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1.
The ability of 0.03% CO2 to stimulate growth has been investigated using etiolated Avena coleoptile sections maintained in buffered solution. This concentration of CO2-stimulated growth after a lag period of 12 to 15 minutes, and a synergistic relationship between indoleacetic acid and CO2 in stimulating growth has been demonstrated. The response to CO2 is inhibited by cycloheximide and is lost approximately 10 minutes after exposure to CO2-free air. Malate can replace CO2 in stimulating growth. In the light of these data and recent literature on a growth response of coleoptile sections to CO2-saturated solutions, the existence of two mechanisms of CO2-simulated growth is proposed. In addition, it is suggested that growth promotion by 0.03% CO2 is mediated by a process involving dark CO2 fixation.  相似文献   

2.
Application of levulinic acid (LA), a competitive inhibitor of δ-aminolevulinic acid (ALA) dehydratase, to greening plant tissues causes ALA to accumulate at the expense of chlorophyll. 4,6-Dioxoheptanoic acid (DA), which has been reported to be an effective inhibitor of this enzyme in animal systems, has a similar but more powerful effect on ALA and chlorophyll metabolism in greening leaves of Hordeum vulgare L. var. Larker. Both LA and DA also inhibit the uptake of [14C]amino acids into etiolated and greening barley leaves and reduce their incorporation into protein. Treatment of etiolated and greening leaves with these compounds results in the inhibition of 14CO2 evolution from labeled precursors, including amino and organic acids. Inhibition of 14CO2 evolution by these compounds is more effective in greening leaves than in etiolated leaves when [4-14C]ALA or [1-14C]glutamate are employed as precursors. Both LA and DA also inhibit the uptake and increase the incorporation of 32Pi into organophosphorus by etiolated barley leaves. These results indicate that LA and DA have more far-reaching effects upon plant metabolism than was previously believed.  相似文献   

3.
Beyer EM 《Plant physiology》1975,56(2):273-278
The effects of various treatments on the recently reported system in pea (Pisum sativum cv. Alaska), which results in (a) the incorporation of 14C2H4 into the tissue and (b) the conversion of 14C2H4 to 14CO2, was investigated using 2-day-old etiolated seedlings which exhibit a maximum response. Heat treatment (80 C, 1 min) completely inhibited both a and b, whereas homogenization completely inhibited b but only partially inhibited a. Detaching the cotyledons from the root-shoot axis immediately before exposing the detached cotyledons together with the root-shoot axis to 14C2H4 markedly reduced both a and b. Increasing the 14C2H4 concentration from 0.14 to over 100 μl/l progressively increased the rate of a and b with tissue incorporation being greater than 14C2H4 to 14CO2 conversion only below 0.3 μl/l 14C2H4. Reduction of the O2 concentration reduced both a and b, with over 99% inhibition occurring under anaerobic conditions. The addition of CO2 (5%) severely inhibited 14C2H4 to 14CO2 conversion without significantly affecting tissue incorporation. Exposure of etiolated seedlings to fluorescent light during 14C2H4 treatment was without effect. Similarly, indoleacetic acid, gibberellic acid, benzyladenine, abscisic acid, and dibutyryl cyclic adenosine monophosphate had no significant effect on either a or b.  相似文献   

4.
Experiments have been performed to investigate whether indoleacetic acid changes the balance between the rates of synthesis of different kinds of proteins. Sub-apical sections of etiolated peas were incubated with 14C- or 3H-labeled amino acid, and combined to give dual-labeled tissue. Cell fractions were prepared by differential centrifugation, and the dual-labeled protein of each fraction analyzed by gel-filtration. When 2 × 10−5 m indoleacetic acid was included with 14C-labeled amino acid, but not with the 3H-labeled amino acid, pronounced changes occurred in the pattern of incorporation of the 14C label into protein. These changes were greatest in the proteins of the particulate fraction which included nuclear material. Although the pattern of incorporation of lysine was shown to be different from that of leucine, the changes induced by indoleacetic acid were quantitatively similar whichever amino acid was used as a precursor. Dual-labeled protein was further fractionated using column chromatography on DEAE-cellulose. The results suggested that the effect of indoleacetic acid may not be completely general, and that the pattern of synthesis of many proteins may be unaltered by indoleacetic acid. When tissue was preincubated with 10 μg/ml actinomycin D for 30 minutes, incorporation of amino acid into protein was reduced but not abolished. Actinomycin D did, however, prevent the changes in the pattern of protein synthesis which were induced by indoleacetic acid.  相似文献   

5.
Abscisic acid inhibited the rate of 14CO2 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 14CO2 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 14CO2 into photosynthetic products.  相似文献   

6.
Littlejohn RO  Ku MS 《Plant physiology》1984,74(4):1050-1054
The nature and sequence of metabolic events during phase II (early morning) Crassulacean acid metabolism in Opuntia erinacea var columbiana (Griffiths) L. Benson were characterized. Gas exchange measurements under 2 and 21% O2 revealed increased O2 inhibition of CO2 fixation with progression of phase II. Malate and titratable acidity patterns indicated continued synthesis of C4 acids for at least 30 minutes into the light period. Potential activities of phosphoenolpyruvate carboxylase (PEPC) and NADP-malic enzyme exhibited little change during phase II, while light activation of NADP-malate dehydrogenase, pyruvate, orthophosphate dikinase, and ribulose-1,5-bisphosphate carboxylase was apparent. Short-term 14CO2 fixation experiments showed that the per cent of 14C incorporated into C4 acids decreased while incorporation into other metabolites increased with time. PEPC exhibited increased sensitivity to 2 millimolar malate, and the Ki(malate) for PEPC decreased markedly with time. Sensitivity of PEPC to malate inhibition was considerably greater at pH 7.5 than at 8.0. The results indicate that decarboxylation and synthesis of malate occur simultaneously during the early morning period, and that phase II acid metabolism is not limited by CO2 diffusion through stomata. With progression of phase II, CO2 fixation by PEPC decreases while fixation by ribulose-1,5-bisphosphate carboxylase increases.  相似文献   

7.
Kent SS 《Plant physiology》1979,64(1):159-161
In the higher plant Vicia faba, anomalous labeling patterns in the organic acids and related amino acids of the tricarboxylic acid cycle which result from photosynthetic 14CO2 fixation (in conjunction with an enzyme localization pattern unique to plant mitochondria) suggest that the tricarboxylic acid cycle functions primarily as a pathway leading to glutamic acid biosynthesis during autotrophic growth. The distribution of isotope in citrate indicates little recycling of oxaloacetate for the resynthesis of citrate. Rather, malate appears to provide both the C2 and C4 fragments for the synthesis of citrate, and [3H]formate and 14CO2-labeling patterns implicate serine as the ultimate C3 precursor of malate.  相似文献   

8.
Beyer EM 《Plant physiology》1979,63(1):169-173
The relationship between ethylene action and metabolism was investigated in the etiolated pea seedling (Pisum sativum L. cv. Alaska) by inhibiting ethylene action with Ag+, high CO2, and low O2 and then determining if ethylene metabolism was inhibited in a similar manner. Ag+ (100 milligrams per liter) was clearly the most potent antiethylene treatment. Ag+ pretreatment inhibited the growth retarding action of 0.2 microliters per liter ethylene by 48% and it also inhibited the incorporation of 0.2 microliters per liter 14C2H4 into pea tips by the same amount. As the ethylene concentration was increased from 0.2 to 30 microliters per liter, the effectiveness of Ag+ in reducing ethylene action and metabolism declined in a similar fashion. Although Ag+ significantly inhibited the incorporation of 14C2H4 into tissue metabolites, the oxidation of 14C2H4 to 14CO2 was unaffected in the same tissue.  相似文献   

9.
The initial products of photosynthesis by the C3 species Flaveria cronquistii, the C4 species F. trinervia, and the C3-C4 intermediate species F. ramosissima were determined using a pulse-chase technique with 14CO2-12CO2. The intermediate species F. ramosissima incorporated at least 42% of the total soluble 14C fixed into malate and aspartate after 10 seconds of photosynthesis in 14CO2, as compared with 90% for the C4 species F. trinervia and 5% for the C3 species F. cronquistii. In both F. ramosissima and F. trinervia, turnover of labeled malate and aspartate occurred during a chase period in 12CO2, although the rate of turnover was slower in the intermediate species. Relative to F. cronquistii, F. ramosissima showed a reduced incorporation of radioactivity into serine and glycine during the pulse period. These results indicate that a functional C4 pathway of photosynthesis is operating in F. ramosissima which can account for its reduced level of photorespiration, and that this species is a true biochemical intermediate between C3 and C4 plants.  相似文献   

10.
The submersed angiosperms Myriophyllum spicatum L. and Hydrilla verticillata (L.f.) Royal exhibited different photosynthetic pulse-chase labeling patterns. In Hydrilla, over 50% of the 14C was initially in malate and aspartate, but the fate of the malate depended upon the photorespiratory state of the plant. In low photorespiration Hydrilla, malate label decreased rapidly during an unlabeled chase, whereas labeling of sucrose and starch increased. In contrast, for high photorespiration Hydrilla, malate labeling continued to increase during a 2-hour chase. Thus, malate formation occurs in both photorespiratory states, but reduced photorespiration results when this malate is utilized in the light. Unlike Hydrilla, in low photorespiration Myriophyllum, 14C incorporation was via the Calvin cycle, and less than 10% was in C4 acids.

Ethoxyzolamide, a carbonic anhydrase inhibitor and a repressor of the low photorespiratory state, increased the label in glycolate, glycine, and serine of Myriophyllum. Isonicotinic acid hydrazide increased glycine labeling of low photorespiration Myriophyllum from 14 to 25%, and from 12 to 48% with high photorespiration plants. Similar trends were observed with Hydrilla. Increasing O2 increased the per cent [14C]glycine and the O2 inhibition of photosynthesis in Myriophyllum. In low photorespiration Myriophyllum, glycine labeling and O2 inhibition of photosynthesis were independent of the CO2 level, but in high photorespiration plants the O2 inhibition was competitively decreased by CO2. Thus, in low but not high photorespiration plants, glycine labeling and O2 inhibition appeared to be uncoupled from the external [O2]/[CO2] ratio.

These data indicate that the low photorespiratory states of Hydrilla and Myriophyllum are mediated by different mechanisms, the former being C4-like, while the latter resembles that of low CO2-grown algae. Both may require carbonic anhydrase to enhance the use of inorganic carbon for reducing photorespiration.

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11.
《Phytochemistry》1986,25(7):1741-1742
When etiolated barley (Hordeum vulgare L. var. Larker) shoots are incubated with [4-13C]levulinic acid, they evolve 14CO2. Cycloheximide inhibits this catabolism, and the effect is distinct from any effect this antimetabolite has on fatty acid oxidation or respiration. We suggest that a protein which is synthesized on 80 S ribosomes and which has a short half-life is necessary for levulinic acid catabolism to CO2.  相似文献   

12.
The distribution of 14C in photosynthetic metabolites of two naturally occurring higher plants with reduced photorespiration, Moricandia arvensis and Panicum milioides, in pulse and pulse-chase 14CO2 incorporation experiments was similar to that for the C3 species, M. foetida and Glycine max. After 6 seconds of 14CO2 incorporation, only about 6% of the total 14C fixed was in malate and aspartate in both M. arvensis and P. milioides. The apparent turnover of the C4 acids was very slow, and malate accumulated during the day in M. arvensis. Thus, C4 acid metabolism by M. arvensis and P. milioides had no significant role in photosynthetic carbon assimilation under the conditions of our experiments (310 microliters CO2 per liter, 21% O2, 1100 or 1900 micromoles photon per square meter per second, 27°C).

After a 36-second chase period in air containing 270 microliters CO2 per liter, about 20% of the total 14C fixed was in glycine with M. arvensis, as compared to 15% with M. foetida, 14% with P. milioides, and 9% with G. max. After a 36-second chase period in 100 microliters CO2 per liter, the percentage in glycine was about twice that at 270 microliters CO2 per liter in the C3 species and P. milioides, but only 20% more 14C was in glycine in M. arvensis. These data suggest that either the photorespiratory glycine pool in M. arvensis is larger than in the other species examined or the apparent turnover rate of glycine and the flow of carbon into glycine during photorespiration are less in M. arvensis. An unusual glycine metabolism in M. arvensis may be linked to the mechanism of photorespiratory reduction in this crucifer.

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13.
Oxidation of proline by plant mitochondria   总被引:11,自引:6,他引:5       下载免费PDF全文
Mitochondria isolated from etiolated shoots of corn (Zea mays), wheat (Triticum aestivum), barley (Hordeum vulgare), soybean (Glycine max L. Merr.), and mung bean (Phaseolus aureus) exhibited a proline-dependent O2 uptake subject to respiratory control. ADP/O ratios with proline as substrate were intermediate between ratios obtained with exogenous NADH and malate + pyruvate as substrates. Isotope studies showed proline metabolism to be dependent on O2, but not NAD. The major ninhydrin-positive product formed via Δ1-pyrroline-5-carboxylic acid was glutamate. Mitochondria were capable of further metabolism of glutamate, as radioactive CO2, organic acids, and aspartate were recovered after [14C]proline feeding experiments. These results demonstrate the mitochondrial association and O2 dependence of plant proline metabolism.  相似文献   

14.
Kinetics and osmoregulation of cotton (Gossypium hirsutum L.) fiber growth (primarily extension) have been studied. Growth is dependent on turgor pressure in the fiber. It is inhibited when a decrease in the water potential of the culture medium due to an addition of Carbowax 6000, equals the turgor pressure of the fiber. Potassium and malate accumulate in the fiber and reach peak levels when the growth rate is highest. Maximum concentrations of potassium and malate reached in the fiber can account for over 50% of the osmotic potential of the fiber. As growth slows down, levels of potassium and malate decrease and turgor pressure declines. Cotton ovules are capable of fixing H14CO3 in the dark, predominantly into malate. Fiber growth is inhibited by the absence of potassium and/or atmospheric CO2. We suggest that potassium and malate act as osmoregulatory solutes and that malate, at least in part, arises from dark CO2 fixation reactions.  相似文献   

15.
Aphanocapsa 6308 metabolizes both NaHCO3 and Na2CO3. The short term incorporation (5-s) metabolic pattern and the patterns of incorporation of bicarbonate for exponential versus stationary phase cultures differ, however. Cells were equilibrated for 10 min in air and distilled water prior to injection of either NaH14CO3 at pH 8.0, or Na2 14CO3 at pH 11.0. Hot ethanol extracts were analyzed via paper chromatography and autoradiography for products of CO2 fixation. At 5 s, malate (51.5%) predominates slightly as a primary bicarbonate fixation product over 3-phosphoglycerate (40.3%); 3-phosphoglycerate is the primary product of carbonate fixation. At 60 s, the carbonate and bicarbonate labelling patterns are similar. Cells in stationary phase fix in 5 s a greater proportion of bicarbonate into malate (36% vs. 14% for 3-phosphoglycerate) than do cells in exponential growth. Likewise, 60 s incorporations show a large amount of bicarbonate fixed into aspartate (30.9%) in stationary phase cells over that of exponential phase (11.6%). These data suggest an operative C4 pathway for purposes not related to carbohydrate synthesis but rather as compensation for the incomplete tricarboxylic acid cycle in cyanobacteria. The enhancement of both aspartate fixation and CO2 fixation into citrulline in stationary phase correlates with an increase in cyanophycin granule production which requires both aspartate and arginine.Nonstandard Abbreviations 3-PGA 3-phosphoglyceric acid - TCA tricarboxylic acid  相似文献   

16.
Enhancement of CO(2) Uptake in Avena Coleoptiles by Fusicoccin   总被引:7,自引:5,他引:2       下载免费PDF全文
When Avena coleoptile segments are immersed in a solution containing H14CO3, the appearance of label in the tissue is stimulated approximately 3-fold by fusicoccin application. This effect is rapid (1-2 minutes lag time), dependent upon respiratory energy, inhibited by carbonyl cyanide m-chlorophenylhydrazone, but not appreciably altered by cycloheximide treatment. A large percentage of the cellular radioactivity is found in the form of malate. Preliminary experiments indicate that CO2, as opposed to HCO3, is the favored species of “CO2” taken up by the segments. These results are consistent with the notion that CO2, presumably by virtue of its fixation and conversion to malic acid, participates in the early events associated with fusicoccin-enhanced acidification of the cell wall region leading to the stimulation of cell extension growth.  相似文献   

17.
Endosperms of quiescent barley grains contained, on average, 54.5 μg of neutral glyceride-glycerol, equivalent to ca 480 μg glyceride. Of this probably 90% was located in the aleurone layer. During germination the level of glyceride-glycerol declined. It also declined in degermed grains and aleurone layers incubated in vitro. The fall was accelerated by GA3, but indoleacetic acid, kinetin and glutamine were without effect. Increases in the levels of malate synthase and isocitrate lyase from very low initial values, and the results of incorporation studies with [14C]-labelled substrates, indicate that the glyoxylate cycle functions to convert glycerides to sucrose in germinating grains and degermed grains incubated with GA3, but not in degermed grains without the hormone. In the absence of GA3 the glyceride could be a respiratory substrate in degermed grains. The aleurone layers converted exogenous glucose to sucrose. Little label from [14C]-amino acids appeared in sucrose but in some cases considerable incorporation occurred into glutamine.  相似文献   

18.
Helal HM  Mengel K 《Plant physiology》1981,67(5):999-1002
Seedings of Vicia faba were grown for four weeks at two different light intensities (55 and 105 watts per square meter) in a saline (50 millimolar NaCl) and nonsaline nutrient solution. NaCl salinity depressed growth and restricted protein formation, CO2 assimilation, and especially the incorporation of photosynthates into the lipid fraction. Conversion of photosynthates in leaves was much more affected by salinity than was photosynthate turnover in roots. The detrimental effect of NaCl salinity on growth, protein formation, and CO2 assimilation was greater under low than under high light conditions. Plants of the high light intensity treatment were more capable of excluding Na+ and Cl and accumulating nutrient cation species (Ca2+, K+, Mg2+) than plants grown under low light intensity. It is suggested that the improved ionic status provided better conditions for protein synthesis, CO2 assimilation, and especially for the conversion of photosynthates into lipids.  相似文献   

19.
When [2,4-14C]porphobilinogen (PBG) or [2 (aminomethyl),5-14C]PBG is administered to etiolated barley (Hordeum vulgare L. var. Larker) leaves in darkness, label becomes incorporated into CO2, organic and amino acids, sugars, lipids, and proteins during a 4-hour incubation. Less than 1% of the label, however, is incorporated into porphyrins. The rate of 14CO2 evolution from leaves fed [2,4-14C]PBG is strongly inhibited by anaerobiosis but is unaffected by aminooxyacetic acid, while the rate of 14CO2 evolution from [2(aminomethyl),5-14C]PBG is strongly inhibited by aminooxyacetic acid but is not affected by anaerobiosis.  相似文献   

20.
W. Hüsemann  A. Plohr  W. Barz 《Protoplasma》1979,100(1):101-112
Summary Cell suspension cultures ofChenopodium rubrum have been grown for more than 2 years photoautotrophically with CO2 as sole carbon source. Average increase in fresh weight is appr. 600% within 14 days. The chlorophyll content of photoautotrophic cells (200 g/g fresh weight) is much higher than of photomixotrophic cells (50 g/g fresh weight). The photosynthetic activity of the cells (190 moles CO2×mg–1 chlorophyllXh–1) is comparable to the values found with intact leaves. As shown by short-term14CO2 photosynthesis, both, the photomixotrophic and the photoautotrophic cell suspension cultures assimilate CO2 predominantly via the Calvin pathway.Major differences were found with cells from either exponential or stationary phase of growth with regard to differential labelling of 3-phosphoglyceric acid, malate, sucrose and glucose/fructose.In vitro measurements of carboxylation reactions only partially corroborate our findings with14CO2 incorporation. The ratio of ribulosebisphosphate to phosphoenolpyruvate carboxylase activity is 4.7 for leaves of C.rubrum, 1.2 for photoautotrophic cells during stationary growth and 0.5 for cells during exponential growth phase, however, 0.18 was found for photomixotrophic cells. Though the14CO2 incorporation into 3-phosphoglyceric acid is clearly higher than into malate, thein vitro activity of phosphoenolpyruvatecarboxylase is 2–6 fold higher than that of ribulosebisphosphate carboxylase. We postulate that anaplerotic reactions of the tricarboxylic acid cycle are involved in the regulation of phosphoenolpyruvate carboxylase.Abbreviations 2,4-D didilorophenoxyacetic acid - EDTA ethylene-diamine-tetraacetic acid - fr. w. fresh weight - HEPES N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid - PGA 3-phosphoglyceric acid - PPO 2,5-diphenyloxazole - PEP phosphoenolpyruvate - RuBP nbulosebisphosphate  相似文献   

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