Effect of Boron Deficiency on Photosynthesis and Reductant Sources and Their Relationship with Nitrogenase Activity in Anabaena PCC 7119

Nitrogenase activity of Anabaena PCC 7119 is inhibited under conditions of boron deficiency. To elucidate the mechanisms of this inhibition, this study examined how the deficiency of boron affected photosynthesis, photosynthetic pigments, the enzymes of the oxidative pentose phosphate pathway, and respiration of Anabaena PCC 7119 cultures. After 24 to 48 hours of boron deficiency, reductions in photosynthetic O₂ evolution and in CO₂ fixation were observed. At the same time, the activities of oxidative pentose phosphate pathway enzymes and respiration increased significantly with boron deficiency. No change was observed in these processes when assays were performed after 4 to 6 hours of deficiency, a time at which nitrogenase activity was severely inhibited. These results suggest that the requirement for boron in N₂ fixation is independent of its effects on photosynthesis and reductant supply.     

Increased CO2 and nutrient status changes affect phytomass and the production of plant defensive secondary chemicals in Salix myrsinifolia (Salisb.)

The effect of CO₂ enrichment (700 and 1050 ppm) on phytomass, soluble sugars, leaf nitrogen and secondary chemicals of three Salix myrsinifolia clones was studied in plants cultivated at very poor (sand seedlings) and moderate (peat seedlings) nutrient availability and under low illumination. The total shoot phytomass production of sand scedlings was less than 10% of that of the peat seedlings. Carbon dioxide increased the total shoot phytomass of peat seedlings. When the ambient carbon supply was doubled (to 700 ppm) the growth of sand seedlings was slightly enhanced but 1050 ppm CO₂ gave growth figures similar to those at the control CO₂ level. Leaf nitrogen content and total soluble sugar contents were significantly higher in peat seedlings than in sand seedlings. Leaf nitrogen showed a decreasing trend in relation to CO₂ increase. On the other hand, CO₂ did not have any clear-cut effect on total sugars. At the control CO₂ level the content of salicortin, which is a dynamic phenolic, was higher in the peat seedlings than in the sand seedlings, but salicin showed the opposite trend. CO₂ enrichment considerably decreased these phenolics in the peat seedlings. At the control CO₂ level, the content of more static phenolics, such as proanthocyanidins, was higher in sand seedlings. An increased carbon supply considerably increased static phenolics in the peat seedlings. Willow defence against generalist herbivores is moderately decreased by enhancement of atmospheric carbon dioxide.     

Essentiality of Boron for Dinitrogen Fixation in Anabaena sp. PCC 7119

The relationship between the requirement for boron and the form of N supplied in nutrient media to cyanobacterium Anabaena sp. PCC 7119 was investigated. When cells were grown in a medium which contained nitrate or ammonium-N, boron deficiency in the nutrient media did not inhibit growth or change cell composition. However, when cells were dependent on N₂ fixation, the lack of boron inhibited growth (i.e. growth ceased after 96 hours under these conditions). Additionally, boron-deficient cells showed a significant decrease in their content of phycobiliproteins and chlorophyll and accumulated carbohydrates within 24 hours of removing boron from the nutrient media. Inhibition of photosynthetic O₂ evolution accompanied the decrease in photosynthetic pigments. Boron deficiency symptoms were relieved when either boron or combined N was added to boron-deficient cultures. The degree of recovery depended upon the age of the cultures. Assays of nitrogenase activity showed that, after 2 hours of growth, nitrogenase activity of boron-deficient cells was inhibited by 40%. After 24 hours a total inactivation of nitrogenase activity was observed in boron-deficient cells. These results strongly suggest an involvement of boron in N₂ fixation in cyanobacteria.     

Growth and tissue senescence inPrunus avium shoots grownin vitro at different CO3/O2 ratios

Summary The rate of metabolism and biosynthetic processes makein vitro cultures very sensitive to environmental changes, and therefore subject to physiological and morphological alterations leading to senescence in the short term. The effect of three different calibrated atmospheric compositions were studied duringin vitro culture ofPrunus avium shoots. At 0.034% CO₂-21% O₂ (vol/vol), which stimulate the natural atmosphere, the highest growth rate and chlorophyll content were recorded. When grown at 0.09% CO₂-8% O₂ (vol/vol), a favorable condition for photosynthesis and growth, cultures showed a higher percentage of dry matter and elevated ethylene production, but total chlorophyll was lower. These shoots were also highly lignified and fibrous with red pigmentation along the leaves and stems. At 0% CO₂-21% O₂ (vol/vol), in contrast, growth and ethylene formation were inhibited; chlorophyll content was lowest in comparison with the other two environmental conditions, but regreening of tissues was observed after the first half of the culture period. Senescence symptoms, as indicated by decreased chlorophyll, appeared after about 18 d of culture for tissues grown in CO₂-containing atmospheres. These experiments provided evidence that in CO₂-enriched cultures biomass production steadily increased even when chlorophyll decreased. A possible role of CO₂ in promoting tissue-senescence through activation of photooxidative events and ethylene synthesis is discussed.     

Innovative development of membrane sparger for carbon dioxide supply in microalgae cultures

The present study was aimed to develop a membrane sparger (MS) integrated into a tubular photobioreactor to promote the increase of the carbon dioxide (CO₂) fixation by Spirulina sp. LEB 18 cultures. The use of MS for the CO₂ supply in Spirulina cultures resulted not only in the increase of DIC concentrations but also in the highest accumulated DIC concentration in the liquid medium (127.4 mg L⁻¹ d⁻¹). The highest values of biomass concentration (1.98 g L⁻¹), biomass productivity (131.8 mg L⁻¹ d⁻¹), carbon in biomass (47.9% w w⁻¹), CO₂ fixation rate (231.6 mg L⁻¹ d⁻¹), and CO₂ use efficiency (80.5% w w⁻¹) by Spirulina were verified with MS, compared to the culture with conventional sparger for CO₂ supply. Spirulina biomass in both culture conditions had high protein contents varying from 64.9 to 69% (w w⁻¹). MS can be considered an innovative system for the supply of carbon for the microalgae cultivation and biomass production. Moreover, the use of membrane system might contribute to increased process efficiency with a reduced cost of biomass production.     

High nocturnal CO2 emanation guides the sand fly Phlebotomus papatasi to sugar‐rich plants

Abstract In arid areas, Phlebotomus papatasi obtains essential carbohydrates by feeding on green tissues of plants. There is a great variation in sugar content, metabolic rates and dark respiration between conspecific plants, and also between branches and leaves of the same plant. It is hypothesized that high nocturnal release of CO₂ may guide the sand flies to rich sugar sources. Comparisons of Ph. papatasi feeding on branches of different plant species demonstrate a significant positive correlation between the level of sugar in leaves, the rate of sand fly feeding on them and the size of ingested sugar meals. Mean nocturnal CO₂ emanation of low‐sugar Ricinus communis branches is 26.5 ppm and that of sugar rich branches is 86.3 ppm above room level. Low‐sugar Capparis spinosa branches release 45.0 ppm and the emission from sugar rich branches is 76.0 ppm above room level. Branches with similar emissions, placed behind net partitions, are used in no‐choice orientation experiments: R. communis branches releasing high CO₂ levels are approached by 53.7% of the flies compared with 3.0% of flies that orientate to low CO₂ branches. Capparis spinosa with high CO₂ emission are approached by 9.8% of the flies compared with 0.95% of flies that orientate to low CO₂ branches.     

Effect of simazine,lindane and ceresan on soil respiration and nitrification rates

Summary The effect of three pesticidesviz, simazine, lindane and ceresan upto 100-fold of field application was studied on organic matter mineralization as well as on nitrification rates in Delhi alluvial soil. The normal rate of simazine (2 ppm) did not influence CO₂ evolution but higher concentrations suppressed it. Lindane and ceresan inhibited CO₂ production from soil by normal concentrations but the same CO₂ production was enhanced in berseem roots treated soil upto 10 ppm of ceresan.The nitrification of ammonium sulphate in soil due to these pesticides was impaired significantly for varying periods. The inhibitory effect of higher concentrations was marked only upto 3 weeks, subsequently the rate of nitrification was restored. Among the nitrifiers, Nitrobacter were more susceptible as compared to Nitrosomonas.     

Enhanced Chlorella vulgaris Buitenzorg growth by photon flux density alteration in serial photobioreactors

Microalgae perform oxygenic photosynthesis and are capable of taking up a large amount of CO₂, using an inducible CO₂ concentrating mechanism (CCM), and fixing CO₂ into higher compounds. These characteristics make the microalgae potentially useful for removal and utilization of CO₂ emitted from industrial plants and, generally, the usage of photosynthetic microorganisms has increased and significantly improved as a solution for CO₂ emissions. In this light and based on previous research using Anabaena cylindrica IAM M1 and Spirulina platensis IAM M 135, enhancement was sought for CO₂ fixation and biomass production by Chlorella vulgaris Buitenzorg by increasing the photon flux density concurrent with increases in culture biomass during the cellular growth phase and was compared to cultures of Chlorella grown at optimal constant illumination, with all cultures grown using Bennick basal medium, 29°C, and a flow of 1.0 atm. 10% CO₂ enriched air delivered to three in serial photobioreactors of 0.200 dm³ capacity each. The results showed that increasing illumination during culture increased biomass production of Chlorella by ∼60% as well as increased CO₂ fixation ability by ∼7.0%. It was also demonstrated that the non-competitive inhibition of [HCO₃ ⁻] as a carbon source significantly affected the cultivation in both the increasing and constant photon flux density regimes.     

INTERACTIVE EFFECTS OF IRRADIANCE AND CO2 ON CO2 FIXATION AND N2 FIXATION IN THE DIAZOTROPH TRICHODESMIUM ERYTHRAEUM (CYANOBACTERIA)1

The diazotrophic cyanobacteria Trichodesmium spp. contribute approximately half of the known marine dinitrogen (N₂) fixation. Rapidly changing environmental factors such as the rising atmospheric partial pressure of carbon dioxide (pCO₂) and shallower mixed layers (higher light intensities) are likely to affect N₂‐fixation rates in the future ocean. Several studies have documented that N₂ fixation in laboratory cultures of T. erythraeum increased when pCO₂ was doubled from present‐day atmospheric concentrations (～380 ppm) to projected future levels (～750 ppm). We examined the interactive effects of light and pCO₂ on two strains of T. erythraeum Ehrenb. (GBRTRLI101 and IMS101) in laboratory semicontinuous cultures. Elevated pCO₂ stimulated gross N₂‐fixation rates in cultures growing at 38 μmol quanta · m^?2 · s^?1 (GBRTRLI101 and IMS101) and 100 μmol quanta · m^?2 · s^?1 (IMS101), but this effect was reduced in both strains growing at 220 μmol quanta · m^?2 · s^?1. Conversely, CO₂‐fixation rates increased significantly (P < 0.05) in response to high pCO₂ under mid‐ and high irradiances only. These data imply that the stimulatory effect of elevated pCO₂ on CO₂ fixation and N₂ fixation by T. erythraeum is correlated with light. The ratio of gross:net N₂ fixation was also correlated with light and trichome length in IMS101. Our study suggests that elevated pCO₂ may have a strong positive effect on Trichodesmium gross N₂ fixation in intermediate and bottom layers of the euphotic zone, but perhaps not in light‐saturated surface layers. Climate change models must consider the interactive effects of multiple environmental variables on phytoplankton and the biogeochemical cycles they mediate.     

Acetate synthesis from 2 CO2 in acetogenic bacteria: is carbon monoxide an intermediate?

Cultures of Acetobacterium woodii and Clostridium thermoaceticum growing on fructose or glucose, respectively, were found to produce small, but significant amounts of carbon monoxide. In the gas phase of the cultures up to 53 ppm CO were determined. The carbon monoxide production was completely inhibited by 1 mM cyanide. Cultures and cell suspensions of both acetogens incorporated ¹⁴CO specifically into the carboxyl group of acetate. This CO fixation into C₁ of acetate was unaffected by cyanide (1 mM). The findings are taken to indicate that CO (in a bound form) is the physiological precursor of the C₁ of acetate in acetate synthesis from CO₂. The cyanide inhibition experiments support the hypothesis that the cyanide-sensitive carbon monoxide dehydrogenase may serve to reduce CO₂ to CO rather than to incorporate the carbonyl into C₁ of acetate.     

The simultaneous effect of soil-borne NaF and air pollutant SO2 on CO2-uptake and pollutant accumulation

Summary Spruce cuttings were potted in quartz sand. One half was watered with tap water, the other with deionized water containing 100 ppm F^- as NaF, during winter till bud break. After flushing the plants were exposed continuously for five weeks (June/July) either to normal air or to air with 0.025 and 0.075 ppm SO₂, respectively. CO₂-uptake was measured in the laboratory (40,000 lux) with an IRGA.Even in the absence of visible symptoms of injury to last year's needles, root-applied fluoride did suppress CO₂-uptake significantly. Also the fumigation with 0.075 ppm SO₂ caused a depression of CO₂-uptake, whereas 0.025 ppm SO₂ remained without significant reaction within five weeks. Fluorides infiltrating through roots and airborne SO₂ acting together may depress CO₂-uptake synergistically.Soil applied fluoride accumulated particularly in roots and twigs, whereas very little was found in the stem. The F^--accumulation even increased with increasing SO₂-concentrations but was without effect on S-accumulation.     

The effect of elevated carbon dioxide and fertilization on primary and secondary metabolites in birch,Betula pendula (Roth)

Seedlings of European white birch (Betula pendula Roth) were grown in growth chambers for one growth season under four carbon dioxide regimes (350, 700, 1050 and 1400 ppm) and at three fertilization levels (0, 100 and 500 kg ha^–1 monthly). The soluble carbohydrates and secondary phenolics in the leaves and stems were analysed. It was found that fertilizer addition reduced the amounts of glucose and fructose while sucrose remained almost unaffected. The sugar content of leaves increased at 700 ppm and 1050 ppm of CO₂ and decreased at the highest CO₂ concentration (1400 ppm). The amounts of proanthocyanidins and flavonoids in leaves decreased with fertilization addition and increased with CO₂ enrichment. The production of simple phenolic glucosides varied according to the fertilization and CO₂ treatments. The triterpenoid content of stems seemed to increase with fertilization and CO₂-addition. Our results indicate that the production of phytochemicals in the birch seedlings is very sensitive to both fertilization and CO₂ addition, which is in agreement with earlier studies, and thus provide some support for the hypothesis of carbon allocation to plant defence when there is an excess of carbon and nutrient. The considerable variation in the production of secondary components may indicate that the synthesis of these defensive metabolites can be regulated by a plant to certain extent, depending on the ability of the plant to acclimate to changes in the physical environment.     

Carbon Dioxide Emission in Relation to the Growth of Geotrichum candidum in Solid Cultures

Geotrichum candidum plays an important role in the ripening of Camembert‐type cheeses. However, the direct measurement of the biomass concentration is rather tedious and, therefore, the development of alternative methods for monitoring the growth on solid media would be very useful. For this purpose, a non‐structured model was previously developed to describe the CO₂ emission during the growth of G. candidum in liquid cultures. The CO₂ production was assumed to be partially associated with growth: a part resulted from growth and the remaining from cellular maintenance. This model has also been validated in solid cultures on peptone‐lactate based medium. The coefficients for growth‐associated and non‐growth‐associated production were found to be 0.301 and 0.123 per day, respectively. Therefore, the CO₂ production may be a non‐destructive and useful tool to monitor fungal growth in solid cultures. In the case of mixed cultures of both fungi (Geotrichum candidum and Penicillium camembertii) involved in the ripening of Camembert cheeses, CO₂ emission can be related to the total viable biomass, while ammonia and volatile sulphur compounds can be linked to G. candidum biomass. Indeed, it was previously shown that Penicillium camembertii released only very low amounts of both compounds.     

Mycelial production, spread and root colonisation by the ectomycorrhizal fungi Hebeloma crustuliniforme and Paxillus involutus under elevated atmospheric CO2

Effects of elevated atmospheric carbon dioxide (CO₂) levels on the production and spread of ectomycorrhizal fungal mycelium from colonised Scots pine roots were investigated. Pinus sylvestris (L.) Karst. seedlings inoculated with either Hebeloma crustuliniforme (Bull:Fr.) Quél. or Paxillus involutus (Fr.) Fr. were grown at either ambient (350 ppm) or elevated (700 ppm) levels of CO₂. Mycelial production was measured after 6 weeks in pots, and mycelial spread from inoculated seedlings was studied after 4 months growth in perlite in shallow boxes containing uncolonised bait seedlings. Plant and fungal biomass were analysed, as well as carbon and nitrogen content of seedling shoots. Mycelial biomass production by H. crustuliniforme was significantly greater under elevated CO₂ (up to a 3-fold increase was observed). Significantly lower concentrations and total amounts of N were found in plants exposed to elevated CO₂.     

Boron Deficiency Induced Changes in Translocation of 14CO2-Photosynthate Into Primary Metabolites in Relation to Essential Oil and Curcumin Accumulation in Turmeric (Curcuma longa L.)

Changes in leaf growth, net photosynthetic rate (P _N), incorporation pattern of photosynthetically fixed ¹⁴CO₂ in leaves 1–4 from top, roots, and rhizome, and in essential oil and curcumin contents were studied in turmeric plants grown in nutrient solution at boron (B) concentrations of 0 and 0.5 g m^-3. B deficiency resulted in decrease in leaf area, fresh and dry mass, chlorophyll (Chl) content, and P _N and total ¹⁴CO₂ incorporated at all leaf positions, the maximum effect being in young growing leaves. The incorporation of ¹⁴CO₂ declined with leaf position being maximal in the youngest leaf. B deficiency resulted in reduced accumulation of sugars, amino acids, and organic acids at all leaf positions. Translocation of the metabolites towards rhizome and roots decreased. In rhizome, the amount of amino acids increased but content of organic acids did not show any change, whereas in roots there was decrease in contents of these metabolites as a result of B deficiency. Photoassimilate partitioning to essential oil in leaf and to curcumin in rhizome decreased. Although the curcumin content of rhizome increased due to B deficiency, the overall rhizome yield and curcumin yield decreased. The influence of B deficiency on leaf area, fresh and dry masses, CO₂ exchange rate, oil content, and rhizome and curcumin yields can be ascribed to reduced photosynthate formation and translocation.     

Photosynthesis of salt-stressed maize as influenced by Ca∶Na ratios in the nutrient solution

The CO₂ fixation rate of salt-stressed maize leaves was influenced by the Ca∶Na ratio in the solution cultures. At an osmotic potential of −0.4 MPa in the root media, both the photosynthetic rate and the water-use efficiency declined as substrate Ca increased. Blade-Ca concentration also increased, while blade-Na and-Mg decreased. Apparently photosynthetic activity was inhibited in part by internal Mg deficiency rather than by Na toxicity or by Na-induced Ca deficiency. Reduction of the Ca∶Mg ratio in the culture stimulated the CO₂ fixation rate.     

Effect of boron on the pollen vitality and yield of rice plants (Oryza sativa L. var. Jaya)

Summary Rice plants were grown in sand cultures with nutrient solution including boron at 0, 1, 2.5 and 5 ppm concentrations.In general, supply of boron improved the pollen vitality of rice flowers. It was stimulating up to 2.5 ppm concentration in the nutrient solution, beyond which (i.e., at 5 ppm) inhibitory effects appeared. The availability of boron also increased the yield of rice grains in the same order.Stimulating effects of boron may be linked with greater availability of sugars, increased enzymatic activity and respiration which favoured better growth of pollen. Inhibitory effects of stronger concentration of boron (5 ppm) may be related with physiological depression and injury to protoplasm itself.     

Effects of increased CO2 levels on growth, photosynthesis, ammonium uptake and cell composition in the macroalga Hypnea spinella (Gigartinales, Rhodophyta)

The red seaweed Hypnea spinella (Gigartinales, Rhodophyta), was cultured at laboratory scale under three different CO₂ conditions, non-enriched air (360?ppm CO₂) and CO₂-enriched air at two final concentrations (750 and 1,600?ppm CO₂), in order to evaluate the influence of increased CO₂ concentrations on growth, photosynthetic capacity, nitrogen removal efficiency, and chemical cellular composition. Average specific growth rates of H. spinella treated with 750 and 1,600?ppm CO₂-enriched air increased by 85.6% and 63.2% compared with non-enriched air cultures. CO₂ reduction percentages close to 12% were measured at 750?ppm CO₂ with respect to 5% and 7% for cultures treated with air and 1,600?ppm CO₂, respectively. Maximum photosynthetic rates were enhanced significantly for high CO₂ treatments, showing P _max values 1.5-fold higher than that for air-treated cultures. N–NH ₄ ⁺ consumption rates were also faster for algae growing at 750 and 1,600?ppm CO₂ than that for non-enriched air cultures. As a consequence of these experimental conditions, soluble carbohydrates increased and soluble protein contents decreased in algae treated with CO₂-enriched air. However, internal C and N contents remained constant at the different CO₂ concentrations. No significant differences in data obtained with both elevated CO₂ treatments, under the assayed conditions, indicate that H. spinella is saturated at dissolved inorganic carbon concentrations close by twice the actual atmospheric levels. The results show that increased CO₂ concentrations might be considered a key factor in order to improve intensively cultured H. spinella production yields and carbon and nitrogen bioremediation efficiencies.     

AMMONIUM STIMULATION OF DARK CARBON FIXATION AS AN INDICATOR OF NITROGEN DEFICIENCY IN PHYTOPLANKTON: POTENTIAL ERRORS CAUSED BY AMMONIUM-OXIDIZING BACTERIA1

Stimulation of dark fixation of carbon by NH₄⁺ is often used as an indicator of phytoplankton N deficiency. This assay is based on the influence of available NH₄⁺ on anaplerotic CO₂ fixation by algae. However, carbon fixation by chemoautotrophic NH₄⁺-oxidizing bacteria may also be stimulated by NH₄⁺ enrichment, a process that can mask the algal response in natural communities. NH₄⁺ addition enhanced dark carbon fixation up to 300%, relative to unamended controls, in organisms collected on a 0.7-μm retention filter in oligotrophic Flathead Lake, Montana, but the effect was not detectable in the presence of nitrapyrin, an inhibitor of NH₄⁺-oxidizing bacteria. Dark carbon fixation was enhanced with addition of NH₄⁺ in organisms retained on 2-μm filters (which should allow passage of most bacteria). NH₄⁺ stimulated dark carbon fixation in N-deficient axenic cultures of Chlamydomonas reinhardtii Dang but not in N-replete cultures in both the presence and absence of nitrapyrin. Application of nitrapyrin or size fractionation treatments, to separate the processes of dark carbon fixation by nitrifiers and phytoplankton, may improve the efficacy of assays using NH₄⁺ stimulation of dark carbon fixation to specifically indicate N deficiency in natural algal communities.     

Combined effects of CO2 concentration and nutrient status on the biomass production and nutrient uptake of birch seedlings (Betula pendula)

Birch seedlings (Betula pendula) were grown for four months in a greenhouse at three nutrient levels (fertilization of 0, 100 and 500 kg ha^-1 monthy) and at four CO₂ concentrations (350, 700, 1050 and 1400 ppm). The effect of CO₂ concentration on the biomass production depended on the nutrient status. When mineralization of the soil material was the only source of nutrients (0 kg ha^-1), CO₂ enhancement reduced the biomass production slightly, whereas the highest production increase occurred at a fertilization of 100 kg ha^-1, being over 100% between 350 and 700 ppm CO₂. At 500 kg ha^-1 the production increase was smaller, and the production decreased beyond a CO₂ concentration of 700 ppm. The CO₂ concentration had a slight effect on the biomass distribution, the leaves accounting for the highest proportion at the lowest CO₂ concentration (350 ppm). An increase in nutrient status led to a longer growth period and increased the nutrient concentrations in the plants, but the CO₂ concentration had no effect on the growth rhythm and higher CO₂ reduced the nutrient concentrations.