Observation of anoxic water mass in a tropical reservoir: the Cirata Reservoir in Java,Indonesia

We conducted a transect survey of water quality and bottom sediments in a large tropical reservoir, the Cirata Reservoir, located on the Citarum River, West Java, Indonesia. In the main basin of this reservoir, the surface water contained high concentrations of chlorophyll a, up to 48 μg l⁻¹, and most of the water body was occupied by thick anoxic water. The thickness of the surface oxygenated water was only 5–7 m, whereas that of the anoxic water mass was more than 70 m. The concentrations of phosphate and ammonia were quite high in the anoxic hypolimnion. The reasons for the formation of the huge anoxic water mass include the oligomictic status of circulation, a relatively weak mixing caused by topography, high hypolimnion temperature, and high loads of organic matter. The carbon/nitrogen (C/N) ratios and the carbon stable isotope ratios of sediments indicated that the major source of organic carbon in the sediments was algal production in the reservoir and fish culture activity. The mechanism of eutrophication in the reservoir is also discussed.     

<Emphasis Type="Italic">In vitro</Emphasis> multiplication of heavy metals hyperaccumulator <Emphasis Type="Italic">Thlaspi caerulescens</Emphasis>

A micropropagation protocol through multiple shoot formation was developed for Thlaspi caerulescens L., one of the most important heavy metals hyperaccumulator plants. In vitro seed-derived young seedlings were used for the initiation of multiple shoots on Murashige and Skoog (MS) medium with combinations of benzylaminopurine (BA; 0.5–1.0 mg dm⁻³), naphthaleneacetic acid (NAA; 0–0.2 mg dm⁻³), gibberellic acid (GA₃; 0–1.0 mg dm⁻³) and riboflavin (0–3.0 mg dm⁻³). The maximum number of shoots was developed on medium containing 1.0 mg dm⁻³ BA and 0.2 mg dm⁻³ NAA. GA₃ (0.5 mg dm⁻³) in combination with BA significantly increased shoot length. In view of shoot numbers, shoot length and further rooting rate, the best combination was 1.0 mg dm⁻³ BA + 0.5 mg dm⁻³ GA₃ + 1.0 mg dm⁻³ riboflavin. Well-developed shoots (35–50 mm) were successfully rooted at approximately 95 % on MS medium containing 20 g dm⁻³ sucrose, 8 g dm⁻³ agar and 1.0 mg dm⁻³ indolebutyric acid. Almost all in vitro plantlets survived when transferred to pots.     

Microplankton respiratory activity and CO2 production rates in the Otranto Strait (Mediterranean Sea)

Respiratory activity and metabolic CO₂production of the microplankton in the Otranto Strait (Mediterranean Sea) were determined by monitoring the Electron Transport System activity. Ten stations were repeatedly investigated during two oceanographic surveys in February–March and August 1994. Respiratory activity and CO₂ production, estimated from the surface to the bottom, were higher in the euphotic layers (0-200 m) during summer (mean values: Winter = 0.024 μg C h⁻¹ dm⁻³; Summer = 0.042 μg C h⁻¹ dm⁻³); in the aphotic zone (deeper than 200 m), the rates were similar throughout different seasons (0.013 and 0.014 μg C h⁻¹ dm⁻³, respectively). A comparison with data collected by other authors from the euphotic layers of the Mediterranean Sea was made. Respiratory activities decreased from Western to Eastern Mediterranean Basins. The values of CO₂ production, integrated between 200 and 1000 m in the Otranto Strait (mean value 237.7 mg C m⁻² d⁻¹), were compared with other data collected from the Mediterranean Sea as well as from the Pacific, Atlantic and Indian Oceans. The comparison showed the Otranto Strait to be a site of organic matter oxidation. This revised version was published online in August 2006 with corrections to the Cover Date.     

Physical and chemical limnology of a wind-swept tropical highland reservoir

Valle de Bravo (VB) is a tropical reservoir located (19°21′30″ N, 100°11′00″ W) in the highlands of Mexico. The reservoir is daily swept by strong (7.4 m s⁻¹ mean speed) diurnal (12:00–19:00 h) winds that blow along its two main arms. As expected from its fetch (6.9 km) and its depth (21.1 m mean), the reservoir behaves as a warm monomictic water body. During 2001, VB was stratified from February to October, and well mixed from November to January. Its mean temperature was 19.9°C; the maximum found was 23.8°C in the epilimnion, while a minimum of 17.8°C was registered during mixing. VB exhibited a thermal regime similar to other water bodies of the Mexican tropical highlands, except for a steady increase of its hypolimnetic temperature during stratification, which is attributed to entrainment of epilimnetic water into the hypolimnion. During stratification, the hypolimnion was anoxic, while the whole water column remained under-saturated (60%) during mixing. The flushing time is 2.2 years. Mineralization and total alkalinity are low, which allows strong changes in pH. Ammonia remained low (2.4 μmol l⁻¹ mean) in the epilimnion, but reached up to 60 μmol l⁻¹ in the hypolimnion. Soluble reactive phosphorous had a mean of 0.28 μmol l⁻¹ in the epilimnion and a mean of 1.25 μmol l⁻¹ in the hypolimnion. Nitrate exhibited maxima (up to 21 μmol l⁻¹) during mixing, and also in the metalimnion (2 μmol l⁻¹) during stratification. Low dissolved inorganic nitrogen indicated nitrogen limitation during stratification. Eutrophication is an emerging problem in VB, where cyanobacteria dominate during stratification. At VB chlorophyll a is low during mixing (mean of 9 μg l⁻¹), and high during stratification (mean 21 μg l⁻¹), when blooms (up to 88 μg l⁻¹) are frequent. This pattern is similar to that found in other eutrophic tropical water bodies. We propose that in VB the wind regime causes vertical displacements of the thermocline (0.58–1.10 m hr⁻¹) and boundary mixing, enhancing the productivity during the stratification period in this tropical reservoir.     

Extracellular Matrix in Early Stages of Direct Somatic Embryogenesis in Leaves of Drosera spathulata

The growth and water relations of Paulownia fortunei in photoautotrophic cultures (nutrient medium lacking sucrose and growth regulator) with CO₂ enrichment (PWAH) or without CO₂ enrichment (PWAL) were compared with those in photomixotrophic shoot (PWC; 30 g dm⁻³ sucrose and 0.3 mg dm⁻³ N⁶-benzyladenine) and root cultures (PWR; 0.3 mg dm⁻³ indole-3-butyric acid). The photoautotrophic and photomixotrophic cultures were incubated under photosynthetic photon flux 125 and 60 μmol m⁻² s⁻¹, respectively. 100 % sprouting and significantly higher number of shoots (1.6) were obtained with PWAH as compared to PWAL and PWC. PWAH and PWAL stimulated spontaneous rooting from the cut end of axillary shoots. In PWAH, 84 % of shoots rooted with an average of 5.9 roots per shoot and 4.0 cm of root length in 21 d. Rooting of photomixotrophic shoot cultures were stimulated by an auxin treatment. In this case, 98.3 % of shoots were rooted with an average of 4.6 roots per shoot and 1.9 cm length. A microscopic observation on leaf abaxial surface prints from photomixotrophic shoot and root cultures showed widely open (6 – 8 μm) spherical stomata (12 – 14 μm) and from photoautotrophic cultures elliptical stomata (10 – 12 μm) with narrow openings (3 – 4 μm). Leaves from photomixo-trophic cultures had higher stomatal index as compared to photoautotrophic cultures. The rate of moisture loss from detached leaves was not varying significantly in different cultures. This revised version was published online in July 2006 with corrections to the Cover Date.     

The geochemistry of methane in Lake Fryxell,an amictic,permanently ice-covered,antarctic lake

The abundance and distribution of dissolved CH₄ were determined from 1987–1990 in Lake Fryxell, Antarctica, an amictic, permanently ice-covered lake in which solute movement is controlled by diffusion. CH₄ concentrations were < 1 υM in the upper oxic waters, but increased below the oxycline to 936 μM at 18 m. Sediment CH₄ was 1100 μmol (1 sed)⁻¹ in the 0–5 cm zone. Upward flux from the sediment was the source of the CH₄, NH₄ ⁺, and DOC in the water column; CH₄ was 27% of the DOC+CH₄ carbon at 18 m. Incubations with surficial sediments indicated that H¹⁴CO₃ ⁻ reduction was 0.4 μmol (1 sed)⁻¹ day⁻¹ or 4× the rate of acetate fermentation to CH₄. There was no measurable CH₄ production in the water column. However, depth profiles of CH₄, NH₄, and DIC normalized to bottom water concentrations demonstrated that a significant CH₄ sink was evident in the anoxic, sulfate-containing zone of the water column (10–18 m). The δ¹³CH₄ in this zone decreased from −72 % at 18 m to −76% at 12 m, indicating that the consumption mechanism did not result in an isotopic enrichment of ¹³CH₄. In contrast, δ¹³CH₄ increased to −55 % at 9 m due to aerobic oxidation, though this was a minor aspect of the CH₄ cycle. The water column CH₄ profile was modeled by coupling diffusive flux with a first order consumption term; the best-fit rate constant for anaerobic CH₄ consumption was 0.012 yr⁻¹. On a total carbon basis, CH₄ consumption in the anoxic water column exerted a major effect on the flux of carbonaceous material from the underlying sediments and serves to exemplify the importance of CH₄ to carbon cycling in Lake Fryxell.     

High efficiency organogenesis and analysis of genetic stability of the regenerants in <Emphasis Type="Italic">Solanum melongena</Emphasis>

A novel protocol for plant regeneration from cotyledon explants of eggplant (Solanum melongena) reducing concentration of sucrose was established. The most efficient bud induction medium consisted of Murashige and Skoog (MS) medium supplemented with 2.0 mg dm⁻³ zeatin, 0.1 mg dm⁻³ indoleacetic acid and 10 g dm⁻³ sucrose. After 15 d, the shoot buds were fragmented and transferred to the shoot elongation MS supplemented with 1.0–2.0 mg dm⁻³ gibberellic acid and 4.0–8.0 mg dm⁻³ AgNO₃, which promoted shoots elongation. The genetic stability of the regenerated plants was analyzed by flow cytometry, RAPD and SSR molecular markers. The results indicated that almost no somaclonal variation was detected among the regenerants.     

Promotion of direct somatic embryogenesis of <Emphasis Type="Italic">Oncidium</Emphasis> by adjusting carbon sources

To further optimize a culture medium for induction of direct embryo formation of Oncidium cvs. Gower Ramsey and Sweet Sugar, five kinds of carbon sources, cellibiose, fructose, glucose, maltose and sucrose at 10, 20, 30 and 60 g dm⁻³ were tested in this study. Cellibiose supply had an inhibitory effect and resulted in high percentage of explant browning in both cultivars. By contrast, fructose, glucose and sucrose were all effective for direct embryo induction. In cv. Gower Ramsey, the suitable ranges of concentration were found at 30–60 g dm⁻³ of sucrose, 10–20 g dm⁻³ of glucose and 20–30 g dm⁻³ of fructose, respectively. The suitable ranges for cv. Sweet Sugar were at 20–60 g dm⁻³ of sucrose, 10–30 g dm⁻³ of glucose, 10–20 g dm⁻³ of fructose and 30–60 g dm⁻³ of maltose, respectively. The highest amount of embryos was obtained at 30 g dm⁻³ of sucrose for cv. Gower Ramsey and at 20 g dm⁻³ of glucose for cv. Sweet Sugar.     

An efficient in vitro propagation of Aristolochia indica

A rapid and efficient in vitro plant regeneration method was developed for Aristolochia indica. Multiple shoot formation was induced from shoot tip and nodal explants on Murashige and Skoog (MS) medium with 1 – 6 mg dm⁻³ 2-isopentenyl-adenine (2-iP) or 1 – 4 mg dm⁻³ 6-benzyladenine (BA). Maximum number of shoots were induced with 5 mg dm⁻³ 2-iP alone (about 12 – 14 shoots). Shoot differentiation occurred directly from the leaf bases as well as from the internodes when cultured on 1 – 4 mg dm⁻³ BA and 0.8 – 2 mg dm⁻³ α-naphthaleneacetic acid (NAA) containing medium. Regeneration from the callus occurred when the calli initiated on MS medium containing 0.6 – 4 mg dm⁻³ NAA in combination with 0.8 – 3 mg dm⁻³ BA were transferred to 1 – 6 mg dm⁻³ BA alone containing medium. Elongated shoots were separated and rooted in MS medium containing 1 mg dm⁻³ indole-3-butyric acid. These were then transferred to soil after gradual acclimatization.     

Spatial and Temporal Variability in Sediment Denitrification Within an Agriculturally Influenced Reservoir

Reservoirs are intrinsically linked to the rivers that feed them, creating a river–reservoir continuum in which water and sediment inputs are a function of the surrounding watershed land use. We examined the spatial and temporal variability of sediment denitrification rates by sampling longitudinally along an agriculturally influenced river–reservoir continuum monthly for 13 months. Sediment denitrification rates ranged from 0 to 63 μg N₂O g ash free dry mass of sediments (AFDM)⁻¹ h⁻¹ or 0–2.7 μg N₂O g dry mass of sediments (DM)⁻¹ h⁻¹ at reservoir sites, vs. 0–12 μg N₂O gAFDM⁻¹ h⁻¹ or 0–0.27 μg N₂O gDM⁻¹ h⁻¹ at riverine sites. Temporally, highest denitrification activity traveled through the reservoir from upper reservoir sites to the dam, following the load of high nitrate (NO₃⁻-N) water associated with spring runoff. Annual mean sediment denitrification rates at different reservoir sites were consistently higher than at riverine sites, yet significant relationships among theses sites differed when denitrification rates were expressed per gDM vs. per gAFDM. There was a significant positive relationship between sediment denitrification rates and NO₃⁻-N concentration up to a threshold of 0.88 mg NO₃⁻ -N l⁻¹, above which it appeared NO₃⁻-N was no longer limiting. Denitrification assays were amended seasonally with NO₃⁻-N and an organic carbon source (glucose) to determine nutrient limitation of sediment denitrification. While organic carbon never limited sediment denitrification, all sites were significantly limited by NO₃⁻-N during fall and winter when ambient NO ₃⁻-N was low.     

Micropropagation of <Emphasis Type="Italic">Zingiber rubens</Emphasis> and assessment of genetic stability through RAPD and ISSR markers

Protocol was developed for high frequency in vitro multiplication of an endemic species, Zingiber rubens Roxb. The sprouted buds of the rhizomes were cultured on Murashige and Skoog (MS) medium supplemented with 6-benzyladenine (BA; 0.5–5.0 mg dm⁻³), indole-3-acetic acid (IAA; 0.5–2.0 mg dm⁻³), kinetin (KIN; 1.0–3.0 mg dm⁻³), naphthaleneacetic acid (NAA; 0.5–1.0 mg dm⁻³) and adenine sulphate (ADS; 80–100 mg dm⁻³). MS basal medium supplemented with 3 mg dm⁻³ BA and 0.5 mg dm⁻³ IAA was optimum for shoot elongation. The elongated shoots (1–2 cm) were transferred to multiplication medium containing 2 mg dm⁻³ BA, 1 mg dm⁻³ IAA and 100 mg dm⁻³ ADS. The multiplication rate remained unchanged in subsequent subcultures. Upon ex vitro transfer, 85 % of plants survived. Genetic stability of micropropagated clones were periodically evaluated at an interval of 6 months up to 30 months in culture using random amplified polymorphic DNA (RAPD) and inter simple sequence repeat (ISSR) analysis and genetic uniformity in all regenerants was confirmed.     

Methane-Oxidizing Bacteria in a Finnish Raised Mire Complex: Effects of Site Fertility and Drainage

Methane-oxidizing bacteria (MOB) are the only biological sinks for methane (CH₄). Drainage of peatlands is known to decrease overall CH₄ emission, but the effect on MOB is unknown. The objective of this work was to characterize the MOB community and activity in two ecohydrologically different pristine peatland ecosystems, a fen and a bog, and their counterparts that were drained in 1961. Oligotrophic fens are groundwater-fed peatlands, but ombrotrophic bogs receive additional water and nutrients only from rainwater. The sites were sampled in August 2003 down to 10 cm below the water table (WT), and cores were divided into 10-cm subsamples. CH₄ oxidation was measured by gas chromatography (GC) to characterize MOB activity. The MOB community structure was characterized by polymerase chain reaction–denaturing gradient gel electrophoresis (DGGE) and sequencing methods using partial pmoA and mmoX genes. The highest CH₄ oxidation rates were measured from the subsamples 20–30 and 30–40 cm above WT at the pristine oligotrophic fen (12.7 and 10.5 μmol CH₄ dm⁻³ h⁻¹, respectively), but the rates decreased to almost zero in the vicinity of WT. In the pristine ombrotrophic bog, the highest oxidation rate at 0–10 cm was lower than in the fen (8.10 μmol CH₄ dm⁻³ h⁻¹), but in contrast to the fen, oxidation rates of 4.5 μmol CH₄ dm⁻³ h⁻¹ were observed at WT and 10 cm below WT. Drainage reduced the CH₄ oxidation rates to maximum values of 1.67 and 5.77 μmol CH₄ dm⁻³ h⁻¹ at 30–40 and 20–30 cm of the fen and bog site, respectively. From the total of 13 pmoA-derived DGGE bands found in the study, 11, 3, 6, and 2 were observed in the pristine fen and bog and their drained counterparts, respectively. According to the nonmetric multidimensional scaling of the DGGE banding pattern, the MOB community of the pristine fen differed from the other sites. The majority of partial pmoA sequences belonged to type I MOB, whereas the partial mmoX bands that were observed only in the bog sites formed a distinct group relating more to type II MOB. This study indicates that fen and bog ecosystems differ in MOB activity and community structure, and both these factors are affected by drainage.     

Artificial destratification of a small tropical reservoir: effects upon the phytoplankton

Seasonal changes in the phytoplankton community of a small tropical reservoir were monitored over a four year period comprising of an initial two seasonal cycles during which the water column stratified strongly for extended periods each year, and two further seasonal cycles after installation of a mechanical aeration system to induce artificial destratification. In the unmanaged reservoir, the concentration of chlorophyll a at 0.5 m reached maximum values (on one occasion > 90 mg m⁻³) when the water column was stratified and the epilimnion was very shallow (ca 2 m depth). The hypolimnion at this time was anoxic (less than 2% oxygen saturation) and had a high concentration of bacteriochlorophyll (100–200 mg m⁻³). The phytoplankton community of the unmanaged reservoir was generally dominated by cyanobacteria (Cylindrospermopsis raciborskii, Anabaena tenericaulis) during the warmer months of the year (November–March) (but replaced by chlorophyta, dinophyceae and euglenophyceae after periods of intense rain) and by bacillariophyceae (Synedra ulna var. chaseana, S. tenera) during the cooler, dry months. In the artificially destratified reservoir (8 h aeration day⁻¹), the phytoplankton community was largely dominated by diatoms except after depletion of the silica content of the water column which caused diatoms to be replaced by cyanobacteria (dominated by A. tenericaulis) and a range of chlorophytes. The changing pattern of stratification and circulation of the water column in the unmanaged reservoir caused repeated disruption of the established phytoplankton assemblage with peaks of high biomass associated with transient cyanobacterial blooms. Continuous aeration and the consequent increase in the ratio mixed: euphotic depth provided conditions suitable for dominance of the phytoplankton by diatoms, as long as silica was available, and resulted in average chlorophyll levels higher than in the unmanaged reservoir (120 ± 10 v. 64 ± 9 mg m⁻²). Hierarchical fusion analysis based on the biomass of species differentiated the phytoplankton samples into cluster groups that could be related primarily to stratification or mixing of the water column.     

Plant regeneration from shoot apical meristems of Melia azedarach L. (Meliaceae)

A protocol was developed for plant regeneration of Melia azedarach L. by in vitro culture of apical meristem (0.5 mm in length). The influence of six clones was investigated. The culture procedure comprised two sequential steps: 1) Induction of shoots by in vitro culture of axillary buds from adult trees (10–15 years old) by culture on Murashige and Skoog (1962) medium (MS) supplemented with 0.5 mg·dm⁻³ BAP (6-benzylaminopurine), 0.1 mg·dm⁻³ IBA (indolebutyric acid), and 0.1 mg·dm⁻³ GA₃ (gibberellic acid). The Multiplication of the regenerated shoots was achieved in MS + 0.5 mg·dm⁻³ BAP + 0.1 mg·dm⁻³ GA₃. 2) In vitro culture of the apical meristems from the regenerated shoots in MS medium (0.7 %) supplemented with various combinations of BAP and IBA. Maximum shoot proliferation was obtained on MS medium supplemented with 0.5 mg·dm⁻³ BAP and 0.1 mg·dm⁻³ IBA. Regenerated shoots were rooted on MS + 3.5 mg·dm⁻³ IBA (4 days) followed by subculture on MS lacking growth regulators (30 days). Complete plants were transferred to soil.     

Somatic Embryogenesis, Plantlet Regeneration and Micropropagation of Cultivars and F1 Hybrids of Manihot esculenta

Explants of four F₁ hybrids (OMR 36-41/1, OMR 36-41/2, OMR 36-41/4 and OMR 36-41/5) and two cultivars (Rayong 1 and Rayong 60) of cassava (Manihot esculenta Crantz) were subjected to different combinations of 2,4-dichlorophenoxyacetic acid (2,4-D), 1-naphthaleneacetic acid (NAA), kinetin (KIN) and N⁶-benzylaminopurine (BAP) to induce somatic embryogenesis, organogenesis and micropropagation. Shoot apices of the F₁ hybrids exhibited higher frequency (62 – 74 %) of proliferation of somatic embryos than the cultivars (21 – 43 %) in Murashige and Skoog basal medium supplemented with 8 mg dm⁻³ 2,4-D and 0.5 mg dm⁻³ NAA. Nodal explants of regenerated plantlets were rapidly micropropagated with 90 % efficiency on a medium containing 0.1 mg dm⁻³ NAA and 0.05 mg dm⁻³ BAP irrespective of explant source. This revised version was published online in July 2006 with corrections to the Cover Date.     

Distribution of iron in Lake Banyoles in relation to the ecology of purple and green sulfur bacteria

The distribution of iron both in suspended sediment and in the water column has been studied during summer stratification in Lake Banyoles. In this lake, near bottom springs, a very fine material suspended sediment remains in suspension. Dissolved Fe²⁺ in interstitial water of this suspended sediment, is related to redox potential and to the bottom water inflow. In the water column, soluble iron is present in the hypolimnion of the six different basins forming Lake Banyoles. Under those conditions Fe²⁺ is partially removed by sulfide produced in the anoxic sediment. In addition, a peak of Fe²⁺ found at the density gradient level in basins C-III, C-IV and C-VI. A three compartment model on the dynamics of the processes involving iron in Lake Banyoles is proposed. The bottom springs supply oxygen to the anoxic hypolimnion affecting chemical processes of the iron cycle. The presence of phototrophic sulfur bacteria in the anoxic monimolimnion of basins C-III and C-IV can be related to the kinetics of Fe²⁺ and sulfide. In C-III sulfide concentration exceeds Fe²⁺ concentration whereas in C-IV sulfide is not detectable and iron reached values up to 60 mM. The presence of phototrophic sulfur bacteria in iron-containing environments with no detectable sulfide is explained by the ability of such microorganisms to use FeS as electron donor instead of H₂S.     

In vitro clonal propagation of Nyctanthes arbor-tristis

Rapid shoot multiplication of Nyctanthes arbor-tristis L. was achieved from axillary meristems on Murashige and Skoog (MS) basal medium supplemented with 1.0–1.5 mg dm⁻³ 6-benzylaminopurine (BA), 50 mg dm⁻³ adenine sulfate (Ads) and 3 % (m/v) sucrose. Inclusion of indole-3-acetic acid (IAA) in the culture medium along with BA + Ads promoted a higher rate of shoot multiplication. Maximum mean number of microshoots per explant (6.65) was achieved on the MS medium supplemented with 1.5 mg dm⁻³ BA, 50 mg dm⁻³ Ads and 0.1 mg dm⁻³ IAA after 4 weeks of culture. The elongated shoots rooted within 13 to 14 d on half-strength MS medium supplemented with either indole-3-butyric acid (IBA), IAA or 1-naphthaleneacetic acid (NAA) with 2 % sucrose. Maximum percentage of rooting was obtained on medium having 0.25 mg dm⁻³ IBA and 0.1 mg dm⁻³ IAA. About 70 % of the rooted plantlets survived in the greenhouse. The in vitro raised plants were grown normally in the field.     

Effect of jasmonic acid on in vitro explant growth and microtuberization in potato

The shoot fresh mass, root length and root numbers of two potato (Solanum tuberosum L.) cultivars Favorita and Helanwuhua were increased significantly by the application of 0.2 – 2 mg dm⁻³ jasmonic acid (JA) in the Murashige and Skoog medium. However, the growth of potato explants was inhibited by JA at high concentrations (20 – 50 mg dm⁻³). Chlorophyll content in explant leaves decreased with an increase in the concentration of JA. In leaves treated with 0.2 mg dm⁻³ JA acid peroxidase activity increased, while in the leaves treated with more than 2 mg dm⁻³ JA peroxidase activity decreased. Under the dark, the microtuber numbers, fresh mass and percentage of big microtubers of two potato cultivars were not promoted by the application of 0.2 – 50 mg dm⁻³ JA.     

Effect of carbon dioxide on cell growth and saponin production in suspension cultures of Panax ginseng

The effects of carbon dioxide supply within the range of 1–5 % (along with purified air), on cell culture of Panax ginseng were investigated in a balloon type bubble bioreactor containing 4 dm³ of Murashige and Skoog (MS) medium supplemented with 7.0 mg dm⁻³ indolebutyric acid, 0.5 mg dm⁻³ kinetin and 30 g dm⁻³ sucrose. A 1 % CO₂ supply was found beneficial for the production of cell mass; however, increasing CO₂ concentration to 2.5 and 5 % decreased the biomass accumulation. CO₂ enrichment was not beneficial for saponin production and 1, 2.5, and 5 % CO₂ supply resulted in decrease in saponin accumulation up to 11.6, 19.5, and 50.6 %, respectively.     

The role of suspended matter in the distribution of dissolved inorganic phosphate,iron and aluminium in the Ems estuary

In winter 1992/1993, a persistent local maximum in fluorescence, dissolved iron, dissolved aluminium and dissolved inorganic phosphate was found, upstream of the turbidity maximum in the freshwater zone of the Ems estuary (The Netherlands — Federal Republic Germany; western Europe). Upstream of this local maximum values ranged from 6 to 9 rel. units fluorescence, 0.9 to 2.4 μmol dm⁻³ iron, 0.5 to 0.7 μmol dm⁻³ aluminium and 0.6 to 2.3 μmol dm⁻³ dissolved inorganic phosphate. Within the maximum peak values of 24 rel. units fluorescence, 5.8 μmol dm⁻³ iron, 1.4 μmol dm⁻³ aluminium and 8.3 μmol dm⁻³ dissolved inorganic phosphate were observed. Downstream, fluorescence (indicator of dissolved organic carbon) showed conservative mixing with sea water, whereas dissolved iron, aluminium and dissolved inorganic phosphate did not. Dissolved aluminium and iron were quickly removed from solution to reach values of ∼100 nmol dm⁻³ aluminium and ∼0.3 μmol·dm⁻³ Fe at salinities of approximately 7 PSU. Further seaward iron concentrations gradually decreased to levels below 0.04 μmol dm⁻³. Dissolved aluminium first decreased to ∼20 nmol dm⁻³ at 29 PSU and increased again to concentrations of 30–44 nmol dm⁻³ at higher salinities. Dissolved inorganic phosphate, however, first decreased to upstream concentrations before reaching a secondary peak in the mid-estuarine reaches. At salinities >25 PSU dissolved inorganic phosphate mixed conservatively with sea water. It is hypothesized that adsorption-desorption equilibria are responsible for the local maximum values of fluorescence (DOC), iron, aluminium and dissolved inorganic phosphate. The similarity between the observed curves suggests a common underlying process, possibly related to the adjustment of new equilibria between suspended matter of marine and riverine origin.