummified woods from the ad Astra Ice Cap region in the Canadian High Arctic

Non-permineralized or mummified ancient wood found within proglacial soil near the ad Astra Ice Cap (81°N, 76°W), Ellesmere Island, Canada was investigated to ascertain the identification of the trees, current morphological and chemical characteristics of the woods and the fungi within them. These woods, identified as Betula, Larix, Picea and Pinus, were found with varying states of physical and chemical degradation. Modern microbial decomposition caused by soft rot fungi was evident and rDNA sequencing of fungi obtained from the samples revealed several species including Cadophora sp., Exophiala sp., Phialocephala sp., as well as others. Analytical ¹³C-labeled tetramethylammonium hydroxide thermochemolysis showed the lignin from the ancient wood was in a high degree of preservation with minor side chain alteration and little to no demethylation or ring hydroxylation. The exposure of these ancient woods to the young soils, where woody debris is not usually prevalent, provides carbon and nutrients into the polar environment that are captured and utilized by unique decay fungi at this Arctic site.     

Estimation of Sheet Thickness Distributions from Linear and Plane Sections

A biological “membrane” or a “barrier” can often be modelled by a sheet, namely a portion of space comprised between two smooth, quasi-parallel faces, such that sheet thickness is in general variable but very small in relation to face extent. Sheet thickness measurements are often of interest to the morphometrist, the physiologist and the pathologist. In the present paper, some stereological techniques are developed for estimating true sheet thickness distributions, and their moments, from the apparent thickness or intercept length measurements obtained, respectively, via random plane or linear sections. An important premise for the models to work is that of isotropic random (‘non-preferential’) sheet orientation relative to the sectioning probe.     

What makes a leaf tough? Patterns of correlated evolution between leaf toughness traits and demographic rates among 197 shade-tolerant woody species in a neotropical forest

Slow-growing juveniles of shade-tolerant plant species are predicted to have tough leaves because of the high cost of leaf replacement in shade relative to potential carbon gain. We assessed the degree of correlated evolution among eight traits associated with leaf toughness and the relationships of those traits with the growth and mortality rates of 197 tree and shrub species from the understory of the 50-ha forest dynamics plot on Barro Colorado Island, Panama. Path analysis with phylogenetically independent contrasts revealed that leaves attained material toughness (resistance to fracture per unit fracture area) through increases in tissue density, percent cellulose per unit dry mass, and vein fracture toughness. Lamina density and cellulose content evolved independently and thus represent different paths to material toughness. Structural toughness (resistance to fracture per unit fracture length) depended on material toughness and lamina thickness. Mortality rates of individuals 1-10 cm in stem diameter were negatively correlated with material toughness and lamina density but were independent of structural toughness and cell wall fiber contents. Leaf toughness traits were uncorrelated with relative growth rates. Results imply that material toughness enhances resistance to natural enemies, which increases survival and offsets the biomass allocation cost of producing tough leaves in the shaded understory.     

Fermentation of woods by rumen anaerobic fungi

Abstract The potential of rumen anaerobic fungi for fermenting untreated woods has been assessed using two Neocallimastix species isolated from sheep. When a strain of N. frontalis was incubated for 11 days with wood from 12 hardwood (angiosperm) species, many woods were measurably fermented, with wood from Populus tremuloides (32%) and Fagus sylvatica (21%) being the most highly degraded. This N. frontalis solubilised celulose, hemicellulose and lignin in P. tremuloides wood. Lower degradation (17%) of P. tremuloides wood by a different species of Neocallimastix showed that the choice of fungus as well as the structure and chemistry of the wood influenced the amount of wood cell wall degraded by anaerobic fungi. The amount of degradation was not related to the length of fungal rhizoids.     

CAMBIUM, a process-based model of daily xylem development in Eucalyptus

In hardwoods such as Eucalyptus spp., xylem (wood) is a heterogeneous tissue consisting of multiple cell types. As such, xylem development involves multiple complex interactions. To describe and understand xylem development, and ultimately predict the resultant wood properties, a process-based approach to modelling wood property variation is potentially very useful. In this paper, a new model (CAMBIUM), which incorporates concepts of these processes, is described. CAMBIUM predicts how wood density and fibre and vessel anatomical properties vary from pith-to-bark at a daily time step as a function of changing environmental conditions and a set of simulated physiological processes. Simulations from an existing process-based model of stand development (CABALA) are used as inputs. A key feature of CAMBIUM is a model of the interaction between different xylem cell types. Some weaknesses were identified in the ability of the model to simulate vessel spatial patterns and frequencies, emphasizing the complexities inherent in this aspect of angiosperm wood formation. The model was, however, able to provide realistic estimates of short-term variation and temporal ranges in eucalypt fibre diameter and secondary wall development and wood density.     

MICROSCOPIC DETERMINATION OF BONE PHOSPHORUS BY QUANTITATIVE AUTORADIOGRAPHY OF NEUTRON-ACTIVATED SECTIONS

Longitudinal sections of human cortical bone were submitted to thermal neutrons. γ-ray spectra were recorded repeatedly during 15 days following irradiation. They showed that Na²⁴ is predominant as early as 3 hours after activation and that all the γ-emitters have decayed on the 15th day. When the γ-rays have disappeared, β-rays are still produced by the sections. It was proved by the absorption curve in aluminium that all these β-rays are issued from the P³² induced in the sections by activation of P³¹. Therefore autoradiograms registered 15 days after activation reveal the distribution of P³² in the sections. γ-ray spectra and β-ray absorption curves of neutron activated sections of ivory demonstrated a mineral composition similar to that of bone. Autoradiograms of ivory sections activated for various times were used to establish the relation between the optical density of the autoradiograms and the radioactivity in P³². When the bone autoradiograms are compared with the ivory standards of known radioactivity, the optical densities of single osteons (Haversian systems), can be related to their phosphorus contents. Autoradiograms and microradiograms of the same sections were examined side by side. The least calcified osteons, that contain 80 per cent of the calcium of the fully calcified osteons, also contain about 80 per cent of the phosphorus of the fully mineralized osteons. It is concluded that the Ca:P ratio remains constant while mineralization of bone tissue is being completed.     

The effect of chemical fixatives on cell walls of Bacillus subtilis.

Cell walls of Bacillus subtilis were treated with several chemical fixatives which are commonly used preparatory to electron microscopy; i.e., osmium tetroxide, formaldehyde, acrolein, crotonaldehyde, and glutaraldehyde. Dimensional analysis was performed on thin sections of fixed walls from plastic embeddings and, by means of the statistical technique of multiple comparisons, significant differences were found between wall thicknesses from the various fixations. These differences varied with the fixation time and the type of fixative used in the reaction. When compared to embedded walls which had been stained before fixation, the overall effect was a reduction in wall thickness which was attributed to fixative action and not to the embedding or staining processes. The reduction of wall thickness was even more apparent when dimensions of fixed walls were compared to published dimensions of both frozen sections and freeze-etch profiles. Since these fixatives bind to reactive sites within the wall fabric, a change in electrochemical charge density is effected which can be monitored in terms of heavy-metal-binding capacity. Most monoaldehyde fixatives and osmium tetroxide render the wall as reactive, or less reactive, to uranyl acetate as unfixed walls, whereas glutaraldehyde can significantly increase the binding capacity.     

三种阔叶树雌雄异株木材结构的比较

在光学显微镜下较详细地比较了重阳木、大叶刺篱木和红毛丹,雌雄异株木材的结构。结果表明：同一种树木两性间木材结构总体上是很相似的,但有的定量特征差异显著甚至极显著。３个种的树木中,雌株木纤维壁腔比值较雄株的大,而分膈纤维和纤维管胞数量较小。雌株木材结构特点可能表明其木材具较强的机械支持能力,利用于果实的支持 。     

Three-dimensional imaging and morphometric analysis of alveolar tissue from microfocal X-ray-computed tomography

We evaluated microfocal X-ray-computed tomography (micro-CT) as a method to visualize lung architecture two and three dimensionally and to obtain morphometric data. Inflated porcine lungs were fixed by formaldehyde ventilation. Tissue samples (8-mm diameter, 10-mm height) were stained with osmium tetroxide, and 400 projection images (1,024 x 1,024 pixel) were obtained. Continuous isometric micro-CT scans (voxel size 9 microm) were acquired to reconstruct two- and three-dimensional images. Tissue samples were sectioned (8-microm thickness) for histological analysis. Alveolar surface density and mean linear intercept were assessed by stereology-based morphometry in micro-CT scans and corresponding histological sections. Furthermore, stereology-based morphometry was compared with morphometric semi-automated micro-CT analysis within the same micro-CT scan. Agreement of methods was assessed by regression and Bland-Altman analysis. Comparing histology with micro-CT, alveolar surface densities (35.4 +/- 2.4 vs. 33.4 +/- 1.9/mm, P < 0.05) showed a correlation (r = 0.72; P = 0.018) with an agreement of 2 +/- 1.6/mm; the mean linear intercept (135.7 +/- 14.5 vs. 135.8 +/- 15 microm) correlated well (r = 0.97; P < 0.0001) with an agreement of -0.1 +/- 3.4 microm. Semi-automated micro-CT analysis resulted in smaller alveolar surface densities (33.4 +/- 1.9 vs. 30.5 +/- 1/mm; P < 0.01) with a correlation (r = 0.70; P = 0.023) and agreement of 2.9 +/- 1.4/mm. Non-destructive micro-CT scanning offers the advantage to visualize the spatial tissue architecture of small lung samples two and three dimensionally.     

The buoyancy of the integument of Atlantic bottlenose dolphins (Tursiops truncatus): Effects of growth,reproduction, and nutritional state

In Atlantic bottlenose dolphins (Tursiops truncatus) the thickness and lipid content of blubber (the integument's specialized hypodermis) varies across ontogeny and with reproductive and nutritional state. Because the integument comprises up to 25% of total body mass in this species, ontogenetic changes in its lipid content may influence whole body buoyancy. The density and volume of the integument were measured and its buoyancy calculated across an ontogenetic series of dolphins and in pregnant and emaciated adults (total n= 45). Regional differences between the metabolically labile trunk integument and the structural tailstock integument were also investigated. Mean densities of both trunk and tailstock integument were similar across life history categories (trunk = 1,040.7 ± 14.1 kg/m³; tailstock = 1,077.1 ± 21.2 kg/m³) and were statistically similar to the density of seawater (1,026 kg/m³). The mean buoyant force of integument from the trunk (−1.01 ± 1.74 N) and tailstock (−0.30 ± 0.21 N) did not vary significantly across ontogeny. In contrast, pregnancy and emaciation did influence the integument's buoyancy, which ranged between 9 N and −45 N in these categories. Although neutral during growth, the integument's contribution to whole body buoyancy can be influenced by an individual's reproductive and nutritional status.     

Effects of competition,herbivory and substrate disturbance on growth and size structure in pin cherry (Prunus pensylvanica L.) seedlings

We examined separate and interactive effects of intraspecific competition, vertebrate browsing and substrate disturbance on the growth and size structure of pin cherry (Prunus pensylvanica L.) in the first two seasons of growth after clearcutting, in a hardwoods forest in New Hampshire, United States. Over the 15-month study period, 97.5% of 1801 individuals survived, and mean plant height increased from 4-fold at high density to 5-fold at low density. Relative height growth was significantly lower at higher plant densities in two of the three growth periods examined. Vertebrate browsers (moose and deer) significantly preferred taller plants. Browsed plants had higher relative height growth following browsing than unbrowsed plants (compensatory growth) at low and intermediate densities. The degree of compensation declined with density and compensation was not significant at the highest density level. At low and intermediate densities, plants browsed early in life regained height dominance through compensatory growth; they failed to regain dominance at high density. Because compensatory growth tended to offset the effects of size-selective browsing, there was no difference in the degree of size inequality between browsed and unbrowsed plots. However, size inequality increased with plant density. Substrate disturbance caused by logging had no significant effects on either relative height growth or size inequality. The slope of the relationship between relative height growth and initial height increased significantly with density and time, and was higher in unbrowsed than in browsed plots, suggesting that competition among plants was size-asymmetric. Despite the preference of browsers for large plants, there was a clear net growth advantage for plants of large initial size, when the effects of competition, browsing and compensatory growth were combined. The interactive effects of density and browsing demonstrate the importance of a multifactorial approach to the analysis of individual plant performance and population structure.     

Response of rhizobacterial communities in watermelon to infection with cucumber green mottle mosaic virus as revealed by cultivation-dependent RISA

We investigated the rhizobacterial densities and community structure in watermelon rhizosphere under the infection of cucumber green mottle mosaic virus (CGMMV) by artificial inoculation. Rhizobacterial densities and communities were analysed from healthy and infected plants under aerobic and anaerobic culture techniques. The highest total number of aerobic rhizobacteria was counted to be 2.7 × 10⁸ colony forming units per gram (CFU · g^?1) and anaerobic rhizobacteria was to be 3.2 × 10⁶ CFU · g^?1, in healthy and infected plants, respectively. Cultivation-dependent ribosomal intergenic spacer analysis (RISA) was employed for further analysis on the rhizobacterial community structure. By incorporating the relative abundance of amplicons, the per cent similarity was determined by the similarity coefficients based only upon the absence or presence of DNA bands. The cluster analysis of RISA showed that the community structure of aerobic rhizobacteria exhibited 60% similarity between healthy and infected plant. The highest community structure similarity (50% similarity) of anaerobic rhizobacteria occurred between before planting and infected plant.     

BIOMECHANICS AND ALGINIC ACID COMPOSITION DURING HYDRODYNAMIC ADAPTATION BY EGREGIA MENZIESII (PHAEOPHYTA) JUVENILES1

To investigate the possible link between cell wall alginic acid composition and tissue mechanics, juveniles of Egregia menziesii (Turn.) Aresch. were grown under controlled conditions in an outdoor flowing seawater system under three different force regimes. After 6–10 weeks of growth, tissue strength, breaking strain, modulus, toughness, work of fracture, and the percentage of polymannuronate, polyguluronate, and alternating sequences in the cell wall alginic acid were examined. The force regime had significant effects on all mechanical indices except toughness. Juveniles grown under high energy conditions (water velocity = 1.2 m · s^?1) were about two times stronger, two times stiffer, and had a 1.5 times greater work of fracture than those from low energy conditions (<1 cm ·^?1). Treatment effects on thallus strength and modulus were predicted from alginic acid composition data to test for the importance of this cell wall material in whole plant adaptation to hydrodynamic stress. However, the prediction that differences in alginic acid composition were responsible for differences in tissue mechanical properties was inconsistent with observations. Therefore, the hypothesis that alginates play a central role in structural adaptation could not be accepted.