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1.
Accumulation of proline in response to NH4Cl was studied indetached leaves of rice (Oryza sativa cv. Taichung Native1). Increasing concentrations of NH4Cl from 50 to 200mMprogressively increased proline content and this was correlated with theincrease in ammonium content. Proline accumulation induced by NH4Clwas related to proteolysis, an increase in ornithine--aminotransferaseactivity, a decrease in proline dehydrogenase activity, and a decrease inproline utilisation and could not be explained by NH4Cl-inducedmodification in 1-pyrroline-5-carboxylate reductase activity.The content of glutamic acid was decreased by NH4Cl, whereas theincrease in arginine and ornithine contents was found to be associated with theincrease in proline content in NH4Cl-treated detached rice leaves.  相似文献   

2.
Ammonium accumulation in relation to prolineaccumulation in detached rice leaves under stressconditions was investigated. Ammonium accumulation indark-treated detached rice leaves preceded prolineaccumulation. Ammonium accumulation caused by waterstress coincided closely with proline accumulation indetached rice leaves. Exogenous NH4Cl andmethionine sulfoximine (MSO), which caused anaccumulation of ammonium in detached rice leaves,increased proline content. It was found that prolinein NH4Cl- or MSO-treated rice leaves is lessutilized than in water-treated rice leaves (controls). These results are in agreement with the observationthat a decrease in proline utilization contributes tothe accumulation of proline in dark-treated and waterstressed rice leaves. Although ammonium contentincreased in Cd- and Cu-treated rice leaves, theincrease in ammonium content was only observed afterthe increase in proline content.  相似文献   

3.
The regulation of proline accumulation in detached rice leaves exposed to excess NiSO4 was investigated. NiSO4 treatment increased proline and Ni contents but had no effect on relative water content, indicating that proline accumulation in Ni-exposed detached rice leaves was due to Ni uptake per se, rather than to water stress. Proline accumulation caused by NiSO4 was related to protein hydrolysis, a decrease in proline dehydrogenase activity, and a decrease in proline utilization. It seems that an increase in the content of ammonia and an increase in the activities of Δ1-pyrroline-5-carboxylate reductase and ornithine-δ-aminotransferase play minor if any role in Ni-induced proline accumulation in detached rice leaves.  相似文献   

4.
The possibility that NH4 + accumulation is linkedto the senescence of detached rice (Oryza sativa) leavesinduced by NaCl was investigated. NaCl was effective in promoting senescenceandin increasing NH4 + content of detached rice leaves.NaCl-promoted senescence is mainly due to the effect of both Na+ andCl- ions. NaCl had no or slight effect on relative water content,suggesting that an osmotic effect is unlikely to be a major factor contributingto senescence of these leaves. NaCl-induced NH4 +accumulation was due to enhanced nitrate reduction and decreased glutaminesynthetase activity. Exogenous NH4Cl, which caused an accumulationofNH4 + in detached rice leaves, also promoted senescence.Itwas found that an increase in NH4 + content preceded theoccurrence of senescence caused by NaCl. Results also show that NaCl-promotedsenescence is unlikely to be due to the lack of glutamate, glutamine,aspartate,and asparagine. The current results suggest that NH4 +accumulation is linked to NaCl-induced rice leaf senescence. Since ethylene isknown to be a potent promoter of leaf senescence, we also investigated the roleof ethylene in the regulation of NH4 +-promoted senescenceof detached rice leaves. NaCl or NH4Cl treatment resulted in adecrease of ethylene production. Evidence was presented to show thatNH4 + accumulation in detached rice leaves does not changetissue sensitivity to ethylene. Clearly, the possible involvement of ethyleneinNH4 +-promoted senescence is excluded.  相似文献   

5.
The regulation of proline accumulation in polyethylene glycol (PEG, –1.5 MPa) treated rice leaves was investigated. PEG treatment resulted in a decrease in relative water content, indicating that PEG treatment caused water stress in rice leaves. Proline accumulation caused by PEG was related to protein hydrolysis, an increase in ornithine--amino- transferase activity, an increase in the content of ammonia, and an increase in the contents of the precursors of proline biosynthesis, glutamic acid, ornithine, and arginine. Results also show that abscisic acid accumulation is not required for proline accumulation in PEG-treated rice leaves.  相似文献   

6.
Ammonium ion accumulation and the decrease in glutamine synthetase (GS)activity induced by CdCl2 were investigated in relation to lipidperoxidation in detached rice leaves. CdCl2 was effective inincreasing ammonium ion content, decreasing GS activity and increasing lipidperoxidation. Free radical scavengers (glutathione, thiourea, sodium benzoate)and an iron chelator (2,2-bipyridine) were able to inhibit the decreasein GS activity and ammonium ion accumulation caused by CdCl2 and atthe same time inhibit CdCl2-induced lipid peroxidation. Paraquat,which is known to produce oxygen radicals, decreased GS activity, increasedammonium ion content, and increased lipid peroxidation. GS1 appears to be thepredominant isoform present. Excess Cd caused a decrease in GS1 but not in GS2in detached rice leaves. An increase in lipid peroxidation preceded ammoniumionaccumulation and the decrease in GS1 activity. These results suggest that thedecrease in GS activity and the accumulation of ammonium ions in detached riceleaves are a consequence of oxidative damage caused by excess Cd.  相似文献   

7.
The effect phosphinothricin (PPT), an inhibitor of glutamine synthetase (GS), on proline accumulation in detached rice leaves was investigated. During 12 h incubation, PPT inhibited GS activity and induced accumulation of NH4 +, and accumulation of proline in the light but not in darkness. Proline accumulation caused by PPT in the light was related to protein hydrolysis, and increase in the contents of precursors of proline, ornithine and arginine. Abscisic acid accumulation was not required for proline accumulation in PPT-treated rice leaves. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

8.
The relation between abscisic acid (ABA) and proline accumulation was investigated in detached rice (Oryza sativa L.) leaves. In darkness, proline content increased about 2-, 2,5- and 6-fold after 24, 48 and 72 h. ABA content reached maximum after 48 h. In the light, proline content remained almost unchanged until 48 h and subsequently increased slightly. ABA content in the light was lower than in darkness, but the maximum was also after 48 h. During 12-h exposure to decreased air humidity, proline content gradually increased, but ABA content increased about 25-fold after 4 h and declined thereafter. Exogenous application of ABA resulted in an increase in proline content in detached rice leaves under both light and darkness.  相似文献   

9.
The possible mediatory role of transition metals in methyl jasmonate- (MJ-)induced senescence of rice leaves was investigated. Metal chelators(2,2-bipyridine, 8-hydroxylquinoline and 1,10-phenanthroline) reducedMJ-promoted senescence of rice leaves. The reduction of MJ-promoted senescenceby 2,2-bipyridine(BP) is closely associated with the decrease in lipidperoxidation and increase in activity of superoxide dismutase (SOD). Our resultssuggest that iron or copper plays a major role in MJ-promoted senescence ofdetached rice leaves. BP-reduced senescence of detached rice leaves induced byMJ was reversed by adding Fe2+ or Cu2+, but notby Mn2+ or Mg2+. Reduction of MJ-promotedsenescence of detached rice leaves by BP is most likely mediated throughchelation of iron or copper and an increase in SOD activity.  相似文献   

10.
Cadmium toxicity of rice leaves is mediated through lipid peroxidation   总被引:8,自引:0,他引:8  
Oxidative stress, in relation to toxicity of detached rice leaves,caused by excess cadmium was investigated. Cd content inCdCl2-treated detached rice leaves increased with increasingdurationof incubation in the light. Cd toxicity was followed by measuring the decreasein chlorophyll and protein. CdCl2 was effective in inducing toxicityand increasing lipid peroxidation of detached rice leaves under both light anddark conditions. These effects were also observed in rice leaves treated withCdSO4, indicating that the toxicity was indeed attributed to cadmiumions. Superoxide dismutase (SOD), ascorbate peroxidase (APOD), and glutathionereductase (GR) activities were reduced by excess CdCl2 in the light.The changes in catalase and peroxidase activities were observed inCdCl2-treated rice leaves after the occurrence of toxicity in thelight. Free radical scavengers reduced CdCl2-induced toxicity and atthe same time reduced CdCl2-induced lipid peroxidation and restoredCdCl2-decreased activities of SOD, APOD, and GR in the light. Metalchelators (2,2-bipyridine and 1,10-phenanthroline) reducedCdCl2 toxicity in rice leaves in the light. The reduction ofCdCl2 toxicity by 2,2-bipyridine (BP) is closely associatedwith a decrease in lipid peroxidation and an increase in activities ofantioxidative enzymes. Furthermore, BP-reduced toxicity of detached riceleaves,induced by CdCl2, was reversed by adding Fe2+ orCu2+, but not by Mn2+ or Mg2+.Reduction of CdCl2 toxicity by BP is most likely mediated throughchelation of iron. It seems that toxicity induced by CdCl2 mayrequire the participation of iron.  相似文献   

11.
The effects of water stress and osmotic stress (sorbitol treatment) on the production of putrescine and proline in excised rice leaves were compared. Osmotic stress and water stress were found to affect differentially the levels of putrescine and proline in excised rice leaves. Putrescine accumulation is induced by osmotic stress, whereas proline accumulation is induced by water stress. The effects of ABA on the levels of proline and putrescine are similar to those of water stress, whereas the effects of jasmonic acid methyl ester (JA-Me) are similar to those of osmotic stress. Water stress results in an increase of endogenous ABA is excised rice leaves. However, neither osmotic stress nor JA-Me has effect on endogenous ABA levels in excised rice leaves. Of particular interest is the finding that proline levels increase when putrescine levels induced by osmotic stress or JA-Me are reduced by D-arginine and -methylornithine. L-arginine and L-ornithine applied exogenously also cause an increase in proline levels. It seems that L-arginine and L-ornithine are preferentially utilized as precursors for putrescine accumulation in excised rice leaves treated with osmotic stress and JA-Me, and for proline accumulation in excised rice leaves exposed to water stress and ABA.Abbreviations ABA abscisic acid - BSA bovine serum albumin - ELISA enzyme-linked immunosorbent assay - HPLC high performance chromatography - JA-Me jasmonic acid methyl ester - PVP poly-vinylpyrrolidone  相似文献   

12.
Proline is synthesized either from glutamate or from ornithine in plants. Relatively little is known about the contribution of the pathway from ornithine to proline biosynthesis. In this paper we investigated the contribution of ornithine--aminotransterase (OAT), an enzyme responsible for ornithine pathway, to proline accumulation in water-stressed detached rice leaves. Although OAT activity increased with the increase of water stress duration, a pattern similar to that obtained for proline accumulation, the ornithine pathway in rice leaves seems to contribute little, if any, to proline accumulation under water stress condition. This conclusion was based on the observations that (a) gabaculine (50 M), an inhibitor of OAT, inhibited about 75% OAT activity caused by water stress but reduced only 20% of proline content and (b) cycloheximide, a protein synthesis inhibitor, had no effect on OAT activity induced by water stress but significantly reduced proline accumulation.  相似文献   

13.
Root treatments of barley (Hordeum distichum L.) plants with 10-7 to 10-4 M abscisic acid (ABA) caused an increase in proline content, especially at higher concentrations, within 2–3 h. Even 3 h after the removal of ABA from the medium the plants continued to accumulate proline. The higher the concentration of the ABA, the higher was the proline level at 6 h. When the highest ABA concentration, 10-4 M, was tested with polyethylene glycol (PEG) (-5.0 bars) in the medium, the ABA treatment resulted in a higher proline content than in control plants. The treatments PEG alone and PEG + ABA resulted in heavy accumulation of proline, especially, 3 h after releasing the plants from the stress. The proline content in PEG+ABA-treated plants was always higher than plants treated with PGE or ABA alone. In peas (Pisum sativum L. cv Alaska) the same trend occurred although to a lesser degree. These findings indicate an influence of ABA on proline accumulation in water-stressed plants.Abbreviations ABA abscisic acid - PEG polyethylene glycol - RWC relative water content  相似文献   

14.
Effects of metal chelators, 2,2-bipyridine, 8-hydroxyquinoline and 1,10-phenenthroline, on the conversion of 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene in detached leaves of light-grown rice (Oryza sativa) seedlings and detached shoots of etiolated rice seedlings were investigated. Metal chelators strongly inhibited the in vivo ACC oxidase activity in detached leaves and detached etiolated shoots. This inhibition could be partially recovered by Fe2+. Our results support the notion that Fe2+ is an essential cofactor for the conversion of ACC to ethylene in vivo.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - BP 2,2-bypyridine - HQ 8-hydroxylquinoline - MJ methyl jasmonate - PA 1,10-phenanthroline - Put putrescine  相似文献   

15.
Proline accumulation was studied in the leaves of Glycine max (L.) Merr. subjected to salt stress in the presence of aminoguanidine (AG, a specific inhibitor of diamine oxidase, DAO) and exogenous putrescine (Put). Both DAO activity and proline content were increased while endogenous Put content was decreased in soybean leaves under 50 to 150 mM NaCl. There was a negative correlation between proline accumulation and endogenous Put content. The addition of AG during NaCl stress inhibited DAO activity, caused Put accumulation and a 15 to 20 % decrease in proline content. Application of 1 mM Put to NaCl solution markedly increased proline content. The promotive effect of Put application could be alleviated by the treatment with Put plus AG. Moreover an application of AG had no effect on proline accumulation in soybean seedlings grown under normal condition. These results indicate that the quantitative contribution of Put degradation to proline formation is 15 to 20 %.  相似文献   

16.
The salt-induced H+-ATPase activity and osmotic adjustment responses of Catharanthus roseus (L.) G. Don suspension cultures were studied. Cells were treated with 0, 50 or 100mM NaCl for 7days or were maintained for 8 months with 50 mM NaCl (50T cells). Growth, osmotic potential (), ions content, soluble sugars, proline and total amino acids were determined in the sap of control and salt-treated cells. Salinity reduced cell growth and . The higher decrease in the in salt-treated cells was due to higher accumulation of Na+ and Cl. The levels of organic solutes, such as soluble sugars, free proline and total amino acids, increased with salt treatment. These results suggest that salt-tolerant cells are able to osmotically adjust. Salinity treatments stimulated H+-ATPase activity. Immunodetection of the enzyme showed that the increased activity was due to an increased amount of protein in the plasmalemma. The induction by NaCl, especially at 100 mM NaCl and for 50T cells, could account for the K+ and Cl uptake but not for higher or lower tolerance.  相似文献   

17.
Chi Lin  Chuan  Huei Kao  Ching 《Plant and Soil》2001,237(1):165-171
The relative importance of endogenous abscisic acid (ABA), as well as Na+ and Cl in NaCl-induced responses related to growth in roots of rice seedlings were investigated. The increase in ammonium, proline and H2O2 levels, and cell wall peroxidase (POD) activity has been shown to be related to NaCl-inhibited root growth of rice seedlings. Increasing concentrations of NaCl from 50 to 150 mM progressively decreased root growth and increased both Na+ and Cl. Treatment with NaCl in the presence of 4,4-diisothiocyano-2,2-disulfonic acid (DIDS, a nonpermeating amino-reactive disulfonic acid known to inhibit the uptake of Cl) had less Cl level in roots than that in the absence of DIDS, but did not affect the levels of Na+, and responses related to growth in roots. Treatment with 50 mM Na-gluconate (the anion of which is not permeable to membrane) had similar Na+ level in roots as that with 100 mM NaCl. It was found that treatment with 50 mM Na-gluconate effected growth reduction and growth-related responses in roots in the same way as 100 mM NaCl. All these results suggest that Cl is not required for NaCl-induced responses in root of rice seedlings. Endogenous ABA level showed no increase in roots of rice seedlings exposed to 150 mM NaCl. It is unlikely that ABA is associated with NaCl-inhibited root growth of rice seedlings.  相似文献   

18.
The possibility that ammonium (NH 4 + ) accumulation is linked to the senescence of detached rice (Oryza sativa) leaves induced by copper (Cu) was investigated. CuSO4 was effective in promoting senescence of detached rice leaves. Both CuSO4 and CuCl2 induced NH 4 + accumulation in detached rice leaves, indicating that NH 4 + accumulation is induced by copper. Sulfate salts of Mg, Mn, Zn, and Fe were ineffective in inducing NH 4 + accumulation in detached rice leaves. The senescence of detached rice leaves induced by Cu was found to be prior to NH 4 + accumulation. Free radical scavengers, such as glutathione and thiourea, inhibited senescence caused by Cu and at the same time inhibited Cu-induced NH 4 + accumulation. The current results suggest that NH 4 + accumulation is not associated with senescence induced by Cu, but is part of the overall expression of oxidative damage caused by an excess of Cu. Evidence was presented to show that copper-induced ammonium accumulation in detached rice leaves is attributed to a decrease in glutamine synthetase activity and an increase in reduction of nitrate.  相似文献   

19.
Lee  T; Liu  C 《Journal of experimental botany》1999,50(341):1855-1862
The involvement of Na+, K+, Cl- or Ca2+ in the regulation of salinity stress-induced proline accumulation via the inhibition of the activity of proline dehydrogenase (PDH; EC 1.4.3.1), a catabolic enzyme of proline, was investigated in the marine green macroalga Ulva fasciata Delile. After 6 h of exposure to elevated artificial seawater (ASW) salinity, adjusted either by increasing the NaCl content in 30 ASW (a change in ion ratio) or by concentrating ASW (a constant ion ratio), the contents of Na+, K+ and Cl- linearly accumulated with increasing salinity from 30-90 (parts per thousand); the accumulation pattern of each ion was similar between the two treatments. An increase in NaCl content in ASW induced proline accumulation, but decreased both the PDH activity and the total water-soluble Ca2+ contents, while concentrated ASW had no effect. As compared to a constant value at 30, both the contents of total and water-soluble CA2+ and the activity of PDH decreased 1 h after exposure to 60 (adjusted by increasing NaCl content in 30 ASW) and concomitantly the content of seawater Ca2+ increased, while proline accumulated after 3 h. The addition of 15 mM ethylene glycol-bis-(2-aminoethyl ether) N,N,N-tetraacetic acid (EGTA) in 60 ASW (adjusted by increasing the NaCl content in 30 ASW) enhanced both the proline accumulation and the decrease in the content of total and water-soluble cellular Ca2+ and the activity of PDH; the effects of EGTA were reversed by 10 mM CaSO4. These results indicate that a loss of cellular Ca2+ is associated with the NaCl induction of proline accumulation via an inhibition of PDH activity in U. fasciata.  相似文献   

20.
Ammonium ion accumulation in detached rice leaves treated with phosphinothricin (PPT), an inhibitior of glutamine synthetase (GS), was investigated in the light and darkness. PPT treatment increased NH4 + content and induced toxicity in rice leaves in the light but not in darkness, suggesting the importance of light in PPT-induced NH4 + toxicity in detached rice leaves. PPT treatment in the light resulted in a decrease of activities of the cytosolic form of GS and the chloroplastic form of GS. The photosynthetic electron transport inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea reduced NH4 + accumulation induced by PPT in the light. In darkness, PPT-induced NH4 + accumulation and toxicity were observed in the presence of glucose or sucrose.  相似文献   

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