Effect of hydrogen peroxide on seedling growth and antioxidants in two wheat cultivars

This study aimed to investigate seed germination, seedling growth, and antioxidative responses in two wheat cultivars, Ningchun and Xihan, exposed to different H₂O₂ concentrations. Ningchun exhibited higher germination rate but lower root and shoot growth than Xihan when exposed to H₂O₂ treatment. Assays using fluorescent dye H₂DCFDA and propidium iodide showed a significantly enhanced H₂O₂ content and a cell elongation inhibition in H₂O₂-treated roots. The malondialdehyde content was elevated with increasing exogenous H₂O₂ concentration. Moreover, treatments of seedlings with H₂O₂ scavenger, catalase (CAT), and antioxidant, butylated hydroxytoluene, partly abolished H₂O₂-induced negative effect on root growth. In both untreated and H₂O₂-treated leaves, SOD activity in Ningchun was higher than that in Xihan, but POD and APX activities in Ningchun were lower than those in Xihan, leading to elevated H₂O₂ level in Ningchun leaves but decreased H₂O₂ content in Xihan ones under H₂O₂ treatment.     

Cell wall peroxidase activity,hydrogen peroxide level and NaCl-inhibited root growth of rice seedlings

The changes in cell-wall peroxidase (POD) activity and H₂O₂ level in roots of NaCl-stressed rice seedlings and their correlation with root growth were investigated. Increasing concentrations of NaCl from 50 to 150 mM progressively reduced root growth and increased ionically bound cell-wall POD activity. NaCl had no effect on covalently bound cell-wall POD activities. The reduction of root growth by NaCl is closely correlated with the increase in H₂O₂ level. Exogenous H₂O₂ was found to inhibit root growth of rice seedlings. Since ammonium and proline accumulation are associated with root growth inhibition caused by NaCl, we determined the effects of NH₄Cl or proline on root growth, cell-wall POD activity and H₂O₂level in roots. External application of NH₄Cl or proline markedly inhibited root growth, increased cell-wall POD activity and increased H₂O₂ level in roots of rice seedlings in the absence of NaCl. An increase in cell-wall POD activity and H₂O₂ level preceded inhibition of root growth caused by NaCl, NH₄Cl or proline. NaCl or proline treatment also increased NADH-POD and diamine oxidase (DAO) activities in roots of rice seedlings, suggesting that NADH-POD and DAO contribute to the H₂O₂ generation in the cell wall of NaCl- or proline-treated roots. NH₄Cl treatment increased NADH-POD activity but had no effect on DAO activity, suggesting that NADH-POD but not DAO is responsible for H₂O₂ generation in cell wall of NH₄Cl-treated roots.     

Osmotic stress-induced changes in cell wall peroxidase activity and hydrogen peroxide level in roots of rice seedlings

The changes in activity of peroxidase (POD) extracted from the cellwalls and the level of H₂O₂ in rice seedling rootstreatedwith mannitol and their correlation with root growth were investigated.Increasing concentrations of mannitol from 92 to 276 mM, which isiso-osmotic with 50 to 150 mM NaCl, progressively reduced rootgrowth and increased POD activities extracted from the cell walls of riceroots.The reduction of growth was also correlated with an increase inH₂O₂ level. Both diamine oxidase (DAO) and NADHperoxidase(NADH-POD) are known to be responsible for the generation ofH₂O₂. Mannitol treatment increased DAO but not NADH-PODactivities in roots of rice seedlings, suggesting that DAO contributes to thegeneration of H₂O₂ in the cell walls of mannitol-treatedroots. An increase in the level of H₂O₂ and the activityof POD extracted from the cell walls of rice roots preceded root growthreduction caused by mannitol. An increase in DAO activity coincided with anincrease in H₂O₂ in roots caused by mannitol. Since DAOcatalyses the oxidation of putrescine, the demonstration that mannitolincreasesthe activity of DAO in roots is consistent with those that mannitol decreasesthe level of putrescine. In conclusion, cell-wall stiffening catalysed by PODispossibly involved in the regulation of root growth reduction caused bymannitol.     

Differences in Cowpea Root Growth Triggered by Salinity and Dehydration are Associated with Oxidative Modulation Involving Types I and III Peroxidases and Apoplastic Ascorbate

The aim of this work was to investigate the balance between the activities of ascorbate peroxidase (APX) and phenol peroxidases (POD) and cowpea root growth in response to dehydration and salt stress. Root growth and indicators of oxidative response were markedly changed in response to salinity and dehydration. Salt treatment strongly inhibited root elongation, which was associated with an increase in lignin content and a significant decrease in the concentrations of apoplastic hydrogen peroxide (H₂O₂) and ascorbate. In conditions of extreme salinity, cytosol–APX activity was significantly decreased. In contrast, cell-wall POD activity was greatly increased, whereas lipid peroxidation was unchanged. These results indicate that POD could be involved in both H₂O₂ scavenging and the inhibition of root elongation under high salinity. In contrast, dehydration stimulated primary root elongation and increased lipid peroxidation and apoplastic ascorbate content, but it did not change APX and POD activities or H₂O₂ concentration. When cowpea roots were subjected to salinity followed by dehydration, the water and pressure potentials were decreased, and lipid peroxidation was markedly increased, highlighting the additive nature of the inhibitory effects caused by salt and dehydration. The proline concentration was markedly increased by dehydration alone, as well as by salt followed by dehydration, suggesting a possible role for proline in osmotic adjustment. Salinity and dehydration induce contrasting responses in the growth and morphology of cowpea roots. These effects are associated with different types of oxidative modulation involving cytosolic-APX and cell-wall POD activities and apoplast H₂O₂ and ascorbate levels.     

Expression of defence-related peroxidases Prx7 and Prx8 during abiotic stresses in barley roots

The expression of defence-related peroxidases Prx7 and Prx8 in barley roots grown under selected abiotic stress conditions (toxic metals: Cd, Al, Co, Cu, Hg; drought, salinity, extreme temperatures: heat, cold) and compounds activating (2,4-D) or inhibiting (SHAM) POD activity as well as H₂O₂ and H₂O₂ scavenger (DTT) was characterized. Strong Cd concentration dependent expression of Prx8 peroxidase gene was observed, which correlated with root growth inhibition induced by Cd- and some other stress factors (heavy metals, heat and salinity). Application of H₂O₂ did not cause changes in expression of Prx8, but H₂O₂ scavenger (DTT) as well as the inhibitor (SHAM) and the activator (2,4-D) of PODs induced increase in Prx8 expression. Our results demonstrate that root growth inhibition during any disturbance of active oxygen species (AOS) in root tissue is correlated with up-regulation of Prx8 gene expression in barley roots.     

Cadmium induces premature xylogenesis in barley roots

The effect of Cd on H₂O₂ production, peroxidase (POD) activity and root hair formation were analyzed in barley root. Cd causes a strong H₂O₂ burst in the root region 0–6 mm behind the root tip. POD activity was activated in root tip and raised toward the root base in Cd treated roots. In situ analyses showed that both elevated H₂O₂ production and POD activity are localized in the early metaxylem vascular bundles. Cd induces root hair formation in the region 2 to 4 mm behind the root tip that was not detected in control roots. These results suggest that Cd-induced root growth inhibition is at least partially the consequence of Cd-stimulated premature root development involving xylogenesis and root hair formation, which is correlated with shortening of root elongation zone and therefore with root growth reduction.     

Apoplastic hydrogen peroxide and superoxide anion exhibited different regulatory functions in salt-induced oxidative stress in wheat leaves

The present work aimed to investigate the mechanisms of nitric oxide (NO) and reactive oxygen species (ROS) generations and to explore their roles in the regulation of antioxidative responses in the wheat leaves under salinity. Except for an insignificant change of NO content and nitrate reductase (NR) activity due to 50 mM NaCl, NO, hydrogen peroxide, superoxide anion (O₂^?-), hydroxyl radical (?OH), chlorophyll and malondialdehyde content, as well as activities of nitric oxide synthase, NR, peroxidases (POD), catalase (CAT), and ascorbate peroxidase rose in response to different NaCl concentrations. Meanwhile, leaf superoxide dismutase activity lowered only at 50 mM NaCl. NaCl-stimulatory effects on NO content as well as POD and CAT activities could be partly alleviated by the application of 2-phenyl-4,4,5,5-tetrame-thylimidazoline-3-oxide-1-oxyl (PTIO, NO scavenger), exogenous CAT, or diphenylene iodonium (DPI, NADPH oxidase inhibitor). Native polyacrylamide gel electrophoresis also showed that the amount of POD (especially POD4, POD5, and POD7) and CAT (especially CAT1, CAT2, and CAT3) isozymes increased with increasing salinity but decreased by application of PTIO, CAT, or DPI. Furthermore, histochemical staining showed a similar change of O₂^?- generation. In addition, the inhibition of diamineoxidase (DAO), polyamine oxidase (PAO), and cell wall-bound POD (cw-POD) activities in NaCl-stressed seedlings seemed to be insensitive to the application of PTIO or DPI. Taken together, salinity-induced NO, H₂O₂, and O₂^?- generation influenced each other and played different roles in the regulation of antioxidant enzyme activities in the leaves of wheat seedlings under NaCl treatment.     

Peroxidase mediated hydrogen peroxide production in barley roots grown under stress conditions

All applied metals (Co, Al, Cu, Cd) and NaCl inhibited barley root growth. No root growth inhibition was caused by drought exposure, in contrast to cold treatment. 0.01 mM H₂O₂ stimulated root growth and GA application did not affect root growth at all. Other activators and inhibitors of H₂O₂ production (SHAM, DTT, 10 mM H₂O₂, 2,4-D) inhibited root growth. Loss of cell viability was most significant after Al treatment, followed by Cd and Cu, but no cell death was induced by Co. Drought led to slight increase in Evans blue uptake, whereas neither NaCl nor cold influenced this parameter. DTT treatment caused slight increase in Evans blue uptake and significant increases were detected after 2,4-D and 10 mM H₂O₂ treatment, but were not induced by others stressors. Metal exposure increased guaiacol-POD activity, which was correlated with oxidation of NADH and production of H₂O₂. Exposure to drought caused a minor change in NADH oxidation, but neither H₂O₂ production nor guaiacol-POD activity was increased. Cold and NaCl application decreased all monitored activities. Increase in NADH oxidation and guaiacol-POD activity was caused by 10 mM H₂O₂ and 0.01 mM 2,4-D treatment, which also caused enhancement of H₂O₂ production. Slight inhibition of all activities was caused by 0.01 mM H₂O₂, GA, DTT; more pronounced inhibition was detected after SHAM treatment. The role of H₂O₂ production mediated by POD activity in relation to root growth and cell viability under exposure to some abiotic stress factors is discussed.     

Antioxidative responses of Ocimum basilicum to sodium chloride or sodium sulphate salinization

Soils and ground water in nature are dominated by chloride and sulphate salts. There have been several studies concerning NaCl salinity, however, little is known about the Na₂SO₄ one. The effects on antioxidative activities of chloride or sodium sulphate in terms of the same Na⁺ equivalents (25 mM Na₂SO₄ and 50 mM NaCl) were studied on 30 day-old plants of Ocimum basilicum L., variety Genovese subjected to 15 and 30 days of treatment. Growth, thiobarbituric acid reactive substances (TBARS), relative ion leakage ratio (RLR), hydrogen peroxide (H₂O₂), ascorbate and glutathione contents as well as the activities of ascorbate peroxidase (APX, EC 1.11.1.11); glutathione reductase (GR, EC 1.6.4.2) and peroxidases (POD, EC 1.11.1.7) were determined. In leaves, growth was more depressed by 25 mM Na₂SO₄ than 50 mM NaCl. The higher sensitivity of basil to Na₂SO₄ was associated with an enhanced accumulation of H₂O₂, an inhibition of APX, GR and POD activities (with the exception of POD under the 30-day-treatment) and a lower regeneration of reduced ascorbate (AsA) and reduced glutathione (GSH). However, the changes in the antioxidant metabolism were enough to limit oxidative damage, explaining the fact that RLR and TBARS levels were unchanged under both Na₂SO₄ and NaCl treatment. Moreover, for both salts the 30-day-treatment reduced H₂O₂ accumulation, unchanged RLR and TBARS levels, and enhanced the levels of antioxidants and antioxidative enzymes, thus achieving an adaptation mechanism against reactive oxygen species.     

Influence of salinity and abscisic acid on the O2 uptake by N2-fixing nodules of common bean

The effects of NaCl and ABA on the respiration of N₂-fixing nodules were analysed in common bean (Phaseolus vulgaris) inoculated with Rhizobium tropici the reference strain CIAT899. Shoot and nodule growth was more inhibited by NaCl than root growth. The O₂ uptake by nodulated roots at 21 kPa O₂ was significantly inhibited by salinity. Raising pO₂ stimulated nodule respiration more under NaCl treatment than for the control, although it did not compensate totally for the inhibitory effect of NaCl. Short NaCl application was less destructive than long term application. Also, the external application of ABA inhibited nodule respiration, and this inhibition was partly compensated by raising pO₂.     

Changes in the antioxidative systems of Ocimum basilicum L. (cv. Fine) under different sodium salts

The effects of different sodium salts on some physiological parameters and antioxidant responses were investigated in a medicinal and aromatic plant, Ocimum basilicum L. (cultivar Fine). Plants were subjected to an equimolar concentration of Na₂SO₄ (25?mM) and NaCl (50?mM) for 15 and 30?days. Growth, oxidative stress parameters [electrolyte leakage, peroxidation, and hydrogen peroxide (H₂O₂) concentration], antioxidant enzyme activities [ascorbate peroxidase (APX, EC 1.11.1.11), glutathione reductase (GR, EC 1.6.4.2), and peroxidases (POD, EC 1.11.1.7)], as well as antioxidant molecules [ascorbate and glutathione] were determined. The two salts affected leaf growth rates to the same extent, after 15 or 30?days of treatment, indicating a similar effect of Na₂SO₄ and NaCl salinity on growth, even if different (enzymatic and non-enzymatic) antioxidant mechanisms were involved in H₂O₂ detoxification. However, under both salts, the efficiency of the antioxidant metabolism seemed to be sufficient to avoid the deleterious effects of reactive oxygen species (ROS). Indeed, both ion leakage and peroxidation did not change under either Na₂SO₄ or NaCl salinity. As a whole, these data suggest that a cooperative process between the antioxidant systems is important for the tolerance of Ocimum basilicum L., cv. Fine to Na₂SO₄ and NaCl salinity.     

外源H2O2对盐胁迫下小白菜种子萌发和幼苗生理特性的影响

以小白菜"甜脆青"为试材,研究不同浓度（5、10、25、50和100 mmol/L）过氧化氢（H₂O₂）浸种处理对100 mmol/L NaCl胁迫下小白菜（Brassica chinensis L.）种子萌发、幼苗生长及生理特性的影响。结果表明：100 mmol/L NaCl胁迫明显抑制小白菜种子的萌发状况和幼苗生长,发芽势、发芽指数、活力指数及幼苗根和芽长度和鲜重均明显降低,根和芽中CAT的活性及K⁺含量明显受到抑制,渗透调节物质、活性氧和MDA含量显著增加。不同浓度H₂O₂浸种处理提高了NaCl胁迫下小白菜种子发芽势、发芽指数和活力指数,促进小白菜根和芽的生长,增强了NaCl胁迫下根和芽中SOD、CAT和APX的活性及K⁺含量,降低O₂^-·产生速率及H₂O₂和MDA含量,进一步促进脯氨酸和可溶性糖含量的增加,降低体内Na⁺含量。其中以10 mmol/L H₂O₂处理缓解盐胁迫效果最好,明显缓解NaCl胁迫对小白菜种子萌发和幼苗生长的抑制。     

Morphological and Physiological Responses of Cotton (Gossypium hirsutum L.) Plants to Salinity

Salinization usually plays a primary role in soil degradation, which consequently reduces agricultural productivity. In this study, the effects of salinity on growth parameters, ion, chlorophyll, and proline content, photosynthesis, antioxidant enzyme activities, and lipid peroxidation of two cotton cultivars, [CCRI-79 (salt tolerant) and Simian 3 (salt sensitive)], were evaluated. Salinity was investigated at 0 mM, 80 mM, 160 mM, and 240 mM NaCl for 7 days. Salinity induced morphological and physiological changes, including a reduction in the dry weight of leaves and roots, root length, root volume, average root diameter, chlorophyll and proline contents, net photosynthesis and stomatal conductance. In addition, salinity caused ion imbalance in plants as shown by higher Na⁺ and Cl⁻ contents and lower K⁺, Ca²⁺, and Mg²⁺ concentrations. Ion imbalance was more pronounced in CCRI-79 than in Simian3. In the leaves and roots of the salt-tolerant cultivar CCRI-79, increasing levels of salinity increased the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), and glutathione reductase (GR), but reduced catalase (CAT) activity. The activities of SOD, CAT, APX, and GR in the leaves and roots of CCRI-79 were higher than those in Simian 3. CAT and APX showed the greatest H₂O₂ scavenging activity in both leaves and roots. Moreover, CAT and APX activities in conjunction with SOD seem to play an essential protective role in the scavenging process. These results indicate that CCRI-79 has a more effective protection mechanism and mitigated oxidative stress and lipid peroxidation by maintaining higher antioxidant activities than those in Simian 3. Overall, the chlorophyll a, chlorophyll b, and Chl (a+b) contents, net photosynthetic rate and stomatal conductance, SOD, CAT, APX, and GR activities showed the most significant variation between the two cotton cultivars.     

H2O2参与AM真菌与烟草共生过程

以烟草((Nicotiana tabacum,品种CF90NF)为寄主,苗期接种丛枝菌根(AM)真菌摩西球囊霉(Glomus mosseae,G.m),测定G.m与烟草共生过程中烟草根部H2O2含量以及多胺氧化酶(PAO)和过氧化物酶(POD)活性;研究外源H2O2对G.m侵染烟草的影响以及H2O2清除剂和合成抑制剂对烟草侧根H2O2含量及烟草侧根和菌丝中H2O2荧光强度的影响,以探究H2O2在AM真菌侵染烟草过程中的作用。结果表明,接种G.m 20d后烟草侧根中出现H2O2含量的猝发,一定浓度的外源H2O2促进G.m对烟草的侵染,而H2O2清除剂抗坏血酸(AsA)显著削弱烟草侧根和菌丝中的H2O2荧光强度,降低G.m对烟草的侵染率,表明H2O2参与G.m与烟草共生过程;在G.m与烟草共生过程中,PAO和POD活性显著升高,PAO抑制剂二氨基十二烷(DADD)和POD抑制剂水杨羟肟酸(SHAM)显著降低烟草侧根中H2O2荧光强度,对菌丝中H2O2荧光强度无显著影响,表明烟草根部和G.m均可产生H2O2,PAO和POD参与烟草侧根中H2O2的合成,菌丝中可能存在其他来源的H2O2。     

Effects of salt stress on ion content,antioxidant enzymes and protein profile in different tissues of Broussonetia papyrifera

Although some plant responses to salinity have been characterized, the precise mechanisms by which salt stress damages plants are still poorly understood especially in woody plants. In the present study, the physiological and biochemical responses of Broussonetia papyrifera, a tree species of the family, Moraceae, to salinity were studied. In vitro-produced plantlets of B. papyrifera were treated with varying levels of NaCl (0, 50, 100 and 150 mM) in hydroponic culture. Changes in ion contents, accumulation of H₂O₂, as well as the activities and isoform profiles of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) in the leaves, stems and roots were investigated. Under salt stress, there was higher Na⁺ accumulation in roots than in stems and leaves, and Ca^2 +, Mg^2 + and P^3 + content, as well as K⁺/Na⁺ ratio were affected. NaCl treatment induced an increase in H₂O₂ contents in the tissues of B. papyrifera. The work demonstrated that activities of antioxidant defense enzymes changed in parallel with the increased H₂O₂ and salinity appeared to be associated with differential regulation of distinct SOD and POD isoenzymes. Moreover, SDS-PAGE analysis of total proteins extracted from leaves and roots of control and NaCl-treated plantlets revealed that in the leaves salt stress was associated with decrease or disappearance of some protein bands, and induction of a new protein band after exposure to 100 and 150 mM NaCl. In contrast, NaCl stress had little effect on the protein pattern in the roots. In summary, these findings may provide insight into the mechanisms of the response of woody plants to salt stress.     

Protein and Peroxidase Modulations in Sunflower Seedlings (Helianthus annuus L.) Treated with a Toxic Amount of Aluminium

The aim of this study is to investigate the effect of aluminium treatment on peroxidases activities and protein content in both soluble and cell-wall-bound fractions of sunflower leaves, stems and roots. Fourteen-day-old seedlings, grown in a nutrient solution, were exposed to a toxic amount of aluminium (500 μM AlNO₃) for 72 h. Under stress conditions, biomass production, root length and leaf expansion were significantly reduced. Also, our results showed modulations on soluble and ionically cell-wall-bound peroxidases activities. In soluble fraction, peroxidases activities were enhanced in all investigated organs. This stimulation was also observed in ionically cell-wall-bound fraction in leaves and stems. Roots showed a differential behaviour: peroxidase activity was severely reduced. Lignifying peroxidases activities assayed using coniferyl alcohol and H₂O₂ as substrates were also modulated. Significant stimulation was shown on soluble fraction in leaves, stems and roots. In ionically cell-wall-bound fraction lignifying peroxidases were enhanced only in stems but severely inhibited in roots. Also, aluminium toxicity caused significant increase on cell wall protein content in sunflower roots.     

Hydrogen peroxide is involved in the regulation of rice (Oryza sativa L.) tolerance to salt stress

In the present study, we investigated the salt tolerance mechanism of two rice cultivars (Zhenghan-2 and Yujing-6), which show different tolerance to drought and disease. NaCl induced higher extent of lipid peroxide and ion leakage in Yujing-6 roots than those in Zhenghan-2 roots. H₂O₂ accumulation in Zhenghan-2 roots was lower than that in Yujing-6 roots under salt stress. Comparatively, NaCl treatment did not increase O₂ ^? contents in both rice roots, however, O₂ ^? level in Yujing-6 roots was higher than that in Zhenghan-2 roots under both control and salt stress conditions. Ascorbate peroxidases (APX) activity increased more significantly in Zhenghan-2 roots than that in Yujing-6 roots. The activity of catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), and glucose-6-phosphate dehydrogenase (G6PDH) was similarly enhanced in both rice roots under salt stress; however, they showed higher levels in Zhenghan-2 roots than in Yujing-6 roots. Exogenous H₂O₂ could enhance APX, CAT, POD, SOD and G6PDH activities in a concentration-dependent manner in both rice roots. Diphenylene iodonium (DPI), a plasma membrane (PM) NADPH oxidase inhibitor, which counteracted the NaCl-induced H₂O₂ accumulation, markedly decreased the activity of above enzymes. Moreover, ion leakage increased dramatically in Zhenghan-2 roots and reached to the similar level of Yujing-6 roots under NaCl+DPI treatment. Taken together, H₂O₂, which is mainly generated from PM NADPH oxidase, is involved in Zhenghan-2 rice tolerance to salt stress by enhancing the cellular antioxidant level.     

Arbuscular mycorrhizas alter root system architecture of Citrus tangerine through regulating metabolism of endogenous polyamines

Cadmium (Cd) is readily taken up by the roots of rice seedlings, leading to growth reduction. H₂O₂ is a constituent of oxidative metabolism and is itself a reactive oxygen species. In this study, the participation of H₂O₂ in CdCl₂-inhibited growth of rice roots was investigated. CdCl₂ treatment increased H₂O₂ production in rice roots. CdCl₂ treatment had no effect on the activities of superoxide dismutase, ascorbate peroxidase, and glutathione reductase, but inhibited the activity of catalase (CAT) in rice roots. CdCl₂-inhibited root growth and -increased H₂O₂ content were lessened in the presence of diphenyleneiodonium chloride, an inhibitor of H₂O₂ generating NADPH oxidase. However, this stimulation of root growth in CdCl₂-treated seedlings is small (about 5%). Calcium (Ca) is important in many physiological processes in plants. Attempts were also made to determine whether the action of Ca on CdCl₂-inhibited growth of rice roots is associated with H₂O₂. CaCl₂ application reduced the production of H₂O₂, the decrease in CAT activity, and the inhibition of root growth caused by CdCl₂. The effects of CaCl₂ application could be reversed by exogenous H₂O₂. Our results indicate that the Cd causes a decline in CAT and to a lower extent a stimulation of NADPH oxidase in rice roots, with the subsequent generation of H₂O₂, an agent responsible for growth inhibition.     

Chromotoxic effects of exogenous hydrogen peroxide (H<Subscript>2</Subscript>O<Subscript>2</Subscript>) in barley seeds exposed to salt stress

The effect of exogenous hydrogen peroxide (H₂O₂) on mitotic activity and chromosomal aberrations in root tip meristems of barley (Hordeum vulgare L. var. Tokak 157/37) germinated under salinity was analyzed. The inhibitory effect of salinity on mitotic index and the frequency of chromosomal aberrations increased with increasing salt concentration (0.00 control, 0.35, 0.40, 0.45 M, molal NaCl). The frequency of chromosomal aberrations of seeds germinated in medium with 0.40 M NaCl after pretreatment with H₂O₂ (30 μM, micromolal) was significantly higher than the control group. The highest concentration of NaCl (0.45 M) together with H₂O₂ caused total inhibition of germination. In this study, the intention was to determine the performance of H₂O₂ in alleviating detrimental effect of salt stress on mitotic activity and chromosomal aberrations. However, H₂O₂ did not reduce the detrimental effect of NaCl on these parameters. Also, it caused higher chromotoxic effect compared to those of control groups.     

茶多酚对盐胁迫下小麦幼苗叶片生理特性的影响

以春小麦"陇春30号"为实验材料,主要研究了150 mmol/L NaCl和不同浓度(25 mg/L和100 mg/L)茶多酚(tea polyphenols, TP)单独或复合处理对小麦幼苗叶片叶绿素含量、叶绿素荧光参数及过氧化氢(H_2O_2)产生等生理特性的影响。结果表明:(1)150 mmol/L NaCl单独处理导致小麦幼苗叶片叶绿素含量及光适应下实际光量子产量[actual light quantum yield,Y(II)]、光化学淬灭(photochemical quenching, qP)、光合电子传递效率(photosynthetic electron transfer efficiency, ETR)均降低,非光化学淬灭(non-photochemical quenching, NPQ)增大;TP单独处理不影响这些指标。(2)盐胁迫诱导细胞壁过氧化物酶(cell wall-peroxidase, cw-POD)、二胺氧化酶(diamine oxidase, DAO)和多胺氧化酶(polyamine oxidase, PAO)活性显著增高;低浓度TP使cw-POD活性显著增大,而DAO和PAO活性无显著变化;不同的是,高浓度TP不影响cw-POD活性,却使DAO和PAO活性显著减小。(3)与NaCl单独处理相比,TP的添加导致NaCl处理下小麦幼苗叶片叶绿素含量增加,最大光化学效率(maximal photochemical efficiency,F_v/F_m)和ETR值增大,而NPQ值、H_2O_2含量及cw-POD、DAO和PAO三种酶活性均降低。总之,TP有效地缓解了盐胁迫诱导的小麦幼苗叶绿素含量的减少及对PS II光合电子传递效率和光化学反应速率的抑制,增强了植物的光合能力,与此同时降低了cw-POD、DAO和PAO活性,减少了H_2O_2的产生,从而缓解盐胁迫对小麦幼苗造成的伤害,提高小麦幼苗对盐环境的耐受性。