Effects of CO(2) and O(2) on Photosynthesis and Growth of Autotrophic Tobacco Callus

Gas exchange measurements were made on plants from two natural populations differing in salt tolerance of Andropogon glomeratus, a C₄ nonhalophyte, to examine the effect of salinity on components responsible for differences in photosynthetic capacity. Net CO₂ uptake and stomatal conductance decreased with increasing salinity in both populations, but to a greater extent in the inland (nontolerant) population. The intercellular CO₂ concentrations increased with increasing salinity in the inland population, but decreased in the marsh (tolerant) population. Water use efficiency decreased as salinity increased in the inland population, and remained unchanged in the marsh population. Carboxylation efficiency decreased and CO₂ compensation points increased with increasing salinity in both populations, but to a lesser extent in the marsh population. Carboxylation efficiencies were higher with 2% relative to 21% atmospheric O₂ in salt stressed plants, suggesting that a decrease in the carboxylation:oxygenation ratio of ribulose 1,5-bisphosphate carboxylase/oxygenase was partly responsible for the decrease in photosynthetic capacity. Populational differences in photosynthetic capacity were the result of greater salinity-induced changes in carboxylation efficiency in the inland population, and not due to differences in the stomatal limitation to CO₂ diffusion.     

Effects of CO2-Enrichment on the Growth of Young Tomato Plants in Low Light

Carbon dioxide-enrichment of young tomato plants grown in controlled-environmentcabinets at low light intensity (14 cal cm^–2 day^–1,visible radiation) increased their net assimilation rates and,initially, relative growth-rates. Subsequently, the relativegrowth-rate fell to near the rate of non-enriched plants, owingto a fall in leaf-area ratio associated with an increase inleaf dry weight/area. Sowing non-enriched plants a few daysearlier to reach the same total dry weight would not have producedidentical plants. The effects of CO₂-enrichment to 1000 vpm could be simulatedby increasing light intensity by approximately one third exceptthat the plants had shorter internodes than those in extra CO₂.This was a morphogenetic effect of light since CO₂-enrichmentitself produced slightly shorter plants than controls for anequivalent total dry weight. CO₂-enrichment did not change the dry-weight distribution inthe plants and had little effect on rate of leaf produoctionor the number of flower primordia. There were no indicationsthat beneficial effects of CO₂-enrichment operated other thanthrough increased photosynthesis.     

Photosynthesis and Growth of Water Hyacinth under CO(2) Enrichment

Water hyacinth (Eichhornia crassipes [Mart.] Solms) plants were grown in environmental chambers at ambient and enriched CO₂ levels (330 and 600 microliters CO₂ per liter). Daughter plants (ramets) produced in the enriched CO₂ gained 39% greater dry weight than those at ambient CO₂, but the original mother plants did not. The CO₂ enrichment increased the number of leaves per ramet and leaf area index, but did not significantly increase leaf size or the number of ramets formed. Flower production was increased 147%. The elevated CO₂ increased the net photosynthetic rate of the mother plants by 40%, but this was not maintained as the plants acclimated to the higher CO₂ level. After 14 days at the elevated CO₂, leaf resistance increased and transpiration decreased, especially from the adaxial leaf surface. After 4 weeks in elevated as compared to ambient CO₂, ribulose bisphosphate carboxylase activity was 40% less, soluble protein content 49% less, and chlorophyll content 26% less; whereas starch content was 40% greater. Although at a given CO₂ level the enriched CO₂ plants had only half the net photosynthetic rate of their counterparts grown at ambient CO₂, they showed similar internal CO₂ concentrations. This suggested that the decreased supply of CO₂ to the mesophyll, as a result of the increased stomatal resistance, was counterbalanced by a decreased utilization of CO₂. Photorespiration and dark respiration were lower, such that the CO₂ compensation point was not altered. The photosynthetic light and CO₂ saturation points were not greatly changed, nor was the O₂ inhibition of photosynthesis (measured at 330 microliters CO₂ per liter). It appears that with CO₂ enrichment the temporary increase in net photosynthesis produced larger ramets. After acclimation, the greater total ramet leaf area more than compensated for the lower net photosynthetic rate on a unit leaf area basis, and resulted in a sustained improvement in dry weight gain.     

Effects of Iron Excess on Nicotiana plumbaginifolia Plants (Implications to Oxidative Stress)

Fe excess is believed to generate oxidative stress. To contribute to the understanding of Fe metabolism, Fe excess was induced in Nicotiana plumbaginifolia grown in hydroponic culture upon root cutting. Toxicity symptoms leading to brown spots covering the leaf surface became visible after 6 h. Photosynthesis was greatly affected within 12 h; the photosynthetic rate was decreased by 40%. Inhibition of photosynthesis was accompanied by photoinhibition, increased reduction of photosystem II, and higher thylakoid energization. Fe excess seemed to stimulate photorespiration because catalase activity doubled. To cope with cellular damage, respiration rate increased and cytosolic glucose-6-phosphate dehydrogenase activity more than doubled. Simultaneously, the content of free hexoses was reduced. Indicative of generation of oxidative stress was doubling of ascorbate peroxidase activity within 12 h. Contents of the antioxidants ascorbate and glutathione were reduced by 30%, resulting in equivalent increases of dehydroascorbate and oxidized glutathione. Taken together, moderate changes in leaf Fe content have a dramatic effect on plant metabolism. This indicates that cellular Fe concentrations must be finely regulated to avoid cellular damage most probably because of oxidative stress induced by Fe.     

Consequence of Absence of Nitrate Reductase Activity on Photosynthesis in Nicotiana plumbaginifolia Plants

Chlorate-resistant Nicotiana plumbaginifolia (cv Viviani) mutants were found to be deficient in the nitrate reductase apoprotein (NR⁻nia). Because they could not grow with nitrate as sole nitrogen source, they were cultivated as graftings on wild-type Nicotiana tabacum plants. The grafts of mutant plants were chlorotic compared to the grafts of wild type. Mutant leaves did not accumulate nitrogen and nitrate but contained less malate and more glutamine than wild leaves. They exhibited a slight increase of the proportion of the light-harvesting chlorophyll a/b protein complexes and a lowering of the efficiency of energy transfer between these complexes and the active centers. After a 3 second ¹⁴CO₂ pulse, the total ¹⁴C incorporation of the mutant leaves was approximately 20% of that of the control. The ¹⁴C was essentially recovered in ribulose bisphosphate in these plants. It was consistent with a decline of ribulose bisphosphate carboxylase activity observed in the mutant. After a 3 second ¹⁴CO₂ pulse followed by a 60 second chase with normal CO₂, ¹⁴C was mainly accumulated in starch which was labeled more in the mutant than in the wild type. These results confirm the observation that in the nitrate reductase deficient leaves, chloroplasts were loaded with large starch inclusions preceding disorganization of the photosynthetic apparatus.     

CO2 Dynamics and Growth in Photoautotrophic and Photomixotrophic Apple Cultures

The daily dynamics of CO₂ concentration in the culture vessels and the photoautotrophic or photomixotrophic growth capacity of apple (Malus pumila hybrid MM 106 paradisiaca× Northern Spy) cultures were studied. The photoautotrophic cultures were grown on a sugar-free growth medium and submitted (0S+CO₂) or not (0S-CO₂) to periodic injections of exogenous CO₂. The photomixotrophic cultures were grown in the presence of 30 g dm⁻³ sucrose, with (30S+CO₂) or without (30S-CO₂) CO₂ enrichment. The photosynthetic photon flux density applied was of 210 ± 5 μmol m⁻²s⁻¹. In the 0S-CO₂ treatment, CO₂ showed rather uniform and narrow light-dark fluctuations throughout the culturing cycle. In the 30S-CO₂ treatment, the daily ratio between CO₂ produced during the dark period and that uptaken during the following light period, was almost always above 1 with the only exception of a few days (from the 5^th to the 9^th day) when the amount of photosynthesised CO₂ was equal to or higher than that produced during dark respiration. The 0S+CO₂ cultures needed to be enriched all days with exogenous CO₂ to avoid periods of gas deficiency while in 30S+CO₂ the CO₂ injected the first culturing day was uptaken over 5 d; thereafter, daily injections were necessary. Culture fresh and dry mass, number of newly formed shoots and number of nodes per shoot in 0S+CO₂ treatment did not statistically differ from the values obtained with 30S−CO₂. The highest growth was observed in 30S+CO₂ treatment. The increase in culture fresh mass due to 1 μmol of CO₂ added to the culture vessels was 1.54 and 1.36 mg for 30S and 0S respectively, while in terms of dry mass the increase was about 2.5 times higher in the sugar-enriched treatment. CO₂ enrichment accounted for 77.3 % and 21.2 % of the final fresh mass in 0S+CO₂ and 30S+CO₂, respectively. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of Atmospheric CO(2) Enrichment on Photosynthesis, Respiration, and Growth of Sour Orange Trees

Numerous net photosynthetic and dark respiratory measurements were made over a period of 4 years on leaves of 24 sour orange (Citrus aurantium) trees; 8 of them growing in ambient air at a mean CO₂ concentration of 400 microliters per liter, and 16 growing in air enriched with CO₂ to concentrations approaching 1000 microliters per liter. Over this CO₂ concentration range, net photosynthesis increased linearly with CO₂ by more than 200%, whereas dark respiration decreased linearly to only 20% of its initial value. These results, together with those of a comprehensive fine-root biomass determination and two independent aboveground trunk and branch volume inventories, suggest that a doubling of the air's current mean CO₂ concentration of 360 microliters per liter would enhance the growth of the trees by a factor of 3.8.     

Amplification of repetitive DNA from Nicotiana plumbaginifolia in asymmetric somatic hybrids between Nicotiana sylvestris and Nicotiana plumbaginifolia

Summary Asymmetric somatic hybrids were obtained between a chlorophyll-deficient mutant of Nicotiana sylvestris (V42) and a nitrate-reductase (NR)-deficient line of N. plumbaginifolia (cnx20 or Nia26), using each of the parents alternately as the irradiated donor. Irradiation doses applied ranged from 10 to 1,000 Gy of gamma-rays. Hybrid selection was based on complementation of NR deficiency with wild-type NR genes. To aid in the analysis of somatic hybrids, species-specific repetitive DNA sequences from N. plumbaginifolia (NPR9 and NPR18) were cloned. NPR18 is a dispersed repetitive sequence occupying about 0.4% of the N. plumbaginifolia genome. In turn, NPR9, which is part of a highly repetitive DNA sequence, occupies approximately 3% of the genome. The species-specific plant DNA repeats, together with cytological analysis data, were used to assess the relative amount of the N. plumbaginifolia genome in the somatic hybrids. In fusion experiments using irradiated N. plumbaginifolia, an increase in irradiation dose prior to fusion led to a decrease in N. plumbaginifolia nuclear DNA content per hybrid genome. For some hybrid lines, an increase in the quantity of repetitive sequences was detected. Thus, hybrid lines 1NV/21, 100NV/7, 100NV/ 9, and 100NV/10 (where N. plumbaginifolia was the irradiated donor) were characterized by amplification of NPR9. In the reverse combination (where N. sylvestris was the irradiated donor), an increase in the copy number of NPR18 was determined for hybrid clones 1VC/2, 1VC/3, 100VC/2 and oct100/7. Possible reasons for the amplification of the repeated sequences are discussed.     

Photoautotrophic Growth and Photosynthesis in Cell Suspension Cultures of Chenopodium rubrum

A method is described for growing cell suspension cultures of Chenopodium rubrum photoautotrophically for prolonged periods of time. By using a two-tier culture vessel the growth medium with the cells was separated from the CO₂ reservoir. Definite CO₂ concentrations were established by a K₂CO₃/KHCO₃ buffer. Photoautotrophic growth in C. rubrum cell suspension cultures was correlated with the CO₂ level. At 0.5% CO₂ the cell cultures contained 68 μg chlorophyll/g fresh weight and showed an increase in fresh weight of about 80% in 18 days. At 1% CO₂ an increase in fresh weight of 165% in 18 days was observed. The chlorophyll content rose up to 84 μg/g fresh weight. The photoautotrophic growth was also greatly influenced by the 2,4-D content of the medium. Cell growth was enhanced by lowering the auxin concentration. Best growth was attained (210% increase in fresh weight) at 10^?8M 2,4-D. The photosynthetic activity of the cells was measured by the light dependent ¹⁴CO₂ incorporation. At 0.5% CO₂ the cell suspensions assimilated about 100 μmol CO₂/mg chlorophyll × h. In the presence of 1% CO₂ the light driven assimilation was raised up to 185 μmol CO₂/mg chlorophyll × h. In both cases, the dark incorporation of CO₂ was merely 1.8% of the values obtained in light.     

不同光质对烟草叶片生长及光合作用的影响

通过对烟草植株覆盖白、红、黄、蓝、紫色滤膜获得不同光质,研究了光质对烟叶生长及光合作用的影响。结果表明,与白膜处理相比,红膜与蓝膜处理下的烟草叶片较厚,比叶面积较小,叶绿素a/b比值、净光合速率、可变荧光强度（Fv）和最大荧光强度（Fm）的比值Fv/Fm（PSⅡ最大光化学量子效率）、PSⅡ实际光化学量子效率（ΦPSⅡ）、光饱和点和CO2饱和点均较高。黄膜处理下的叶片较白膜处理的更薄,净光合速率、Fv/Fm、ΦPSⅡ、光饱和点、CO2饱和点均较低。紫膜处理的叶片比叶面积比白膜处理的小,净光合速率和Fv/Fm比白膜的大。实验结果表明红光、蓝光和紫光促进了烟叶的生长,这种促进作用是与其高光合效率紧密相连的;而黄光对烟叶的生长有一定程度的抑制作用。     

Ethylene Contamination of CO(2) Cylinders: Effects on Plant Growth in CO(2) Enrichment Studies

The mechanical extensibilities of stage IVb Phycomyces were measured before and after a humidified wind stimulus. We find that when the humidity of the wind is greater than that of the ambient air, there is an increase in the mechanical extensibility of the cell wall. We also find that a step decrease in wind humidity results in a decrease in the mechanical extensibility of the cell wall.     

Photosynthesis and Plant Growth at Elevated Levels of CO2

In this review, we discuss the effects of elevated CO₂ levelson photosynthesis in relation to the whole plant growth in terrestrialhigher C₃ plants. Short-term CO₂ enrichment stimulates the rateof photosynthesis. Plant mass is also enhanced by CO₂ enrichment.However, the effects of long-term CO₂ enrichment on photosynthesisare variable. Generally, the prolonged exposure to CO₂ enrichmentreduces the initial stimulation of photosynthesis in many species,and frequently suppresses photosynthesis. These responses areattributed to secondary responses related to either excess carbohydrateaccumulation or decreased N content rather than direct responsesto CO₂. Accumulation of carbohydrates in leaves may lead tothe repression of photosynthetic gene expression and excessstarch seems to hinder CO₂ diffusion. Therefore, the specieswhich have the sink organs for carbohydrate accumulation donot show the suppression of photosynthesis. The suppressionof photosynthesis by CO₂ enrichment is always associated withdecreases in leaf N and Rubisco contents. These decreases arenot due to dilution of N caused by a relative increase in theplant mass but are the result of a decrease in N allocationto leaves at the level of the whole plant, and the decreasein Rubisco content is not selective. Leaf senescence and plantdevelopment are also accelerated by CO₂ enrichment. However,they are independent of each other in some species. Thus, variousresponses to CO₂ observed at the level of a single leaf resultfrom manifold responses at the level of the whole plant grownunder conditions of CO₂ enrichment. (Received July 8, 1999; Accepted August 12, 1999)     

Note on the chromosomes of Nicotiana plumbaginifolia Viviani

The centromere position on the chromosomes of three European stocks of Nicotiana plumbaginifolia (2n=20) was determined by investigating in root tip mitoses the shape of the chromosomes during congression and polar movement and during C-metaphase. One pair of chromosomes is subtelocentric and 9 pairs are acrocentric. Some chromosomes mimic (sub-)metacentrics by having noncentric constrictions. A recently published (A. Villa; Genetica 64: 145–148, 1984) idiogram of one of the stocks is commented on.     

Effects of RNases on rejection of pollen from Nicotiana tabacum and N. plumbaginifolia

S-RNases are implicated in both inter- and intra-specific pollen rejection in Nicotiana. At least two mechanisms contribute to S-RNase dependent rejection of pollen from self compatilble species such as Nicotiana plumbaginifolia and N. tabacum. Cloned S-RNases from self incompatible N. alata expressed in styles of self compatible N. tabacum cause rejection of N. tabacum pollen through a factor-independent mechanism. However, rejection of N. plumbaginifolia pollen occurs only when S-RNases are expressed in conjunction with non-S-RNase factors from N. alata (factor-dependent pollen rejection). Here, we compared the pollen rejection activity of four RNases in these two systems. Recombinant RNase expression levels in the factor-dependent N. plumbaginifolia system were insufficient to cause pollen rejection. However, three S-RNases were active in the factor-independent N. tabacum pollen rejection system. This system shows the broadest specificity of any system so far examined. However, RNaseI from E. coli could not cause N. tabacum pollen rejection. Thus, RNase activity alone is not sufficient for pollen rejection. Our results suggest that S-RNases are specially adapted to function in pollen rejection. Received: 15 December 2000 / Accepted: 1 May 2001     

Effects of Temperature on Photosynthesis and CO(2) Evolution in Light and Darkness by Green Leaves

Using an open and a closed system of gas analysis, it was found that CO₂ evolution in light and in darkness from plant leaves (sunflower, soybean, watermelon, eggplant, and jackbean) have a different response to temperature. While the rate of CO₂ evolution in light increased with increasing temperature from 17 to 35° and then declined, the rate of CO₂ evolution in darkness increased continuously up to 40°. The rate of CO₂ evolution in light was affected by light intensity. At 1800 ft-c and below 35° the rate of CO₂ evolution in light was greater than in darkness, but above 35° it became lower than in darkness. The Q₁₀ for CO₂ evolution in light was consistently lower than that in darkness.     

CO(2) Enhancement of Growth and Photosynthesis in Rice (Oryza sativa) : Modification by Increased Ultraviolet-B Radiation

Two cultivars of rice (Oryza sativa L.) IR-36 and Fujiyama-5 were grown at ambient (360 microbars) and elevated CO₂ (660 microbars) from germination through reproduction in unshaded greenhouses at the Duke University Phytotron. Growth at elevated CO₂ resulted in significant decreases in nighttime respiration and increases in photosynthesis, total biomass, and yield for both cultivars. However, in plants exposed to simultaneous increases in CO₂ and ultraviolet-B (UV-B) radiation, CO₂ enhancement effects on respiration, photosynthesis, and biomass were eliminated in IR-36 and significantly reduced in Fujiyama-5. UV-B radiation simulated a 25% depletion in stratospheric ozone at Durham, North Carolina. Analysis of the response of CO₂ uptake to internal CO₂ concentration at light saturation suggested that, for IR-36, the predominant limitation to photosynthesis with increased UV-B radiation was the capacity for regeneration of ribulose bisphosphate (RuBP), whereas for Fujiyama-5 the primary photosynthetic decrease appeared to be related to a decline in apparent carboxylation efficiency. Changes in the RuBP regeneration limitation in IR-36 were consistent with damage to the photochemical efficiency of photosystem II as estimated from the ratio of variable to maximum chlorophyll fluorescence. Little change in RuBP regeneration and photochemistry was evident in cultivar Fujiyama-5, however. The degree of sensitivity of photochemical reactions with increased UV-B radiation appeared to be related to leaf production of UV-B-absorbing compounds. Fujiyama-5 had a higher concentration of these compounds than IR-36 in all environments, and the production of these compounds in Fujiyama-5 was stimulated by UV-B fluence. Results from this study suggest that in rice alterations in growth or photosynthesis as a result of enhanced CO₂ may be eliminated or reduced if UV-B radiation continues to increase.     

Effects of CO(2) Concentration on Rubisco Activity, Amount, and Photosynthesis in Soybean Leaves

Growth at an elevated CO₂ concentration resulted in an enhanced capacity for soybean (Glycine max L. Merr. cv Bragg) leaflet photosynthesis. Plants were grown from seed in outdoor controlled-environment chambers under natural solar irradiance. Photosynthetic rates, measured during the seed filling stage, were up to 150% greater with leaflets grown at 660 compared to 330 microliters of CO₂ per liter when measured across a range of intercellular CO₂ concentrations and irradiance. Soybean plants grown at elevated CO₂ concentrations had heavier pod weights per plant, 44% heavier with 660 compared to 330 microliters of CO₂ per liter grown plants, and also greater specific leaf weights. Ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco) activity showed no response (mean activity of 96 micromoles of CO₂ per square meter per second expressed on a leaflet area basis) to short-term (~1 hour) exposures to a range of CO₂ concentrations (110-880 microliters per liter), nor was a response of activity (mean activity of 1.01 micromoles of CO₂ per minute per milligram of protein) to growth CO₂ concentration (160-990 microliters per liter) observed. The amount of rubisco protein was constant, as growth CO₂ concentration was varied, and averaged 55% of the total leaflet soluble protein. Although CO₂ is required for activation of rubisco, results indicated that within the range of CO₂ concentrations used (110-990 microliters per liter), rubisco activity in soybean leaflets, in the light, was not regulated by CO₂.     

Effects of CO2 Enrichment on Photosynthesis, Growth, and Biochemical Composition of Seagrass Thalassia hemprichii (Ehrenb.) Aschers

The effects of CO2 enrichment on various ecophysiological parameters of tropical seagrass Thalassia hemprichii(Ehrenb.)Aschers were tested.T.hemprichii,collected from a seagrass bed in Xincun Bay,Hainan island of Southern China,was cultured at 4 CO2(aq)concentrations in flow-through seawater aquaria bubbled with CO2.CO2 enrichment considerably enhanced the relative maximum electron transport rate(RETRmax)and minimum saturating irradiance(Ek)of T.hemprichii.Leaf growth rate of CO2enriched plants was significantly higher than that in unenriched treatment.Nonstructural carbohydrates(NSC)of T.hemprichii,especially in belowground tissues,increased strongly with elevated CO2(aq),suggesting a translocation of photosynthate from aboveground to belowground tissues.Carbon content in belowground tissues showed a similar response with NSC,while in aboveground tissues,carbon content was not affected by CO2 treatments.In contrast,with increasing CO2(aq),nitrogen content in aboveground tissues markedly decreased,but nitrogen content in belowground was nearly constant.Carbon: nitrogen ratio in both tissues were obviously enhanced by increasing CO2(aq).Thus,these results indicate that T.hemprichii may respond positively to CO2-induced acidification of the coastal ocean.Moreover,the CO2-stimulated improvement of photosynthesis and NSC content may partially offset negative effects of severe environmental disturbance such as underwater light reduction.     

CO2浓度升高对斜生栅藻生长和光合作用的影响

升高大气中CO2 浓度可提高斜生栅藻的生物量和光合作用速率 ,对光合效率、暗呼吸速率、光饱和点和光系统Ⅱ的光化学效率 (Fv Fm)没有明显影响 ,但藻细胞光合作用对无机碳的亲和力降低