Intracellular purine deposits in the gecarcinid land crab Gecarcoidea natalis

The terrestrial crab Gecarcoidea natalis stores large amounts of purine in the body. The major component of the purine deposits is urate (85% of the total purines). The other 15% is comprised of hypoxanthine, guanine, and xanthine. Microscopy studies reveal that these urate deposits are located intracellularly in spongy connective tissue cells throughout the body. Urate exists as numerous membrane-bound crystals 1 μm in diameter. Vesicles thought to represent urate vesicles at various stages of development are also present in the cytoplasm of the cell. Few organelles are visible in the urate storage cells, and it is unlikely that the urate is synthesized on site. Crabs (N = 2) fed a high-nitrogen diet have greater numbers of urate storage cells at more connective tissue sites, and the cells are larger (36.3 ± 1.8 μm (mean ± SE) and 44.0 ± 1.4 μm (mean ± SE)) and contain more urate than urate storage cells in animals collected from the field (N = 3) or maintained in the laboratory on a low-nitrogen diet (N = 1). The mean diameter of urate storage cells in animals fed a diet low in nitrogen and field-collected animals ranges from (13.5 ± 0.5 μm (SE) - 22.3 ± 1.0 μm (SE)). This histological study supports a strong correlation between purine accumulation and the nitrogen content of the diet. J. Morphol. 231:101-110, 1997. © 1997 Wiley-Liss, Inc.     

Spawn and development of the olivid gastropod Olivancillaria carcellesi from north Patagonia,Argentina

Olivancillaria carcellesi occurs in shallow sandy shores from north Patagonia, in intertidal and subtidal sandy bottoms. Females of O. carcellesi exhibited a remarkable specificity for spawning on the shells of living males and females, indiscriminately, of the buccinanopsid Buccinastrum deforme, measuring 26.9 ± 4.7 mm in shell length. The egg capsule was semispherical and attached to B. deforme shells by a small elliptical and wide base. The capsule was translucid when spawned, with a thick and semirigid wall and a hatching aperture of 1.8 ± 0.1 mm (n = 111) in diameter. Each egg capsule contained a single egg that measured 1367 ± 34 μm (n = 5) in diameter before cleavage. The embryo developed a small bilobed velum and an operculum, which were both lost before hatching as a crawling juvenile of 1762 ± 47 μm (n = 28) in shell length. As in other species in the genus, the eggs of O. carcellesi are among the largest in the caenogastropods with direct development. The time from oviposition to hatching is estimated to be approximately 6 months.     

The effect of surface roughness on claw and adhesive hair performance in the dock beetle Gastrophysa viridula

Abstract Natural adhesive systems are adapted to attach to rough surfaces, but the underlying mechanisms have not been fully clarified. Attachment forces for the beetle Gastrophysa viridula were recorded on epoxy casts of surfaces with different roughness using a centrifuge device. Replicas were made of standardized polishing paper with asperity sizes ranging from 0.05 to 30 μm and of dock leaves (Rumex obtusifolius). Beetles adhered with a safety factor of up to 36 times body weight on smooth substrates or on casts of leaves of their host plant. On the rough substrates, forces were much lower and a minimum at small scale roughness (0.05 μm asperity size, with a mean safety factor of 5) was observed. Removal of the claws led to a significant reduction in force for rough substrates with asperity sizes ≥ 12 μm. Attachment forces of the hairy adhesive system itself (without the claws) slightly increased from small‐scale to large‐scale surface roughness, but remained below the level seen on the smooth substrate. This is explained by the inability of setal tips to make full contact to the surface.     

Hypotonic Ca2+ signaling and volume regulation in proliferating and quiescent cells from multicellular spheroids

Hypotonicity-induced Ca²⁺ signals and volume regulation were studied in proliferating and quiescent subpopulations of multicellular prostate cancer spheroids. Enzymatic dissociation of multicellular spheroids 100 ± 19 μm in diameter, which are entirely proliferative, yielded a population of cells with a mean cell diameter of 17.5 ± 1.4 μm. After dissociation of spheroids in a size class of 200 ± 30, 300 ± 60, and 400 ± 65 μm in diameter, two subpopulations of cells with mean cell diameters corresponding to 12.9 ± 1.9 μm and 16.7 ± 2 μm were discriminated. The subpopulation of large cells was shown to be proliferative by positive Ki-67 antibody staining; the subpopulation of small cells was Ki-67 negative, indicating cell quiescence. In a spheroid size class of 100 ± 19 μm, a distinct subpopulation of quiescent cells was absent. Superfusion by hypotonic solutions revealed that only the proliferating cell fraction showed a regulatory volume decrease (RVD) and a [Ca²⁺]_i transient. Both effects were absent in the quiescent cell population. The [Ca²⁺]_i transient persisted in low (10 nM) Ca²⁺ solution and in the presence of 4 mM extracellular Ni²⁺ but was abolished in the presence of the endoplasmic reticulum Ca²⁺-ATPase blocker 2,5-di-tert-butylhydrochinone (t-BHQ). The t-BHQ likewise inhibited RVD, indicating that Ca²⁺ release from intracellular stores was necessary for RVD. Moreover, [Ca²⁺]_i and RVD were dependent on an intact microfilament cytoskeleton because after 30 min of preincubation with cytochalasin B the [Ca²⁺]_i transient was significantly reduced and RVD was abolished. The absence of RVD and [Ca²⁺]_i transient in quiescent cells may be due to differences in the amount and the cytosolic arrangement of F-actin observed in quiescent cells. J. Cell. Physiol. 175:129–140, 1998. © 1998 Wiley-Liss, Inc.     

Pollen morphology of andruris japonica (triuridaceae)

Pollen morphology of Andruris japonica (Triuridaceae) was investigated by light and electron microscopy. The pollen is monosulcate and has a size of 22–25 μm × 25–28 μm in polar view. In the non-apertural region the exine has gemmate to nearly verrucate protrusions of 0.4–0.5 μm in diameter and 0.3–0.5 μm in height, and a foot layer of 0.4–0.5 μm in thickness. The sporoderm of the apertural region has large gemmae of 0.7–0.8 μm in diameter and 0.6–0.7 μm in height, with a thin foot layer of 0.1 μm thickness.     

The distribution of single P2x1-receptor clusters on smooth muscle cells in relation to nerve varicosities in the rat urinary bladder

The distribution of purinergic (P2x1) receptors on smooth muscle cells in relation to autonomic nerve varicosities in the rat urinary bladder has been determined using immunofluorescence and confocal microscopy. P2x1 receptors were visualized using rabbit polyclonal antibodies against the extracellular domain of the P2x1 receptor, and varicosities were visualized using a mouse monoclonal antibody against the ubiquitous synaptic vesicle proteoglycan SV2. Two size classes of P2x1 receptor clusters were observed on the smooth muscle cells of the detrusor, namely, a large ellipse of mean long axis 1.23 ± 0.21 μm and short axis 0.92 ± 0.17 μm and a smaller spherical cluster with a mean diameter of 0.40 ± 0.04 μm. The latter occured in much greater numbers than the former in selected areas, with a density as high as 0.8 per μm2 or two orders of magnitude more than the larger-sized clusters. The large clusters are in general located beneath varicosities, with only 4.5% of P2x1 clusters not possessing an overlying varicosity. None of the small clusters was associated with varicosities. Three-dimensional reconstruction of the P2x1 and SV2 labelling at individual varicosities showed that the varicosities were immediately apposed to the P2x1 receptor clusters. On occasions, two or more small SV2-labelled varicosities about 0.7 μm in diameter each with a receptor patch were found juxtaposed to each other; these might represent the splitting up of a single large varicosity. These observations are discussed in relation to the identity of the autonomic neuromuscular junction.     

Two New Species of Eimeria from Peacocks (Pavo cristatus) in Saudi Arabia1

Fifteen fecal samples from peacocks (Pavo cristatus) in Saudi Arabia contained oocysts of Eimeria riyadhae n. sp. in two peacocks and oocysts of E. arabica n. sp. in one peacock. Sporulated oocysts of Eimeria riyadhae are ellipsoidal, 27–30.5 times 20.5–25 (28.8 ± 1.3 × 22.4 ± 1.6) μm, with a two-layered wall and bilobed polar body, but without a micropyle or residuum. The sporocysts are ovoid, 11–14.5 × 6.5–8 (13.2 ± 1.2 × 7.2 ± 0.6) μm with a thick, knob-like Stieda body and a residuum. Sporulated oocysts of Eimena arabica are spheroidal, 17.5–21.5 × 17.5–21.5 (19.2 ± 1.6 × 19.2 ± 1.6) μm, with a two-layered wall and two refractile polar bodies, but without a micropyle or residuum. The sporocysts are elongate ovoid, 9.5–12 × 4–6.5 (11.2 ± 0.9 × 5.5 ± 0.88), with a small crescent-shaped Stieda body. The host bird belongs to the order Galliformis.     

Application of QuickBird and aerial imagery to detect Pinus radiata in remnant vegetation

The invasion of Pinus radiata from long‐term established plantations is contributing to the degradation of fragmented and isolated remnants of native vegetation. Within the south‐east of South Australia, the 20 vegetation communities that occur within 500 m of a plantation edge are at risk, including nine state threatened communities. To plan effective mitigation strategies, the current extent and distribution of P. radiata needs to be ascertained. High spatial resolution, multispectral QuickBird imagery and aerial photography were used to classify P. radiata within eucalypt and acacia woodlands, melaleuca shrubland, modified pasture and an Eucalyptus globulus plantation. Unsupervised classification of aerial photography gave the best result showing reasonable conformity with the observed distribution of P. radiata at the site scale. However, the 9.4 ± 13.5 (SD) cover classified in the quadrats sampled for the accuracy assessment exceeded the 1.4 ± 2.4 (SD) P. radiata cover determined from an independent dataset. Only 30.1 ± 37.9% (SD) of trees within the quadrats and 9.40 ± 13.49% (SD) of their foliage cover were classified. Trees detected by partial classification of canopy were positively correlated with both tree height and canopy diameter. Overall, the low detection rates were attributed to insufficient spectral resolution. Using higher resolution imagery, together with an object‐based image analysis or combination of multispectral and airborne digital image classification, restricted to large emergent adult trees using LiDAR analysis, is likely to improve adult P. radiata detection accuracy.     

Quantitative analysis of time-series fluorescence microscopy using a spot tracking method: application to Min protein dynamics

The dynamics of MinD protein has been recognized as playing an important role in the accurate positioning of the septum during cell division. In this work, spot tracking technique (STT) was applied to track the motion and quantitatively characterize the dynamic behavior of green fluorescent protein-labeled MinD (GFP-MinD) in an Escherichia coli system. We investigated MinD dynamics on the level of particle ensemble or cluster focusing on the position and motion of the maximum in the spatial distribution of MinD proteins. The main results are twofold: (i) a demonstration of how STT could be an acceptable tool for MinD dynamics studies; and (ii) quantitative findings with parametric and non-parametric analyses. Specifically, experimental data monitored from the dividing E. coli cells (typically 4.98 ± 0.75 μm in length) has demonstrated a fast oscillation of the MinD protein between the two poles, with an average period of 54.6 ± 8.6 s. Observations of the oscillating trajectory and velocity show a trapping or localized behavior of MinD around the polar zone, with average localization velocity of 0.29 ± 0.06 μm/s; and flight switching was observed at the pole-to-pole leading edge, with an average switching velocity of 2.95 ± 0.31 μm/s. Subdiffusive motion of MinD proteins at the polar zone was found and investigated with the dynamic exponent, α of 0.34 ± 0.16. To compare with the Gaussian-based analysis, non-parametric statistical analysis and noise consideration were also performed. Co-first authors     

Dispersal of Septoria nodorum Pycnidiospores by Simulated Rain and Wind

The influence of wind on the splash dispersal of Septoria nodorum pycnidiospores was studied in a raintower/wind tunnel complex with single drops or simulated rain falling on spore suspensions or infected stubble with windspeeds of 1.5 to 4 m/sec. When single drops fell on spore suspensions (depth 0.5 mm, concentration 7.8 × 10⁵ spores/ml) most of the spore-carrying droplets collected on fixed photographic film between 0–4 m downwind (windspeed 3 m/sec) were >200 μm in diameter. However, most spores were carried in droplets with diameter > 1000 μm, 70 % of which carried more than 100 spores. When simulated rain fell on infected stubble most of the spore-carrying droplets collected beyond 1 m downwind (windspeeds 1.4 and 4 m/sec) were <200 μm in diameter and none were >600 μm; most of these droplets carried only one spore. The distribution of splash droplets (with diameter >100 μm) deposited on chromatography paper showed a maximum at 40–50 cm upwind of the target but many more droplets were deposited 20–30 cm downwind, when single drops fell on a spore suspension (concentration 1.2 × 10⁵ spores/ ml) containing fluorescein dye with a windspeed of 2 m/sec; droplets were collected up to 3 m downwind but not more than 70 cm upwind. With a windspeed of 3 m/sec, numbers of sporecarrying droplets and spores collected on film decreased with increasing distance downwind; most were collected within 2 m of the target but some were found up to 4 m. When simulated rain fell on infected stubble, increasing the windspeed from 1.5 to 4 m/sec greatly increased the number of spores deposited more than 1 m downwind. At 1.5 m/sec none were collected beyond 2 m downwind, whereas at 4 m/sec some were collected at 4 m. A few air-borne S. nodorum spores were collected by suction samplers at a height of 40 cm at distances up to 10 m downwind of a target spore suspension on which simulated rain fell.     

Dispersal of Septoria nodorum Pycnidiospores by Simulated Raindrops in Still Air

Simulated raindrops, diameter c. 3 or 4 mm, fell 13 m down a raintower onto suspensions of Septoria nodorum pycnidiospores, depth 0.5 mm, or infected straw pieces. Splash droplets were collected on pieces of fixed photographic film. It was estimated that one drop generated c. 300 spore carrying splash droplets, containing c. 6000 spores, from a concentrated spore suspension (6.5 × 10⁵ spores/ml) and c. 25 spore-carrying droplets, containing c. 30 spores, from infected straw pieces (11 × 10⁶ spores/g dry wt). When the target was a spore suspension in water without surfactant, most spore-carrying droplets were in the 200—400 μm size category and most spores were carried in droplets with diameter >1000 μm. When surfactant was added to spore suspensions, most spore-carrying droplets were in the 0–200 μm category and most spores were carried in droplets with diameter 200–400 μm and none in droplets >1000 μm. Regression analyses showed a significant (p < 0.001) relationship between square root (number of spores per droplet) and droplet diameter; the slope of the regression line was greatest when surfactant was added to the spore suspensions. The distribution of splash droplets with distance travelled from the target was better fitted by an exponential model than by power law or Gaussian models. The distributions of spore-carrying droplets and spores with distance were fitted better by an exponential model than by a power law model. Thus regressions of log, (number collected) against distance were all significant (p < 0.01); the slopes of the regression lines were steepest when surfactant was added to the spore suspension. At a distance of 10 cm from target spore suspensions most splash droplets and spore-carrying droplets were collected at height 10–20 cm, with none above 40 cm; at a distance of 20 cm there were most at heights 0–10 cm and 40–50 cm.     

Small microcapsules of crystal proteins and spores of Bacillus thuringiensis by an emulsification/internal gelation method

This paper describes a microencapsulation process of a spore crystal aggregate produced by Bacillus thuringiensis var. kurstaki HD-1. The methodology is based on the emulsification/internal gelation method, and was implemented to produce microcapsules of small diameter (<10 μm) with the capacity to protect the spore crystal aggregate from extreme ultraviolet radiation. The diameter of microcapsules was in the range of 3.1 ± 0.2–6.8 ± 0.4 μm, which is considered adequate for biological control purposes. The protective effect of the alginate coat was verified by the remaining 60 ± 2% and 40 ± 1% of spore viability and protein activity, respectively, after UV-B radiation of 236 J, and with bioassays with Spodoptera frugiperda. It is expected that the protective effect of the alginate coat will improve the effectiveness of the Bt-HD1 formulated as small diameter microcapsules, and their yield, once they are released into the environment, will also be improved.     

Changes in the second stage juveniles of Globodeva rostochiensis prior to hatching in response to potato root diffusate

cAMP levels in eggs of G. rostochiensis and the diameter of the nucleolus of the nucleus within the dorsal pharyngeal gland cell of the second stage juvenile have been measured as indicators of the response of the nematode to the hatching stimulus in potato root diffusate. The nucleolus increased from 2.72 ± 0.103 μm for unhatched individuals to 3.28 ± 0.14 μm and 3.88 ± 0.15 μm after soaking eggs in potato root diffusate for 3 and 4 days respectively. Juveniles expressed from unstimulated eggs in water to potato root diffusate for 4–5 days showed a similar increase in size of the nucleolus to 3.94 ±0.15 μm but those released into water for this time had smaller nucleoli of 3.20 ± 0.98 μm. The change in diameter of the nucleolus is probably related to the accumulation of secretions in this gland cell before hatching. Preliminary results with dibutyryl analogues of CAMP and cGMP showed some inhibition of hatch in 10% potato root diffusate. Theophylline had a similar effect but NaF was dissimilar in that the effect of this inhibitor was not reversible. A standard radioimmunoassay showed that significant changes in cAMP levels occurred in the unhatched juveniles within cysts after treatment with potato root diffusate for 2.5 or 8 h compared with values for cysts kept in water. This change occurs before other known responses of the juveniles to potato root diffusate and it defines the period of interest for future work on the initial action of hatching factor.     

Parastrombidinopsis minima n. sp. (Ciliophora: Oligotrichia) from the Coastal Waters of Northeastern Taiwan: Morphology and Small Subunit Ribosomal DNA Sequence

ABSTRACT. Parastrombidinopsis minima n. sp. is investigated, using live observations, protargol preparations, and molecular data. In living cells, the ranges of cell length are 85–95 μm, cell width 60–70 μm, and oral diameter 40–50 μm. In protargol‐impregnated specimens, cell length ranges between 43 and 71 μm, cell width between 23 and 42 μm, and oral diameter between 13 and 24 μm. The numbers of external oral polykinetids are 12–16 and of somatic kineties are 11–13. There are always two ovoid macronuclei (9–16 × 4–9 μm). Based on the analysis of morphologic data, the new species can be placed in the family Strombidinopsidae, but based on the small subunit rRNA gene sequence data, the Parastrombidinopsis species are more closely associated with strobilidiids and tintinnids.     

Dispersal of Rhynchosporium secalis conidia from infected barley leaves or straw by simulated rain

Simulated rain (mean drop diameter c. 1 or 3 mm) was allowed to fall for 10 – 15 min on to barley leaves or straw infected by Rhynchosporium secalis (leaf blotch). The leaves were supported on a mesh through which run-off water drained and the straw was supported on a rigid surface on which run-off water collected. The numbers of R. secalis conidia and spore-carrying splash droplets collected by horizontal samplers (microscope slides and pieces of photographic film) decreased rapidly with increasing distance from and increasing height above the sources, with half-distances of 2 – 10 cm. Less than 10% of the spores or droplets reached heights of more than 30 cm. Incident drops 3 mm in diameter produced more spore-carrying droplets and dispersed more conidia than did 1 mm drops. The size category of splash droplets with the greatest proportion of the spore-carrying droplets dispersed by 3 mm drops was 200 – 400 μm, whether the source was infected barley leaves or barley straw. For leaves or straw the greatest proportions of spores were carried in droplets > 1000 μm in diameter. The mean diameter of spore-carrying droplets (478 μm) dispersed from free-draining leaves was less than that of droplets from straw plus run-off water (563 μm). However, the leaf source had more spores cm^-2 and the mean number of spores per droplet was greater (113 as opposed to 6·8) than for the straw source.     

Ultrastructure of Microplitis croceipes (Cresson) (Braconidae : Hymenoptera) teratocytes

The developing embryo of the braconid, Microplitis croceipes (Braconidae : Hymenoptera), is encased in an extraembryonic serosal membrane. Hatching of the parasitoid within the larva of its habitual host, Hehothis virescens (Noctuidae : Lepidoptera), is initiated about 40 hr after oviposition when held at 25 ± 2°C. At this time, the monolayered serosal membrane begins to dissociate into individual cells (teratocytes). After dissociation, teratocytes become dispersed in the hemolymph of the host. The average number of teratocytes released from each parasitoid embryo is 914 ± 43. Teratocytes average 14.1 ± 2.4 μm in diameter when first released, and reach a maximum average diameter of 68.1 ± 4.6 μm 6 days after liberation. Newly released teratocytes have ovoid nuclei, simple mitochondria and a limited number of profiles of the endoplasmic reticulum, all of which indicate relative metabolic inactivity. The ramified nuclei, extensive endoplasmic reticulum, polymorphic mitochondria and accumulation of glycogen granules and lipid droplets observed in older teratocytes provide circumstantial evidence that protein synthesis is occurring. Within hours after dissociation, microvilli begin to cover the surface of the teratocytes. Anatomical deformation (blebs) that occurred on some older (8-day-old) teratocytes probably resulted from enlargement or expansion of microvilli.     

Bidirectional pharmacodynamic interaction between pegylated liposomal CKD-602 (S-CKD602) and monocytes in patients with refractory solid tumors

Background:?STEALTH^® liposomal CKD-602 (S-CKD602), a camptothecin analog, is eliminated by the reticuloendothelial system (RES), which consists of cells, including monocytes. We evaluated the relationship between monocyte and absolute neutrophil counts (ANCs) in the blood and pharmacokinetic disposition of S-CKD602 and nonliposomal CKD-602 (NL-CKD602) in patients.

Methods:?As part of a phase I study of S-CKD602 and phase I and II studies of NL-CKD602, the percent decreases in ANC and monocytes at their nadir were calculated. After S-CKD602, the amount of CKD-602 recovered in urine was measured.

Results:?For S-CKD602 in patients <60 years, the percent decrease in ANC and monocytes were 43?±?31 and 58?±?26%, respectively (P?=?0.001). For S-CKD602 in patients ≥60, the percent decrease in ANC and monocytes were 41?±?31 and 45?±?36%, respectively (P?=?0.50). For NL-CKD602 (n?=?42), the percent decrease in ANC and monocytes were similar (P?>?0.05). For S-CKD602, the relationship between the percent decrease in monocytes and CKD-602 recovered in urine was stronger in patients <60 (R²?=?0.82), compared with patients ≥60 (R²?=?0.30).

Conclusions:?Monocytes are more sensitive to S-CKD602, compared with neutrophils, and the increased sensitivity is related to the liposomal formulation, not CKD-602. These results suggest that monocytes engulf S-CKD602, which causes the release of CKD-602 from the liposome and toxicity to the monocytes, and that the effects are more prominent in patients <60.     

Ultrastructural characterization of porcine oocytes and adjacent follicular cells during follicle development: Lipid component evolution

The objective of this study was to characterize the morphometry and ultrastructure of porcine preantral and antral follicles, especially the lipid component evolution. Ovarian tissue was processed for light microscopy. Ovarian tissue and dissected antral follicles (< 2, 2–4, and 4–6 mm) were also processed for transmission electron microscopy using routine methods and using an osmium-imidazole method for lipid detection. Primordial follicles (34 ± 5 μm in diameter, mean ± SD) had one layer of flattened-cuboidal granulosa cells around the oocyte, primary follicles (40 ± 7 μm) had a single layer of cuboidal granulosa cells around the oocyte, and secondary follicles (102 ± 58 μm) had two or more layers of cuboidal granulosa cells around the oocyte. Preantral follicle oocytes had many round mitochondria and both rough and smooth endoplasmic reticulum. In oocytes of primordial and primary follicles, lipid droplets were abundant and were mostly located at the cell poles. In secondary and antral follicles, the zona pellucida completely surrounded the oocyte, whereas some microvilli and granulosa cells projected through it. Numerous electron-lucent vesicles and vacuoles were present in the oolemma of secondary and antral follicles. Based on osmium-imidazole staining, most of these structures were shown to be lipid droplets. As the follicle developed, the appearance of the lipid droplets changed from small and black to large and gray, dark or dark with light streaks, suggesting that their nature may change over time. In summary, although porcine follicles and oocytes had many similarities to those of other mammalian species, they were rich in lipids, with lipid droplets with varying morphological patterns as the follicle developed.     

Detection of a mixed-backbone oligonucleotide (GEM 231) in liver and tumor tissues by capillary electrophoresis

A simple, rapid and sensitive method has been developed and validated for the analysis of a mixed-backbone oligonucleotide (GEM 231) in tumor tissues. The analysis was performed using a capillary electrophoresis (CE) system with UV detection. An extended light path (bubble cell) capillary column of 64.5 cm (effective length 56 cm)×50 μm I.D. is used as the separation column. The optimized chromatographic conditions were background electrolyte: sodium borate buffer (60 mM, pH 9.1), electrokinetic injection: 10 s, applied voltage: 30 kV, detection at λ=210 nm. A linear relationship was observed between the peak area and the amount of GEM 231 in the range of 1.0–1000 μg/ml. The lower detection limit of the drug was 100 pg with an average recovery of about 75±5%. The inter-day and intra-day relative standard deviations were <10%. Assay validation studies revealed that CE method is reproducible and specific for the determination of GEM 231 in tissue homogenates with a run time of less than 5 min.     

Ecological applications of differences in the hydraulic efficiency of palms and broad-leaved trees

Key message

In tropical forests, co-occurring woody monocot and dicot species adapted different water use strategies highly depending on their investment in the hydraulic conduit properties.

Abstract

We studied the hydraulic efficiency of palms and broad-leaved tropical tree species from a moist tropical lowland forest in the Central Brazilian Amazon. Therefore, we harvested 34 trees and 10 açai palms and measured vessel size and frequency at diameter at breast height and additionally at the base of the crown shaft for the palms. Further, we assessed the active xylem area to estimate the hydraulic conductivity through Hagen Poiseuille’s adapted theoretical equation. Mean vessel diameter in dicot trees was 127.62 ± 49.22 μm with an average 9.09 ± 6.50 vessels per mm². Mean conduits sizes at the base (h = 0.10 m) of palm trees were larger with 288.20 ± 32.96 μm and less frequent with 1.40 ± 0.46 vessels per mm². Hydraulic conductivity was on average 3.31 ± 4.59 kg m^?1 s^?1 MPa^?1 for dicot trees. Mean hydraulic conductivity in açai palms was 20.45 ± 10.6 kg m^?1 s^?1 MPa^?1 at the base, and increased to 124.73 ± 55.2 kg m^?1 s^?1 MPa^?1 at the crown base. Hydraulic conductivity at the base of the crown was higher than in the base of the trunk due to the high density of vessels in a small cross-section in this height. Furthermore, we found a species-independent relationship between vessel diameter and frequency. We conclude that the differences found in the hydraulic efficiency give some evidence that palms have a lower occurrence of embolism and cavitation than trees, which is due to stiffer and stronger conduit pathways and efficient drought-avoiding strategies. The differences in hydraulic architecture between palms and trees imply different water use patterns thus varying niche differentiation, but this does not consequently need to be an excluding factor for coexistence in the same environment.