Energy metabolism of underwater swimming in river-otters (Lutra lutra L.)

We used a still-water swim channel in conjunction with open-flow oxygen and carbon dioxide respirometry to examine the energy requirements of river-otters (Lutra lutra L.) swimming voluntarily underwater in Neumünster Zoo (Germany). While at rest on land (5 °C), river-otters had a respiratory quotient of 0.77 and a resting metabolic rate of 4.1 W kg⁻¹. This increased to an estimated 6.4 W kg⁻¹ during rest in water (11–15 °C) and to 12.3 W kg⁻¹ when the animals were feeding in the channel. River-otters swimming under water preferred a mean speed of 0.89 m s⁻¹, and their energy requirements attained 11.6 W kg⁻¹. Cost of transport, however, was minimal at 1.3 m s⁻¹ and amounted to 0.95 J N⁻¹ m⁻¹. Accepted: 3 November 1997     

Biofiltering efficiency, uptake and assimilation rates of Ulva clathrata (Roth) J. Agardh (Clorophyceae) cultivated in shrimp aquaculture waste water

The growth, biofiltering efficiency and uptake rates of Ulva clathrata were studied in a series of outdoor tanks, receiving waste water directly from a shrimp (Litopenaeus vannamei) aquaculture pond, under constant aeration and two different water regimes: (1) continuous flow, with 1 volume exchange a day (VE day^-1) and (2) static regime, with 1 VE after 4 days. Water temperature, salinity, pH, dissolved inorganic nitrogen (DIN), phosphate (PO₄), chlorophyll-a (chl-a), total suspended solids (TSS), macroalgal biomass (fresh weight) and tissue nutrient assimilation were monitored over 12 days. Ulva clathrata was highly efficient in removing the main inorganic nutrients from effluent water, stripping 70–82% of the total ammonium nitrogen (TAN) and 50% PO₄ within 15 h. Reductions in control tanks were much lower (Tukey HSD, P < 0.05). After 3 days, the mean uptake rates by the seaweed biomass under continuous flow were 3.09 mg DIN g DW day⁻¹ (383 mg DIN m⁻² day⁻¹) and 0.13 mg PO₄ g DW day⁻¹ (99 mg PO₄ m⁻² day⁻¹), being significantly higher than in the static regime (Tukey HSD, P < 0.05). The chl-a decreased in seaweed tanks, suggesting that U. clathrata inhibited phytoplankton growth. Correlations between the cumulative values of DIN removed from the water and total nitrogen assimilated into the seaweed biomass (r = 0.7 and 0.8, P < 0.05), suggest that nutrient removal by U. clathrata dominated over other processes such as phytoplankton and bacterial assimilation, ammonia volatilization and nutrient precipitation.     

Heavy metal pollution monitoring using the brown seaweed Padina durvillaei in the coastal zone of the Santa Rosalía mining region, Baja California Peninsula, Mexico

The coastal marine sediments near Santa Rosalía on the eastern coast of the Baja California Peninsula (Mexico) are heavily polluted by metals due to copper mining and smelting over the past century (up to 1984). The present study compares the accumulation of metals in the brown seaweed Padina durvillaei from the central segment of the coast of Santa Rosalía (polluted by Co, Cu, Mn and Zn) and from two segments north and south of the known “hot spot”. The seaweed samples were collected in May and August 2004 and June 2005 at 13 stations located along the Santa Rosalía mining region. Heavy metal concentrations were measured by instrumental neutron activation analysis (Co and Fe) directly in dried homogenized subsamples or by flame atomic absorption spectrophotometry (Cd, Cu, Mn, Ni, Pb and Zn) after complete strong acid digestion of sub-samples. The means and standard deviations of the concentrations in dry tissues of Padina durvillaei specimens for all the studied metals and stations lie in the following sequence: Cd (3.6 ± 1.6 mg kg⁻¹) < Co (6.5 ± 6.1 mg kg⁻¹) < Pb (7.8 ± 6.2) < Ni (9.96 ± 5.28 mg kg⁻¹) < Cu (53 ± 38 mg kg⁻¹) < Zn (63 ± 43 mg kg⁻¹) < Mn (295 ± 269 mg kg⁻¹) < Fe (2243 ± 2325 mg kg⁻¹). This increase of the average concentrations was statistically significant. Principal Component Analysis showed that Factor 1 (36.46%) displays high positive loadings for Co, Cu, Mn and Zn, reflecting the influence of local anthropogenic pollution on the seaweed composition, while Factor 2 (26.91%) is important for Co, Fe and Ni and probably corresponds to the adsorption or accumulation of terrigenous elements of the regional origin, while Factor 3, with a high positive loading for Pb and a high negative loading for Cd, is probably controlled by local and regional anthropogenic input of Pb and episodic supply of Cd by local upwellings. The results of ANOVA for each element do not show any significant differences between the average concentrations for Cd, Fe, Ni and Pb in the seaweed of the three segments, or between the central and southern segments for Cu, Mn and Zn. Cobalt contents in the seaweed from the northern and central segments are, however, significantly different from the southern segment. This indicates that element concentrations in Padina durvillaei generally do not follow the drastic increases and gradients of Cu, Co, Mn and Zn contents detected in surface sediments. The apparent contradiction could be explained by a low geochemical mobility of these metals in the polluted sediments, composed mainly of stable residues of smelter wastes, with very low content of organic matter usually driving diagenetic mobilization of some metals into interstitial waters and then to the overlying water.     

Comparative analysis of the digestive efficiency and nitrogen and energy requirements of the phyllostomid fruit-bat (Artibeus jamaicensis) and the pteropodid fruit-bat (Rousettus aegyptiacus)

Nitrogen (N) and energy (E) requirements of the phyllostomid fruit bat, Artibeus jamaicensis, and the pteropodid fruit bat Rousettus aegyptiacus, were measured in adults that were fed on four experimental diets. Mean daily food intake by A. jamaicensis and R. aegyptiacus ranged from 1.1–1.6 times body mass and 0.8–1.0 times body mass, respectively. Dry matter digestibility and metabolizable E coefficient were high (81.1% and 82.4%, respectively) for A. jamaicensis and (77.5% and 78.0%, respectively) for R. aegyptiacus. Across the four diets, bats maintained constant body mass with mean metabolizable E intakes ranging from 1357.3 kJ · kg^−0.75 · day⁻¹ to 1767.3 kJ · kg^−0.75 · day⁻¹ for A. jamaicensis and 1282.6–1545.2 kJ · kg^−0.75 · day⁻¹ for R. aegyptiacus. Maintenance E costs were high, in the order of 3.6–5.4 times the basal metabolic rate (BMR). It is unlikely that the E intakes that we observed represent a true measure of maintenance E requirements. All evidence seems to indicate that fruit bats are E maximizers, ingesting more E than required and regulating storage by adjusting metabolic output. We suggest that true maintenance E requirements are substantially lower than what we observed. If it follows the eutherian norm of two times the BMR, fruit bats must necessarily over-ingest E on low-N fruit diet. Dietary E content did affect N metabolism of A. jamaicensis. On respective low- and high-E diets, metabolic fecal N were 0.492 mg N · g⁻¹ and 0.756 mg N · g⁻¹ dry matter intake and endogenous urinary N losses were 163.31 mg N · kg^−0.75 · day⁻¹ and 71.54 mg N · kg^−0.75 · day⁻¹. A. jamaicensis required 332.3 mg · kg^−0.75 · day⁻¹ and 885.3 mg · kg^−0.75 · day⁻¹ of total N on high- and low-E diets, respectively, and 213.7 mg · kg^−0.75 · day⁻¹ of truly digestible N to achieve N balance. True N digestibilities were low (29% and 49%) for low- and high-E diets, respectively. For R. aegyptiacus, metabolic fecal N and endogenous urinary N losses were 1.27 mg N · g⁻¹ dry matter intake and 96.0 mg N · kg^−0.75 · day⁻¹, respectively, and bats required 529.8 mg · kg^−0.75 · day⁻¹ (total N) or 284.0 mg · kg^−0.75 · day⁻¹ (truly digestible N). True N digestibility was relatively low (50%). Based on direct comparison, we found no evidence that R. aegyptiacus exhibits a greater degree of specialization in digestive function and N retention than A. jamaicensis. When combined with results from previous studies, our results indicate that all fruit bats appear to be specialized in their ability to retain N when faced with low N diet. Accepted: 24 November 1998     

New insights on toluene biodegradation by Pseudomonas putida F1: influence of pollutant concentration and excreted metabolites

The influence of toluene concentration on the specific growth rate, cellular yield, specific CO₂, and metabolite production by Pseudomonas putida F1 (PpF1) was investigated. Both cellular yield and specific CO₂ production remained constant at 1.0 ± 0.1 g biomass dry weight (DW) g⁻¹ toluene and 1.91 ± 0.31 g CO₂ g⁻¹ biomass, respectively, under the tested range of concentrations (2–250 mg toluene l⁻¹). The specific growth rate increased up to 70 mg toluene l⁻¹. Further increases in toluene concentration inhibited PpF1 growth, although inhibitory concentrations were far from the application range of biological treatment processes. The specific ATP content increased with toluene concentration up to toluene concentrations of 170 mg l⁻¹. 3-Methyl catechol (3-MC) was never detected in the cultivation medium despite being an intermediary in the TOD pathway. This suggested that the transformation from toluene to 3-MC was the limiting step in the biodegradation process. On the other hand, benzyl alcohol (BA) was produced from toluene in a side chain reaction. This is, to the best of our knowledge, the first reported case of methyl monoxygenation of toluene by PpF1 not harboring the pWW0 TOL plasmid. In addition, the influence of 3-MC, BA, and o-cresol on toluene degradation was investigated respirometrically, showing that toluene-associated respiration was not significantly inhibited in the presence of 10–100 mg l⁻¹ of the above-mentioned compounds.     

Palm oil mill effluent (POME) cultured marine microalgae as supplementary diet for rotifer culture

Malaysia is the world’s leading producer of palm oil products that contribute US$ 7.5 billion in export revenues. Like any other agro-based industries, it generates waste that could be utilized as a source of organic nutrients for microalgae culture. Present investigation delves upon Isochrysis sp. culture in POME modified medium and its utilization as a supplement to Nanochloropsis sp. in rotifer cultures. The culture conditions were optimized using a 1 L photobioreactor (Temp: 23°C, illumination: 180 ∼ 200 μmol photons m⁻²s⁻¹, n = 6) and scaled up to 10 L outdoor system (Temp: 26–29°C, illumination: 50 ∼ 180 μmol photons m⁻²s⁻¹, n = 3). Algal growth rate in photobioreactor (μ = 0.0363 h⁻¹) was 55% higher compared to outdoor culture (μ = 0.0163 h⁻¹), but biomass production was 1.3 times higher in outdoor culture (Outdoor = 91.7 mg m⁻²d⁻¹; Photobioreactor = 69 mg m⁻²d⁻¹). Outdoor culture produced 18% higher lipid; while total fatty acids (FA) was not significantly affected by the change in culture systems as both cultures yield almost similar concentrations of fatty acids per gram of sample (photobioreactor = 119.17 mg g⁻¹; outdoor culture = 104.50 mg g⁻¹); however, outdoor cultured Isochrysis sp. had 26% more polyunsaturated fatty acids (PUFAs). Rotifers cultured in Isochrysis sp./ Nanochloropsis sp. (1:1, v/v) mixture gave similar growth rate as 100% Nanochoropsis sp. culture (μ = 0.40 d⁻¹), but had 45% higher counts of rotifers with eggs (t = 7, maximum). The Isochrysis sp. culture successfully lowered the nitrate (46%) and orthophosphate (83%) during outdoor culture.     

Spatial distributions and net deposition rates of mineral elements in the elongating wheat (Triticum aestivum L.) leaf under saline soil conditions

Wheat leaf growth is known to be spatially affected by salinity. The altered spatial distribution of leaf growth under saline conditions may be associated with spatial changes in tissue mineral elements. The objective of this study was to evaluate the spatial distributions of mineral elements and their net deposition rates in the elongating and mature zones of leaf 4 of the main stem of spring wheat (Triticum aestivum L. cv. Lona) during its linear growth phase under saline soil conditions. Plants were grown in an illitic-chloritic silty loam with 0 and 120 mM NaCl. Three days after emergence of leaf 4, sampling was begun at 3 and 13 h into the 16-h light period. Spatial distributions of fresh weight (FW), dry weight (DW), and Na⁺, K⁺, Cl⁻, NO⁻ ₃, Ca²⁺, Mg²⁺, total P, and total N in the elongating and mature tissues were determined on a millimeter scale. The patterns of spatial distribution of Na⁺, Cl⁻, K⁺, NO₃ ⁻, and Ca²⁺ in the growing leaves were affected by salinity, while those of Mg²⁺, total P, and total N were not. Sodium, K⁺, Cl⁻, Ca²⁺, Mg²⁺, and total N concentrations (mmol · kg⁻¹ FW) were consistently higher at 120 mM NaCl than at 0 mM NaCl along the leaf axis from the leaf base, whereas NO₃ ⁻ concentration was lower at 120 mM NaCl. Deposition rates of all nutrients were greatest in the elongation zone. The elongation zone was the strongest sink for mineral elements in the leaf tissues. Local net deposition rates of Na⁺, Cl⁻, Ca²⁺, and Mg²⁺ (mmol · kg⁻¹ FW · h⁻¹) in the most actively elongating zone were enhanced by 120 mM NaCl, whereas for NO₃ ⁻ this was depressed. The lower supply of NO⁻ ₃ to growing leaves may be responsible for the inhibition of growth under saline conditions. Higher tissue concentrations of Na⁺ and Cl⁻ may cause ion imbalance but probably did not result in ion toxicity in the growing leaves. Potassium, Ca²⁺, Mg²⁺, total P, and total N are less plausibly responsible for the reduction in leaf growth in this study. Higher tissue K⁺ and Ca²⁺ concentrations at 120 mM NaCl are probably due to the presence of high Ca²⁺ in the soil of this study. Received: 13 March 1997 / Accepted: 9 June 1997     

Physiological responses induced by copper bioaccumulation in <Emphasis Type="Italic">Eichhornia crassipes</Emphasis> (Mart.)

Eichhornia crassipes (Mart.) has strong ability to remove Cu²⁺ from copper-contaminated water. Physiological responses in E. crassipes exposed to known concentrations of Cu²⁺ were examined in this study, and demonstrated that E. crassipes could accumulate 314 mg kg⁻¹ dry weight of Cu when exposed to 5 mg l⁻¹ of Cu²⁺ for periods up to 14 d. However, there were marked changes in physiology of the plant commencing at Cu²⁺ concentrations of 1 mg l⁻¹. Results of this study showed that E. crassipes could tolerate moderate concentrations (i.e. 0.5 mg l⁻¹) of Cu²⁺, without significant changes in photosynthetic pigment concentrations, while high concentrations (i.e. 5 and 10 mg l⁻¹) of Cu²⁺ resulted in substantial loss in pigment concentrations. Increases in malondiadehyde (MDA) content were also demonstrated in plant exposure to high Cu²⁺ concentrations. Soluble protein content increased to a level slightly higher than the control at <0.5 mg l⁻¹ of Cu²⁺, but then decreased with exposure to >1 mg l⁻¹ of Cu²⁺. Our results suggest that E. crassipes has a substantial capacity to accumulate copper when cultivated at moderate concentrations of Cu²⁺, without marked changes in its physiology. The findings indicate that E. crassipes is a promising possibility for phytoremediation of moderately Cu-contaminated water bodies. Handling editor: S. M. Thomaz     

Large-scale cultivation of adventitious roots of Echinacea purpurea in airlift bioreactors for the production of chichoric acid, chlorogenic acid and caftaric acid

Adventitious roots of Echinacea purpurea were cultured in airlift bioreactors (20 l, 500 l balloon-type, bubble bioreactors and 1,000 l drum-type bubble bioreactor) using Murashige and Skoog (MS) medium with 2 mg indole butyric acid l⁻¹ and 50 g sucrose l⁻¹ for the production of chichoric acid, chlorogenic acid and caftaric acid. In the 20 l bioreactor (containing 14 l MS medium) a maximum yield of 11 g dry biomass l⁻¹ was achieved after 60 days. However, the amount of total phenolics (57 mg g⁻¹ DW), flavonoids (34 mg g⁻¹ DW) and caffeic acid derivatives (38 mg g⁻¹ DW) were highest after 50 days. Based on these studies, pilot-scale cultures were established and 3.6 kg and 5.1 kg dry biomass were achieved in the 500 l and 1,000 l bioreactors, respectively. The accumulation of 5 mg chlorogenic acid g⁻¹ DW, 22 mg chichoric acid g⁻¹ DW and 4 mg caftaric acids g⁻¹ DW were achieved with adventitious roots grown in 1,000 l bioreactors.     

Arsenic hyperaccumulation induces metabolic reprogramming in Pityrogramma calomelanos to reduce oxidative stress

Arsenic (As) pollution is a major environmental concern due to its worldwide distribution and high toxicity to organisms. The fern Pityrogramma calomelanos is one of the few plant species known to be able to hyperaccumulate As, although the mechanisms involved are largely unknown. This study aimed to investigate the metabolic adjustments involved in the As‐tolerance of P. calomelanos. For this purpose, ferns with five to seven fronds were exposed to a series of As concentrations. Young fronds were used for biochemical analysis and metabolite profiling using gas chromatography–mass spectrometry. As treatment increased the total concentration of proteins and soluble phenols, enhanced peroxidase activities, and promoted disturbances in nitrogen and carbon metabolism. The reduction of the glucose pool was one of the striking responses to As. Remarkable changes in amino acids levels were observed in As‐treated plants, including those related to biosynthesis of glutathione and phenols, osmoregulation and two photorespiratory intermediates. In addition, increases in polyamines levels and antioxidant enzyme activities were observed. In summary, this study indicates that P. calomelanos tolerates high concentration of As due to its capacity to upregulate biosynthesis of amino acids and antioxidants, without greatly disturbing central carbon metabolism. At extremely high As concentrations, however, this protective mechanism fails to block reactive oxygen species production, leading to lipid peroxidation and leaf necrosis.     

Micropropagation and induction of autotetraploid plants of <Emphasis Type="Italic">Chrysanthemum cinerariifolium</Emphasis> (Trev.) Vis

Rapid propagation technology was established and optimized in vitro for Chrysanthemum cinerariifolium (Trev.) Vis., an important botanical insecticide plant with a huge international market. A large number of buds could be induced directly from epicotyl and hypocotyl explants on Murashige T; Skoog F. J. Plant. Physiol. 15: 473–479; (1962) medium [Murashige and Skoog (MS) medium] supplemented with 0.3 mg l⁻¹ benzyladenine (BA) and 0.3 mg l⁻¹ α-naphthaleneacetic acid (NAA). Root induction and development could be observed within 15 d after inoculation on 1/2 MS medium supplemented with 0.2 mg l⁻¹ indole-3-acetic acid (IAA) and 0.1 mg l⁻¹ rooting powder (ABT). Furthermore, a polyploid breeding study in vitro was reported to obtain superior breeding lines with high yield and good quality. Autotetraploid lines of C. cinerariifolium were obtained by colchicine treatments and identified by root-tip chromosome determination and stoma observation. The chromosome number of the autotetraploid plantlet was 2N = 4x = 36. Obtained autotetraploid lines will be of important genetic and breeding value and be used for further selection and plant breeding.     

Characteristics of Arsenic Accumulation by Pteris and non-Pteris Ferns

This research was conducted to understand the mechanisms of arsenic hyperaccumulation in Pteris vittata by comparing the characteristics of arsenic accumulation in Pteris and non-Pteris ferns. Seven Pteris (P.vittata, P. Cretica Rowerii, P. Cretica Parkerii, P. Cretica Albo-lineata, P. Quadriavrita, P. Ensiformis and P. Dentata) and six non-Pteris (Arachnoides simplicor, Didymochlaena truncatula, Dryopteris atrata, Dryopteris erythrosora, Cyrtomium falcatum, and Adiantum hispidulum) ferns were exposed to 0, 1 and 10 mgL⁻¹ arsenic as sodium arsenate for 14-d in hydroponic systems. As a group, the Pteris ferns were more efficient in arsenic accumulation than the non-Pteris ferns, with P. vittata being the most efficient followed by P. cretica. When exposed to 10 mg L⁻¹ As, arsenic concentrations in the fronds and roots of P. vittata were 1748 and 503 mg kg⁻¹. Though not all Pteris ferns were efficient in accumulating arsenic, none of the non-Pteris ferns was an efficient As accumulator (the highest concentration being 452 mg kg⁻¹). The fact that frond arsenic concentrations in the control were highly correlated with those exposed to As (r ² = 0.76–0.87) may suggest that they may be used as a preliminary tool to screen potential arsenic hyperaccumulators. Our research confirms that the ability of P. vittata to translocate arsenic from the roots to the fronds (73–77% As in the fronds), reduce arsenate to arsenite in the fronds (>50% AsIII in the fronds), and maintain high concentrations of phosphate in the roots (48–53% in the roots) all contributed to its arsenic tolerance and hyperaccumulation.     

Role of VA-mycorrhiza in growth and mineral nutrition of apple (Malus pumila var.domestica) rootstock cuttings

One-year-old apple cuttings (Malus pumila var.domestica cv. M26) were grown for 6 months in pot culture with and without inoculum of the VA-mycorrhizal fungus (VAMF)Glomus macrocarpum in soil from a long-term fertilizer field experiment with different P availability (20, 210, and 280 mg CAL-extractable P kg⁻¹). The indigenous VAMF propagule density was reduced by 0.5 Mrad X-irradiation. At harvest, non-inoculated and inoculated plants had similar proportions of root length bearing vesicles. Net dry weight of tree cuttings was significantly increased by inoculation only at 20 mg P kg⁻¹ (+62%). Increasing P availability from 210 to 280 mg P kg⁻¹ led to a 4-week depression of shoot elongation rate only in the inoculated plants. Uptake of P was significantly enhanced by inoculation at 20 and 210 mg P kg⁻¹ (+64 and +12%, respectively). On average, inoculated plants had significantly higher concentrations of Zn in leaves and in roots (+16 and +14%, respectively) and of copper in stems and in roots (+13 and +126%, respectively). Proportion of vesicle bearing root length was significantly correlated with root caloric content. A lipid content of 0.9–4.5% in the root dry matter was attributed to the presence of vesicles corresponding to 1.6–8.2% of total root caloric content. As the control plants were also infected, the beneficial effect of VA-mycorrhiza on nutrient uptake and growth of apple cuttings was underestimated at all P levels. Furthermore, VAM-potential at the lowest P level was not fully exploited as onset of infection was most certainly delayed because of a decreased photosynthetic rate due to P deficiency. Energy drain by VAMF-infection was most probably underestimated considerably, due to, among others, loss of infected root cortex during root growth, sampling and staining. It is concluded that apple cuttings rely on VA-mycorrhizal P-uptake at least in low P soils. In high P soils, apple cuttings may profit predominantly from the uptake of Zn and Cu by the fungal symbionts.     

The shikonin derivatives and pyrrolizidine alkaloids in hairy root cultures of Lithospermum canescens (Michx.) Lehm.

Hairy root cultures of Lithospermum canescens were established using three strains of Agrobacterium rhizogenes: ATCC 15834, LBA 9402 and NCIB 8196. Eight lines resulting from infection with A. rhizogenes ATCC 15834 demonstrated sufficient biomass increase and were submitted to further investigations. The contents of acetylshikonin (ACS) and isobutyrylshikonin (IBS) in transformed hairy roots made up ca. 10% of those observed in natural roots of L. canescens (24.35 and 14.48 mg g⁻¹ DW, respectively). One line, Lc1-D, produced the largest amounts of ACS (2.72 mg g⁻¹ DW) and IBS (0.307 mg g⁻¹ DW). Traces of pyrrolizidine alkaloids (PA), canescine and canescenine, were found in all lines of transformed hairy roots.     

Plasma arginine vasotocin and angiotensin II responses to body temperature elevation in the Pekin duck

The relationship between body temperature (T _b) and the plasma concentrations of arginine vasotocin (AVT) and angiotensin II (AII) was examined in conscious, adult Pekin ducks. Exposure of birds to an ambient temperature of 40 °C for 3 h increased T _b by about 1.5 °C and increased breathing rate five-fold. Plasma osmolality was elevated from the normothermic value of 294.9 ± 1.4 mosmol kg⁻¹ by about 8 mosmol kg⁻¹ Circulating AVT levels increased by about 2 pg ml⁻¹ from a basal concentration of 4.98 ± 0.15 pg ml⁻¹, a rise which could be accounted for by the change in osmotic status. Plasma AII concentrations were unchanged from the pre-heat exposure value of 31.8 ± 3.4 pg ml⁻¹. Time control birds, exposed only to an ambient temperature of 22 °C demonstrated no significant changes in any of the measured variables. The results suggest that an increased T _b has no direct effect on the circulating concentrations of AVT or AII in ducks. Accepted: 2 June 1997     

Dynamics of zinc uptake and accumulation in the hyperaccumulating and non-hyperaccumulating ecotypes of Sedum alfredii Hance

Sedum alfredii Hance has been identified as a Zn-hyperaccumulating plant species native to China. The characteristics of Zn uptake and accumulation in the hyperaccumulating ecotype (HE) and non-hyperaccumulating ecotype (NHE) of S. alfredii were investigated under nutrient solution and soil culture conditions. The growth of HE was normal up to 1000 μM Zn in nutrient solution, and 1600 mg Zn kg⁻¹ soil in a Zn-amended soil. Growth of the NHE was inhibited at Zn levels ≥250 μM in nutrient solution. Zinc concentrations in the leaves and stems increased with increasing Zn supply levels, peaking at 500 and 250 μM Zn in nutrient solution for the HE and the NHE, respectively, and then gradually decreased or leveled off with further increase in solution Zn. Minimal increases in root Zn were noted at Zn levels up to 50 μM; root Zn sharply increased at higher Zn supply. The maximum Zn concentration in the shoots of the HE reached 20,000 and 29,000 mg kg⁻¹ in the nutrient solution and soil experiments, respectively, approximately 20 times greater than those of the NHE. Root Zn concentrations were higher in the NHE than in the HE when plants were grown at Zn levels ≥50 μM. The time-course of Zn uptake and accumulation exhibited a hyperbolic saturation curve: a rapid linear increase during the first 6 days in the long-term and 60 min in the short-term studies; followed by a slower increase or leveling off with time. More than 80% of Zn accumulated in the shoots of the HE at half time (day 16) of the long-term uptake in 500 μM Zn, and also at half time (120 min) of the short-term uptake in 10 μM ⁶⁵Zn²⁺. These results indicate that Zn uptake and accumulation in the shoots of S. alfredii exhibited a down-regulation by internal Zn accumulated in roots or leaves under both nutrient solution and soil conditions. An altered Zn transport system and increased metal sequestration capacity in the shoot tissues, especially in the stems, may be the factors that allow increased Zn accumulation in the hyperaccumulating ecotype of S. alfredii. Section Editor: F. J. Zhao     

Differential Effects of Sodium Selenite and Nano-Se on Growth Performance,Tissue Se Distribution,and Glutathione Peroxidase Activity of Avian Broiler

The present research evaluated differential effects of sodium selenite and nano-Se on growth performance, tissue Se distribution, and glutathione peroxidase (GSH-Px) activity of avian broiler. Broilers were randomly segregated into 12 groups so that three replicates were available for each of the three treatments (T-1, T-2, and T-3) and control groups. The control groups were fed basal diets without Se addition. T-1, T-2, and T-3 were fed with diets containing 0.2 mg kg⁻¹ sodium selenite, 0.2 mg kg⁻¹ nano-Se, and 0.5 mg kg⁻¹ nano-Se, respectively. Compared with the control, Se supplementation remarkably improved daily weight gain and survival rate and decreased feed conversion ratio (P < 0.05). However, no significant difference was observed between T-1, T-2, and T-3. The tissue Se content was significantly higher (P < 0.05) in Se-supplemented groups than the control, and T-3 showed the highest. Furthermore, higher Se content was observed in liver, and there was a significant difference (P < 0.05) compared with that in muscle. As for serum and hepatic GSH-Px activities, Se supplementation remarkably improved GSH-Px activity (P < 0.05), and there was no significant difference (P > 0.05) between treatments (T-1, T-2, and T-3).     

Osmoregulation and water balance in the springhare (Pedetes capensis)

Springhares are large rodents that live in arid and semi-arid regions of Africa. We deprived springhares of water for periods of up to 7 days to determine what physiological adaptations, if any, enable them to survive in arid regions without drinking. During water deprivation, springhares lost up to 30% body weight and produced a mean maximum urine concentration of 2548 mosmol kg⁻¹ with a maximum of 3076 mosmol kg⁻¹ in an individual animal. Haematocrit and plasma sodium and potassium concentrations were well regulated throughout water deprivation at 47.5 ± 3.8% and 132.6 ± 7.4 mmol l⁻¹ and 3.5 ± 0.7 mmol l⁻¹, respectively, while plasma osmolality increased slightly from 293 ± 12.5 mosmol kg⁻¹ to 324 ± 7.3 mosmol kg⁻¹. Springhares thus appeared to be good osmoregulators and were able to maintain plasma volume during 7 days of water deprivation. In addition to the production of a relatively concentrated urine, water loss was limited by the lowered solute load and faecal water loss achieved by a reduction in food consumption and by the production of very dry faeces. These abilities, together with a favourable burrow microclimate and nocturnal activity pattern, enable them to survive in arid regions. Accepted: 8 September 1998     

Efficient induction of apospory and apogamy in vitro in silver fern (Pityrogramma calomelanos L.)

Silver fern (Pityrogramma calomelanos L.) is a terrestrial or lithophytic herbaceous fern used for ornamental and medicinal purposes. In its farina it produces the cytotoxic and anticancer compound dihydrochalcone. In vitro induction of apospory and apogamy, and direct field establishment of aposporous gametophytes and subsequent sporophyte development has been accomplished. Half-strength Murashige and Skoog (MS) medium with 3.33 μM N⁶-benzyladenine (BA) and 2.32 μM kinetin (Kn) showed earlier development and produced higher numbers of aposporous gametophytes than half-strength MS basal medium. Crozier explants developed higher numbers (mean value 29.2) of gametophytes, but were slower than frond explants (mean value 23.2). The gametophytes originated from the epidermal hairs progressed from uniseriate filamentous to cordate through bi-, tri- and multiseriate and spatulate stage with the development of antheridia. Reduction in the nutrient and sucrose concentrations in the media favoured apogamy. Sucrose-free 1/10 strength MS medium and agar plates developed a mean of 30.4 and 29.9 sporophytes, respectively in the light. The greenhouse-established gametophytes developed sporophytes. The established sporophytes ex vitro showed 95% survival rate. Apogamous sporophytes and the source plant showed the same chromosome numbers (2n=116). The established protocol accomplishes apogamy and apospory in silver fern, and the aposporous gametophytes can be used for genetic transformation and development of transgenic silver fern.     

Growth and carrageenan quality of <Emphasis Type="Italic">Kappaphycus striatum</Emphasis> var. <Emphasis Type="Italic">sacol</Emphasis> grown at different stocking densities,duration of culture and depth

Kappaphycus striatum var. sacol was grown in two separate studies: (1) at two stocking densities, and (2) at four different depths, each for three different durations of culture (30, 45 and 60 days) in order to determine the growth rate of the seaweed and evaluate the carrageenan content and its molecular weight. The results demonstrated that stocking density, duration of culture and depth significantly (P < 0.01) affected the growth rate, carrageenan content and molecular weight of K. striatum var. sacol. Decreasing growth rate was observed at both stocking densities and at four depths as duration of culture increased. A lower stocking density (500 g m⁻¹line⁻¹) showed a higher growth rate for the shortest durations, i.e. 30 days, as compared to those grown at a higher density. Likewise, decreasing growth rate was observed as depth increased, except at 50 cm after 60 days of culture. A 45-day culture period produced the highest molecular weight at both stocking densities (500 g m⁻¹line⁻¹ = 1,079.5 ± 31.8 kDa, 1,000 g m⁻¹line⁻¹ = 1,167 ± 270.6 kDa). ‘Sacol’ grown for 30 days at 50 cm (1,178 kDa) to 100 cm (1,200 kDa) depth showed the highest values of molecular weight of carrageenan extracted. The results suggested that K. striatum var. sacol is best grown at a stocking density of 500 g m⁻¹line⁻¹, at a depth of 50–100 cm, and for a duration of 30 days in order to provide the highest growth rate, carrageenan content and molecular weight.