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1.
Heterotrophic activity in macroalgae has been little studied, but the red macroalga Grateloupia doryphora is known to grow in light at a higher rate in a glycerol-containing medium than in seawater. The effects of 0·1 M exogenous glycerol in seawater (SW90-gly) on the respiration rate of G. doryphora and the role played by light were investigated. The algae pretreated for 2 h in the light and in SW90-gly evolved oxygen and fixed carbon dioxide (H14CO3 ?), but also evolved radioactive 14CO2 from [14C]glycerol. The rate of oxygen evolution was lower than that of samples in seawater, due to a high respiration rate and/or a partial inhibition of photosynthesis induced by glycerol. In contrast, the rate of inorganic carbon fixation was higher in SW90-gly than in control samples in seawater, suggesting that non-photosynthetic patterns were operating. In darkness, after pretreatment in the light in SW90-gly, samples showed a high oxygen uptake rate just after the light was turned off. Twenty minutes of darkness were enough to decrease this high respiration rate to that of samples in seawater. The oxygen uptake observed in all experiments with glycerol was mitochondrial as it was inhibited by potassium cyanide and salicylhydroxamic acid (SHAM). Pretreatment of samples in the light in SW90-gly with the photosynthetic inhibitor DCMU did not inhibit ensuing dark respiration, thus providing evidence for a non-photosynthetic effect of the light. The highest dark respiration rate was observed after the samples were pretreated in monochromatic blue light in glycerol-containing media. 相似文献
2.
The chlorophyll repair potential of mature Cucumis chloroplasts incubated in a simple Tris-HCI/sucrose medium is described. The chloroplasts were isolated from green, fully expanded Cucumis cotyledons which were capable of chlorophyll repair. This was evidenced by a functional chlorophyll biosynthetic pathway in the mature tissue. The biosynthesis of protochlorophyllide from exogenous δ-aminolevulinic acid was used as a marker for the operation of the chlorophyll biosynthetic chain between δ-aminolevulinic acid and protochlorophyllide. The conversion of exogenous protochlorophyllide into chlorophyll a was used as a marker for the operation of the chlorophyll pathway beyond protochlorophyllide. It appeared from these studies that contrary to published reports, unfortified fully developed Cucumis chloroplasts incubated in Tris-HCl/sucrose without the addition of cofactors exhibited a partial and limited chlorophyll repair capability. Their net tetrapyrrole biosynthetic competence from δ-aminolevulinic acid was confined to the accumulation of coproporphyrin. No net tetrapyrrole biosynthesis beyond coproporphyrin was observed. However, the plastids were capable of incorporating small amounts of δ-amino-[4-14C]levulinic acid into [14C] protochlorophyllide but were incapable of converting exogenous protochlorophyllide into chlorophyll. After prolonged incubation of the unfortified chloroplasts in the dark, a fluorescent protochlorophyllide-like compound accumulated. This compound [Cp (E430-F631)] exhibited a soret excitation maximum at 430 nm (E430) and a fluorescence emission maximum at 631 nm (F631) in methanol/acetone (4 : 1, v/v). Cp (E430-F631) was shown to be neither protochlorophyllide nor zinc-protochlorophyllide but an enzymatic degradation product of chlorophyll. The exact chemical identity of this compound has not yet been determined. 相似文献
3.
LENNART AXELSSON 《Physiologia plantarum》1974,31(2):77-85
Dark-grown leaves of wheat fed with δ-aminolevulinic acid accumulate protochlorophyllide636 in excess. After the leaves had been illuminated with high intensity red light (154 W × m?2) for half a minute, a treatment which blocks the phototrans-formation protochlorophyllide chlorophyllide, the sensitivity of chlorophyllide and protochlorophyllide to light was examined. The decrease in pigment content, caused by photo-oxidation was found to be very close to a second order reaction. The second order “rate constant” for decrease in absorbance was found to be eight times greater for the formed chlorophyllide than for protochlorophyllide. The light intensity dependence of the decomposition was found to be linear within the intensity range used (E= 25 – 154 W × m?2). In samples in which the pigments had been heat denatured, it was possible to photodecompose the chlorophyllide without affecting the protochlorophyllide. The results are discussed in connection with the theory of a photodynamic action involving oxygen in the singlet state (1ΔO2). 相似文献
4.
Photosynthesis, Respiration and Post-illumination Fixation of CO2 by Corn Leaves as Influenced by Light and Oxygen Concentration 总被引:1,自引:0,他引:1
J. Poskuta 《Physiologia plantarum》1969,22(1):76-85
The effect of oxygen concentration on the rate of CO2-uptake in continuous and intermittent light was studied as well as the CO2-fixation during a short dark period after light was turned off. In addition the dark respiration and the CO2-compensation point of attached and detached corn leaves were determined. Leaves of 4 to 22-day old plants were used as experimental material. A closed circuit system of an infrared carbon dioxide analyzer was employed to measure the rate of CO2-exchange. It was found that in an atmosphere consisting of 100 % oxygen, there was about 50 per cent inhibition of the rate of CO2-uptake in continuous and intermittent light compared to that in an atmosphere consisting of 21% oxygen. The same was true of the rate of CO2-fixation in darkness during a short period after the light was turned off. Since the response to oxygen concentration of the CO2-uptake in light and of the CO2-fixation in darkness after the light was turned off were similar, it is concluded that the fixation of CO2 in the short dark period represents an over- shoot of photosynthesis. The rate of dark respiration was little affected by the oxygen concentration in the ranges used in the experiments. The carbon dioxide compensation point which has been observed in leaves of 4 to 14-day old plants was not influenced by either oxygen concentration or light intensity. Since the changes in the rate of CO2-uptake due to changes in the concentration of oxygen and light intensity had no effect on the CO2-compensation point, it is concluded that a reabsorption of respiratory CO2 by photosynthesis could not account for the low value of this point. These results are interpreted as a further corroboration of the statement that the leaves of corn lack the process of photorespiration and that dark respiration is inhibited in light. It was observed that the rate of the CO2-uptake gradually increased in plants which were from 4 to 22-days old. The inhibitory effect of high concentration of oxygen on the rate of CO2-uptake was relatively higher in old plants than in young ones. 相似文献
5.
Anacystis nidulans (Richt.) Drouet & Daily (UTEX 625), grown in batch culture with 0.5% CO2 in air, was supplied with chloride labelled with 36Cl in light and dark. Uptake in light was stimulated relative to uptake in darkness. A single transport system for Cl? with an apparent Km for Cl? of 0.14 mM was identified. Chloride in the cells reached a maximum value after 30–50 min at 25 C. At this point the internal Cl? concentration was calculated to be 60-fold the external (0.1 mM) in light and 37-fold in darkness. DCMU (3-[3,4-dichlorophenyl]–1, 1-dime-thylurea), at concentrations which abolished photosynthetic O2 evolution did not inhibit Cl? uptake in light. Carbonyl cyanide m-chlorophenyl hydrazone (CCCP), at uncoupling concentrations for photosynthesis and dark respiration, strongly inhibited Cl? uptake in light and darkness. N,N'-dicyclohexyl carbodiimide (DCCD), an energy transfer inhibitor, inhibited light Cl? uptake more slowly than photosynthesis but had no effect on dark Cl? uptake. It is concluded that Cl? uptake in A. nidulans was active in light and darkness, and that ATP was the probable energy source for transport. 相似文献
6.
Heather Adamson Trevor Griffiths Nicolle Packer Mark Sutherland 《Physiologia plantarum》1985,64(3):345-352
Barley ( Hordeum vulgare L. cvs Clipper, Procter, Astrix) seedlings were transferred from daylight to darkness and changes in chlorophyll a , chlorophyll b , protochlorophyllide and chlorophyllide (μ leaf−1 ) in either the first or second leaf determined spectrophotometrically after separating the esterified from unesterified pigments by partitioning between ammoniacal acetone and light petroleum ether. Chlorophyll a and b as well as protochlorophyllide accumulated in the dark. The ratio of chlorophyll to protochlorophyllide formed in the absence of light was 18:1. 5-aminolevulinic acid (10 m M ) promoted the synthesis of chlorophyll a and b and protochlorophyllide. Pigment synthesis and response to 5-aminolevulinic acid addition was related to tissue age. Mature tissue in the apical third of the leaf accumulated most chlorophyll, but per μg chlorophyll present at the time of transfer to darkness, was less efficient than immature tissue towards the base of the leaf. Immature tissue was also most responsive to added 5-aminolevulinic acid. Chlorophyll synthesis in the dark was accompanied by chloroplast development. Chloroplasts in immature leaf tissue increased in size and extent of thylakoid development when transferred from daylight to darkness. The results indicate that chlorophyll synthesis and chloroplast membrane development in light-grown barley continue into the dark phase of the diurnal cycle. A light-independent protochlorophyllide reductase in light-grown barley seedlings is postulated. 相似文献
7.
Wild-type cells of the unicellular rhodophyte, Cyanidium caldarium, synthesize chlorophyll a, phycobiliproteins, and heme from δ-aminolevulinic acid during light-dependent chloroplast development but are unable to make photosynthetic pigments in the dark. C. caldarium, mutant GGB-Y, is an obligate heterotroph which, in the light, produces a chloroplast devoid of photosynthetic pigments. The present investigation has shown that δ-aminolevulinic acid is synthesized in cells of mutant GGB-Y incubated with levulinic acid, a competitive inhibitor of δ-aminolevulinic acid dehydrase (the second enzyme in the porphyrin biosynthetic pathway). In vivo, cells of mutant GGB-Y preferentially incorporated C1 of glutamate and α-ketoglutarate into the C5 fragment (formaldehyde) of δ-aminolevulinic acid after alkaline periodate degradation. This suggested that δ-aminolevulinic acid arises directly from the carbon skeleton of glutamate and α-ketoglutaric acid. The pattern of incorporation of C3, C4, and C5 of α-ketoglutarate into the C1–C4 (succinic acid) fragment of δ-aminolevulinic acid after alkaline periodate degradation was consistent with the origin of δ-aminolevulinic acid from a five-carbon precursor. C1 and C2 of glycine and C2 and C3 of succinate were incorporated into both the formaldehyde and succinate fragments of δ-aminolevulinic acid in a manner inconsistent with condensation of glycine and succinyl CoA by δ-aminolevulinic acid synthetase, the rate-limiting enzyme in the porphyrin pathway in animals and bacteria. Extracts of the soluble protein from cells of mutant GGB-Y displayed a Soret band at 410 nm indicating the presence of hemoproteins. This shows that mutant GGB-Y cells synthesize heme. The respiration of radiolabeled glutamate, α-ketoglutarate, and glycine to 14CO2 is consistent with the existence of mitochondrial cytochromes in cells of mutant GGB-Y and with the ability of the mutant to synthesize δ-aminolevulinic acid. The present results suggest that δ-aminolevulinic acid is synthesized directly from glutamate or α-ketoglutarate and that this is the only process by which the rate-limiting intermediate in the porphyrin pathway is synthesized in C. caldarium. If correct, the rate-limiting, regulative enzyme in the biosynthetic pathway for synthesis of chlorophyll a, bile pigment (phycocyanobilin), and heme must have been completely different in the evolutionary antecedents of modern-day plants and animals. 相似文献
8.
Absorbancy changes in dark-grown, excised wheal leaves fed with δ-aminolevulinic acid are measured in vivo. The treatment with σ-aminolevulinic acid caused accumulation of protochlorophyllide, absorbing at 636 nm. After flashlight this form is found to convert in darkness to protochlorophyllide, absorbing at 650 nm. The conversion starts instantly after the leaves have been exposed to the flashlight, and the pre-existent pool of protocholorophyllidc absorbing at 650 nm will become emptied. The conversion is completed after 15–20 minutes, when a new pool of protochlorophyllide has been filled up. This new pool is transformed to chlorophyllide by a second flash and the sequence is repeated. The conversion may be composed of two reactions, a conclusion which can be drawn from the behaviour at different temperatures. One of these reactions is fairly temperature independent while the other is temperature dependent. The action of the protochlorophyllide holochrome is discussed. 相似文献
9.
Studies on the regeneration of protochlorophyllide after brief illumination of etiolated bean leaves 总被引:13,自引:12,他引:1
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The effects of various inhibitors of nucleic acid and protein synthesis on protochlorophyllide synthesis in dark-grown Phaseolus vulgaris var. Red Kidney have been studied. Actinomycin D, chloramphenicol, and puromycin inhibit the regeneration of protochlorophyllide holochrome (detected as a 650 mμ absorption peak) in vivo in darkness after photoconversion of endogenous protochlorophyllide a to chlorophyllide a; this inhibition does not occur in similarly treated leaves supplied with δ-aminolevulinic acid.
These data suggest that the regeneration of protochlorophyllide results from the synthesis of RNA and enzymes required for the production of δ-aminolevulinate.
相似文献10.
M. P. M. Derkx W. J. Smidt L. H. W. Van der Plas C. M. Karssen 《Physiologia plantarum》1993,89(4):707-718
Effects of dark incubation at different temperatures were studied on dormancy and respiratory activity of seeds of Sisymbrium officinale (L.) Scop. Because germination of this species absolutely depends on the simultaneous action of light and nitrate, changes in dormancy could be studied in darkness without the interference of early germination events. Upon the start of incubation rates of O2 uptake and CO2 release rose. This was followed by a gradual decrease until stable levels of O2 uptake and CO2 release were achieved. Seeds kept for prolonged periods at 24°C, showed neither a change in germination capacity nor in rates of O2 uptake and CO2 release. Respiratory quotients were 0.55–0.7. The initial rise in O2 uptake correlated with the rate of water uptake and with breaking of primary dormancy. However, the subsequent decline in O2 uptake was not generally linked to induction of secondary dormancy. An increased O2 uptake was not required during breaking of secondary dormancy. It is concluded that changes in dormancy are not generally related to changes in respiratory activity. However, germination strongly depends on respiration. The increase in O2 uptake started well before radicle protrusion. A far red irradiation only reversed this increase when it was given before germination escaped from its red light antagonising action. The contribution of different respiratory pathways was followed during prolonged incubation at 24°C in darkness. KCN at 1.5 mM was needed to inhibit the cytochrome pathway (CP) and benzohydroxamic acid (BHAM) at 30 mM to inhibit the alternative pathway (AP). These concentrations did not exert any side effects. Electron flow was predominantly via the CP, maximally 10% was via the AP. Flow through the CP declined during the first 6 days and residual respiration remained constant. Therefore, the contribution of residual respiration became relatively more important with prolonged incubation. KCN at concentrations that almost completely inhibited flow through the CP, did not dramatically reduce germination. BHAM already inhibited germination at concentrations that do not inhibit oxygen uptake. 相似文献
11.
CURT BENGTSON BIRGITTA KLOCKARE STIG LARSSON CHRISTER SUNDQVIST 《Physiologia plantarum》1977,40(3):198-204
The influence of phytohormones on chlorophyll and carotenoid formation during the greening of irradiated dark grown wheat leaves (Triticum aestivum L. cv. Starke II Weibull) was studied. Leaves were floated on solutions of abscisic acid, gibberellic acid and kinetin for 24 h. The chlorophyll and carotenoid contents were determined during a subsequent period of 48 h of continuous irradiation. Leaves treated with abscisic acid showed a longer lag phase and a lower rate of accumulation of chlorophyll as compared to the control than did leaves treated with gibberellic acid and kinetin. The carotenoid content was low both in leaves treated with abscisic acid and in those treated with gibberellic acid. Treatment with abscisic acid lowered the protochlorophyllide regeneration after a saturating light flash while gibberellic acid as well as kinetin had no effect. The influence of ABA was partly dependent on an increase of the wounded part of the cut leaf segments. The accumulation of protochlorophyllide in leaves treated with δ-aminolevulinic acid was not affected by the different hormonal treatments. These results suggest that the main effect of abscisic acid is probably outside the chloroplast, i.e. on the formation or transport of δ-aminolevulinic acid. 相似文献
12.
The rate of regeneration of protochlorophyllide650 was examined spectrophotometrically after a saturating light flash using 8- to 9-day-old dark-grown bean leaves. The regeneration occurred to the extent of 15% with a half rise time of about 20 seconds. Feeding δ-aminolevulinic acid to the excised leaves in the dark increased protochlorophyllides635 but not the absorption at 650 nanometers, suggesting that the holochrome was normally saturated with protochlorophyllide and that the holochrome protein was not controlled by the level of protochlorophyllide. After a light flash, the excess protochlorophyllide, formed from exogenous δ-aminolevulinic acid, readily combined to regenerate the 650 nanometer absorbing species; the regeneration occurred to the extent of 60 to 80% with a half rise time of about 50 seconds. Regeneration was blocked at 0°, suggesting that there was some enzymic process required for regeneration, possibly the formation of a reductant component of the protochlorophyllides650 holochrome. 相似文献
13.
Variations in the Alternative Oxidase in Chlamydomonas Grown in Air or High CO(2) 总被引:3,自引:3,他引:0
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Chlamydomonas in the resting phase of growth has an equal capacity of about 15 micromole O2 uptake per hour per milligram of chlorophyll for both the cytochrome c, CN-sensitive respiration, and for the alternative, salicylhydroxamic acid-sensitive respiration. Alternative respiration capacity was measured as salicylhydroxamic acid inhibited O2 uptake in the presence of CN, and cytochrome c respiration capacity as CN inhibition of O2 uptake in the presence of salicylhydroxamic acid. Measured total respiration was considerably less than the combined capacities for respiration. During the log phase of growth on high (2-5%) CO2, the alternative respiration capacity decreased about 90% but returned as the culture entered the lag phase. When the alternative oxidase capacity was low, addition of salicylic acid or cyanide induced its reappearance. When cells were grown on low (air-level) CO2, which induced a CO2 concentrating mechanism, the alternative oxidase capacity did not decrease during the growth phase. Attempts to measure in vivo distribution of respiration between the two pathways with either CN or salicylhydroxamic acid alone were inconclusive. 相似文献
14.
Photosynthetic O2 production and photorespiratory O2 uptake were measured using isotopic techniques, in the C3 species Hirschfeldia incana Lowe., Helianthus annuus L., and Phaseolus vulgaris L. At high CO2 and normal O2, O2 production increased linearly with light intensity. At low O2 or low CO2, O2 production was suppressed, indicating that increased concentrations of both O2 and CO2 can stimulate O2 production. At the CO2 compensation point, O2 uptake equaled O2 production over a wide range of O2 concentrations. O2 uptake increased with light intensity and O2 concentration. At low light intensities, O2 uptake was suppressed by increased CO2 concentrations so that O2 uptake at 1,000 microliters per liter CO2 was 28 to 35% of the uptake at the CO2 compensation point. At high light intensities, O2 uptake was stimulated by low concentrations of CO2 and suppressed by higher concentrations of CO2. O2 uptake at high light intensity and 1000 microliters per liter CO2 was 75% or more of the rate of O2 uptake at the compensation point. The response of O2 uptake to light intensity extrapolated to zero in darkness, suggesting that O2 uptake via dark respiration may be suppressed in the light. The response of O2 uptake to O2 concentration saturated at about 30% O2 in high light and at a lower O2 concentration in low light. O2 uptake was also observed with the C4 plant Amaranthus edulis; the rate of uptake at the CO2 compensation point was 20% of that observed at the same light intensity with the C3 species, and this rate was not influenced by the CO2 concentration. The results are discussed and interpreted in terms of the ribulose-1,5-bisphosphate oxygenase reaction, the associated metabolism of the photorespiratory pathway, and direct photosynthetic reduction of O2. 相似文献
15.
SILKE LAUTNER MICHAELA STUMMER RAINER MATYSSEK JÖRG FROMM THORSTEN E. E. GRAMS 《Plant, cell & environment》2014,37(1):254-260
Leaf photosynthesis of the sensitive plant Mimosa pudica displays a transient knockout in response to electrical signals induced by heat stimulation. This study aims at clarifying the underlying mechanisms, in particular, the involvement of respiration. To this end, leaf gas exchange and light reactions of photosynthesis were assessed under atmospheric conditions largely eliminating photorespiration by either elevated atmospheric CO2 or lowered O2 concentration (i.e. 2000 μmol mol?1 or 1%, respectively). In addition, leaf gas exchange was studied in the absence of light. Under darkness, heat stimulation caused a transient increase of respiratory CO2 release simultaneously with stomatal opening, hence reflecting direct involvement of respiratory stimulation in the drop of the net CO2 uptake rate. However, persistence of the transient decline in net CO2 uptake rate under illumination and elevated CO2 or 1% O2 makes it unlikely that photorespiration is the metabolic origin of the respiratory CO2 release. In conclusion, the transient knockout of net CO2 uptake is at least partially attributed to an increased CO2 release through mitochondrial respiration as stimulated by electrical signals. Putative CO2 limitation of Rubisco due to decreased activity of carbonic anhydrase was ruled out as the photosynthesis effect was not prevented by elevated CO2. 相似文献
16.
为了进一步了解光照下植物呼吸作用的内在机理以及呼吸作用和光合作用的关系,该文研究了在光照下菜豆(Phaseolus vulgaris)叶片抗氰呼吸与光合作用的关系。研究发现,将黑暗下生长的菜豆幼苗叶片转到光照下10 h,总呼吸、抗氰呼吸以及抗氰呼吸在总呼吸中的比例均逐步上升;光照也导致了叶片叶绿体光合放氧和CO2固定的出现及其速率的增加,但光合放氧和CO2固定速率的增加均滞后于抗氰呼吸的增加。将黑暗下生长的叶片转到光照下之前用抗氰呼吸的抑制剂水杨基氧肟酸(SHAM)处理叶片,发现用SHAM处理并没有导致叶片在光照下光合放氧和CO2固定速率的明显变化,这也提示了黑暗下生长的叶片转至光照的过程中,抗氰呼吸和光合作用没有产生偶联。进一步研究发现,在黑暗中对叶片施加短时间的光照能够增加抗氰呼吸在总呼吸中的比例,但短时间的光照对叶片光合CO2固定速率没有影响。这些结果表明了光照对抗氰呼吸的诱导可以不依赖于光合作用,光照可能是作为一种直接的信号去诱导抗氰呼吸。 相似文献
17.
The Conversion of Photoinactive Protochlorophyllide(633) to Phototransformable Protochlorophyllide(650) in Etiolated Bean Leaves Treated with delta-Aminolevulinic Acid 总被引:1,自引:0,他引:1
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Gassman ML 《Plant physiology》1973,52(6):590-594
The relationship of phototransformable protochlorophyllide to photoinactive protochlorophyllide has been studied in primary leaves of 7- to 9-day-old dark-grown bean (Phaseolus vulgaris L. var. Red Kidney) seedlings. Various levels of photoinactive protochlorophyllide, absorbing at 633 nm in vivo, were induced by administering δ-aminolevulinic acid to the leaves in darkness. Phototransformable protochlorophyllide, absorbing at 650 nm in vivo, was subsequently transformed to chlorophyllide by a light flash, and the regeneration of the photoactive pigment was followed by monitoring the absorbance increase at 650 nm in vivo. A small increase in the level of protochlorophyllide633 causes a marked increase in the extent of regeneration of protochlorphyllide650 following a flash. High levels of the inactive pigment species, however, retard the capacity to reform photoactive protochlorophyllide. A nonstoichiometric and kinetically complex decrease in absorbance at 633 nm in vivo accompanied the absorbance increase at 650 nm. The half-time for protochlorophyllide650 regeneration in control leaves was found to be three times longer than the half-time for conversion of chlorophyllide678 to chlorophyllide683 at 22 C. The results are consistent with the hypothesis that protochlorophyllide633 is a direct precursor of protochlorophyllide650 and that the protein moiety of the protochlorophyllide holochrome acts as a “photoenzyme” in the conversion of protochlorophylide to chlorophyllide. 相似文献
18.
Carbon Dioxide Efflux from Leaves in Light and Darkness 总被引:2,自引:0,他引:2
Efflux of carbon dioxide in light and darkness was measured at low ambient CO2 concentrations in leaves of Rumex acetosa. Light carbon dioxide production (photo-respiration) was found to depend on irradiance and to differ from dark production as to the response to temperature and ambient concentrations of O2 and CO2. These observations support previously made suggestions that photorespiration follows a different metabolic pathway to dark respiration. 相似文献
19.
CURT BENGTSON BIRGITTA KLOCKARE RUNE KLOCKARE STIG LARSSON CHRISTER SUNDQVIST 《Physiologia plantarum》1978,43(3):205-212
Cut seedlings of wheat plants (Triticum aestivum L. cv. Starke II Weibull) between 6 and 7 days old were water stressed in darkness by exposing them to air of 35% relative humidity 2.5 to 20 h. This treatment resulted in a water potential of -11 bars in the leaves after 20 h. The leaves were then rewatered and irradiated. The chlorophyll formation that took place in fully turgid leaves during the greening was markedly decreased in the case of the water-stress pretreatmet. and especially the lag phase was prolonged. The longer the stress pretreatment the more evident was the subsequent effect on chlorophyll formation. However, no linear relationship was found between the amount of stress and the chlorophyll content. Protochlorophyllide regeneration from endogenously formed δ-aminolevulinic acid was markedly decreased even after the shortest water-stress period. However, protochlorophyllide accumulation from exogenously supplied δ-aminolevulinic acid was only slightly decreased following the water-stress pretreatment. Further more, the ratio of protochlorophyllide650 to protochlorophyllide628 was slightly reduced by the same conditions. During the stress period both abscisic acid and proline were accumulated in the leaves. The content of abscisic acid increased up to six times the normal level during water stress lasting for 20 h. The increase of proline was about three-fold for similar treatment. After rewatering the leaves the levels of both abscisic acid and proline rapidly declined and reached. 10 h later, the levels found in unstressed seedlings. The increase in abscisic acid during water stress associated with impaired chlorophyll metabolism suggested that the after-effect of water stress might be linked to chlorophyll metabolism through abscisic acid or some of its metabolites. The changes in proline content open the possibility that this substance could function as a reserve substance for the formation of chlorophyll after the discon tinuation of the stress. 相似文献
20.
《Phytochemistry》1986,25(8):1829-1836
When etiolated barley (Hordeum vulgare L. var. Larker) shoots are incubated with [4-14C]levulinic acid, 14CO2 is evolved, and amino and organic acids are labelled. Respiratory inhibitors and short-chain fatty acids, similar in size to levulinic acid, reduce the production of 14CO2 from [4-14C]levulinic acid, while δ-aminolevulinic acid treatment or illuminating the tissue increase 14CO2 evolution. The contribution of levulinic acid metabolism to α-aminolevulinic acid biosynthesis is no greater than that of a general cellular metabolite. The data suggest that fatty acid oxidation and the citric acid cycle are involved in levulinic acid metabolism. 相似文献