Autecological investigations on marine diatoms 6:Rhizosolenia robusta Norman,Rhizosolenia imbricata Brightwell andRhizosolenia shrubsolei Cleve

The warm oligo-eurytherm diatomsRhizosolenia robusta Norman andRhizosolenia imbricata Brightwell were cultured to determine the temperature range for the best competitive position by growth. Comparison of their generation times with those of other diatoms indicate thatR. robusta reaches this position around 20 °C andR. imbricata above 25 °C. The temperature ranges for growth were 12 °C up to 28 °C forR. robusta and 12 °C to above 30 °C forR. imbricata. The use of both species as indicator species for warm water currents is discussed on account of their lower temperature limit. The cold oligo-eurytherm diatomRhizosolenia shrubsolei had a temperature range for growth of below –1.0 °C to 25 °C. Our experimental results demonstrate thatR. imbricata andR. shrubsolei can be considered separate species.     

Field observations in the Oosterschelde (The Netherlands) onCoscinodiscus concinnus andCoscinodiscus granii (Bacillariophyceae) infected by the marine fungusLagenisma coscinodisci (Oomycetes)

During 1985–1990Coscinodiscus concinnus andCoscinodiscus granii from the Oosterschelde were infected by the marine fungusLagenisma coscinodisci, although not every year with the same intensity. Infected cells were only observed during the period July–October at water temperatures between 13.2 and 20.2°C. In 1986 and 1987 the course of the infection withL. coscinodisci inC. concinnus andC. granii, was recorded at three stations. The highest infection percentages varied between 22.2 and 58.3% inC. concinnus and between 7.1 and 41.9% inC. granii. It is concluded that the water temperature may play an important role in the appearance ofL. coscinodisci inC. concinnus andC. granii and that silicate limitation is of minor importance. Finally it is discussed that the infection was not of great importance for the phytoplankton community in the Oosterschelde.     

Influence of root temperature on growth of Pinus sylvestris,Fagus sylvatica,Tilia cordata and Quercus robur

One-year-old tree seedlings were incubated in a greenhouse from April to July, under natural daylight conditions, with their root systems at constant temperatures of 5, 10, 15, 20, 25, 30 and 35 °C and with the above ground parts kept at a constant air temperature of 18–20 °C. The course of height growth, total mass increment, root, shoot and leaf weight as well as leaf areas were measured. The results indicate that clear differences exist in the optimal root zone temperatures for various growth parameters in different tree species. Pinus sylvestris had a maximal height increment at about 5–10 °C and maximal total mass increment at 15 °C root temperature. In contrast, the optimum for Quercus robur was at 25 °C. Tilia cordata and Fagus sylvatica had their optima for most growth parameters at 20 °C. The root temperature apparently indirectly influenced photosynthesis (dry weight accumulation) and respiration loss. From the observed symptoms and indications in the literature it seems probable that a change in hormone levels is involved as the main factor in the described effects. Variation of root temperature had only an insignificant effect on bud burst and the time at which the shoots sprouted. Apparently species of northern origin seem to have lower root temperature optima than those of more southern origin. This is to be verified by investigation of other tree species.     

Reproductive biology of Stictosiphonia hookeri (Rhodomelaceae,Rhodophyta) from Argentina,Chile, South Africa and Australia in laboratory culture

The red alga Stictosiphonia hookeri is epilithic in shaded habitats of the upper intertidal zone from 30 to 55° S. Thalli of this species from Argentina, Chile, South Africa and Australia, usually without reproductive structures when collected, all developed tetrasporangia in culture. Although good vegetative growth occurred in all nine isolates at 20–25 °C, 12:12 light: dark cycle, 10–30 µmol photons m^–2 s^–1, none reproduced in these conditions except one isolate from Australia. At 15 °C the four South African (34 °S) isolates developed tetrasporangial stichidia, and three completed a Polysiphonia-type life history. Gametophytes were unisexual or bisexual. At 15 °C one isolate from Chile (36 °S) formed tetrasporangia, but sporelings were not viable. At 10 °C isolates from Argentina and Chile (53 °S and 54 °S) formed tetrasporangia; however, only the Chile isolate completed a Polysiphonia-type life history with unisexual gametophytes. The temperature required to induce sporogenesis correlates with the range of water and air temperatures in the natural habitats of each isolate. In irradiances >50 µmol m^–2 s^–1 the thalli became yellow- brown within two weeks because of phycobiliprotein loss, but this did not impair growth or reproduction. The Argentina and Chile isolates were resistant to freezing in seawater for at least two days, showing no cell damage. The protein cuticle of the outer cell wall is repeatedly shed in culture. This may serve to minimize the attachment of epiphytes in the field.     

Characteristics of mixotrophic growth of Synechocystis sp. in an enclosed photobioreactor

Synechocystis sp. PCC 6803 was grown in a 2.5 l enclosed photobioreactor on medium with or without glucose. The incident light intensities ranged from 1.5 klux to 7 klux. The highest average specific growth rates of mixotrophic culture and photoautotrophic culture were, respectively, 1.3 h^–1 at a light intensity of 7 klux on 3.2 g l^–1 glucose and 0.3 h^–1 at both light intensities of 5 klux and 7 klux. The highest cell density 2.5 g l ^–1 was obtained at both of light intensities 5 klux and 7 klux on 3.2 g glucose l^–1. Glucose consumption decreased with decreasing light intensity. The energy yields of mixotrophic cultures were 4 to 6 times higher than that of photoautotrophic cultures. Light favored mixotrophic growth of Synechocystis sp. PCC 6803, especially at higher light intensities (5–7 klux).     

Aquacultural characteristics of <Emphasis Type="Italic">Rhizoclonium</Emphasis><Emphasis Type="Italic">riparium</Emphasis> and an evaluation of its biomass growth potential

A study was made of environmental factors affecting the growth of Rhizoclonium riparium in order to evaluate its suitability for large-scale culturing. The results indicate that under the natural conditions prevailing at Taishi, Taiwan, this species can grow year-round, with a monthly biomass production (oven-dried) of 945–1540 kg ha⁻¹ pond surface (assuming a pond depth of 1 m). The specific growth rate ranged from –2.1 to 10.4% per day. Salinity and temperature, both influenced the rate significantly, with optimal values at 20% and 25 °C, respectively. Short (2-mm) lengths of filaments had a higher specific growth rate than longer (20 mm) filaments. Under rotational culturing conditions, the specific growth rate was reduced when flow was increased.     

Fluorescent chromosome banding in the cultivated species ofCapsicum (Solanaceae)

Fluorochrome chromosome banding is applied for the first time to 15 samples of five cultivatedCapsicum species, all with 2n = 24, and allows a detailed analysis of the karyotypes (Tables 2–3, Fig. 8). Banding patterns differ between cytotypes, species and groups, reflecting the dynamics of chromosomal differentiation and evolutionary divergence. Taxa have from 1 to 4 NOR-bearing satellited chromosome pairs and exhibit increasing numbers of terminal (rarely intercalary and indistinct centromeric) heterochromatic fluorescent bands. Amounts of heterochromatin (expressed in % of karyotype length) increase from the group withC. annuum (1.80–2.88),C. chinense (3.91–5.52), andC. frutescens (5.55) toC. baccatum (7.30–7.56), and finally toC. pubescens (18.95). In all taxa CMA+DAPI—(GC-rich) constitutive heterochromatin dominates, onlyC. pubescens has an additional CMAo DAPI+ (AT-rich) band. The fluorochrome bands generally (but not completely) correspond to the Giemsa C-bands. Structural heterozygosity can be demonstrated but is not prominent. The independent origin of at least three evolutionary lines leading to the cultivated taxa ofCapsicum is supported.Chromosome studies inCapsicum (Solanaceae), V. For the fourth part seeMoscone & al. 1995.     

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.     

Cold hardiness of the green gemmules of Spongilla lacustris L. (Porifera: Spongillidae)

Most green gemmules of Spongilla lacustris survived enclosure in ice at –20 °C for up to 30 days; however, their rate of germination at 20 °C was less rapid than that of control gemmules. The length of time spent at low temperature had little effect on gemmule survival. In contrast, repeated cooling to –20 °C and warming to 4 °C led to a progressive decline in gemmule viability. These results indicate that cold injury occurs primarily during transitions between high and low temperatures.     

An efficient protocol for plant regeneration from protoplasts of the moss <Emphasis Type="Italic">Atrichum undulatum P. Beauv in vitro</Emphasis>

A system for plant regeneration from protoplasts of the moss, Atrichum undulatum (Hedw.) P. Beauv. in vitro, is first reported. Viable protoplasts were isolated at about 9 × 10⁵ protoplasts g⁻¹ fresh weight from 10 to 18 days protonemata. For regeneration of protoplasts, viable protoplasts were cultured in liquid–solid medium containing surface liquid medium MS (0.4 M mannitol) and subnatant solid medium Benecke (0.3 M mannitol) at 20 °C under a 16-h photoperiod white light after 12 h preculture in darkness at 20 °C. The great majority of protoplasts follow a regenerative sequence: formation of asymmetric cells in 2–3 days; division of the asymmetric cells to 2–3 cells in 4–5 days, and further develop to produce a new chloronemal filament in 15 days. Juvenile gametophyte can be visible in 20 days. The plating ratio of cell cluster regenerated from protoplasts reaches up to 45%. Transient expression experiments indicate the electroporation uptake of DNA is possible.     

Effects of species of VA-mycorrhizal fungi on growth and mineral uptake of sorghum at different temperatures

Sorghum [Sorghum bicolor (L.) Moench] plants were grown in growth chambers at 20, 25 and 30°C in a low P Typic Argiudoll (3.65 µg P g^–1 soil, pH 8.3) inoculated with Glomus fasciculatum, Glomus intraradices, and Glomus macrocarpum to determine effects of vesicular-arbuscular mycorrhizal fungi (VAMF) species on plant growth and mineral nutrient uptake. Sorghum root colonization by VAMF and plant responses to Glomus species were temperature dependent. G. macrocarpum colonized sorghum roots best and enhanced plant growth and mineral uptake considerably more than the other VAMF species, especially at 30°C. G. fasciculatum enhanced shoot growth at 20 and 25°C, and mineral uptake only at 20°C. G. intraradices depressed shoot growth and mineral uptake at 30°C. G. macrocarpum enhanced shoot P, K, and Zn at all temperatures, and Fe at 25 and 30°C above that which could be accounted for by increased biomass. Sorghum plant growth responses to colonization by VAMF species may need to be evaluated at different temperatures to optimize beneficial effects.     

Effects of environmental parameters on net photosynthesis of a free-living brown seaweed,Cystoseira barbata formarepens: determination of optimal photosynthetic culture conditions

The net photosynthesis of the Mediterranean brown seaweedCystoseira barbata f.repens is measured according to irradiance, temperature and salinity. There is not only, a good utilization of low light intensities (light-shade adaptation), but also a specific ability to use a broad range of irradiance, which corresponds in the photosynthesis-irradiance curves to a high initial slope and an extended light saturation level from 300 to 1500 mol photon m^–2 s^–1; only very high irradiances induce photoinhibition. Maximum net photosynthesis occurred at temperatures ranging from 20 °C to 30 °C. The alga tolerates not only a low level of salinity, but also a slight increase in salinity; however, at more than 47.5 g 1^–1 NaCl, oxygen exchange is significantly reduced.Light, temperature and salinity requirements are discussed, taking into account ecological considerations. Yields and quality of alginic acid are presented according to the irradiance and yearly evolutionin situ in order to aid future cultivation of this species.     

Chironomidae (Diptera) of Baldwin Lake,Illinois, a cooling reservoir

The chironomid fauna of Baldwin Lake, a closed-cycle cooling reservoir for a power plant, was sampled monthly to semi-monthly for one year at four stations, two in the discharge channel and two in the main basin. Qualitative samples were also taken elsewhere and with multiple-plate samplers. Twenty-four species were collected. Annual mean population density was less than 100 larvae m^–2 in the channel, 1037 M^–2 in the main basin. Three species of Tanypodinae formed over 96 percent of the larval population in the main basin: Tanypus stellatus Coquillett, Procladius bellus (Loew), and Coelotanypus concinnus (Coquillett). The principal species on the multiple-plate samplers were Dicrotendipes nervosus (Staeger), Glyptotendipes lobiferus (Say), and Parachironomus monochromus (Wulp). Temperatures of 35°C or more in the channel virtually eliminated the chironomids, whereas temperatures up to 32°C in the main basin increased the number of generations of T. stellatus from the usual two to four at Station 3 and three at Station 4. Station 3 had almost 1,000 degree-days more heat than Station 4.     

Purification and some properties of glyceraldehyde 3-phosphate dehydrogenase fromSynechococcus sp.

Glyceraldehyde 3-phosphate dehydrogenase (EC 1.2.1.13) was purified 386 fold to apparent homogeneity from the thermophilic cyanobacteriumSynechococcus sp. grown at optimum light intensities in batch cultures. The molecular mass of the tetrameric form of the enzyme was 160 kDa as determined by gel filtration and sucrose gradient centrifugation in a phosphate buffer containing DTT. The pH optimum for the oxidation of NADPH was broad (6–8) and the enzyme had a pI of 4.5. The turnover number was 36,000 min^–1 at 40° C. The activation energy was 12.4 Kcal for t>29° C and 20.6 Kcal for t<29° C. The specific absorption coefficient, A _{280 mm} ^{1% 1cm} of the pure enzyme in phosphate buffer at pH 6.8 was 15.2.By SDS gel electrophoresis molecular masses of 78 kDa and 39 kDa were found, indicating that the purified enzyme is a tetramer, probably a homotetramer.When Tris was used as buffer in the homogenization and phosphate and DTT were omitted, a high molecular form with a molecular mass above 500 kDa was found. This form was less active than the purified tetrameric form. Acetone and other organic solvents stimulated the native enzyme several fold.     

Life history and growth in culture of the endemic New Zealand kelp <Emphasis Type="Italic">Lessonia variegata</Emphasis> J. Agardh in response to differing regimes of temperature,photoperiod and light

Lessonia variegata J. Agardh (Laminariales, Phaeophyta) is endemic to New Zealand, where it occurs in subtidal kelp forests on wave exposed coasts in the North, South and Stewart Islands. This is the first account of the growth in culture and life history of L. variegata. Microscopic gametophytes alternate with macroscopic sporophytes, characteristic of members of the order Laminariales. The life history was completed in culture within 14 days under growth conditions of 12 °C, 12:12 (L:D) and 15 °C, 15:9 (L:D). Maximum growth of sporophytes occurred at 15 °C, 15:9, and slowest growth at 10 °C, 9:15. Under low light conditions (8–9 μmol photon m⁻² s⁻¹) filamentous growth of gametophytes predominated, and both the proportion of gametogenesis and the growth of sporophytes after 30 days was much reduced from equivalent cultures grown under conditions of higher light (16–17.5 μmol photon m⁻² s⁻¹). Interest in this species relates both to its potential for commercial utilisation as well as in the role it plays in coastal rocky reef ecosystems.     

A thermophilic green sulfur bacterium from New Zealand hot springs,Chlorobium tepidum sp. nov.

Thermophilic green sulfur bacteria of the genus Chlorobium were isolated from certain acidic high sulfide New Zealand hot springs. Cells were Gram-negative nonmotile rods of variable length and contained bacteriochlorophyll c and chlorosomes. Cultures of thermophilic chlorobia grew only under anaerobic, phototrophic conditions, either photoautotrophically or photoheterotrophically. The optimum growth temperature for the strains of thermophilic green sulfur bacteria isolated was 47–48°C with generation times of about 2 h being observed. The upper temperature limit for growth was about 52°C. Thiosulfate was a major electron donor for photoautotrophic growth while sulfide alone was only poorly used. N₂ fixation was observed at 48°C and cell suspensions readily reduced acetylene to ethylene. The G+C content of DNA from strains of thermophilic chlorobia was 56.5–58.2 mol% and the organisms positioned phylogenetically within the green sulfur bacterial branch of the domain Bacteria. The new phototrophs are described as a new species of the genus Chlorobium, Chlorobium tepidum.This paper is dedicated to Professor Norbert Pfennig on the occasion of his 65th birthday     

Biological control of strawberry tarsonemid mite Phytonemus pallidus and two-spotted spider mite Tetranychus urticae on strawberry in the UK using species of Neoseiulus (Amblyseius) (Acari: Phytoseiidae)

Two species of Neoseiulus, N. californicus and N. cucumeris, showed potential for biocontrol of phytophagous mites on strawberry. N. californicus controlled Tetranychus urticae on potted strawberry plants in a gauze-sided glasshouse at temperatures comparableto early summer in the UK (8–20°C). Both species of phytoseiid reducednumbers of the tarsonemid Phytonemus pallidus on potted strawberry plants under glasshouse conditions (15–23°C). In several experiments reductions in the range of 71–81% in numbers of tarsonemid active stages and eggs, compared to non-release plants, were obtained. The importance of establishing a suitable predator: prey ratio at an earlystage was demonstrated in an experiment where an initial ratio of 1 N. cucumeris: 10 P. pallidus gave a greater degree of controlthan 1:20 or 1:40.     

Germination responses of <Emphasis Type="Italic">Caragana korshinskii</Emphasis> Kom. to light,temperature and water stress

Caragana korshinskii Kom. is a very important shrub species for vegetation rehabilitation in northern China for its high ecological and economic values. Experiments were conducted to determine its germination responses to (i) different temperature regimes under light and/or dark conditions, (ii) different light intensities, and (iii) different water potentials combined with varied constant temperatures. Under alternating temperatures (from 5:15 to 25:35°C), final percent germinations of Caragana korshinskii were quite similar. In dark conditions, constant temperatures resulted in lower final percent germinations than alternating temperatures. At a controlled temperature regime of 10:20°C, neither final percent germinations nor germination rates showed significant differences among varied light intensities. As water potentials were reduced from 0 (distilled water) to –0.6MPa, final percent germinations increased slightly and reached the peak at approximately –0.6MPa, however, the increment was not significant. Beyond –0.6MPa, further water potential reduction led to decreased final percent germinations and few seeds could germinate at –1.4MPa. Water stress also strongly inhibited germination at very high or low temperatures. The experimental results suggested that middle May might be a suitable time for aerial seeding for this species.     

Demographic costs of Chaoborus-induced phenotypic plasticity in Daphnia pulex

Summary It has been proposed that morphological defenses against predation have demographic costs. We measured the cost of a predator-induced morphological defense, using predaceous phantom midge larvae Chaoborus americanus (Insecta, Diptera) and the prey species Daphnia pulex (Crustacea, Cladocera). The induced defense is a neck tooth (and other pleiotropic structures) developed in juvenile D. pulex in the presence of C. americanus. Laboratory life table experiments, in the absence of predation, indicated the population growth rate of typical D. pulex was 11% to 39% greater than that of D. pulex exposed to C. americanus extract, or C. americanus-conditioned water. The reduction in population growth rate was most frequently associated with an increase in the time between birth and first reproduction. Induced individuals required twenty more hours at 23°C, and twenty five more hours at 20°C, to develop to the age of first reproduction. Under limiting food conditions age-specific survivorship and the number of offspring produced per female by the induced form were reduced relative to the typical form. As a result, the difference in population growth rates among forms was greater at the low food level as indicated by a highly significant food by form interaction effect. In addition to neck teeth and lowered reproductive rates, the offspring of induced form individuals had significantly longer tail-spines (7.2–7.5%), and primiparous adults from the induction treatment were significantly shorter than controls (3–8%).     

Biological control of alligatorweed (Alternanthera philoxeroides) with a Fusarium sp.

Alligatorweed (Alternanthera philoxeroidesG.) has become a serious weed in different crops in China. A fungal pathogen was found in Chongqing and Sichuan Provinces and was identified as a species in the Fusarium genus. The fungus produced macroconidia and chlamydospores abundantly on potato sucrose agar (PSA) plates. The bestconidial production and germination and colonygrowth of Fusarium sp. were at 23–31°C and pH 6.7–7.0. Light period and flooding did not affect fungal growth and conidium formation. The herbicides, glyphosate and paraquat, inhibited the fungal development in vitro. The fungus did not affect seed germination and seedling growth of paddy rice, wheat, maize, oilseed rape and broad bean inlaboratory or greenhouse trials. Inoculum density and wetness duration influenced the efficiency of Fusarium sp. to control alligatorweed; a concentration of 1.0 × 10⁵ spores^–1 ml and 12 h of high humidity duration after inoculation produced goodinfections on the weed at 23°C in the laboratory. When the fungus was applied to alligatorweed grown in greenhouse and in the field, good biocontrol efficiency was obtained: the plants started to wilt after four to five (greenhouse) or six days (field), and were killed 9–10 (greenhouse) or 13–14 (field) days after spraying the fungal inoculum. This was similar to the control efficiency resulting from glyphosate treatment. Therefore, this Fusarium sp. appeared to be a good candidatefor further studies and a promising biocontrol agent to manage alligatorweed in some terrestrial and aquatic crops.