Regulation of Sorus Formation by Auxin in Laminariales Sporophyte

Young sporophytes of Laminaria japonica Areshoug were cultured in six indole-acetic acid (IAA) concentrations (0, 10⁻⁸, 10⁻⁷, 10⁻⁶, 10⁻⁵, 10⁻⁴ M) to examine the effect of auxin on growth. The effects of auxin on sorus formation were also examined by using discs taken from the adult sporophyte. The auxin contents and IAA oxidase activities in the thallus and sorus parts of the sporophyte were determined with the blade and sporophyll of other Laminariales plants, Undaria pinnatifida (Harvey) Suringar and Alaria crassifolia Kjellman. The young sporophytes of L. japonica showed highest elongation rate in 10⁻⁵ M IAA. In contrast, the sorus formation on the discs cultured in 10⁻⁵ M IAA was markedly delayed in comparison with other concentrations, indicating that sorus formation was suppressed by IAA. Free and conjugated auxin contents were lower in the reproductive parts than in the vegetative parts. In three Laminariales sporophytes, IAA oxidase activity was about 3–9 times higher in the reproductive parts than in the vegetative parts. Taken together these results suggest that the growth and reproduction of Laminariales sporophytes are regulated by internal auxin levels. Elucidating the regulation mechanism is likely to provide information that is important for the management of plant production and the assessment of the physiological status of plants in the field.     

Contribution of fern gametophytes to the growth of produced sporophytes on the basis of carbon gain

Sporophytes appeared on most gametophytes of Thelypteris palustris (Salisb.) Schott that reached a certain size, which is interpreted to be a critical size of gametophytes for the production of sporophytes. After sporophytes were produced, attached gametophytes ceased dry weight growth, but the gametophytes which did not produce sporophytes grew successively. It was hypothesized that matter produced by gametophytes was being supplied to young sporophytes. Photosynthesis and respiration of gametophytes with attached sporophytes were not significantly different from that of gametophytes without sporophytes. Photosynthetic activity of gametophytes dropped from 0.18 to 0.03 mol CO₂ g^–1 s^–1 during the growth period. The higher photosynthetic rates of gametophytes in the early growth stage were important for reaching the critical size for sporophyte production in a short time. Sporophytes in the one leaf stage averaged 0.14 mol CO₂ g^–1 s^–1 of photosynthetic activity. The results show that sporophytes that had expanded the first leaf grow by their own photosynthetic production. Gametophytes allocated the photosynthate for sporophytes and it was an important aid before the one-leaf stage. The supportive role of gametophytes ended at that stage.     

Changes in Abscisic Acid During Leaf Yellowing of Cut Stock Flowers

Leaf pigments, such as chlorophyll and carotenoids, are essential plant molecules. They provide carbohydrates and energy during all plant life. Leaf pigments are also important parameters of decorative plants, such as floriculture items, cut foliage and flowers. Leaf yellowing is a form of senescence caused by an internal hormone imbalance, such as a lack of cytokinins. The aim of this study was to investigate the changes in total carotenoids and endogenous ABA in cut flower stock leaves during post-harvest life. The effect of pulse treatment with 5 or 10 M thidiazuron (TDZ), 150 mg l^–1 8-hydroxyquinoline sulphate (8-HQS) and combinations of TDZ with 8-HQS on total carotenoids and ABA concentration was also investigated. Results showed that total carotenoids drastically decreased from 1548 g cm^–2, until reaching 565 g cm_–2 at the end of vase life. Endogenous ABA strongly increased at the same time, going from 167 ng g^–1 DW at the beginning of the experiment to 1322 ng g^–1 DW at the end of vase life. The TDZ inhibited carotenoid degradation, but did not affect the ABA concentration, while the 8-HQS did not prevent carotenoid degradation and the ABA concentration was only slightly affected. ABA seems to be a secondary senescence bio-product that may have a synergic effect with other senescence inducers dramatically accelerating leaf senescence.     

An abscisic acid analog inhibits abscisic acid-induced freezing tolerance and protein accumulation, but not abscisic acid-induced sucrose uptake in a bromegrass (Bromus inermis Leyss) cell culture

The application of abscisic acid (ABA), either as a racemic mixture or as optically resolved isomers, increases freezing tolerance in a bromegrass (Bromus inermis Leyss) cell culture and induces the accumulation of several heat-stable proteins. Two stereoisomers of an ABA analog, 23 dihydroacetylenic abscisyl alcohol (DHA), were used to study the role of ABA-induced processes in the acquisition of freezing tolerance in these cells. Freezing tolerance was unchanged in the presence of (–) DHA (LT₅₀ -9°C), and no increase in heat-stable protein accumulation was detected; however, the (+) enantiomer increased the freezing tolerance (LT₅₀ -13°C) and induced the accumulation of these polypeptides. All three forms of ABA increased freezing tolerance in the bromegrass cells, although (–) ABA was less effective than either (+) or (±) ABA when added at equal concentrations. Cells pretreated with 20 or 50 M (–) DHA displayed lower levels of freezing tolerance following the addition of 2.5, 7.5 or 25 M (±) ABA. Full freezing tolerance could be restored by increasing the concentration of (±) ABA to > 25 M. Pretreatment of cells with (–) DHA (20 or 50 M) had no effect on freezing tolerance when 25 M (+) ABA was added. The induction of freezing tolerance by 25 M (–) ABA was completely inhibited by the presence of 20 M (–) DHA. The accumulation of ABA-responsive heat-stable proteins was inhibited by pretreatment with 20 M (–) DHA in cells treated with 2.5 or 7.5M (+) ABA, and in cells treated with 25 M (–) ABA. The accumulation of these polypeptides was restored when (±) or (+) ABA was added at a concentration of 25 M. The analysis of proteins which cross-reacted with a dehydrin antibody revealed a similar inhibitory pattern as seen with the other ABA-responsive proteins. The effects of the various isomers of ABA and DHA on cell osmolarity and sucrose uptake was also investigated. In both cases, (±) and (+) ABA had pronounced effects on the parameters measured, whereas (–) ABA treated cells gave substantially different results. In both sucrose uptake and cell osmolarity, DHA had no significant effect on the results obtained following (±) or (+) ABA treatment. Maximum freezing tolerance was only observed in cells when both heat-stable protein accumulation and sucrose uptake were observed.Abbreviations ABA abscisic acid - DHA 2,3 dihydroacetylenicabscisyl alcohols - DMSO dimethyl sulfoxide - LT₅₀ temperature at which 50% of cells are killed The authors would like to acknowledge the technical assistance of Angela Bollman, Bruce Ewan and Angela Shaw. This work was supported by grants from the Natural Science and Engineering Research Council of Canada to L.V.G. and N.H.L., and a grant from the University of Saskatchewan to R.W.W.     

Anthraquinones production,hydrogen peroxide level and antioxidant vitamins in Morinda elliptica cell suspension cultures from intermediary and production medium strategies

The effects of medium strategies [maintenance (M), intermediary (G), and production (P) medium] on cell growth, anthraquinone (AQ) production, hydrogen peroxide (H₂O₂) level, lipid peroxidation, and antioxidant vitamins in Morinda elliptica cell suspension cultures were investigated. These were compared with third-stage leaf and 1-month-old callus culture. With P medium strategy, cell growth at 49 g l^–1, intracellular AQ content at 42 mg g^–1 DW, and H₂O₂ level at 9 mol g^–1 FW medium were the highest as compared to the others. However, the extent of lipid peroxidation at 40.4 nmol g^–1 FW and total carotenoids at 13.3 mg g^–1 FW for cultures in P medium were comparable to that in the leaf, which had registered sevenfold lower AQ and 2.2-fold lower H₂O₂ levels. Vitamin C content at 30–120 g g^–1 FW in all culture systems was almost half the leaf content. On the other hand, vitamin E content was around 400–500 g g^–1 FW in 7-day-old cultures from all medium strategies and reduced to 50–150 g g^–1 FW on day 14 and 21; as compared to 60 g g^–1 FW in callus and 200 g g^–1 FW in the leaf. This study suggests that medium strategies and cell growth phase in cell culture could influence the competition between primary and secondary metabolism, oxidative stresses and antioxidative measures. When compared with the leaf metabolism, these activities are dynamic depending on the types and availability of antioxidants.Abbreviations AQ Anthraquinone - DW Dry cell weight - FW Fresh cell weight - G Intermediary medium - M Maintenance medium - MDA Malondialdehyde - P Production medium - ROS Reactive oxygen species - TBA Thiobarbituric acid - t_d Doubling time     

[3H]Histamine uptake and release by astrocytes from rat brain: Effects of sodium deprivation,high potassium,and potassium channel blockers

Histamine transport has been characterized in cultured astroglial cells of rat brain. The kinetics of [³H]-histamine uptake yielded a K_m of 0.19±0.03 M and a V_max of 3.12±0.75 pmol×mg protein^–1×min^–1. Transport system revealed high affinity for histamine and an approximately ten times higher capacity than that shown in cultured glial cells of chick embryonic brain. Ouabain which interferes with utilization of ATP to generate ion gradients, and the replacement of Na⁺ with choline inhibited the initial rate of uptake showing a strong Na⁺-dependency and suggesting the presence of a tightly coupled sodium/histamine symporter. Dissipation of K⁺-gradient (in>out) by high K⁺ or by K⁺-channel blockers, BaCl₂, (100 M), quinine (100 M) or Sparteine (20 M) produced also remarkable inhibitions in the uptake of [³H]-histamine. Impromidine, a structural histamine-analogue could inhibit the uptake non-competitively in a range of concentrations of 1 to 10 M with a K_i value of 2.8 M, indicating the specificity of the uptake. [³H]histamine uptake measurements carried out by using a suspension of dissociated hypothalamic cells, of rat brain showed a strong gliotoxin-sensitivity and yielded a Km of 0.33±0.08 M; and a V_max of 2.65±0.35 pmoles×mg protein^–1×min^–1. The uptake could be reversed by incubating the cells in histamine-free Krebs medium. The [³H]histamine efflux was sensitive to Na⁺ omission, ouabain treatment and high K⁺ or K⁺ channel blockers, resulting in marked elevations in the efflux. Data indicate that glial uptake of histamine is a high affinity, Na⁺-dependent and electrogenic, driven by an inward-oriented sodium ion gradient and an outward-oriented potassium ion gradient and functions as part of histamine inactivation, at least in a shunt mechanism.Abbreviations used HA histamine - [³H]HA [2.5-³H]-histamine - dl--aAA dl-alpha-aminoadipic acid - (Na⁺+K⁺) ATP-ase sodium and potassium activated adenosine triphosphatase - SAH S-Adenosyl-d-Homocysteine - HNMT histamine-N-methyltransferase     

Photosynthetic performance of transplanted ecotypes ofEcklonia cava(Laminariales, Phaeophyta)

Young sporophytes of short-stipe ecotype ofEcklonia cavafrom a warmer locality (Tei, Kochi Pref., southern Japan) and those of long-stipe ecotype from a cooler locality (Nabeta, Shizuoka Pref., central Japan) were transplanted in 1995 to artificial reefs immersed at the habitat of long-stipe ecotype in Nabeta Bay, Shizuoka Pref., central Japan. The characteristics of photosynthesis and respiration of bladelets of the transplanted sporophytes of the two ecotypes were compared in winter and summer 1997; the results were assessed per unit area, per unit chlorophyllacontent and per unit dry weight. In photosynthesis-light curves at 10–29 °C, light saturation occurred at 200–400 mol photon m^–2s^–1in sporophytes from both Tei and Nabeta. The maximum photosynthetic rate (P _max) at 10–29 °C and the light-saturation index (I _k) at 25–29 °C in sporophytes from both localities were generally higher in winter than in summer.P _maxat 25–29 °C (per unit area and chlorophylla) were higher in sporophytes from Tei than those from Nabeta in both seasons. The optimum temperature for photosynthesis was 25 °C in winter and 27 °C in summer at high light intensities of 100–400 mol photon m^–2s^–1. However, at lower light intensities of 12.5–50 mol photon m^–2s^–1, it was 20 °C in winter and 25–27 °C in summer for sporophytes from both locations. Dark respiration increased with temperature rise in the range of 10–29 °C in sporophytes from both locations in summer and winter. The sporophytes transplanted from Tei (warmer area) showed higher photosynthetic activities than those from Nabeta (cooler area) at warmer temperatures even under the same environmental conditions. This indicates that these physiological ecotypes have arisen from genetic differentiation.     

Factors affecting in vitro microrhizome production in turmeric

In vitro microrhizome production was obtained in turmeric (Curcuma longa Linn.). Freshly sprouted buds with small rhizome portions excised from stored mature rhizomes were cultured on semi-solid culture initiation medium –- MS basal medium + 0.88 M BAP (6-benzylaminopurine) + 0.92 M kinetin + 5% coconut water + 2% sucrose + 0.5% agar –- resulting in bud elongation. Multiple shoots were produced from these elongated buds by culturing in liquid shoot multiplication medium –- MS basal medium + 2.2 M BAP + 0.92 M kinetin + 5% coconut water + 2% sucrose –- at 25±1°C and 16-h light (at 11.7 mol m^–2 s^–1)/8-h dark cycles. Clumps of four to five multiple shoots/single shoots were used in various experiments. Cultures were incubated in the dark at 25±1°C. Half strength MS basal medium supplemented with 80 g l^–1 sucrose was found to be optimal for microrhizome production. Cytokinin BAP had an inhibitory effect on microrhizome production. At the highest concentration of BAP tried (35.2 M) microrhizome production was totally inhibited. Microrhizome production depended on the size of the multiple shoots used. Microrhizomes produced were of a wide range in size (0.1–2.0 g) and, readily regenerated when isolated and cultured in vitro on culture initiation medium or shoot multiplication medium. Under in vivo conditions, small (0.1–0.4 g), medium (0.41–0.8 g) and big (>0.81 g) microrhizomes regenerated. Plantlets developed from big microrhizomes grew faster.     

The contribution of size-fractionated plankton to biomass and primary production of phytoplankton in saline–alkaline ponds

Primary productivity, biomass and chlorophyll-a of size fractionated phytoplankton (<0.22 m, <3 m, <8 m, <10 m, <40 m, <64 m, <112 m and <200 m) were estimated in 6 ponds and 5 experimental enclosures. The results showed that the planktonic algae less than 10 m are important in the biomass and production of phytoplankton in saline–alkaline ponds. The production of size fractionated phytoplankton corresponding to <112 m, <10 m and <3 m in saline–alkaline ponds were 10.5 ± 6.6 , 8.6 ± 5.4 and 0.33 ± 0.1 mgC l^–1 d^–1, respectively. Mean community respiration rate was 1.80 ± 0.73, 1.69 ± 0.90 and 1.38 ± 1.12 mgC l^–1 d^–1, respectively. The average production of phytoplankton corresponding to micro- (10–112 m), nano- (3–10 m) and pico- (<3 m) were 1.61, 8.30 and 0.33 mgC l^–1 d^–1, respectively. The ratio of those to the total phytoplankton production was 15%, 79% and 3%, respectively. The mean respiration rate of the different size groups was 0.11, 0.31 and 1.38 mgC l^–1 d^–1; the ratio of those to total respiration of phytoplankton was 6%, 17% and 77%, respectively. The production of size-fractionated phytoplankton corresponding to <200 m, <10 m and <3 m in enclosures was 2.19 ± 1.63, 2.08 ± 1.75 and 0.22 ± 0.08 mgC l^–1 d^-1, respectively. Mean community respiration rates were 1.25 ± 1.55, 1.17 ± 1.42 and 0.47 ± 0.32 mgC l^–1 d^–1, respectively. The average production of phytoplankton corresponding to micro- (10–200 m), nano- (3–10 m) and pico- (<3 m) plankton was 0.11, 1.86 and 0.22 mgC l^–1 d^–1, respectively. The ratio of those to the total production of phytoplankton was 5%, 85% and 10%, respectively. The mean respiration rate of different size groups were 0.08, 0.72 and 0.46 mgC l^–1 d^–1, the ratio of those to total respiration of phytoplankton was 6%, 57% and 37%, respectively. The concentrations of chlorophyll-a of the phytoplankton in the corresponding size of micro- (10–112 m), nano- (3–10 m) and pico- (<3 m) plankton in the experimental ponds were 19.3, 98.2 and 11. 9 g l^–1, respectively. The ratio of those to the total chlorophyll-a was 15%, 76% and 9%, respectively. The concentrations of chlorophyll-a of phytoplankton micro- (10–200 m), nano- (3–10 m) and pico- (<3 m) plankton in enclosures were 1.7, 34.3 and 3.0 g l^–1, respectively. The ratio of those to the total chlorophyll-a was 4%, 88% and 8%, respectively.     

High frequency shoot regeneration from leaf explants of muskmelon

Efficient in vitro plant regeneration systems are critical for many purposes including plant transformation. Current regeneration systems for melon (Cucumis melo L.) plants generally utilize cotyledon explants; regeneration from melon leaves has received limited attention. We investigated several factors that influence regeneration from melon leaves including: genotype growth conditions and age of the source plant, leaf age, explant orientation, gelling agent, and the addition of silver nitrate and sulfonylurea herbicide to the culture media. Critical factors that influenced regeneration were preculture conditions of the donor plants, leaf size, and the use of silver nitrate and Phytagel in the medium. The best results were obtained with 3–4 cm diam leaves excised from pot grown greenhouse or growth chamber plants cultured on MS medium with 5 M IAA, 5 M BA, 1 M ABA, 30 M silver nitrate and 2.6 g l^-1 Phytagel. Low concentratons of sulfonylurea herbicide (0.25 mg l^-1 DPX-M 6316) also enhanced regeneration. Under optimized conditions 80–100% of the explants regenerated, with 10–100 shoots per explantAbbreviations ABA abscisic acid - BA benzyladenine - IAA indole-3-acetic acid - MS Murashige and Skoog medium - NAA naphthalene acetic acid     

Momordica charantia fruit juice stimulates glucose and amino acid uptakes in L6 myotubes

The fruit of Momordica charantia (family: Cucurbitacea) is used widely as a hypoglycaemic agent to treat diabetes mellitus (DM). The mechanism of the hypoglycaemic action of M. charantia in vitro is not fully understood. This study investigated the effect of M. charantia juice on either ³H-2-deoxyglucose or N-methyl-amino-a-isobutyric acid (¹⁴C-Me-AIB) uptake in L6 rat muscle cells cultured to the myotube stage. The fresh juice was centrifuged at 5000 rpm and the supernatant lyophilised. L6 myotubes were incubated with either insulin (100 nM), different concentrations (1–10 g ml^–1) of the juice or its chloroform extract or wortmannin (100 nM) over a period of 1–6 h. The results were expressed as pmol min^–1 (mg cell protein)^–1, n= 6–8 for each value. Basal ³H-deoxyglucose and ¹⁴C-Me-AIB uptakes by L6 myotubes after 1 h of incubation were (means ± S.E.M.) 32.14 ± 1.34 and 13.48 ± 1.86 pmol min^–1 (mg cell protein)^–1, respectively. Incubation of L6 myotubes with 100 nM insulin for 1 h resulted in significant (ANOVA, p < 0.05) increases in ³H-deoxyglucose and ¹⁴C-Me-AIB uptakes. Typically, ³H-deoxyglucose and ¹⁴C-Me-AIB uptakes in the presence of insulin were 58.57 ± 4.49 and 29.52 ± 3.41 pmol min^–1 (mg cell protein^–1), respectively. Incubation of L6 myotubes with three different concentrations (1, 5 and 10 g ml^–1) of either the lyophilised juice or its chloroform extract resulted in time-dependent increases in ³H-deoxy-D-glucose and ¹⁴C-Me-AIB uptakes, with maximal uptakes occurring at a concentration of 5 g ml^–1. Incubation of either insulin or the juice in the presence of wortmannin (a phosphatidylinositol 3-kinase inhibitor) resulted in a marked inhibition of ³H-deoxyglucose by L6 myotubes compared to the uptake obtained with either insulin or the juice alone. The results indicate that M. charantia fruit juice acts like insulin to exert its hypoglycaemic effect and moreover, it can stimulate amino acid uptake into skeletal muscle cells just like insulin. (Mol Cell Biochem 261: 99–104, 2004)     

LHRH-receptor-regulated Ca2+-ATPase activity in murine pituitary gland

Addition of luteinizing hormone releasing hormone (LHRH) in vitro (10^–5–5×10^–9 M) to murine pituitary membranes resulted in a dose-related decrease in Ca²⁺-ATPase activity within 15 min. Inhibitory effects of LHRH (10^–7 M) occurred after 90 sec, and appeared maximal by 120 sec. Eadie-Hofstee analysis at 10^–7 M LHRH, at varying [Ca²⁺]_free, resulted in aK _m=0.89±0.06 M and aV _max=18.8±0.71 nmol/mg per 2 min, compared to aK _m=0.69±0.06 M and aV _max=32.8±1.21 nmol/mg per 2 min for controls. Pre-incubation for 5 min with LHRH antagonist (10^–8 M) significantly attenuated (50%) the inhibitory effects of 10^–7 M LHRH on pituitary Ca²⁺ ATPase activity with aK _m=0.97±0.24 M and aV _max=28.1±2.8 nmol/mg per 2 min. The addition of LHRH (10^–7 M) to pituitary homogenates significantly increased luteinizing hormone (LH) release already at 10 and up to 40 sec compared to basal LH release. Systemic administration of 50 ng LHRH (i.p.), significantly (P<0.05) reduced pituitary Ca²⁺-ATPase after 30, 60 and 90 min, with a return to control levels by 120 min. Pituitary LH content was reduced slightly at 15 min, but was increased significantly at 90 and 120 min post-treatment. Plasma LH levels were elevated by 5 min, reached a peak by 15 min and returned to control within 60 min. The present findings indicate that LHRH receptor activation may influence cytosolic Ca²⁺ transport through effects on membrane Ca²⁺-ATPase activity. These actions may regulate LHRH-induced synthesis, storage and release of LH from pituitary gonadotropes.     

Influence of inorganic microelements on the production of camptothecin with suspension cultures of <Emphasis Type="Italic">Camptotheca acuminata</Emphasis>

The effects of eight microelements (I^–, BO₃ ^3–, MoO₄ ^2–, Co²⁺, Cu²⁺, Mn²⁺, Fe²⁺, Zn²⁺) on the biosynthesis of camptothecin and the growth of suspension cultures of Camptotheca acuminata were studied. The increase of I^– to 25 M l^–1, Cu²⁺ to 1 M l^–1, Co²⁺ to 2 M l^–1 and MoO₄ ^2– to 10 M l^–1 in Murashige and Skoog (MS) medium resulted in 1.66, 2.84, 2.53 and 2.04 times higher of camptothecin yield than that in standard MS medium respectively. Combined treatment of I^– (25 M l^–1), Cu²⁺ (1 M l^–1), Co²⁺ (2 M l^–1) and MoO₄ ^2– (10 M l^–1) lead to improve cell dry weight, camptothecin content, and camptothecin yield to 30.56 g l^–1, 0.0299%, and 9.15 mg l^–1, respectively, which were 20.2, 208.9 and 273.8% increment respectively when compared with those of control.     

Arsenic concentrations in water and fish from Chautauqua Lake,New York

Synopsis Arsenic persists in Chautauqua Lake, New York waters 13 years after cessation of herbicide (sodium arsenite) application and continues to cycle within the lake. Arsenic concentrations in lake water ranged from 22.4–114.81 g l^–1, = 49.0 ag l^–1. Well water samples generally contained less than 10 g l^–1 arsenic. Arsenic concentrations in lake water exceeded U.S. Public Health Service recommended maximum concentrations (10 g l^–1) and many samples exceeded the maximum permissible limit (50 g l^–1). Fish accumulated arsenic from water but did not magnify it. Fish to water arsenic ratios ranged from 0.4–41.6. Black crappie (Pomoxis nigromaculatus) contained the highest arsenic concentrations (0.14–2.04 g g^–1 ), X = 0.7 g g^–1) while perch (Perca flavescens), muskellunge (Esox masquinongy) and largemouth bass (Micropterus salmoides) contained the lowest concentrations (0.02–0.13 g g^–1). Arsenic concentrations in fish do not appear to pose a health hazard for human consumers.     

Increased taxane accumulation in callus cultures of Taxus cuspidata and Taxus × media by some elicitors and precursors

In Taxus cuspidata callus, vanadyl sulfate (10 mg l^–1) induced a high (146 g g^–1 dry wt) production of 10-deacetylbaccatin III in comparison to 7 g g^–1 dry wt of the control. The content of paclitaxel in this species increased from 16 g g^–1 to 74 g g^–1 dry wt when 20 mg phenylalanine l^–1 was used. In T. media, p-aminobenzoic acid induced the highest content of 10-deacetylbaccatin III (481 g g^–1 dry wt) versus 181 g g^–1 in the control. Paclitaxel increased from 89 to 139 g g^–1 dry wt after adding chitosan (20 mg l^–1) to the cultures.     

Mercury budget of an upland-peatland watershed

Inputs, outputs, and pool sizes oftotal mercury (Hg) were measured in a forested 10 hawatershed consisting of a 7 ha hardwood-dominatedupland surrounding a 3 ha conifer-dominatedpeatland. Hydrologic inputs via throughfall andstemflow, 13±0.4 g m^–2 yr^–1over the entire watershed, were about doubleprecipitation inputs in the open and weresignificantly higher in the peatland than in theupland (19.6 vs. 9.8 g m^–2 yr^–1). Inputs of Hg via litterfall were 12.3±0.7g m^–2 yr^–1, not different in thepeatland and upland (11.7 vs. 12.5 g m^–2yr^–1). Hydrologic outputs via streamflow were2.8±0.3 g m^–2 yr^–1 and thecontribution from the peatland was higher despiteits smaller area. The sum of Hg inputs were lessthan that in the overstory trees, 33±3 gm^–2 above-ground, and much less than eitherthat in the upland soil, 5250±520 gm^–2, or in the peat, 3900±100 gm^–2 in the upper 50 cm. The annual flux of Hgmeasured in streamflow and the calculated annualaccumulation in the peatland are consistent withvalues reported by others. A sink for Hg of about20 g m^–2 yr^–1 apparently exists inthe upland, and could be due to either or bothstorage in the soil or volatilization.     

Abscisic acid and its influence on development of the embryonal root cap,storage product and secondary metabolite accumulation in hybrid larch somatic embryos

Somatic embryos of Larix × leptoeuropaea were grown on modified MSG media with 60 M abscisic acid (ABA). These were compared to control embryos raised on the same medium without ABA. Transmission electron microscopy demonstrated that zonation of polyphenol production as well as presence of extracellular mucilage was markedly different in embryos raised with and without ABA. Idioblasts were found in subepidermal and pith regions of hypocotyls and among the subepidermal cells of cotyledons in embryos matured on ABA, but not in embryos matured without ABA. The embryonal root caps of ABA-treated embryos had substantial deposition of lipids and proteins in both the column and inner pericolumn regions, but not in the outer layer of the pericolumn. Control embryos showed no accumulation of proteins or lipids, but an increase in polyphenol accumulation, which had spread to the epidermal and sub-epidermal layers of the cotyledons and hypocotyl. Starch accumulation was similar over the course of development in embryos treated with or without ABA. Using gas chromatography-selected reaction monitoring mass spectrometry, it was shown that concentrations of ABA averaged 186 ± 17 g g^–1 dry weight (DW) in embryos raised on medium supplemented with this plant growth regulator, versus an average concentration of 55 ± 19 g g^–1 DW in embryos raised in the absence of ABA. No difference in ABA concentration was found between the root cap and the rest of ABA-treated embryos.     

Mercury contamination in Lake Xolotlán (Managua)

Total mercury was measured in different compartments of Lake Xolotlán's (Managua) ecosystemviz., sediments, water, fish and men. Sediments from 18 localities at 5 depths inside the sediment (5, 10, 15, 20 and 25 cm) contained an average concentration of 0.62 g Hg.g^–1±0.46 at the surface, with extreme values of 0.16 and 1.8 g.g^–1. The highest concentration was observed at 25 cm depth in front of the chlor-alkaly factory (ELPESA). This maximum is associated with the period of highest production of this factory. The highest mercury concentrations in water were also measured close to the discharge of ELPESA,viz. 787 g.Hg^–1 in January and 506 g.g^–1 in April. The mean mercury concentrations measured in the muscles of the most consumed fish were 0.63 g.g^–1±0.22 (extreme values 0.22 and 1.45) inCichlasoma managuense, and 0.07 g.g^–1±0.14 (extreme values 0.004 and 0.63) inC. citrinellum. The concentration in the liver was 0.79 g.g^–1±1.29 inC. managuense and 0.62 g.g^–1±0.44 inC. citrinellum. Human hairs (n=98) of fishermen and their families contained 5.03 g.g^–1±6.2 (extreme values 0.02 and 38.22). The mean concentration measured in men was 6.22 g.g^–1±6.34 (n=58), and in women 3.39 g.g^–1±5.7 (n=40). The average mercury concentration of hairs of workers of ELPESA was 91.24 g.g^–1±156.9 (extreme values 0.46 and 724.53; n=32). We conclude that total mercury levels in the various ecosystem compartments are very high and mercury contamination in the lake may be considered as dangerous for human health.     

Identification and measurement of indoleacetic and abscisic acids in the cambial region of Picea sitchensis (Bong.) Carr. by combined gas chromatography-mass spectrometry

Indole-3-acetic acid (IAA) and abscisic acid (ABA) were identified by combined gas chromatography-mass spectrometry (GCMS) in fractions obtained by diffusion and extraction from bark peelings of Sitka spruce. A procedure is described for the quantitative analysis of IAA and ABA levels in the same extract using the GCMS technique of single-ion current monitoring. This procedure was used to measure the diffusible, free, and bound fractions of IAA and ABA in the cambial region of Sitka spruce throughout one year; the range in concentration for these fractions was 0.06–0.30, 0.46–3.85, and 0.04–0.20 g/g oven-dry weight, respectively, for IAA, and 0–0.08, 0.03–2.21, and 0.13–0.66 g/g oven-dry weight, respectively, for ABA. Movement in the cambial region was found to be polar for endogenous IAA and nonpolar for endogenous ABA. Recoveries of [¹⁴C]IAA internal standards showed that 73–99.5% of the IAA was lost during purification, and that there could be up to 5-fold differences in recovery between purifications, indicating that IAA loss shold be measured in quantitative analyses.Abbreviations ABA aoscisic acid - GCMS combined gas chromatography-mass spectrometry - IAA indole-3-acetic acid - PVP polyvinylpyrrolidone - SICM single ion current monitoring - TMS trimethylsilyl     

Population growth of some genera of cladocerans (Cladocera) in relation to algal food (Chlorella vulgaris) levels

We studied the patterns of population growth of 7 cladoceran species (Alona rectangula, Ceriodaphnia dubia, Daphnia laevis, Diaphanosoma brachyurum, Moina macrocopa, Scapholeberis kingi and Simocephalus vetulus) using 6 algal densities, viz. 0.05×10⁶, 0.1×10⁶, 0.2×10⁶, 0.4×10⁶, 0.8×10⁶ and 1.6×10⁶ cells ml^–1, of Chlorella vulgaris for 18 – 30 days. In terms of carbon content these algal concentrations corresponded to 0.29, 0.58, 1.16, 2.33, 4.65 and 9.31 g ml^–1, respectively. Cladocerans in the tested range of algal levels responded similarly, in that increasing the food concentrations resulted in higher numerical abundance and population growth rates (r). The peak population densities were (mean±standard error) 71±5; 17.1±0.4, 3.6±0.3, 12.7±1.1, 18.2±2.7, 15.8±1.0 and 10.9±0.02 ind. ml^–1, respectively for A. rectangula, C. dubia, D. laevis, D. brachyurum, M. macrocopa, S. kingi and S. vetulus. In general, the lowest r values were obtained for D. laevis (0.01±0.001) at 0.05×10⁶ cells ml^–1 food level while the highest was 0.283±0.004 for A. rectangula at 1.6×10⁶ cells ml^–1 of Chlorella. When the data of peak population density for each cladoceran species were plotted against the body length, we found an inverse relation, broadly curvilinear in shape. From regression equations between the food level and rate of population increase, we calculated the theoretical food quantity (the threshold level) required to maintain a zero population growth (r = 0) for each cladoceran species, which varied from 0.107 to 0.289 g ml^–1 d^–1 depending on the body size. When we plotted the cladoceran body size against the corresponding threshold food levels, we obtained a normal distribution curve. From this it became evident that for up to 1300 m body size, the threshold food level increased with increasing body size; however, beyond this, the threshold level decreased supporting earlier observations on rotifers and large cladocerans.