Competition between the green alga Scenedesmus and the cyanobacterium Synechococcus under different modes of inorganic nitrogen supply

In this study, we evaluated growth responses of the green alga Scenedesmus and the cyanobacterium Synechococcus supplied with inorganic nitrogen in different ways. A competitive situation in which nitrogen was limiting was created in mixed cultures as well as in cultures growing in the same vessel but separated by a permeable dialysis membrane. Supplying inorganic nitrogen in small pulses at a high frequency favoured the cyanobacterium Synechococcus, whereas batch additions favoured the green alga Scenedesmus. When using a large-pulse/low-frequency supply mode, the yield of the green alga was higher when ammonium was added as nitrogen source compared to when nitrate was added. By contrast, the yield of the cyanobacterium was higher in the nitrate regime. However, uptake experiments using unialgal cultures showed that both organisms depleted the medium of ammonium more rapidly than they depleted the medium of nitrate; i.e. the higher yield of the cyanobacterium in the nitrate regime than in the ammonium regime can be attributed to the effects of competition with the green alga. Since nitrate assimilation involves the consumption of reductive power, we suggest that the outcome of competition was governed by the fact that green alga was light limited and therefore better able to compete for ammonium than for nitrate. The results from the laboratory studies are discussed in relation to results from an enclosure experiment performed in Lake Erken, Sweden. In that field experiment, in which additions of both phosphate and ammonium were applied every second day to 350-l enclosures, the green algal biomass increased exponentially during an incubation period of 22 days.     

Effect ofin vitro storage at 4°C on survival and proliferation of two apple rootstocks

One cm long shoot explants of dwarf apple rootstocks P 2 and M.9 taken from 2 year-old cultures were stored at 4°C in the dark in three media differing in concentration of growth regulators. Every 6 weeks, some explants were transferred into proliferation medium and multiplication rate was observed during three or four consecutive passages. In a second experiment, the influence of explant type (1 cm long shoot tips, 1 cm long middle part of shoots or three-shoot tufts smaller than 1 cm) and transfer time to the cold room (immediately, 10 days, or 20 days after subculture) on explant survival and proliferation were analysed.Survival of explants was influenced by composition of the storage media. On medium without 6-benzylaminopurine, 70% of P 2 and 17% of M.9 explants became necrotic during 18 weeks of storage. P 2 rootstock proliferated better in three passages after storage than did unstored controls. Storage of M.9 rootstock reduced proliferation in the first and second passages if stored in media containing 6-benzylaminopurine in comparison with unstored controls. Explants stored as tufts and transferred to the cold room directly after subculture produced more shoots during two passages than cultures stored as single shoots.     

In vitro control of adventitious bud differentiation by inorganic medium components and silver thiosulfate in explants of Passiflora edulis F. flavicarpa

Summary Hypocotyl and leaf explants from Passiflora edulis F. flavicarpa were evaluated for morphogenesis when cultured on several nutrient media supplemented with benzyladenine and indoleacetic acid. The effect of silver thiosulfate on growth-regulator-induced morphogenesis was also investigated. Murashige and Skoog medium was more effective than woody plant medium in promoting adventitious bud differentiation. The omission of ammonium or nitrate from the Murashige and Skoog medium and a disequilibrium from the Murashige and Skoog nitrate: ammonium ratio drastically reduced the bud-forming capacity of the explants. The inclusion of silver thiosulfate in the culture medium significantly increased the differentiation and development of adventitious shoots. Regenerated shoots were excised and induced to root on basal Murashige and Skoog medium. Plants were transplanted to pots and grown ex vitro.     

Effects of amino acids, nitrate, and ammonium on the growth and taxol production in cell cultures of Taxus yunnanensis

The effects of concentration of amino acids, nitrate, and ammonium on the growth and taxol production in cultures of cell line TY-21 of Taxus yunnanensis were investigated. Addition of 20 different amino acids each at 15–20 mg l^–1 to B5 medium significantly improved callus growth but inhibited taxol formation in the cultures. The optimum nitrate concentration was 20–30 mM for both growth and taxol production. Ammonium greatly suppressed growth but strongly promoted taxol formation in the cells when it was the sole inorganic nitrogen in the medium. Culturing the suspension cells in nitrate-containing medium for 15 days and then in a medium in which ammonium was the sole inorganic nitrogen for 7 days increased taxol yield by 104%, reaching up to 28.1 mg l^–1.     

Developmental phases and STM expression during Arabidopsis shoot organogenesis

Shoot organogenesis in Arabidopsis thaliana wasstudied with regard to the timing of key developmental phases and expression ofthe SHOOTMERISTEMLESS (STM) gene.Shoot regeneration in the highly organogenic ecotype C24 was affected byexplanttype and age. The percentage of C24 cotyledon explants producing shootsdecreased from 90% to 26% when donor seedlings were more than 6 dold, but 96% of root explants produced shoots regardless of the age of thedonorplant. Using explant transfer experiments, it was shown that C24 cotyledonexplants required about 2 days to become competent and another 8-10 days tobecome determined for shoot organogenesis. A C24 line containing the promoterofthe SHOOTMERISTEMLESS (STM) genelinked to the -glucuronidase(GUS) gene was used as a tool for determining the timingofde novo shoot apical meristem (SAM) development incotyledon and root explants. Cotyledon and root explants from anSTM:GUS transgenic C24 line were placed on shoot inductionmedium and GUS expression was examined after 6-16 days ofculture. GUS expression could be found in localizedregionsof callus cells on root and cotyledon explants after 12 days indicating thatthese groups of cells were expressing the STM gene, hadreached the key time point of determination, and were producing an organizedSAM. This was consistent with the timing of determination as indicated byexplant transfer experiments. Root explants from anSTM:GUStransgenic Landsberg erecta line and a two-step tissue culture method revealedasimilar pattern of localized GUS expression duringde novo shoot organogenesis. This is the first studydocumenting the timing and pattern of expression of theSTMgene during de novo shoot organogenesis.     

Actinidia deliciosa C.F. Liang in vitro

In vitro growth of Actinidia deliciosa C.F. Liang, cv Hayward and changes in mineral composition of the medium and in the different parts of the explants (callus, stem and leaves), were analyzed after 0, 15, 30, 45 and 60 days of culturing in each of three successive 60 days subcultures.Fresh (FW) and dry weight (DW) of the explants increased mainly during the first 30 days of culturing, with a predominant increase of FW in leaves and an equal distribution in DW in callus and leaves. Stem FW and DW changes were lower than those observed with callus and leaves. As FW and DW of the explants increased the FW and DW of the medium decreased.The presence of the explants induced a large decrease of medium pH during the first 15 days of culturing followed by a return to the initial level at the end of the culturing.The initial P content of the MS medium was insufficient for the long term culturing, as after 30 days of culturing almost all (94.5%) the P present in the medium was absorbed by the explants and evenly distributed in their different parts. During the first month, 85% of the initial N was absorbed. At the end of the culture only 2% of the initial P and 5% of N remained in the medium. These two elements were equally distributed in callus and leaves during the first month of culturing, while in the last 30 days they increased only in the callus.MS medium initial concentrations of K, Mg, Ca, Fe, Zn, Mn and Cu were sufficient for 60 days explants growth. Almost all these elements were absorbed during the first 30 days of culturing. Their distribution in the different parts of the explant was uneven throughout the culture period. Callus tissue was the main site for accumulation of all these mineral elements.     

Effect of nitrogen form at various levels of potassium,on the Meloidogyne-Fusarium wilt complex in muskmelon

Summary The influence of various potassium concentration and of nitrate or ammonium was evaluated on non inoculated muskmelon plants and on plants inoculated with theFusarium wilt pathogen (F), the root-knot nematode (Meloidogyne javanica) (Nem), or a combination of both pathogens (F+Nem). Increasing potassium concentrations raised top fresh weights (TFW) in all four groups. Nitrate fertilized plants weighed more than plants receiving ammonium, independent of the K⁺ level in the medium. In the Nem+F infected plants TFW values were one and half to two times greater in those receiving the nitrate than in those receiving the ammonium. Number of nematodes in the roots were not affected by nutritional difference. In the ammonium fertilized F and Nem+F plants 30% more wilting was found than after nitrate application. Irrespective of the form of nitrogen that was applied accumulation of N, P and K was found in the roots of the Nem+F and/or Nem plants, while in the shoots Ca, Mg, Na and P accumulated and K was depleted.Contribution from the Agricultural Research Organization, (ARO), No. 944-E, 1983 series.     

Bulk soil pH and rhizosphere pH of peach trees in calcareous and alkaline soils as affected by the form of nitrogen fertilizers

One-year old nectarine trees [Prunus persica, Batsch var. nectarina (Ait.) Maxim.], cv Nectaross grafted on P.S.B2 peach seedlings [Prunus persica (L.) Batsch] were grown for five months in 4-litre pots filled with two alkaline soils, one of which was also calcareous. Soils were regularly subjected to fertigation with either ammonium sulphate or calcium nitrate providing a total of 550 mg N/tree. Trees were also grown in such soils receiving only deionized water, as controls. Rhizosphere pH, measured by the use of a microelectrode inserted in agar sheet containing a bromocresol purple as pH indicator and placed on selected roots, was decreased by about 2–3 units compared to the bulk soil pH in all treatments. This decrease was slightly less marked when plants were supplied with calcium nitrate rather than ammonium sulphate or control. Measurements conducted during the course of the experiment indicated that ammonium concentration was similar in the solution of soils receiving the two N fertilizers. During the experiment, soil solution nitrate-N averaged 115 mg L^–1 in soil fertilized with calcium nitrate, 68 mg L^–1 in those receiving ammonium sulphate and 1 mg L^–1 in control soils. At the end of the experiment nitrate concentrations were similar in soils receiving the two N sources and bulk soil pH was decreased by about 0.4 units by ammonium sulphate fertigation: these evidences suggest a rapid soil nitriflcation activity of added ammonium. Symptoms of interveinal chlorosis in apical leaves appeared during the course of the experiment in trees planted in the alkaline-calcareous soil when calcium nitrate was added. The slightly higher rhizosphere pH for calcium nitrate-fed plants may have contributed to this. The findings suggest that using ammonium sulphate in a liquid form (e.g. by fertigation) in high-pH soils leads to their acidification and the micronutrient availability may be improved.     

Nitrate assimilation in Candida nitratophila and other yeasts

Nitrate assimilation has been studied in four species of yeasts; Candida nitratophila, Candida utilis, Hansenula anomala and Rhodotorula glutinis. Ammonium-grown cultures of these organisms did not assimilate nitrate but acquired the capacity to do so after a 3 h period of nitrogenstarvation. Ammonium inhibited nitrate assimilation completely in nitrate-grown cultures of R. glutinis. With Candida spp. ammonium and nitrate were assimilated simultaneously but each was assimilated at a lower rate than when either was supplied alone. Nitrogen-starved cultures of C. nitratophila contained enough nitrate reductase activity to sustain high rates of nitrate assimilation. Results indicate that the high levels of nitrate reductase in nitrate-grown cultures of C. nitratophila do not limit nitrate assimilation. Nitrate assimilation appears to be limited by nitrate uptake and/or the supply of reducing equivalents for nitrate reduction in these cultures.     

Use of chitin for controlling plant-parasitic nematodes

Cabbage plants were grown in soil amended with Clandosan (CLA) prepared from crustacean chitin (0.3% w/w). The plants were maintained in constant temperature tanks set to 15° or 30°C, in soils naturally infested with cyst nematodeHeterodera schachtii, or inoculated with the root-knot nematode,Meloidogyne javanica, respectively. At 30°C, after the first month following inoculation, CLA caused an increase in top fresh weight of plants but no reduction in nematode—induced root galling was recorded. However, when fresh plants were planted, CLA induced a large reduction in gall formation and caused an increase in top fresh weight of nematode-inoculated plants. At 15°C, CLA significantly affected the plants only after 60 days: an increase in top fresh weight and a reduction in the number of eggs per cyst were recorded. Ammonium was not detected in soil after 30 days, at 30°C, whereas at 15°C, CLA-treated soil contained twice as much ammonium as non-treated soil. After 60 days, ammonium was not detected at all. After 30 days nitrate concentrations in soil attained higher values at 30°C than at 15°C, whereas after 60 days high levels were detected only at 15°C. At 30°C, CLA induced an increase in the number of fungi, chitinolytic bacteria, and total amount of bacteria; at 15°C, such an increase was detected only with the chitinolytic microorganisms.Contribution from the Agricultural Research Organization (ARO), Bet Dagan, Israel No. 2196-E, 1987 series.     

Growth of embryogenic sweet orange callus on media varying in the ratio of nitrate to ammonium nitrogen

Embryogenic callus from Citrus sinensis (L.) Osbeck cv. Hamlin was cultured for 28 days on 20 media arranged in a 5×2×2 factorial varying in the ratio of nitrate to ammonium nitrogen, total inorganic nitrogen, and benzyladenine. Fresh weight increase of callus and final medium pH were significantly affected by total inorganic nitrogen and the ratio of nitrate to ammonium. The nitrate to ammonium ratio accounted for 55% of the variation in the fresh weight increase of the callus and 93% of the variation in the final medium pH. Varying the NO₃ ^-:NH₄ ^- ratio provided adequate pH control.Abbreviation BA benzyladenine     

Fertilization influences nitrogen dynamics in soils under Dalbergia sissoo

The influence of added ammonium, phosphorus, potassium, and gypsum on net nitrogen mineralization was studied in soil beneath a six-year-old plantation of the N₂-fixing tree Dalbergia sissoo in Pakistan. Soil with and without amendments was placed in polyethylene bags and incubated, buried in the soil, for 30 days. After that time the soil was analyzed and net ammonium and nitrate production and net nitrogen mineralization were calculated. The addition of ammonium stimulated nitrification indicating that the process was substrate limited. The inhibition of nitrification by Nitrapyrin showed that the process is autotrophic in these soils. Gypsum addition lowered soil pH from 8.0 to 7.2 and significantly stimulated ammonification, nitrification and net nitrogen mineralization. The addition of potassium more than tripled the soil K:Na ratio. Net ammonium and nitrate production and net nitrogen mineralization all increased in this treatment. The addition of phosphorus had no significant effect on soil nitrogen dynamics.     

Root biomass distribution in a moist tropical montane forest

Effects of N sources (ammonium, nitrate and ammonitrate) and VA mycorrhizae (Glomus intraradices) on rhizosphere soil characteristics (pH, exchangeable acidity, exchangeable cations, inorganic N concentrations) growth and nutrient acquisition of coffee seedlings (Coffea arabica L. cv guatemala) were investigated in a pot study with an acid soil (Red Bluff Loam) sterilized by autoclaving. Ammonium addition decreased rhizosphere pH while nitrate and ammonitrate additions both increased rhizosphere pH. Mycorrhizae induced a higher pH, a lower exchangeable acidity and higher values of exchangeable cations in the rhizosphere. Ammonium addition resulted in a lower mycorrhizal infection than the two other N sources. Mycorrhizal plants grew better and accumulated more N, Ca and Mg than non-mycorrhizal plants.     

In vitro control of adventitious bud differentiation by inorganic media components in leaves of matureJuniperus oxycedrus

Summary The effects of changes in the concentration of macronutrients on BA-induced caulogenesis from leaves of matureJuniperus oxycedrus cultured on modified Murashige and Skoog or Schenk and Hildebrandt media are reported. The bud-forming capacity of the explants depended mainly on the ratios among the levels of ammonium, nitrate, and potassium. The most favorable media formulations for differentiation of adventitious buds were those with nitrate:potassium, ammonium:potassium, and nitrate:ammonium ratios near 1, around 0.1, and between 9 and 15, respectively. The total ionic strength of the media limited bud induction, but only when a disequilibrium of these ratios was produced.     

Effects of nitrate,ammonium and pH on the growth of conifer seedlings and their production of nitrate reductase

Summary Lodgepole pine (Pinus contorta Dougl.), Engelmann spruce (Picea engelmanni Parry), and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings were grown in open-ended tube cultures of sand and perlite, irrigated with nitrate, ammonium, and a 1∶1 mixture of ammonium and nitrate, combined factorially with pH values of 4.6, 5.3 and 6.0 giving a total of nine treatments. Douglas-fir showed intolerance to ammonium which was especially marked in root weight. Lodgepole pine and Engelmann spruce made poor growth with nitrate, but showed little difference between ammonium and mixed sources. Only Douglas-fir showed a significant response to pH treatments with pH 5.3 plants being largest. Contamination of the sand with carbonate-bicarbonate, apparently caused seedlings grown in ammonium solutions to be larger in sand than in perlite. Douglas-fir grown in perlite cultures showed a growth response like the first experiment and nitrate reductase activity in the order nitrate > nitrateammonium mixture > ammonium. Plastic bead cultures had poor growth response due to low retention of water by the substrate, but the nitrate reductase assays produced results like the perlite cultures. Lodgepole pine grown in water culture demonstrated the well known pH shift associated with different nitrogen forms, and when assayed for nitrate reductase these seedlings had larger relative activities than Douglas-fir, but the order of activity remained nitrate > mixed source > ammonium.     

Vertebroplasty--high viscosity cement versus low viscosity cement

The patients with intensive pain caused by the vertebra body fracture were treated by application of low viscosity cement (LVC), (Vertebroplastic, DePuy) and high viscosity cement (HVC), (Confidence, DePuy,) into the body, by means of diascopy through unilateral transpendicular approach. Application of LVC was made in 75 patients, on 109 vertebrae, and HVC was applied in 12 patients on 14 vertebrae. Application of LVC was performed on 48 thoracic and 61 lumbar vertebrae and 5 thoracic and 9 lumbar vertebrae were stabilized with HVC. 43 patients were treated for malignancy and in 38 for osteoporosis. For LVC, preoperative VAS score was 8.32 and 2.23 (p < 0.00001) 24 hours after surgery, and it remained stable 3 month later. For HVC, preoperative VAS score was 7.99 and it was 2.5 (p < 0.00001) 24 hours after surgery and 3 months later. In the group of patients treated with LVC, there was 1 serious complication, a paraparesis caused by the leakage of cement into the spinal canal, which was partially recovered after decompression and rehabilitation treatment and 2 superificial infections with S. epidermidis which were cured by means of antibiotics. In 32 vertebrae (32) cement leakage extra ossal, either into vein plexus or intradiscal during surgery were noticed. When HVC was applied, intradiscal leakage occurred in one case only (8%). By means od Wilcoxon paired test a significant difference was found between the preoperative VAS, and the values immediately after surgery and 3 months later (Z = 7.52, p < 0.00001) when LVC was applied., and with HVC it was ( Z = 3.04, p < 0.00001), which indicates that the fast achieved pain reduction remained stable during the 3 month follow-up. The vertebroplasty is a safe and efficient surgical method in treatment of compressive vertebrae fractures which do not react to the conventional method of treatment. This method, when HVC is applied, shows significantly less complications related to cement leakage.     

青蒿毛状根生长、青蒿素合成以及 营养物消耗的动力学

诱导产生的青蒿毛状根培养物置于MS培养基(含30 g/L蔗糖)进行悬浮培养,并对悬浮培养过程中毛状根生长、青蒿素合成、蔗糖、磷酸盐和不同氮源的消耗、pH和电导率的动力学过程进行分析。经30 d培养,生物量干重和青蒿素产量分别达到13.7 g/L和0.23 g/L,碳源和氮源在培养过程中被逐渐利用,而磷酸盐的利用速率最快,培养至15 d所有的磷酸盐均被吸收,pH在培养初期降低,后又逐渐上升,电导率由于毛状根生长对无机离子的吸收而逐渐减低。     

The effects of nitrate:ammonium ratios and nitrapyrin on the nitrogen response ofZea mays L. under field conditions

Five nitrate:ammonium ratios at two N-levels were tested with and without nitrapyrin [2 chloro-6-(trichloromethyl) pyridine] for grain production on a sandy soil. Treatments were applied to field maize as nutrient solutions, in one application, six weeks after planting. Nytrapyrin resulted in an increase in grain yield at a nitrate:ammonium ratio of 1:3 but in a decrease at a 0:1 ratio. The optimum nitrate:ammonium ratio was close to 1:3 with nitrapyrin and close to 3:1 without nitrapyrin. Nitrapyrin had an effect on NH₄ ⁺-N in the topsoil and NO₃ ⁻-N in the subsoil at 70 days after application. Interactions of nitrate:ammonium ratios and N-levels were shown for leaf N concentration, soil mineral N and soil pH.     

Heterotrophic nitrification in a health soil demonstrated by anin situ method

Summary Nitrate reductase activity (NRA) in the leaves of two subspecies ofHypochaeris radicata was taken as a parameter for nitrate production in the soilin situ. Ammonium addition to the soil ofH. radicata ssp.radicata (soil pH 6.2) resulted in an increase of NRA, thus indicating nitrate formation by chemolithotrophic nitrifiers after a certain time-lag. Addition of ammonium to the soil ofH. radicata ssp.ericetorum (soil pH 4.3) dit not affect NRA in the leaves. Tests based on the MPN method failed to demonstrate the occurrence of chemolithotrophic nitrifiers in this soil. However, the addition of peptone led to an increase of NRA within seven days, which indicates the presence of heterotrophic nitrifying organisms. The results obtainedin situ were confirmed in a laboratory experiment, where soil samples were incubated in the presence and absence of (NH₄)₂SO₄ or peptone. The addition of ammonium led to a decrease in the production of nitrate to zero as compared with the control in the acid soil of ssp.ericetorum, whereas the addition of peptone resulted in nitrate levels amounting to about twice the control value. In the soil of ssp.radicata nitrate formation showed a rapid increase, compared with the control, after the addition of ammonium as well as after the addition of peptone.Grassland species research group, publication no27     

Establishment of Physalis minima hairy roots culture for the production of physalins

This report describes the technique used to induce the hairy roots in Physalis minima (Linn.). Different types of explants obtained from in vitro germinated seedlings were aseptically co-cultivated with A. rhizogenesstrain LBA9402 in different media. Root growth and production of physalins were investigated in various basal media grown under dark and light conditions, and compared to that of normal root cultures. Transformed hairy root cultures grew rapidly and reach stationary phase after 15 days on a B5 medium. HPLC analysis of extracts of hairy root cultures showed that the maximum content of physalin B and F was 1.82 and 4.15 mg g^–1 DW, respectively, when grown under dark conditions. Normal root cultures produced higher physalin B (1.60–1.62 mg g^–1 DW) and F (3.30–3.75 mg g^–1 DW) under the same culture conditions. Physalin F synthesis in light-grown root cultures was reduced significantly.