Floral scent emission is the highest at the second night of anthesis in Lonicera japonica (Caprifoliaceae)

Floral color change in diverse plants has been thought to be a visual signal reflecting changes in floral rewards, promoting pollinator foraging efficiency as well as plant reproductive success. It remains unclear whether olfactory signals co-vary with floral color change. We investigated the production rhythms of floral scent and nectar associated with floral color change in Lonicera japonica. The flowers generally last 2–3 days. They are white on opening at night (N1) and become light yellow the following day (D1), yellow on the second night (N2), and golden on the second day of flowering (D2). Our measurements in the four stages indicated that nectar production decreased significantly from N1 and D1 to N2 and D2, tracking the floral color change. A total of 34 compounds were detected in floral scent and total scent emission was significantly higher in N2 than in the other three stages. The scent emission of three major compounds, Linalool, cis-3-Hexenyl tiglate, and Germacrene D was also significantly higher in N2, but the relative content of Linalool decreased gradually, cis-3-Hexenyl tiglate increased gradually, and the relative content of Germacrene D did not differ among the four measured stages. Greater scent emission by night than by day suggested a strong olfactory signal to attract nocturnal hawkmoths, the effective pollinators. However, floral scent rhythms in the four stages did not match the color change and nectar secretion, suggesting that floral color (visual) and scent (olfactory) in this species may play different roles in attracting or filtering various visitors.     

Inorganic nitrogen regulation of glutamate uptake in the cyanobacterium Nostoc muscorum

In Nostoc muscorum (Anabaena ATCC 27893) glutamate was not metabolised as a fixed nitrogen source, rather it functioned as an inhibitor of growth. The latter effect was nitrogen source specific and occurred in N₂-fixing cultures but not in cultures assimilating nitrate or ammonium. NO₃^--grown cultures lacked heterocysts and nitrogenase activity and showed a nearly 50% reduction in glutamate uptake rates, as well as in the final extent of glutamate taken up, compared to N₂-fixing or nitrogen-limited control cultures. NH₄⁺-grown cultures showed a similar response, except that the reduction in glutamate uptake rates and the final exten of glutamate taken up was over 80%. The present results suggest a relation between nitrate/ammounium nitrogen-dependent inhibition of glutamate uptake, probably via repression of the glutamate transport system, and glutamate toxicity.     

Distribution of NO3− reduction between roots and shoots of peachtree seedlings as affected by NO3− uptake rate

The distribution of NO₃^? reduction between roots and shoots was studied in hydro-ponically-grown peach-tree seedlings (Prunus persica L.) during recovery from N starvation. Uptake, translocation and reduction of NO₃^?, together with transport through xylem and phloem of the newly reduced N were estimated, using ¹⁵N labellings, in intact plants supplied for 90 h with 0.5 mM NH₄⁺ and 0.5, 1.5 or 10 mM NO₃^?. Xylem transport of NO₃^? was further investigated by xylem sap analysis in a similar experiment. The roots were the main site of NO₃^? reduction at all 3 levels of NO₃^? nutrition. However, the contribution of the shoots to the whole plant NO₃^? reduction increased with increasing external NO₃^? availability. This contribution was estimated to be 20, 23 and 42% of the total assimilation at 0.5, 1.5 and 10 mM NO₃^?, respectively. Both ¹⁵N results and xylem sap analysis confirmed that this trend was due to an enhancement of NO₃^? translocation from roots to shoots. It is proposed that the lack of NO₃^? export to the shoots at low NO₃^? uptake rate resulted from a competition between NO₃^? reduction in the root epidermis/cortex and NO₃^? diffusion to the stele. On the other hand, net xylem transport of newly reduced N was very efficient since ca 70% of the amino acids synthesized in the roots were translocated to the shoots, regardless of the level of NO₃^? nutrition. This net xylem transport by far exceeded the net downward phloem transport of the reduced N assimilated in shoots. As a consequence, the reduced N resulting from NO₃^? assimilation, principally occurring in the roots, was mainly incorporated in the shoots.     

Nitrous oxide emissions from silage maize fields under different mineral nitrogen fertilizer and slurry applications

Intensive dairy farming systems are a large source of emission of the greenhouse gas nitrous oxide (N₂O), because of high nitrogen (N) application rates to grasslands and silage maize fields. The objective of this study was to compare measured N₂O emissions from two different soils to default N₂O emission factors, and to look at alternative emission factors based on (i) the N uptake in the crop and (ii) the N surplus of the system, i.e., N applied minus N uptake by the crop. Twelve N fertilization regimes were implemented on a sandy soil (typic endoaquoll) and a clay soil (typic endoaquept) in the Netherlands, and N₂O emissions were measured throughout the growing season. Highest cumulative fluxes of 1.92 and 6.81 kg N₂O-N ha^–1 for the sandy soil and clay soil were measured at the highest slurry application rate of 250 kg N ha^–1. Background emissions from unfertilized soils were 0.14 and 1.52 kg N₂O-N ha^–1 for the sandy soil and the clay soil, respectively. Emission factors for the sandy soil averaged 0.08, 0.51 and 0.26% of the N applied via fertilizer, slurry, and combinations of both. For the clay soil, these numbers were 1.18, 1.21 and 1.69%, respectively. Surplus N was linearly related to N₂O emission for both the sandy soil (R²=0.60) and the clay soil (R²=0.40), indicating a possible alternative emission factor. We concluded that, in our study, N₂O emission was not linearly related to N application rates, and varied with type and application rate of fertilizer. Finally, the relatively high emission from the clay soil indicates that background emissions might have to be taken into account in N₂O budgets.     

SPONTANEOUS AND STIMULATED BIOLUMINESCENCE OF THE DINOFLAGELLATE CERATOCORYS HORRZDA (PERIDINIALES)1

This is the first report of spontaneous bioluminescence in the autotrophic dinoflagellate Ceratocorys horrida von Stein. Bioluminescence was measured, using an automated data acquisition system, in a strain of cultured cells isolated from the Sargasso Sea. Ceratocorys horrida is only the second dinoflagellate species to exhibit rhythmicity in the rate of spontaneous flashing, flash quantum flux (intensity), and level of spontaneous glowing. The rate of spontaneous flashing was maximal during hours 2–4 of the dark phase [i.e. circadian time (CT)16–18 for a 14:10 h LD cycle (LD14:10)], with approximately 2% of the population flashing-min^?1, a rate approximately one order of magnitude greater than that of the dinoflagellate Gonyaulax polyedra. Flash quantum flux was also maximal during this period. Spontaneous flashes were 134 ms in duration with a maximum flux (intensity) of 3.1×10⁹ quanta-s^?1. Light emission presumably originated from blue fluorescent microsources distributed in the cell periphery and not from the spines. Values of both spontaneous flash rate and maximum flux were independent of cell concentration. Isolated cells also produced spontaneous flashes. Spontaneous glowing was dim except for a peak of 6.4× 10⁴quanta-s^?1 cell^?1, which occurred at CT22.9 for LD14:10 and at CT22.8 for LD12:12. The total integrated emission of spontaneous flashing and glowing during the dark phase was 4×10⁹ quantacell^?1, equivalent to the total stimulable luminescence. The rhythms for C. horrida flash and glow behavior were similar to those of Gonyaulax polyedra, although flash rate and quantum flux were greater. Spontaneous bioluminescence in C. horrida may be a circadian rhythm because it persisted for at least three cycles in constant dark conditions. This is also the first detailed study of the stimulated bioluminescence of C. horrida, which also displayed a diurnal rhythm. Cultures exhibited >200 times more mechanically stimulated bioluminescence during the dark phase than during the light phase. Mechanical stimulation during the dark phase resulted in 6.7 flashes. cell^?1; flashes were brighter and longer in duration than spontaneous flashes. Cruise-collected cells exhibited variability in quantum flux with few differences in flash kinetics. The role of dinoflagellate spontaneous bioluminescence in the dynamics of near-surface oceanic communities is unknown, but it may be an important source of natural in situ bioluminescence.     

Methane emission from a wetland rice field as affected by salinity

The impact of salinity on CH₄ emission was studied by adding salt to a Philippine rice paddy, increasing pore water EC to approx. 4 dS.m^-1 Methane emission from the salt-amended plot and adjacent control plots was monitored with a closed chamber technique. The addition of salt to the rice field caused a reduction by 25% in CH₄ emission. Rates of methane emissions from intact soil cores were measured during aerobic and anaerobic incubations. The anaerobic CH₄ fluxes from the salt-amended soil cores were three to four times lower than from cores of the control plot, whereas the aerobic CH₄ fluxes were about equal. Measurements of the potential CH₄ production with depth showed that the CH₄ production in the salt-amended field was strongly reduced compared to the control field. Calculation of the percentage CH₄ oxidized of the anaerobic flux indicated that CH₄ oxidation in the salt-amended plot was even more inhibited than CH₄ production. The net result was about equal aerobic CH₄ fluxes from both salt-amended plots and non-amended plots. The data illustrate the importance of both CH₄ production and CH₄ oxidation when estimating CH₄ emission and show that the ratio between CH₄ production and CH₄ oxidation may depend on environmental conditions. The reduction in CH₄ emission from rice paddies upon amendment with salt low in sulfate is considerably smaller than the reduction in CH₄ emission observed in a similar study where fields were amended with high-sulfate containing salt (gypsum). The results indicate that CH₄ emissions from wetland rice fields on saline, low-sulfate soils are lower than CH₄ emissions from otherwise comparable non-saline rice tields. However, the reduction in CH₄ emission is not proportional to the reduction in CH₄ production     

Zolpidem Displays Heterogeneity in Its Binding to the Nonhuman Primate Benzodiazepine Receptor In Vivo

Abstract: The distinctive pharmacological activity of zolpidem in rats compared with classical benzodiazepines has been related to its differential affinity for benzodiazepine receptor (BZR) subtypes. By contrast, in nonhuman primates the pharmacological activity of zolpidem was found to be quite similar to that of classical BZR agonists. In an attempt to explain this discrepancy, we examined the ability of zolpidem to differentiate BZR subtypes in vivo in primate brain using positron emission tomography. The BZRs were specifically labeled with [¹¹C]flumazenil. Radiotracer displacement by zolpidem was monophasic in cerebellum and neocortex, with in vivo Hill coefficients close to 1. Conversely, displacement of [¹¹C]flumazenil was biphasic in hippocampus, amygdala, septum, insula, striatum, and pons, with Hill coefficients significantly smaller than 1, suggesting two different binding sites for zolpidem. In these cerebral regions, the half-maximal inhibitory doses for the high-affinity binding site were similar to those found in cerebellum and neocortex and ～100-fold higher for the low-affinity binding site. The low-affinity binding site accounted for <32% of the specific [¹¹C]-flumazenil binding. Such zolpidem binding characteristics contrast with those reported for rodents, where three different binding sites were found. Species differences in binding characteristics may explain why zolpidem has a distinctive pharmacological activity in rodents, whereas its pharmacological activity in primates is quite similar to that of classical BZR agonists, except for the absence of severe effects on memory functions, which may be due to the lack of substantial zolpidem affinity for a distinct BZR subtype in cerebral structures belonging to the limbic system.     

Nitric Oxide-Induced [3H]GABA Release from Cerebral Cortical Neurons Is Mediated by Peroxynitrite

Abstract: The functional significance of peroxynitrite in the release of [³H]GABA induced by nitric oxide (NO) liberated from NO generators was investigated using cerebral cortical neurons in primary culture. NO generators such as sodium nitroprusside (SNP) and S -nitroso- N -acetylpenicillamine (SNAP) increased [³H]GABA release in a dose-dependent manner. These increases in [³H]GABA release were significantly inhibited by hemoglobin, indicating that those NO generators evoke the release of [³H]GABA by the formation of NO. Two types of superoxide scavengers, Cu²⁺/Zn²⁺ superoxide dismutase and ceruloplasmin, significantly reduced the increase in [³H]GABA release induced by both SNP and SNAP, which assumes that NO requires superoxide to induce [³H]GABA release from the neurons. In addition, synthesized peroxynitrite induced a dose-dependent increase in [³H]GABA release from the neurons. These results indicate that NO-induced [³H]GABA release is mediated by peroxynitrite formed by the reaction of NO with superoxide.