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1.
The time course of 14CO 2 dark fixation was studied in leaves of the facultatively halophytic plant species Mesembryanthemum crystallinum cultivated with and without 400 mM NaCl in the nutrient medium. It is generally known from the literature that plants grown under saline conditions incorporate 14C predominately into amino acids. By contrast in leaves of M. crystallinum grown on NaCl and exposed to 14CO 2 in the dark, relatively more radioactivity is incorporated in the organic acids (especially malate) than in amino acids. The data obtained are discussed in relation to the NaCl induced Crassulacean acid metabolism in M. crystallinum reported earlier. 相似文献
2.
The carbon isotope composition of the halophyte Mesembryanthemum crystallinum L. (Aizoaceae) changes when plants are exposed to environmental stress and when they shift from C 3 to crassulacean acid metabolism (CAM). We examined the coupling between carbon isotope composition and photosynthetic pathway by subjecting plants of different ages to salinity and humidity treatments. Whole shoot 13C values became less negative in plants that were exposed to 400 mM NaCl in the hydroponic solution. The isotopic change had two components: a direct NaCl effect that was greatest in plants still operating in the C 3 mode and decreased proportionally with increasing levels of dark fixation, and a second component related to the degree of CAM expression. Ignoring the presumably diffusion-related NaCl effect on carbon isotope ratios results in an overestimation of nocturnal CO 2 gain in comparison to an isotope versus nocturnal CO 2 gain calibration established previously for C 3 and CAM species grown under well-watered conditions. It is widely taken for granted that the shift to CAM in M. crystallinum is partially under developmental control and that CAM is inevitably expressed in mature plants. Plants, cultivated under non-saline conditions and high relative humidity (RH) for up to 63 days, maintained diel CO 2 gas-exchange patterns and 13C values typical of C 3 plants. However, a weak CAM gas-exchange pattern and an increase in 13C value were observed in non-salt-treated plants grown at reduced RH. These observations are consistent with environmental control rather than developmental control of the induction of CAM in mature M. crystallinum under non-saline conditions. 相似文献
3.
Abscisic acid inhibited the rate of 14CO 2 fixation in leaves of Pennisetum typhoides (Burm. f.) Stapf & Hubbard seedlings, but increased the activities of phosphoenol-pyruvate-carboxylase and malic enzyme. The leaves of the seedlings grown in the presence of abscisic acid incorporated, in comparison to the control, more radioactivity in the fraction of organic acids, but less radioactivity was recorded in the amino acid fraction. On the other hand, gibberellic acid which also inhibits photosynthetic 14CO 2 assimilation and decreases the activities of photosynthetic enzymes, favours greater incorporation in alanine, and reduces that in malate. It is deduced that bio-regulants can greatly influence the flow of 14C into individual photosynthetic products. As in growth, abscisic and gibberellic acids in combination tended to antagonize each other in their effects on enzyme activity as well as in incorporation of 14CO 2 into photosynthetic products. 相似文献
4.
Abstract C 14O 2 fixation in plant tissues « in vitro ». — In the present work it has been examinated the autotrophic and heterotrophic CO 2 fixation of explants of « Helianthus tuberosus » « in vitro » and the photosyntetic efficiency of leaves produced from buds of « in vitro » explants of « Cichorium intybus » compared with that of mature leaves from normal plants of the same species. From our results it is evident that « in vitro » explants of « Helianthus tuberosus », grown, in the light, are able to autotrophically incorporate C 14O 2; the distribution of the radioactivity into the various fractions shows a large influence of the light on the neutral fraction containing sugars (50% of the total radioactivity). In the chlorophyllous explants the dark CO 2 fixation is obviously of heterotrophic type: 97% of the total radioactivity is incorporated in amine acids (43%) and the organic acids (53%); on the other hand in the dark grown explants the radioactivity is differently distributed between amino acids (59%) and organic acids (39%). Mature leaves from normal plants and leaves produced from buds of « in vitro » explants of « Cichorium intybus » incorporate the same quantity of C 14O 2 when expressed per mg of chlorophyll; the different distribution of the radioactivity in the neutral and acid fractions could be explained in terms of a different utilization pathway of the photosynthates in the two tissues. 相似文献
5.
Vascular plants have respiring tissues which are perfused by the transpiration stream, allowing solubilization of respiratory CO 2 in the xylem sap. The transpiration stream could provide a conduit for the internal delivery of respiratory CO 2 to leaves. Trees have large amounts of respiring tissues in the root systems and stems, and may have elevated levels of CO 2 in the xylem sap which could be delivered to and refixed by the leaves. Xylem sap from the shoots of three Populus deltoides trees had mean dissolved inorganic carbon concentrations (CO 2+H 2CO 3+HCO ?3) ranging from 0. 5 to 0. 9 m M. When excised leaves were allowed to transpire 1 m M[ 14C]NaHCO 3, 99. 6% of the label was fixed in the light. Seventy-seven percent of the label was fixed in major veins and the remainder was fixed in the minor veins. Autoradiography confirmed that label was confined to the vasculature. In the dark, approximately 80% of the transpired label escaped the leaf, the remainder was fixed in the major veins, slightly elevating dark respiration measurements. This indicates that the vascular tissue in P. deltoides leaves is supplied with a carbon source distinct from the atmospheric source fixed by interveinal lamina. However, the contribution of CO 2 delivered to the leaves in the transpiration stream and fixed in the veins was only 0. 5% of atmospheric CO 2 uptake. In the light 90% of the label was found in sugar, starch and protein, a pattern similar to that found for atmospheric uptake of[ 14C]CO 2. Compared with leaves labelled in the light, leaves labelled in the dark had more label in organic acid, amino acid and protein and less label in sugar and starch. After a 5-s pulse the majority of the label fed to petioles in both the light and the dark was found in malate. The majority of the label was found in malate at 120 s in the dark; only 2% of the label was found in phosphorylated compounds at 120 s. The proportion of label found in phosphorylated compounds increased from 17% at 5 s to 80% at 120 s in the light. This suggests that CO 2 delivered to leaves in the light via the transpiration stream is fixed in the veins, a small portion through dark fixation into malate, the remainder by C-3 photosynthesis. 相似文献
6.
Summary The photosynthetic products of Portulaca oleracea differ greatly depending on leaf age and length of exposure to 14CO 2. Mature leaves of P. oleracea fix 14CO 2 primarily into organic and amino acids during a 10-s exposure period. Less than 2% of the 14CO 2 fixed appears in phosphorylated compounds. In contrast, incorporation into amino acids can account for over 60% of the total 14CO 2 fixed by young leaves in an equal time period, and incorporation into alanine alone can account for up to one half of this amount. Senescent leaves display a quantitative shift of primary products toward phosphorylated compounds with a concomitant reduction of the label residing in malate and asparate. About 8 times more phosphoglyceric acid is produced in senescent leaves than in mature leaves. The aspartate/ malate ratio is not constant and depends on the length of time the leaves are exposed to 14CO 2 and the age of the leaves under study. It appears as if the stage of leaf development is one of the most important factors determining the operation of a particular enzyme system in C 4 plants. 相似文献
7.
Muhlenbergia sobolifera (Muhl.) Trin., a C 4 grass, occurs in understory habitats in the northeastern United States. Plants of M. sobolifera were grown at 23 and 30°C at 150 and 700 μmol photons m −2 s −1. The photosynthetic CO 2 compensation point, maximum CO 2 assimilation, dark respiration and the absorbed quantum use efficiency (QUE) were measured at 23 and 30°C at 2 and 20% O 2. Photosynthetic CO 2 compensation points ranged from 4 to 14mm 3 dm −3 CO 2 and showed limited O 2 sensitivity. The mean photosynthetic CO 2 compensation point of plants grown at 30°C (4·5 mm 3 dm −3) was 57% lower and 80% less inhibited by O 2 than that of plants grown at 23°C. Photosynthesis was similarly affected by growth temperature, with 70% more O 2 inhibition in plants grown at 23°C; suppression over all treatments ranging from 2 to 11%. Unlike typical C 4 species, plants of M. sobolifera from both temperature regimes exhibited higher CO 2 assimilation rates when grown at low light. Growth temperature and light also affected QUE; plants grown at low light and 23°C had the highest value (0·068 mol CO 2/mol quanta). Measurement temperature and growth light regime significantly affected dark respiration; however, O 2 did not affect QUE or dark respiration under any growth or measurement conditions. The results indicate that M. sobolifera is adapted to low PPFD, and that complete suppression of photorespiration is dependent upon high growth temperature. 相似文献
8.
Summary It is possible to obtain autotrophic callus cultures by inhibiting cell respiration. During a first passage of four weeks the cultures synthesized chlorophyll on an agar-medium with a minimum of organic substances such as sugar, amino acids and vitamins. In the second passage these cultures were kept on the same medium but were aerated with a mixture of 99% N 2 and 1% CO 2. In the third and last passage the medium contained only mineral substances and the same mixture of N 2 and CO 2 was used for aeration. This pure mineral medium was supplemented with the Hoagland's solution.These autotrophic callus cultures were grown for about two years under these conditions and showed a growth quotient of ten.Three different groups of tissues were taken for the 14CO 2-fixation. The first group was grown for four weeks on a heterotrophic medium and aerated with O 2. This is the socalled respirating group. The second and third group were both aerated with the mixture of N 2/CO 2 but they were grown on different mediums. One of these groups was grown on a heterotrophic medium for four weeks: these are heterotrophic photosynthesizing tissues. The third group was grown on a pure mineral medium, and these are the autotrophic photosynthesizing callus tissues.Respirating tissues are different from photosynthesizing cultures in respect to the quantity of light-induced CO 2-fixation.The thin-layer chromatograms reveal the difference between heterotrophic and autotrophic tissues. In the light dependent 14CO 2-incorporation the difference is in the amounts of the labelled amino acids glycine and serine. In the dark dependent incorporation the difference is found in the amount of the labelled amino acid aspartic acid. The more autotrophic these tissues are, the higher the level of the CO 2-fixation in these amino acids is.
Mit Hilfe der Deutschen Forschungsgemeinschaft. 相似文献
9.
Summary The correlation of CO 2-fixation metabolism to various environmental conditions such as NaCl content of culture medium, air humidity and light intensity was investigated in the halophytic species Mesembryanthemum crystallinum. The data obtained demonstrate that a change in photosynthesis from C 3-pathway to crassulacean acid metabolism (CAM) is observed not only in NaCl treated plants as reported earlier but also in control plants grown in non-saline medium when environmental conditions (high light intensity, low air humidity) cause a water deficit in the leaves. It is suggested that water stress plays an important role in regulation between C 3- and CAM-pathway of photosynthesis in Mesembryanthemum crystallinum.
Abkürzungen CAM
Crassulaceensäurestoffwechsel
- FG
Frischgewicht
- TG
Trockengewicht
- D
Ende Dunkelphase
- L
Ende Lichtphase
Herrn Prof. Dr. Otto Stocker zum 85. Geburtstag gewidmet 相似文献
10.
NaCl treated Mesembryanthemum crystallinum plants exhibit a Crassulacean acid metabolism. The activity of phosphoenolpyruvate (PEP) carboxylase, the enzyme responsible for CO 2 dark fixation, depends on leaf age showing maximum activity in mature leaves. Electrophoresis revealed that the young leaves possess only two protein bands with PEP carboxylase activity, while older leaves have 3 bands. The removal of NaCl from the soil resulted in the disappearance of the 3rd band obtained after electrophoresis and a decline in the total activity of the PEP carboxylase. The reintroduction of NaCl at the same concentration as before did not restore the activity of the PEP carboxylase nor did it restore the initial electrophoretic band pattern. 相似文献
11.
The facultative halophyte Mesembryanthemum crystallinum responds to salt stress by increasing the levels of phospho enolpyruvate carboxylase (PEPCase) and other enzymes associated with Crassulacean acid metabolism. A more common response to salt stress in sensitive and tolerant species, including M. crystallinum, is the accumulation of proline. We have established M. crystallinum suspension cultures to investigate whether both these salt-induced responses occur at the cellular level. Leaf-and root-derived cultures maintain 5% of the total soluble amino acids as proline. Cell culture growth slows upon addition of 400 millimolar NaCl, and proline levels increase to 40% of the total soluble amino acids. These results suggest a functional salt-stress and response program in Mesembryanthemum cells. Suspension cultures grown with or without 400 millimolar NaCl have PEPCase levels that compare with those from roots and unstressed leaves. The predominant protein cross-reacting with an anti-PEPCase antibody corresponds to 105 kilodaltons (apparent molecular mass), whereas a second species of approximately 110 kilodaltons is present at low levels. In salt-stressed leaves, the 110 kilodalton protein is more prevalent. Levels of mRNA for both ppc1 (salt stress induced in leaves) and ppc2 (constitutive) genes in salt-treated suspensions cultures are equal to unstressed leaves, and only twice the levels found in untreated suspension cultures. Whereas cells accumulate proline in response to NaCl, PEPCase protein amounts remain similar in salt-treated and untreated cultures. The induction upon salt stress of the 110 kilodalton PEPCase protein and other Crassulacean acid metabolism enzymes in organized tissues is not observed in cell culture and may depend on tissue-dependent or photoautotrophy-dependent programs. 相似文献
12.
Experiments were designed to determine the significance of dark CO 2 fixation in excised maize roots, carrot slices and excised tomato roots grown in tissue culture. Bicarbonate- 14C was used to determine the pathway and amounts of CO 2 fixation, while leucine- 14C was used to estimate protein synthesis in tissues aerated with various levels of CO 2. Organic acids were labeled from bicarbonate-14C, with malate being the major labeled acid. Only glutamate and aspartate were labeled in the amino acid fraction and these 2 amino acids comprised over 90% of the 14C label in the ethanol-water insoluble residue. Studies with leucine-14C as an indicator of protein synthesis in carrot slices and tomato roots showed that those tissues aerated with air incorporated 33% more leucine-14C into protein than those aerated with CO2-free air. Growth of excised tomato roots aerated with air was 50% more than growth of tissue aerated with CO2-free air. These studies are consistent with the suggestion that dark fixation of CO2 is involved in the growth of plant tissues. 相似文献
13.
The uptake and metabolism of α-[5- 14C]ketoglutarate by phosphorus-deficient and full nutrient (control) lemon ( Citrus limon) leaves were studied over various time intervals. After 45 minutes in P-deficient leaves, the bulk of incorporated 14C appeared in organic acids and much less in amino acids, while in the control leaves, the 14C contents of organic and amino acids were equal. In P-deficient leaves, after longer incubation times the 14C content of organic acids and amino acids increased, while that of CO 2 and residue fractions remained low. In full nutrient leaves the 14C content of amino acids and organic acids decreased after longer incubation time and increased in the insoluble residue and CO 2. In full nutrient leaves the organic and amino acid metabolism were closely related and accompanied by protein synthesis and CO 2 release, while in P-deficient leaves an accelerating accumulation of arginine and citric acid was linked together with inhibition of protein synthesis and CO 2 liberation. 相似文献
14.
The variations of δ 13C in leaf metabolites (lipids, organic acids, starch and soluble sugars), leaf organic matter and CO 2 respired in the dark from leaves of Nicotiana sylvestris and Helianthus annuus were investigated during a progressive drought. Under well‐watered conditions, CO 2 respired in the dark was 13C‐enriched compared to sucrose by about 4‰ in N. sylvestris and by about 3‰ and 6‰ in two different sets of experiments in H. annuus plants. In a previous work on cotyledonary leaves of Phaseolus vulgaris, we observed a constant 13C‐enrichment by about 6‰ in respired CO 2 compared to sucrose, suggesting a constant fractionation during dark respiration, whatever the leaf age and relative water content. In contrast, the 13C‐enrichment in respired CO 2 increased in dehydrated N. sylvestris and decreased in dehydrated H. annuus in comparison with control plants. We conclude that (i) carbon isotope fractionation during dark respiration is a widespread phenomenon occurring in C 3 plants, but that (ii) this fractionation is not constant and varies among species and (iii) it also varies with environmental conditions (water deficit in the present work) but differently among species. We also conclude that (iv) a discrimination during dark respiration processes occurred, releasing CO 2 enriched in 13C compared to several major leaf reserves (carbohydrates, lipids and organic acids) and whole leaf organic matter. 相似文献
15.
Changes in leaf growth, net photosynthetic rate ( P
N), incorporation pattern of photosynthetically fixed 14CO 2 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 14CO 2 incorporated at all leaf positions, the maximum effect being in young growing leaves. The incorporation of 14CO 2 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, CO 2 exchange rate, oil content, and rhizome and curcumin yields can be ascribed to reduced photosynthate formation and translocation. 相似文献
16.
Our previous work indicated that salinity caused a shift in the predominant site of nitrate reduction and assimilation from the shoot to the root in tomato plants. In the present work we tested whether an enhanced supply of dissolved inorganic carbon (DIC, CO 2+ HCO 3) to the root solution could increase anaplerotic provision of carbon compounds for the increased nitrogen assimilation in the root of salinity-stressed Lycopersicon esculentum (L.) Mill. cv. F144. The seedlings were grown in hydroponic culture with 0 or 100m M NaCl and aeration of the root solution with either ambient or CO 2-enriched air (5000 μmol mol ?1). The salinity-treated plants accumulated more dry weight and higher total N when the roots were supplied with CO 2-enriched aeration than when aerated with ambient air. Plants grown with salinity and enriched DIC also had higher rates of NO ?3 uptake and translocated more NO ?3 and reduced N in the xylem sap than did equivalent plants grown with ambient DIC. Incorporation of DIC was measured by supplying a 1 -h pulse of H 14CO ?3 to the roots followed by extraction with 80% ethanol. Enriched DIC increased root incorporation of DIC 10-fold in both salinized and non-salinized plants. In salinity-stressed plants, the products of dissolved inorganic 14C were preferentially diverted into amino acid synthesis to a greater extent than in non-salinized plants in which label was accumulated in organic acids. It was concluded that enriched DIC can increase the supply of N and anaplerotic carbon for amino acid synthesis in roots of salinized plants. Thus enriched DIC could relieve the limitation of carbon supply for ammonium assimilation and thus ameliorate the influence of salinity on NO ?3 uptake and assimilation as well as on plant growth. 相似文献
17.
Changes in leaf growth, photosynthetic efficiency, and incorporation pattern of photosynthetically fixed 14CO 2 in leaves 1 and 2 from plant apex, in roots, and rhizome induced in Curcuma by growing in a solution culture at Fe concentration of 0 and 5.6 g m –3 were studied. 14C was incorporated into primary metabolites (sugars, amino acids, and organic acids) and secondary metabolites (essential oil and curcumin). Fe deficiency resulted in a decrease in leaf area, its fresh and dry mass, chlorophyll (Chl) content, and CO 2 exchange rate at all leaf positions. The rate of 14CO 2 fixation declined with leaf position, maximum being in the youngest leaf. Fe deficiency resulted in higher accumulation of sugars, amino acids, and organic acids in leaves at both positions. This is due to poor translocation of metabolites. Roots and rhizomes of Fe-deficient plants had lower concentrations of total photosynthate, sugars, and amino acids whereas organic acid concentration was higher in rhizomes. 14CO 2 incorporation in essential oil was lower in the youngest leaf, as well as incorporation in curcumin content in rhizome. Fe deficiency influenced leaf area, its fresh and dry masses, CO 2 exchange rate, and oil and curcumin accumulation by affecting translocation of assimilated photosynthates. 相似文献
18.
Flower buds of `Valencia' orange ( Citrus sinensis [L.] Osbeck) were able to fix 14CO 2 into a number of compounds in their own tissues under both light and dark conditions. The total incorporation, however, was about 4-fold higher in the light than in the dark. In the light, 50% of the total 14C label was found in the neutral fraction (sugars), 22% in the basic fraction (amino acids), and 26% in the acid-1 fraction (organic acids). In the dark, about 95% of the 14C label was incorporated into the basic and acid-1 fractions. Activities of ribulose bisphosphate carboxylase and phosphoenolpyruvate carboxylase (expressed in micromoles CO 2 per milligram protein per hour) averaged 1.95 and 8.87 for the flower buds, and 28.5 and 3.6 for the leaves, respectively. The ability of orange flower buds to fix ambient CO 2 into different compounds suggests that this CO 2 assimilation may have some regulatory role during the early reproductive stages in determining citrus fruit initiation and setting. 相似文献
19.
Effects of elevated CO 2 levels on the amino acid constituents of cotton aphid, Aphis gossypii (Glover), fed on transgenic Bacillus thuringiensis (Berliner) (Bt) cotton [ Cryl A(c)], grown in ambient and double‐ambient CO 2 levels in closed‐dynamics CO 2 chambers, were investigated. Lower amounts of amino acids were found in cotton phloem under elevated CO 2 than under ambient CO 2 levels. However, higher amounts of free amino acids were found in A. gossypii fed on elevated CO 2‐grown cotton than those fed ambient CO 2‐grown cotton, and the contents of amino acids in honeydew were not significantly affected by elevated CO 2 levels. A larger amount of honeydew was produced by cotton aphids feeding on leaves under elevated CO 2 treatment than those feeding on leaves under ambient CO 2 treatment, which indicates that A. gossypii ingests more cotton phloem because of the higher C:N ratio of cotton phloem under elevated CO 2 levels. Moreover, the amino acid composition was similar in bodies of aphids ingesting leaves under both CO 2 treatments, except for two alkaline amino acids, lysine and arginine. This suggests that the nutritional constitution of the phloem sap was important for A. gossypii. Our data suggest that more phloem sap will be ingested by A. gossypii to satisfy its nutritional requirement and balance the break‐even point of amino acid in elevated CO 2. Larger amounts of honeydew produced by A. gossypii under elevated CO 2 will reduce the photosynthesis and result in the occurrence of some Entomophthora spp. 相似文献
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