A versatile chamber for simultaneous measurements of oxygen exchange and fluorescence in filamentous and thallous algae as well as higher plants

A new chamber was developed for a simultaneous measurement of fluorescence kinetics and oxygen exchange in filamentous and thallous algae as well as in small leaves of water plants. Algal filaments or thalli are kept by a stainless grid close to the bottom window of the chamber in the sample compartment. The grid separates the object from the electrode compartment with the oxygen electrode at the top. This compartment accommodates, in addition, a magnetic stirrer that provides efficient circulation of the medium between the sample and the electrode. This magnetic bar spins on a fixed axis and is driven by an electronically commutated magnetic field produced by four coils which are arranged around the chamber. This design yields a very favourable signal to noise ratio in the oxygen electrode records. Consequently, measurements can be performed even of algae with very low photosynthetic rates such as marine low-light red algae or algae under severe stress. For irradiation of the samples and for fluorescence measurements a fibre optic light guide is used facing the window of the chamber. The four branches of a commercially available light guide serve the following purposes: collection of sample fluorescence and supply of measuring, actinic, and saturating light, respectively.     

Influence of medium frequency light/dark cycles of equal duration on the photosynthesis and respiration of Chlorella pyrenoidosa

Chlorella pyrenoidosa was grown in three continuous cultures each receiving a different light regime during the light period of a diurnal cycle. Hourly samples taken during the light period were subjected to medium frequency light/dark oscillations of equal duration, ranging from 3 to 240 seconds. The oxygen consumption and production of each sample were measured with an oxygen electrode in a small oxygen chamber. Although the light/dark cycles had little overall influence on photosynthetic activity, the microalgae appeared to adapt to the light regime to which they were subjected. Large differences were found between the maximum chlorophyll-specific production rates (P _infmax ^supB ), the chlorophyll-specific production rates (P^B) and the respiration rates between the cultures and treated subsamples. Respiration rates increased during the light period, whilst P^B either increased, or had a mid light period minimum or maximum. The culture which received an hourly light oscillation during the light period had the highest P _infmax ^supB and lowest respiration rates, and it is suggested that these algae react as in nature, whereas either a sinusoidal or a block light pattern is unnatural. The latter light regime is commonly used in laboratory studies.     

Use of photoacclimation in the design of a novel photobioreactor to achieve high yields in algal mass cultivation

The concept of a completely new and novel photobioreactor consisting of various compartments each with a specific light regime is described. This is in response to the debate and development which have taken place in recent years concerning photobioreactor design and closed systems. It is well known that algae can photo-acclimate to various light intensities. At the extremes, they can be high light (HL) or low light (LL) acclimated. Both HL and LL acclimated algae typically have very specific characteristics indicating the plasticity of the organisms, which have developed specific strategies during evolution to cope with continuous and dynamic light fields. Not only are these considerations important in photobioreactor design, but also for the production of certain biocompounds, whose synthesis has specific light requirements. In the continuous flow photobioreactor described here, algal cells acclimated to different light conditions together permit utilization of the entire light gradient found in an optically dense medium, such as in a high-density culture. Compared to a single compartment vertical flat-plate photobioreactor, the multicompartment reactor yielded a 37% higher productivity rate. This is a significant improvement in photobioreactor performance.     

Measurement of photosynthetic oxygen evolution with a new type of oxygen sensor

We measured the light response curve of photosynthetic oxygen evolution by illuminating a leaf disc in an air-tight windowed chamber. Oxygen production was measured by monitoring the quenching of luminescence of an organometallic ruthenium compound. A photodiode based chlorophyll a fluorometer was used to measure the luminescence intensity. Oxygen evolution measurements with a traditional oxygen electrode gave the same numerical values at different light intensities when the same leaf disk was tested. The quality of the measurement signal of the new method was found to be similar to that obtained with the oxygen electrode method. The new luminescence based system is more stable against electrical disturbances than an oxygen electrode, its response to oxygen pressure changes is very rapid, and the new method allows the same basic equipment to be used for chlorophyll fluorescence and oxygen measurements.     

A Method to Estimate Practical Radial Oxygen Loss of Wetland Plant Roots

The estimation of practical radial oxygen loss (ROL) of wetland plant roots was attempted in this study. We have devised a new method to measure ROL of wetland plant roots. The whole root system was bathed in an anoxic nutrient solution. Oxygen released from the root was removed immediately by introducing oxygen-free nitrogen gas (O₂ < 4 nmol L⁻¹) to mimic natural habitats where released oxygen is consumed rapidly due to chemical and biological oxidation processes. Oxygen removed from the root-bathing chamber was simultaneously detected colorimetrically by use of the highly oxygen-sensitive anthraquinone radical anion (AQ·⁻) in a cell outside the root-bathing chamber, which decolorized by a rapid reaction with oxygen. An emergent macrophyte Typha latifolia L. was incubated, and its ROL was measured by both the new method and one of the conventional methods, the closed chamber/electrode method, by which the ROL of Typha latifolia L. had not yet been measured. The new method succeeded in detecting the ROL, whereas the conventional method was not able to detect oxygen, due to the level being below the detection limit of the oxygen electrode. The oxygen supply via the seedlings of Typha latifolia L. was ca. 10 times higher compared with control measurements without plant. Light illumination significantly enhanced the ROL of Typha latifolia L. (0.33 nmol O₂ g⁻¹ root dry weight s⁻¹ under light and 0.18 nmol O₂ g⁻¹ root dry weight s⁻¹ in the dark). Theses values fall between those previously reported by the closed chamber/titanium citrate method and the open chamber/electrode method.     

Ultrastructure and Development of the Ooecial Walls in Some Calloporid Bryozoans (Gymnolaemata: Cheilostomata)

In the brood chambers (ovicells) of six calloporid cheilostomes studied each skeletal wall consists of four calcified layers: (1) a very thin superficial layer of planar spherulitic crystallites, (2) an upper (outer) layer with wall-perpendicular prismatic ultrastructure, (3) an intermediate lamellar layer, and (4) a lower (inner) wall-perpendicular prismatic layer. Comparative studies of both the ovicell wall ultrastructure and early ovicell formation showed a hypothetical opportunity for evolving complex (multilayered) skeletal walls by fusion of the initially separated gymnocystal and cryptocystal calcifications in Cheilostomata. In two species studied, a bilobate pattern in the final stage of the formation of the ooecial roof was encountered in specimens with the cuticle preserved. A possible explanation to this finding is discussed – the bilobate pattern is suggestive of the hypothetical origin of the brood chamber from (1) two flattened spines, or (2) reduction in spine number of an originally multispinous ovicell.     

Photobehaviour of Paramecium bursaria infected with different symbiotic and aposymbiotic species of Chlorella

The endosymbiotic unit of Paramecium bursaria and Chlorella spec. shows two types of photobehaviour: 1) A step-up photophobic response which possibly depends on photosensitive agents in the ciliate cell itself — as is also shown by alga-free Paramecium bursaria - and can be drastically enhanced by photosynthetic activity of symbiotic algae; and 2) a step-down photophobic response. The step-down response leads to photoaccumulation of green paramecia. Both types of photobehaviour in Paramecium bursaria do not depend on any special kind of algal partners: The infection of alga-free Paramecium bursaria with different Chlorella species results in new ciliatealgae-associations. They are formed not only by combination of the original symbiotic algae with their host, but also by infection with other symbiotic or free-living (aposymbiotic) chlorellae, respecitively. Systems with other than the original algae are not permanently stable — algae are lost under stress conditions — but show the same types of photobehaviour. Photoaccumulation in general requires algal photosynthesis and occurs only with ciliates containing more than fifty algae/cell. It is not mediated by a chemotactic response to oxygen in the medium, since it occurs at light fluence rates not sufficient for a release of oxygen by the symbiotic system, e.g., below its photosynthetic compensation point. Photoresponses can be inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). Sensory transduction does not depend on any special symbiotic features of the algae, e.g., sugar excretion. The participation of oxygen in the Paramecium cell, of its cytoplasmic pH and of ions released or taken up by endosymbiotic algae in sensory transduction is discussed.     

Simple light guide for measuring irradiance in an aqueous oxygen electrode chamber

The light-dependent reactions of photosynthesis are often measured with Clark-type oxygen electrodes yet the irradiance level inside aqueous oxygen electrode reaction vessels is seldom reported due to the difficulty of measuring light inside a small volume chamber. We describe a simple light guide terminating in a 90° prism that can be inserted into a reaction vessel. Incoming irradiation is directed to a commercially available quantum sensor positioned at the other end of the light guide. Both materials for and construction of the device are inexpensive. This revised version was published online in June 2006 with corrections to the Cover Date.     

Genetic and environmental variation in performance of a marine isopod: effects of eutrophication

Environmental variation in food resources modifies performance of herbivores, in addition to genetic variation and maternal effects. In marine benthic habitats, eutrophication may modify herbivores diets by changing host species composition or nutritional quality of algae for herbivores. We studied experimentally the effects of diet breadth and nutrient availability for the host algae on fitness components of the herbivorous isopod Idotea baltica. We fed the adult isopods with the brown algae Fucus vesiculosus and Pilayella littoralis and juveniles with the green alga Cladophora glomerata. By using half-sib families, we were able to separate the genetic, environmental and maternal effects on intermolt duration and size of the juveniles. The mothers confined to the diet consisting of both Fucus and Pilayella grew better and produced larger egg mass than those having consumed Fucus alone. Nutrient enhancement of algae did not influence the performance of the adult herbivores. However, the juveniles achieved twice the weight as well as shorter intermolt duration when consuming nutrient-treated C. glomerata. Mothers nutrition, either nutrient enrichment of her food algae or diet breadth, did not affect juvenile survival or growth as such, but we found evidence that the broader diet consumed by the mother mediated offspring performance by further accelerating growth rate of the offspring that fed on nutrient-treated alga. Intermolt duration was a highly heritable trait, but size showed very low heritability. Instead, maternal effects on size were substantial, suggesting that differences among mothers in their egg-provisioning ability strongly affect weight gain of their offspring. A high amount of additive genetic variance in intermolt duration implies potential for quick evolutionary responses in the growth schedule in the face of changes in the selective environment. We conclude that eutrophication, in addition to improving growth and reproduction of I. baltica by enhancing food quality and by providing opportunity for broader, more profitable diets, may act as a selective agent on life-history traits. Eutrophication of coastal waters is thus likely to reflect in herbivore density, population dynamics and eventually, grazing pressure of littoral macroalgae.     

In vivo fluorometric method for early detection of cyanobacterial waterblooms

A specific method was developed for monitoring the concentration of cyanobacteria (blue-green algae) before waterblooms, based on their characteristics ofin vivo fluorescence. The excitation and emission spectra of cyanobacteria are very different from those of eukaryotic algae, due to the importance of phycocyanin, rather than chlorophylla, in determining the fluorescence characteristics. Our results, based on four cyanobacteria:Microcystis aeruginosa, Anabaena cylindrica, Phormidium tenue andSpirulina platensis, indicate that excitation at 620 nm and its emission at 645 nm is a sensitive and specific method for their detection. Furthermore, the addition of 10 M photosynthesis inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) induced only 3% increase in phycocyanin fluorescence, suggesting that this measurement is almost independent of the ongoing rate of photosynthesis.Author for correspondence     

Probing the archaeal diversity of a mixed thermophilic bioleaching culture by TGGE and FISH

The archaeal community present in a sample of Mixed Thermophilic Culture-B (MTC-B) from a laboratory-scale thermophilic bioleaching reactor was investigated by temperature gradient gel electrophoresis (TGGE) and fluorescence in situ hybridisation (FISH). Both techniques were specifically adapted for use on native state bioleaching samples, with a view to establishing convenient means for monitoring culture composition. Using the TGGE protocol developed, the relative species composition of the thermophilic bioleaching sample was analysed, and included four phylotypes belonging to the Sulfolobales, which were related to Stygiolobus azoricus, Metallosphaera sp. J1, Acidianus infernus and Sulfurisphaera ohwakuensis. However, the St. azoricus-like phylotype was difficult to resolve and some micro-heterogeneity was observed within this phylotype. Specific FISH probes were designed to qualitatively assess the presence of the phylotypes in MTC-B. The sample was dominated by Sf. ohwakuensis-like Archaea. In addition, the St. azoricus-like, Metallosphaera species-like and Acidianus species-like cells appeared in similar low abundance in the community. Most strikingly, FISH identified Sulfolobus shibatae-like cells present in low numbers in the sample even though these were not detected by PCR-dependent TGGE. These results highlight the importance of using more than one molecular technique when investigating the archaeal diversity of complex bioleaching reactor samples.     

Photosynthetic functions of cembran pines and dwarf pines during winter at timberline as regulated by different temperatures,snowcover and light

Trees at timberline in the high Alps are exposed to a variety of climatic conditions. Most climatic stresses occur during winter and spring, when frost, occasionally low snow cover, and high irradiation interact. In this study, we follow reactions of photosynthesis from high winter to spring in two dominating tree species of the alpine timberline, which may indicate the status of stress response to a changing environment. The results indicate a level of physiological stability in trees, which are important for stabilising natural high mountain ecosystems. Trees of Pinus cembra and of Pinus mugo were selected at altitudes between 1850 m a.s.l. and 1950 m a.s.l. near innsbruck, Austria. At six sampling times from January to May, fast chlorophyll fluorescence was measured in the field and twigs were collected for further investigation in the laboratory. The following measurements were taken: photosynthetic oxygen formation, needle chlorophyll and carotenoid determination, and kinetic studies of the xanthophyll cycle. In general, both tree species showed similar results in most parameters studied. P. mugo seems to have some advantages if winter precipitation is high, when, because of its growth habitus, most needles will be snow covered. Primary photochemistry (trapping per reaction centre) in PS II does not change with sampling dates despite the fact that temperature and light are changing. However, first events in electron transport and whole needle photosynthesis are strongly affected by light and temperature conditions during the days before sampling. The kinetics of the xanthophyll cycle indicate not only light, but also strong temperature effects. P. mugo photosynthesis seems to have a higher stability under changing weather. Both tree species are well prepared to start with photosynthesis in winter, if favourable conditions, like foehn events, occur.     

Influence of high frequency light/dark fluctuations on photosynthetic characteristics of microalgae photoacclimated to different light intensities and implications for mass algal cultivation

Oxygen evolution from aScenedesmus obliquus dominated outdoor culture was followed in a small volume chamber, irradiated either by continuous white light or under light/dark frequencies between 0.05 to 5000 Hz, using arrays of high intensity red light emitting diodes (LED's). By placing neutral density filters in the path of the white light, light saturation curves of the oxygen evolution (P/I curves) were measured using diluted aliquots of algal cultures. The results clearly showed that photosynthetic rates increased exponentially with increasing light/dark frequencies, that a longer dark period in relation to the light period does not necessarily lead to higher photosynthetic rates (efficiencies), and that algae do not acclimate to a specific light/dark frequency. One of the most important factors that influenced photosynthetic rates, either under continuous illumination or intermittent, was whether the algae were dark or light acclimated. Low light/dark frequencies were perceived by the algae as low light conditions, whilst the opposite was true for high frequencies. The light utilisation efficiency in a fluctuating light/dark environment depended on the acclimated state of the algae, the specific frequency of the fluctuations and the duration of the exposure. Since the frequencies determined the perceived quantities of light, dark reactions played an important role in determining the average photosynthetic efficiencies. These results have important implications for algal biotechnology.     

Effects of live coral,epilithic algal communities and substrate type on algal recruitment

The recruitment of algae is a critical process during algal colonization and invasions, including coral-to-algal phase shifts. Although algae are widely assumed to colonize and kill corals, there is very little known about the recruitment dynamics of coral reef algae. This study tested the ability of two dominant macroalgae (Fucales including Sargassum spp. and Lobophora variegata) to settle and grow on healthy coral tissue. The study also explored the effects of interactions with prior occupants, and of abiotic substrate properties (texture, and ceramic and carbonate material). The results indicate that healthy corals were able to prevent attachment or survival of recruits of these macroalgae. This is a significant point, since it suggests that the replacement of corals by algae may often require prior stress or death in the coral tissue. Pre-conditioning of plates at different sites had some effects, but these were relatively minor, whereas there was considerable variation within sites. Some of this variation appeared to be related to the amount of turf algae or crustose coralline algae on the plates. Recruitment was generally, but not always, higher on plates with rougher texture. Overall, this preliminary exploration indicates considerable potential for variability in outcomes of algal colonization, with implications for the dynamics of algal invasions. In particular, the results do not support suggestions that planktonic algal propagules can directly settle on and colonize healthy coral tissue.Communicated by Topic Editor D. Barnes     

Bloom formation of Gloeotrichia echinulata and Aphanizomenon flos-aquae in a shallow,eutrophic, Danish lake

Over a period of four years, the seasonal periodicity of dominant phytoplankton species in a shallow, eutrophic Danish lake changed markedly. Cyanophytes prevailed during the summer period of all four years. In the first three years, species of Microcystis, Anabaena and Aphanothece dominated, whereas in the fourth year of investigation, these algae were replaced by Gloeotrichia echinulata (J. E. Smith) Richter and Aphanizomenon flos-aquae (L.) Ralfs. The most striking environmental differences in the fourth year as compared with the previous three years, were an increase in tranparency, from about 0.5 meter in 1989–1991 to more than 2 metres preceding the summer maximum in 1992, and a simultaneous occurrence of low oxygen concentrations. A collapse of the fish population was followed by an increased proportion of large Cladocerans in the zooplankton. Improved light conditions at the bottom and grazing pressure from large Cladocerans favoured growth of the large colony forming blue-green algae, Gloeotrichia echinulata and Aphanizomenon flos-aquae. These species germinate from resting spores in the sediment and are able to sustain some growth there before migration to the lake water. The transfer of algal biomass from the bottom sediment to the water phase was accompanied by a marked increase in concentrations of particulate phosphorus and nitrogen in the entire lake.     

Relations between electron transport rates determined by pulse amplitude modulated chlorophyll fluorescence and oxygen evolution in macroalgae under different light conditions

The relationship between O₂-based gross photosynthesis (GP) and in vivo chlorophyll fluorescence of Photosystem II-based electron transport rate (ETR) as well as the relationship between effective quantum yield of fluorescence (Φ_PSII) and quantum yield of oxygen evolution (Φ_{O_2}) were examined in the green algae Ulva rotundata and Ulva olivascens and the red alga Porphyra leucosticta collected from the field and incubated for 3 days at 100 μmol m⁻² s⁻¹ in nutrient enriched seawater. Maximal GP was twice as high in Ulva species than that measured in P. leucosticta. In all species ETR was saturated at much higher irradiance than GP. The initial slope of ETR versus absorbed irradiance was higher than that of GP versus absorbed irradiance. Only under absorbed irradiances below saturation or at values of GP <2 μmol O₂ m⁻² s⁻¹ a linear relationship was observed. In the linear phase, calculated O₂ evolved /ETR molar ratios were closed to the theoretical value of 0.25 in Ulva species. In P. leucosticta, the estimated GP was associated to the estimated ETR only at high irradiances. ETR was determined under white light, red light emitting by diodes and solar radiation. In Ulva species the maximal ETR was reached under red light and solar radiation whereas in P. leucosticta the maximal ETR was reached under white light and minimal under red light. These results are in agreement with the known action spectra for photosynthesis in these species. In the case of P. leucosticta, GP and ETR were additionally determined under saturating irradiance in algae pre-incubated for one week under white light at different irradiances and at white light (100 μmol m⁻² s⁻¹) enriched with far-red light. GP and growth rate increased at a growth irradiance of 500 μmol m⁻² s⁻¹ becoming photoinhibited at higher irradiances, while ETR increased when algae were exposed to the highest growth irradiance applied (2000 μmol m⁻² s⁻¹). The calculated O₂ evolved /ETR molar ratios were close to the theoretical value of 0.25 when algae were pre-incubated under 500–1000 μmol m⁻² s⁻¹. The enrichment by FR light provoked a decrease in both GP and ETR and an increase of nonphotochemical quenching although the irradiance of PAR was maintained at a constant level. In addition to C assimilation, other electron sinks, such as nitrogen assimilation, affected the GP–ETR relationship. The slopes of GP versus ETR or Φ_PSII versus Φ_{O_2} were lower in the algae with the highest N assimilation capacity, estimated as nitrate reductase activity and internal nitrogen contents, i.e., Ulva rotundata and Porphyra leucosticta, than that observed in U. olivascens. The possible mechanisms to explain this discrepancy between GP and ETR are discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Successful expression of heterologous egfp gene in the mitochondria of a photosynthetic eukaryote Chlamydomonas reinhardtii

The efficient expression of exogenous gene in mitochondria of photosynthetic organism has been an insurmountable problem. In this study, the pBsLPNCG was constructed by inserting the egfp gene into a site between TERMINVREP-Left repeats and the cob gene in a fragment of mitochondrial DNA of Chlamydomonas reinhardtii CC-124 and introduced into the mitochondria of respiratory deficient dum-1 mutation of C. reinhardtii CC-2654. Sequencing and DNA Southern analyses revealed that egfp gene had been integrated into the mitochondrial genome of transgenic algae as expected and no other copy of egfp existed in their nucleic genome. Both the fluorescence detection and Western blot analysis confirmed the presence of eGFP protein in the transgenic algae; it indicated that the egfp gene was successfully expressed in the mitochondria of C. reinhardtii.     

Marine algal symbionts benefit benthic invertebrate embryos deposited in gelatinous egg masses

Algae colonize the gelatinous egg masses of marine invertebrates. This study demonstrates a symbiotic relationship between marine algae and the invertebrate embryos in gelatinous egg masses found in Indian River Lagoon, FL, USA. The benefits to the embryos in this association differ among host species investigated. The embryos of the polychaete Axiothella mucosa graze on the diatom assemblage in their egg masses and the fitness of the crawl-away juveniles is improved by this food source. The tenuous egg masses of the polychaete Arenicola cristata and the mollusk Haminoea succinea are negatively buoyant when spawned and become buoyant when symbiotic algae are present. In addition to increased dispersal of their lecithotrophic larvae, the potential of the egg masses of A. cristata and H. succinea to float may reduce predation on the embryos by benthic predators such as the gastropod Nassarius vibex. Photosynthetically derived oxygen from the algae may benefit the embryos of the opisthobranch Haminoea elegans by increasing oxygen supply when crawl-away juveniles emerge from the egg mass. However, when mostly earlier stage larvae are hatched from egg masses of H. elegans, the additional oxygen supplied by the algae does not provide a substantial advantage. Algae were absent in the gelatinous egg mass core of only one of the five species examined, Haminoea antillarum. H. antillarum has both a short embryonic development time and denser egg mass gel than the other four species tested. What is not understood is whether invertebrate egg masses are an opportunistic space for algae to colonize or whether only a few microalgal species can exploit the gelatinous substrate.     

The application of image cytometry to viability assessment in dual fluorescence-stained fish spermatozoa

The viability of spermatozoa has been assessed using SYBR 14 staining for DNA of living cells and propidium iodide staining for DNA of degenerate cells. This dual staining was performed on four fish species (Siberian sturgeon, Acipenser baerii; common carp, Cyprinus carpio; tench, Tinca tinca and wels, Silurus glanis) and the proportions of live and dead spermatozoa were assessed by epifluorescence microscopy and image cytometry. Ten phase contrast and epifluorescent images were recorded per sample, corresponding images were overlaid, and the blended images were evaluated for live and dead spermatozoa, represented by green and red fluorescence signals. Live/dead proportions were assessed, after dual thresholding, by imaging software that counted absolute numbers of objects and computed their frequencies. All sperm heads were found to be labelled, emitting either green or red light. Mean numbers of spermatozoa per image were in the ranges 32-113, 61-105, 48-104 and 29-91 for Siberian sturgeon, common carp, tench and wels, respectively. The corresponding proportions of live spermatozoa were in the ranges 83.56-94.59%, 93.92-97.02%, 76.14-97.76% and 79.45-83.76%. Standard deviations did not exceed 5% of the means. The image cytometric system using dual staining with SYBR 14 and propidium iodide was clearly suitable for assessing the viability of freshwater fish spermatozoa.     

Calculation of the field and current density distributions in a non-self-sustained discharge in the discharge chamber of a CO laser

Two-dimensional spatial distributions of the electric field and current density in a non-self-sustained discharge controlled by a fast electron beam were calculated in the quasineutral plasma approximation. The calculations were carried out for a gas-discharge chamber with an antistreamer electrode grid placed in parallel to the output window of the ionizer. The voltage drop near the grid surface that appears due to the inhomogeneity of the spatial distribution of the current density was calculated. The fraction of the discharge current that passes the grid and flows onto the foil separating the vacuum volume of the ionizer from the gas-discharge chamber was estimated. The dependence of the calculated values on the geometric parameters of the electrode grid and its position with respect to the output of the ionizer was analyzed.