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1.
The changes of granule bound starch synthetase activity in cucumber leaves ( Cucumis sativus L. cv. Suisei No. 2) were investigated during ammonium toxicity. Generally speaking the quantity of starch granules of injured plants were less than that of normal plants. ADPG is a more effective glucose donor to starch synthesis than UDPG. It was found that the starch synthetase activity of injured plants was decreased compared to the normal plants. This variation of enzyme activity was higher when UDPG was used as glucose donor. The addition of K + and NH 4+ generally inhibited the enzyme activity when UDPG was used as glucose donor, but stimulated it when ADPG was used. This stimulation was found to be more effective in enzymes prepared from injured plants than from normal plants. The level of potassium bound to starch granules was not changed markedly between normal and injured plants. 相似文献
2.
The activity of enzymes participating in the systems of antioxidant protection was assayed in the second leaf and roots of 21-day-old wheat seedlings ( Triticum aestivum L.) grown in a medium with nitrate (NO –
3 treatment), ammonium (NH +
4 treatment), or without nitrogen added (N-deficiency treatment). The activities of superoxide dismutase (SOD), peroxidase, ascorbate peroxidase, glutathione reductase, and catalase in the leaves and roots of the NH +
4 plants was significantly higher than in the plants grown in the nitrate medium. The activity of SOD decreased and ascorbate peroxidase markedly increased in leaves, whereas the activity of ascorbate peroxidase increased in the roots of N-deficient plants, as compared to the plants grown in nitrate and ammonium. Low-temperature incubation (5°, 12 h) differentially affected the antioxidant activity of the studied plants. Whereas leaf enzyme activities did not change in the NH +
4 plants, the activities of SOD, peroxidase, ascorbate peroxidase, and catalase markedly increased in the NO –
3 plants. In leaves of the N-deficient plant, the activity of SOD decreased; however, the activity of other enzymes increased. In response to temperature decrease, catalase activity increased in the roots of NO –
3 and NH +
4-plants, whereas in the N-deficient plants, the activity of peroxidase increased. Thus, in wheat, both nitrogen form and nitrogen deficiency changed the time-course of antioxidant enzyme activities in response to low temperature. 相似文献
3.
The relationship between leaf K + concentration, in vitro dehydration, and nonstomatal-controlled photosynthesis was investigated using leaf slices that were vacuum infiltrated with media containing varying sorbitol concentrations. The leaf slices were from plants either supplied with complete or K +-deficient medium throughout a 35-day growth period. During this time, leaf K + concentration, water potential, osmotic potential, and turgor pressure were monitored. Leaf K + concentration averaged 239 micomoles per gram (fresh weight) in control plants, and dropped to 74.3 micromoles per gram (fresh weight) in K +-deficient plants. Less negative osmotic potentials and resultant turgor loss in K +-deficient plants indicated that the osmotically active pool of cellular K + was lower in those plants. The decrease in leaf K+ concentration enhanced the dehydration inhibition of photosynthesis. For example, increasing sorbitol from 0.33 to 0.5 molar during incubation inhibited photosynthesis in the controls by 14% or less. This same protocol resulted in an inhibition of photosynthesis by as much as 41% in K+-deficient tissue. In contrast to the data obtained with leaf slices, dehydration inhibition of isolated chloroplast photosynthesis was not affected by K+ status of parent plant material. These data are consistent with the hypothesis that one effect of leaf K+ deficiencies on photosynthetic response to dehydration may be mediated by extra-choloroplastic factors. Ammonium ions, which facilitate stromal alkalinization, reversed the increased sensitivity of K+-deficient leaf slice photosynthesis to cell dehydration. However, NH4+ had no effect on photosynthesis of K+-deficient leaf slices under nonhypertonic conditions. These data suggest that endogenous extra-chloroplastic K+ may modulate dehydration inhibition of photosynthesis, possibly by facilitating stromal alkalinization. 相似文献
4.
The effect of external inorganic nitrogen and K + content on K + uptake from low-K + solutions and plasma membrane (PM) H +-ATPase activity of sorghum roots was studied. Plants were grown for 15 days in full-nutrient solutions containing 0.2 or 1.4 mM K + and inorganic nitrogen as NO 3-, NO 3-/NH 4+ or NH 4+ and then starved of K + for 24, 48 and 72 h. NH 4+ in full nutrient solution significantly affected the uptake efficiency and accumulation of K +, and this effect was less pronounced at the high K + concentration. In contrast, the translocation rate of K + to the shoot was not altered. Depletion assays showed that plants grown with NH 4+ more efficiently depleted the external K + and reached higher initial rates of low-K + uptake than plants grown with NO 3-. One possible influence of K + content of shoot, but not of roots, on K + uptake was evidenced. Enhanced K +-uptake capacity was correlated with the induction of H + extrusion by PM H +-ATPase. In plants grown in high K + solutions, the increase in the active H + gradient was associated with an increase of the PM H +-ATPase protein concentration. In contrast, in plants grown in solutions containing 0.2 mM K +, only the initial rate of H +-pumping and ATP hydrolysis were affected. Under these conditions, two specific isoforms of PM H +-ATPase were detected, independent of the nitrogen source and deficiency period. No change in enzyme activity was observed in NO 3--grown plants. The results suggest that K + homeostasis in NH 4+-grown sorghum plants may be regulated by a high capacity for K + uptake, which is dependent upon the H +-pumping activity of PM H +-ATPase. 相似文献
5.
In saline environments, bread wheat, Triticum aestivum L. (genomes AABBDD), accumulates less Na + and more K + in expanding and young leaves than durum wheat, T. turgidum L. (genomes AABB). Higher K +/Na + ratios in leaves of bread wheat correlate with its higher salt tolerance. Chromosome 4D from bread wheat was shown in previous work to play an important role in the control of this trait and was recombined with chromosome 4B in the absence of the Ph1 locus. A population of plants disomic for 4D/4B recombined chromosomes in the genetic background of T. turgidum was developed to investigate the genetic control of K +/Na + discrimination by chromosome 4D. Evidence was obtained that the trait is controlled by a single locus, designated Kna1, in the long arm of chromosome 4D. In the present work, K +/Na + discrimination was determined for additional families with 4D/4B chromosomes. The concentrations of Na + and K +/Na + ratios in the youngest leaf blades clustered in two nonoverlapping classes, and all recombinant families could be unequivocally assigned to Kna1 and kna1 classes. The Kna1 locus scored this way was mapped on a short region in the 4DL arm and was completely linked to Xwg199, Xabc305, Xbcd.402, Xpsr567, and Xpsr375; it was also mapped as a quantitative trait. The results of the QTL analysis, based on the K +/Na + ratios in the young leaves of greenhousegrown plants and flag leaves of field-grown plants, agreed with the position of Knal determined as a qualitative trait. Several aspects of gene introgression by manipulation of the Ph1 locus are discussed. 相似文献
6.
分别采用5 mJ.s -1.mm -2 He-Ne激光辐照、10.08 kJ.m -2.d -1增强UV-B辐射及二者组合对小麦(Triticum aestivum)晋麦8号(Triticum aestivum ‘Jinmai8’)幼苗进行处理。第5 天开始测定各处理小麦幼苗叶片中线粒体、叶绿体及细胞溶质中Na +/K +-ATP酶活性的变化。结果表明, 随着处理天数的增加, 小麦幼苗叶片线粒体、叶绿体及细胞溶质中Na +/K +-ATP酶活性均在第6天下降, 第7天升高, 而后又逐渐下降。在处理的第7天, 仅He-Ne激光辐照可使小麦幼苗叶片线粒体、叶绿体及细胞溶质中Na +/K +-ATP酶活性升高; 增强UV-B辐射使各细胞器中Na +/K +-ATP酶活性下降; 复合处理后小麦各细胞器中Na +/K +-ATP酶活性均高于UV-B单独辐射处理。实验结果表明 , 一定剂量的He-Ne激光辐照能够部分修复UV-B辐射对小麦幼苗细胞器中Na +/K +-ATP酶造成的损伤。 相似文献
7.
Polyamine analogues have been studied as potential inhibitors or substrates of barley leaf polyamine oxidase. NH 2(CH 2) 3NH(CH 2) 10NH 2 was particularly effective as an inhibitor of spermine oxidation at pH 4·5 (K i = 5 × 10 ?6 M). Methylglyoxal- bis(guanylhydrazone) inhibited spermine oxidation only slightly (K i = 10 ?4 M). Activity with the polyamine analogues as substrates was generally 10% or less of the activity with spermine. The Km for oxygen was 3 × 10 ?4 M. The Km for spermine oxidation was independent of oxygen concentration. Using the N-methyl-2-benzothiazolone hydrazine reagent, 1-(3-aminopropyl)pyrroline was shown to be formed stoichiometrically by the enzyme on oxidation of spermine. The enzyme will not function as a dehydrogenase in the presence of oxygen with either potassium ferricyanide or dichlorophenolindophenol as electron acceptors. Activity in the leaves increased with age, up to 4 weeks. In the leaves of 11-week-old plants activity was lower than in leaves of 1-week-old plants. The enzyme was mainly associated with an easily-sedimented particulate fraction, and relatively small proportions were found in the cell wall or soluble fractions. 相似文献
8.
In plants of wheat ( Triticum aestivum L.) grown in the media with nitrate (NO 3 ? plants), ammonium (NH 4 + plants), and without nitrogen (N-deficient plants), the response to oxidative stress induced by the addition of 300 mM NaCl to the nutrient solution was investigated. Three-day-long salinization induced chlorophyll degradation and accumulation of malondialdehyde (MDA) in the leaves. These signs of oxidative stress were clearly expressed in NO 3 ? and N-deficient plants and weakly manifested in NH 4 + plants. In none of the treatments, salinization induced the accumulation of MDA in the roots. Depending on the conditions of N nutrition, salt stress was accompanied by diverse changes in the activity of antioxidant enzymes in the leaves and roots. Resistance of leaves of NH 4 + plants to oxidative stress correlated with a considerable increase in the activities of ascorbate peroxidase and glutathione reductase. Thus, wheat plants grown on the NH 4 + -containing medium were more resistant to the development of oxidative stress in the leaves than those supplied with nitrate. 相似文献
9.
Wheat irrigated with nutrient solutions containing 0, 0.2, 0.5, 1, 2, or 6 millimolar K + had maximum photosynthetic rates at 1 to 2 millimolar K + concentrations. Rates in the 6 millimolar K +-grown plants were not higher than the 2 millimolar K +-grown wheat, and rates were inhibited below 0.5 millimolar K +. Photosynthesis was measured by both attached whole leaf CO 2 uptake and by 14CO 2 fixation of leaf slices in solution. Exposure of leaf slices from 0.2, 2, and 6 millimolar K +-grown wheat to various assay media water potentials showed that photosynthesis of the 0.2 millimolar K +-grown wheat decreased from control (high water potential) rates by 35%, that of the 2 millimolar K +-grown wheat by 20.4%, and that of the 6 millimolar K +-grown wheat by only 8.3% at −3.11 megapascals. Also, photosynthesis of the 6 millimolar K +-grown wheat was enhanced by 28% over that of the 2 millimolar K + wheat at the most severe water stress (−3.11 megapascals), indicating that the excess leaf K + in the 6 millimolar K +-grown wheat partially reversed dehydration effects on photosynthesis. Oligomycin eliminated the protective effects of high K + on photosynthesis in dehydrated leaf slices. These results suggest that the protective effect of high K + under water stress may involve the exchange of K + in the cytoplasm for stroma H +, thus altering stromal pH and restoring photosynthesis. The protective effect of high K + was also observed in attached whole leaf photosynthesis of in situ water-stressed wheat grown on 0.2, 2, and 6 millimolar K +. Under water stress, rates of the 6 millimolar K +-grown wheat were enhanced by 66.2% and 113.9% over that of 2 millimolar K +-grown wheat in two separate experiments. Internal CO 2 concentration of the 6 millimolar K +-grown wheat was lower than that of the 0.2 and 2 millimolar K +-grown wheat. These results suggest that the high K + effects on chloroplast photosynthesis seen in leaf slices also occur at the whole plant level. 相似文献
10.
Studies were conducted to characterize ATPase activity associated with purified chloroplast inner envelope preparations from spinach ( Spinacea oleracea L.) plants. Comparison of free Mg 2+ and Mg·ATP complex effects on ATPase activity revealed that any Mg 2+ stimulation of activity was likely a function of the use of the Mg·ATP complex as a substrate by the enzyme; free Mg 2+ may be inhibitory. In contrast, a marked (one- to twofold) stimulation of ATPase activity was noted in the presence of K +. This stimulation had a pH optimum of approximately pH 8.0, the same pH optimum found for enzyme activity in the absence of K +. K + stimulation of enzyme activity did not follow simple Michaelis-Menton kinetics. Rather, K + effects were consistent with a negative cooperativity-type binding of the cation to the enzyme, with the Km increasing at increasing substrate. Of the total ATPase activity associated with the chloroplast inner envelope, the K +-stimulated component was most sensitive to the inhibitors oligomycin and vanadate. It was concluded that K + effects on this chloroplast envelope ATPase were similar to this cation's effects on other transport ATPases (such as the plasmalemma H +-ATPase). Such ATPases are thought to be indirectly involved in active K + uptake, which can be facilitated by ATPase-dependent generation of an electrical driving force. Thus, K + effects on the chloroplast enzyme in vitro were found to be consistent with the hypothesized role of this envelope ATPase in facilitating active cation transport in vivo. 相似文献
12.
Young bean plants ( Phaseolus vulgaris L. var Saxa) were fed with 3.5 or 10 millimolar N in either the form of NO 3− or NH 4+, after being grown on N-free nutrient solution for 8 days. The pH of the nutrient solutions was either 6 or 4. The cell sap pH and the extractable activities of phosphoenolpyruvate carboxylase and of pyruvate kinase from roots and primary leaves were measured over several days. The extractable activity of phosphoenolpyruvate carboxylase (based on soluble protein) from primary leaves increased with NO3− nutrition, whereas with NH4+ nutrition and on N-free nutrient solution the activity remained at a low level. Phosphoenopyruvate carboxylase activity from the roots of NH4+-fed plants at pH 4 was finally somewhat higher than from the roots of plants grown on NO3− at the same pH. There was no difference in activity from the root between the N treatments when pH in the nutrient solutions was 6. The extractable activity of pyruvate kinase from roots and primary leaves seemed not to be influenced by the N nutrition of the plants. The results are discussed in relation to the physiological function of both enzymes with special regard to the postulated functions of phosphoenolpyruvate carboxylase in C3 plants as an anaplerotic enzyme and as part of a cellular pH stat. 相似文献
13.
Physiological responses of two wheat ( Triticum aestivum L.) genotypes (salt-tolerant DK961 and salt-sensitive JN17) to increased salt concentrations (50, 100, 150 mM NaCl: NaCl 50, NaCl 100, NaCl 150) were studied. Photosynthetic capacity, irradiance response curves, contents of soluble sugars, proteins, and chlorophyll
(Chl), K +/Na + ratio, and activities of antioxidant enzymes (superoxide dismutase, peroxidase, and catalase) in flag leaves were measured
on 7 d after anthesis. In control (NaCl 0) plants, non-significant ( p>0.05) differences were found in gas exchange and saturation irradiance (SI) between salt-tolerant (ST) and salt-sensitive
(SS) wheat genotypes. However, we found higher soluble sugar and protein contents, K +/Na + ratio, and antioxidant enzyme activities, but lower Chl content and yield in ST wheat. Salinity stresses remarkably increased
soluble sugar and protein contents and the antioxidant activities, but decreased K +/Na + ratio, Chl contents, SI, photosynthetic capacities, and yield, the extent being considerably larger in JN17 than DK961. Although
the soluble sugar and protein contents and the antioxidant activities of JN17 elevated more evidently under salt stresses,
those variables never reached the high levels of DK961. The antioxidant enzyme activities of SS wheat increased in NaCl 50 and NaCl 100, but decreased rapidly when the NaCl concentration reached 150 mM. Thus the ST wheat could maintain higher grain yield than
the SS one by remaining higher osmoregulation and antioxidative abilities, which led to higher photosynthetic capacity. Hence
the ST wheat could harmonize the relationship between CO 2 assimilation (source) and the grain yield (sink) under the experimental conditions. 相似文献
14.
Summary Dihydrofolate synthetase (EC 6.3.2.12) from N. gonorrhoeae was isolated and enzyme characteristics were determined. The purified enzyme was found quite stable when stored at –60 °C. About 50% of the enzyme activity wag destroyed within 6 weeks when kept at 4 °C. Maximum velocity was observed at pH 9.3. The enzyme required a monovalent cation, K + or NH 4
+ , and divalent cation, Mg 2+ or Mn 2+ for its function. ATP at 5 mM concentration gave maximum activity. K m values for dihydropteroate and L-glutamate at pH 9.3 were 3.5 × 10 –5 M and 6.5 × 10 –4 M, respectively. Patterns of product inhibition by dihydrofolate were found to be non-competitive with respect to dihydropteroate, having a K i value of 5.1 ± 0.8 × 10 –4 M, and competitive with respect to L-glutamate, having a K i value of 6.2 × 10 –4 M. 相似文献
15.
Pea plants grown in nutrient solution in which K + ions were equimolarly replaced with Na +, NH 4 + or Rb + did not show morphological symptoms of potassium-deficiency. The activity of diamine oxidase in these plants was higher than in controls. Similarly higher diamine oxidase activity was found in plants grown in a complete nutrient solution supplemented with putrescine. 相似文献
16.
The author studied the effect of different nickel concentrations (0, 0.4, 40 and 80 μM Ni) on the nitrate reductase (NR) activity
of New Zealand spinach ( Tetragonia expansa Murr.) and lettuce ( Lactuca sativa L. cv. Justyna) plants supplied with different nitrogen forms (NO 3
−–N, NH 4
+–N, NH 4NO 3). A low concentration of Ni (0.4 μM) did not cause statistically significant changes of the nitrate reductase activity in
lettuce plants supplied with nitrate nitrogen (NO 3
−–N) or mixed (NH 4NO 3) nitrogen form, but in New Zealand spinach leaves the enzyme activity decreased and increased, respectively. The introduction
of 0.4 μM Ni in the medium containing ammonium ions as a sole source of nitrogen resulted in significantly increased NR activity
in lettuce roots, and did not cause statistically significant changes of the enzyme activity in New Zealand spinach plants.
At a high nickel level (Ni 40 or 80 μM), a significant decrease in the NR activity was observed in New Zealand spinach plants
treated with nitrate or mixed nitrogen form, but it was much more marked in leaves than in roots. An exception was lack of
significant changes of the enzyme activity in spinach leaves when plants were treated with 40 μM Ni and supplied with mixed
nitrogen form, which resulted in the stronger reduction of the enzyme activity in roots than in leaves. The statistically
significant drop in the NR activity was recorded in the aboveground parts of nickel-stressed lettuce plants supplied with
NO 3
−–N or NH 4NO 3. At the same time, there were no statistically significant changes recorded in lettuce roots, except for the drop of the
enzyme activity in the roots of NO 3
−-fed plants grown in the nutrient solution containing 80 μM Ni. An addition of high nickel doses to the nutrient solution
contained ammonium nitrogen (NH 4
+–N) did not affect the NR activity in New Zealand spinach plants and caused a high increase of this enzyme in lettuce organs,
especially in roots. It should be stressed that, independently of nickel dose in New Zealand spinach plants supplied with
ammonium form, NR activity in roots was dramatically higher than that in leaves. Moreover, in New Zealand spinach plants treated
with NH 4
+–N the enzyme activity in roots was even higher than in those supplied with NO 3
−–N. 相似文献
17.
The interaction of low water potential effects on photosynthesis, and leaf K + levels in wheat ( Triticum aestivum L.) plants was studied. Plants were grown at three K + fertilization levels; 0.2, 2, and 6 millimolar. With well watered plants, 2 millimolar K + supported maximal photosynthetic rates; 0.2 millimolar K + was inhibitory, and 6 millimolar K + was superoptimal ( i.e. rates were no greater than at 2 millimolar K +). Photosynthesis was monitored at high (930 parts per million) and low (330 parts per million) external CO 2 throughout a series of water stress cycles. Plants subjected to one stress cycle were considered nonacclimated; plants subjected to two successive cycles were considered acclimated during the second cycle. Sensitivity of photosynthesis to declining leaf water potential was affected by K + status; 6 millimolar K + plants were less sensitive, and 0.2 millimolar K + plants were more sensitive than 2 millimolar K + plants to declining water potential. This occurred with nonacclimated and acclimated plants at both high and low assay CO 2. It was concluded that the K + effect on photosynthesis under stress was not mediated by treatment effects on stomatal resistance. Differences between the K + treatments were much less pronounced, however, when photosynthesis of nonacclimated and acclimated plants was plotted at a function of declining relative water content during the stress cycles. These results suggest that K + effects on the relationship between relative water content and water potential in stressed plants was primarily responsible for the bulk of the K +-protective effect on photosynthesis in stressed plants. In vitro experiments with chloroplasts and protoplasts isolated from 2 millimolar K + and 6 millimolar K + plants indicated that upon dehydration, K + efflux from the chloroplast stroma into the cytoplasm is less pronounced in 6 millimolar K + protoplasts. 相似文献
18.
The thermal stability and kinetic properties of purified NADP +-malate dehydrogenase (NADP +-MDH; EC 1.1.1.82) isomorphs were analyzed from plants of two populations of Barnyard grass from contrasting thermal environments. Plants from Québec (QUE) and Mississippi (MISS) were acclimated under controlled conditions at 26/20°C and 14/8°C (day/night). While the enzyme from QUE showed one isomorph, 3 isomorphs were detected in all plants from MISS, suggesting the presence of gene duplication and fixed heterozygosity for the expression of this dimeric enzyme. This findig raises the possibility that the enhanced acclimatory potential of NADP +-MDH from MISS plants, as found from previous studies with the partially purified and unfractioned enzyme, may result from differential kinetic properties of isomorphs which would allow for the proper modulation of catalysis over a wide temperature range. The thermal stability of the QUE isomorph was significantly higher than that of any of the MISS isomorphs. The apparent activation energy of the QUE isomorph was within the range of values found for the 3 MISS isomorphs which were similar to each other. The Michaelis-Menten constants (K m) for oxalacetic acid were not significantly different among isomorphs or between thermoperiods, but K m (NADP +) values for the QUE isomorph were significantly higher than those of two of the MISS isomorphs over the 15–25°C assay range V max/K m ratios for OAA and NADP + were not significantly different among isomorphs or between thermoperiods. Our data indicate that, under highly purified conditions, the single NADP +-MDH isomorph of QUE plants possesses good acclimatory potential for maintaining catalytic efficiency under a wide range of temperature conditions. In vitro thermal and kinetic data do not support the hypothesis that the the multiple NADP +-MDH isomorphs found in MISS plants may have been selected to optimize the thermal and catalytic efficiency of NADP +-MDH under warm temperature conditions. 相似文献
19.
Abstract. Propagules of the mangrove, Rhizophora mangle L., were precultivated for 9 months in a greenhouse. The young plants were transferred into unaerated nutrient solutions without and with 200 mol m 3 NaCl and subsequently their growth, their water relations and the photosynthetic properties of their leaves were studied. Growth of the salttreated plants was significantly increased, while the control plants gradually died off after finishing the experiments. The shoot water potential and the stomatal resistance of the leaves were lowered while the chlorophyll contents and the chlorophyll a/b ratio in the leaves of salt-treated plants were increased by NaCl, the net result being an enhanced rate of CO 2 assimilation. The leaves of both sets of plants showed diurnal fluctuations in malic acid concentration which were more pronounced in the leaves of salt treated plants which, additionally, were more succulent. However, the plants showed no net CO 2 fixation at night, indicating that Rhizophora mangle is a CAM-cycling plant. After 200 d of cultivation without or with NaCl, the Na +, Cl and K + concentrations in tissues and vacuoles were measured. Energy-dispersive X-ray microprobe analyses on root vacuoles of control plants reveal Na + preference, on those of salt treated plants a strong K + preference. Vacuolar K + concentrations are neither affected by NaCl nor do they vary across the root radius. High vacuolar Na + and Cl concentrations are found in the hypodermis followed by a stepwise decrease towards the inner root cortex cells. Ion concentrations of the photosynthetically active leaf tissues seem to be regulated by (1) radial filtration across the root cortex: (2) ion exchange of the xlem parenchyma cells: and (3) sequestration of Na + and Cl in the hypodermal water storage tissue of the leaves. 相似文献
20.
Mesophyll K + retention ability has been recently reported as an important component of salinity stress tolerance in wheat. In order to investigate the role of ROS in regulating NaCl -induced K + efflux in wheat leaf mesophyll, a series of pharmacological experiments was conducted using MV (methyl viologen, superoxide radical inducer), DPI (an inhibitor of NADPH oxidase), H 2O 2 (to mimic apoplastic ROS), and EGCG ((−)-Epigallocatechin gallate, ROS scavenger). Mesophyll pre-treatment with 10 μM MV resulted in a significantly higher NaCl -induced K + efflux in leaf mesophyll, while 50 μM EGCG pre-treatment alleviated K + leakage under salt stress. No significant change in NaCl -induced K + efflux in leaf mesophyll was found in specimens pre-treated by H 2O 2 and DPI, compared with the control. The highest NaCl -induced H + efflux in leaf mesophyll was also found in samples pre-treated with MV, suggesting a futile cycle between increased H +-ATPase activity and ROS-induced K + leak. Overall, it is suggested that, under saline stress, K + efflux from wheat mesophyll is mediated predominantly by non-selective cation channels (NSCC) regulated by ROS produced in chloroplasts, at least in bread wheat. 相似文献
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