Growth,photosynthesis and H+-ATPase activity in two Jerusalem artichoke varieties under NaCl-induced stress

In order to evaluate differential growth, photosynthesis and H⁺-ATPase activity responses to salt-induced stress, two Jerusalem artichoke (Helianthus tuberosus L.) genotypes (Nanyu No. 1 and Qingyu No. 2) were used in sand-culture experiment with different concentrations of NaCl (0, 30, 60, 90, 120 and 150 mM). After 20 days of growth, the NaCl stress resulted in a decrease of biomass accumulation, relative leaf expansion rate and photosynthetic rate, but an increase of proline content in both genotypes. Compared with Qingyu No. 2, Nanyu No. 1 had lower biomass, photosynthetic rate, gas exchange and transpiration rate, but higher proline content, activities of plasma membrane H⁺-ATPase (PM H⁺-ATPase) and vacuolar membrane H⁺-ATPase (VM H⁺-ATPase). Hence, the NaCl adaptation strategy in Nanyu No. 1 was by lowering photosynthetic rate, stomatal conductance and transpiration rate while maintaining high H⁺-ATPase activities, whereas the adjustment of Qingyu No. 2 was by keeping much higher rate of proline accumulation and concentration of chlorophyll. The differences in salt tolerance showed that different adaptation mechanisms existed between cultivars of Jerusalem artichoke. The findings offered the possibility of selecting salt-tolerant genotypes of Jerusalem artichoke.     

Physiological responses of two Jerusalem artichoke cultivars to drought stress induced by polyethylene glycol

Physiological responses of two Jerusalem artichoke (Helianthus tuberosus L.) cultivars with different drought sensitivity to drought stress induced by polyethylene glycol (PEG) 6000 were investigated by characterizing water status, membrane lipid peroxidation, key antioxidant enzymes activity, and proline accumulation. It was observed that the drought-tolerant Jerusalem artichoke cv. Xiuyan maintained a relatively higher water status than the drought-sensitive cv. Yulin upon drought treatments. Meanwhile, lower levels of malondialdehyde (MDA) as well as higher levels of free proline occurred in cv. Xiuyan after 36 h drought treatments. Moreover, the activities of catalase (CAT) and superoxide dismutase (SOD) in cv. Xiuyan were higher than cv. Yulin after drought stress. These results indicated that drought sensitivities actually differ between Jerusalem artichoke cv. Xiuyan and cv. Yulin, and the cv. Xiuyan was more tolerant to drought stress caused by polyethylene glycol.     

Effect of soil salinity on physiological characteristics of functional leaves of cotton plants

This study analyzes the effects of soil salinity on fatty acid composition, antioxidative enzyme activity, lipid peroxidation, and photosynthesis in functional leaves during the flowering and boll-forming stages of two cotton cultivars, namely, CCRI-44 (salt-tolerant) and Sumian 12 (salt-sensitive), grown under different soil salinity conditions. Saturated (C16:0 and C18:0) and unsaturated fatty acid (FA) contents (C18:1), as well as superoxide dismutase activity increased, whereas high-unsaturated FA (C18:2 and C18:3) decreased, with the increase in soil salinity. The production of malondialdehyde increased with increasing lipoxygenase (LOX) activity, indicating that LOX catalyzed FA peroxidation under salt stress. Soil salinity had no significant effect on catalase (CAT) and peroxidases (POD) activity in the salt-sensitive cultivar Sumian 12, but significantly increased CAT and POD activities in the salt-tolerant cultivar CCRI-44. Net photosynthesis and stomatal conductance of the cotton cultivars decreased in response to salt stress; however, CCRI-44 showed a smaller reduction in photosynthesis than Sumian 12. The results indicated that stomatal apparatus limited leaf photosynthetic capacity in the salinity-treated plants of both cultivars. The net photosynthetic rate, maximum photochemical efficiency, and photochemical quantum yield of the cotton functional leaves showed positive correlation with double-bond index (DBI). These results suggested that salt stress caused DBI reduction and decreased the photochemical conversion efficiency of solar radiation and, thereby resulting in lower net photosynthetic rates.     

Effect of salt stress on antioxidant defense systems,lipid peroxidation,and chlorophyll content in green bean

Salt stress-induced changes in antioxidant enzymes, such as catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR), total chlorophyll content, and lipid peroxidation measured as malondialdehyde (MDA) content, in leaves of a green bean genotype Gevas sirsk 57 (GS57) and cv. Fransiz 4F-89 differing in salt tolerance were investigated. Plants were subjected to three salt treatments (0, 50, and 100 mM NaCl) under controlled climatic conditions for 7 days. The salt-sensitive cv. 4F-89 exhibited a decrease in GR activity at all salt treatments, but the salt-tolerant genotype GS57 showed only a slight decrease in GR under 50 mM salt treatment and an increase under 100 mM salt treatment. CAT and APX activities increased with increasing salt stress in both varieties. CAT and APX activities were higher in the salt-tolerant GS57 than salt-ensitive cv. 4F-89. The two varieties showed an increase in MDA content with an increase in salinity, but the increase in sensitive cv. 4F-89 under salt stress was higher than that in salt-tolerant GS57 genotype. The increasing NaCl concentration caused a reduction in the chlorophyll content in cv. 4F-89 but not in GS57.     

The activity of antioxidative enzymes in three strawberry cultivars related to salt-stress tolerance

Effects of salt stress on the time course of stomatal behaviors and the activity of antioxidative enzymes such as catalase (CAT) (EC 1.11.1.6), ascorbate peroxidase (APX) (EC 1.11.1.11), and glutathione reductase (GR) (EC. 1.6.4.2) were studied in three strawberry cultivars. The responses of the cultivars ‘Camarosa’, ‘Tioga,’ and ‘Chandler’ were compared when they were irrigated with nutrient solution containing 0, 8.5, 17.0, and 34.0 mM sodium chloride (NaCl) for 30 days. A significant reduction in stomatal conductance (g_s) was seen particularly on the 30th day of the salt treatments only in Camarosa, which is parallel to transpiration rate (E). CAT activities decreased in all of the salt treatments only in Tioga, while it remained almost unchanged or slightly increased depending on the period in Camarosa and Chandler. APX activity sharply increased in 17.0 and 8.5-mM NaCl treatments for 30 days in Camarosa and Tioga, respectively, whereas it linearly increased based on the NaCl treatments in Chandler. On the other hand, only Camarosa demonstrated a sharp increase in GR activity induced by salinity applied for 30 days. All the data indicated that control of the stomatal behavior, the higher salt-stress tolerance (LT₅₀) and higher constitutive activity of antioxidant enzymes made Camarosa and Tioga relatively salt-tolerant cultivars.     

Comparative lipid peroxidation,antioxidant defense systems and proline content in roots of two rice cultivars differing in salt tolerance

The changes in the activity of antioxidant enzymes such as superoxide dismutase (SOD: EC 1.15.1.1), catalase (CAT: EC 1.11.1.6), peroxidase (POX: EC 1.11.1.7), ascorbate peroxidase (APOX: EC 1.11.1.11) and glutathione reductase (GR: EC 1.6.4.2), free proline content, and the rate of lipid peroxidation level in terms of malondialdehyde (MDA) in roots of two rice cultivars (cvs.) differing in salt tolerance were investigated. Plants were subjected to three salt treatments, 0, 60, and 120 mol m⁻³ NaCl for 7 days. The results showed that activated oxygen species may play a role in cellular toxicity of NaCl and indicated differences in activation of antioxidant defense systems between the two cvs. The roots of both cultivars showed a decrease in GR activity with increase in salinity. CAT and APOX activities increased with increasing salt stress in roots of salt-tolerant cultivar Pokkali but decreased and showed no change, respectively, in roots of IR-28 cultivar. POX activity decreased with increasing NaCl concentrations in salt-tolerant Pokkali but increased in IR-28. SOD activity showed no change in roots of both cultivars under increasing salinity. MDA level in the roots increased under salt stress in sensitive IR-28 but showed no change in Pokkali. IR-28 produced higher amount of proline under salt stress than in Pokkali. Increasing NaCl concentration caused a reduction in root fresh weight of Pokkali and root dry weight of IR-28. The results indicate that improved tolerance to salt stress in root tissues of rice plants may be accomplished by increased capacity of antioxidative system.     

Effect of salt on malondialdehyde and antioxidant enzymes in seedling roots of Jerusalem artichoke (<Emphasis Type="Italic">Helianthus tuberosus</Emphasis> L.)

Two cultivars of Jerusalem artichoke (Helianthus tuberosus L.) differing in genotype, Red skin (cv. R., salt-tolerant but low-yield) and White skin (cv. W., salt-sensitive but high-yield), were used to investigate malondialdehyde (MDA) content and antioxidant enzyme activity changes in their roots under a hydroponic culture system with 250 mM NaCl. The results showed that MDA contents in roots of the two genotypes increased, but MDA content of cv. R. was higher than that of cv. W. Changes in all antioxidant enzymes in roots of both varieties exhibited a similar trend, namely increased initially and then decreased. However, there were still some differences existing between the two cultivars. In other words, activities of the other two antioxidant enzymes except catalase (CAT) and peroxidase (POD) in roots of cv. R. were less than controls at 48 h, while all others except ascorbate peroxidase (APX) in roots of cv. W. were greater than controls. The peak of superoxide dismutase (SOD) activity of cv. W. was observed to appear earlier than that of cv. R. CAT activity of cv. W. was significantly greater than the value of cv. R. and the latter showed a moderate trend. POD activity of cv. R. obtained the maximum at 6 h, whereas the peak of cv. W. displayed at 24 h. APX activity of cv. R. declined more than that of cv. W. These results suggested that there was a lower efficiency of scavenging reactive oxygen species (ROS) in cv. R. roots. Concomitantly, salt stress caused more severe damage to roots of cv. R. Antioxidant enzymes in roots were inadequate to elucidate salt-tolerance mechanisms of the whole plant.     

等渗NaCl、干旱胁迫对番茄幼苗光合特性及叶绿体超微结构的影响

为分析等渗盐分和水分胁迫对番茄叶片光合功能的影响,选用耐盐性不同的4种基因型番茄(小果型的辽园红玛瑙、野生醋栗番茄、大果型的金田粉冠、超402)进行等渗的140 mmol·L^-1NaCl和15%PEG6000模拟盐分和水分胁迫.结果表明: 在光合特性方面,处理12 d后,两种胁迫导致4种不同基因型番茄的叶绿素含量(叶绿素a、叶绿素b、叶绿素总量)、光合速率、气孔导度、胞间CO₂浓度、蒸腾效率降低,气孔限制值升高.两种胁迫导致的光合下降由气孔性因素所致.等渗的盐分胁迫对番茄的光合系统损伤大于水分胁迫,这是因为盐分胁迫除了渗透胁迫还会导致离子伤害.4种不同基因型番茄中,耐盐型的辽园红玛瑙具有高光合特性,金田粉冠光合效率最差.在叶绿体超微结构方面,两种胁迫会造成番茄叶片的气孔密度增加,气孔张开率降低,叶绿体长度增加,宽度变小,长宽比增大,叶绿体内基粒数减少,嗜锇颗粒数增多.盐分胁迫下两种番茄叶绿体结构的影响大于水分胁迫,耐盐种醋栗番茄气孔变化小于盐敏感品种金田粉冠.     

Alleviation of exogenous 6-benzyladenine on two genotypes of eggplant (Solanum melongena Mill.) growth under salt stress

Cytokinins were recently shown to control plant adaptation to environmental stresses. To characterize the roles of cytokinins in the tolerance of eggplant (Solanum melongena Mill.) to salt stress, the protective effects of 6-benzyladenine (6-BA) on the growth, photosynthesis, and antioxidant capacity in the leaves of two eggplant cultivars Huqie12 (salt-sensitive) and Huqie4 (salt-tolerant) were investigated. Under 90 mM NaCl stress, Huqie4 showed higher biomass accumulation and less oxidative damage compared to the Huqie12. Application of exogenous 10 μM 6-BA significantly alleviated the growth suppression caused by salt stress in two eggplant genotypes. In parallel with the growth, 6-BA application in salt-stressed plants resulted in enhanced chlorophyll contents, as well as photosynthetic parameters such as net CO₂ assimilation rate (P _n), stomatal conductance (g _s), transpiration rate (E), and intercellular CO₂ concentration (C _i). Furthermore, exogenous 6-BA also significantly reduced the O₂ ^? production rate and malondialdehyde content and markedly increased the antioxidant enzymes superoxide dismutase and peroxidase, the antioxidant metabolites ascorbate and reduced glutathione (GSH), and proline in both genotypes under salt stress. The results indicate that exogenous 6-BA is useful to improve the salt resistance of eggplant, which is most likely related to the increase in photosynthesis and antioxidant capacity.     

Effective salt criteria in callus-cultured tomato genotypes

Na+, Cl-, K+, Ca2+, and proline contents, the rate of lipid peroxidation level in terms of malondialdehyde (MDA) and chlorophyll content, and the changes in the activity of antioxidant enzymes, such as superoxide dismutase (SOD: EC 1.15.1.1), catalase (CAT: EC 1.11.1.6), ascorbate peroxidase (APX: EC 1.11.1.11), and glutathione reductase (GR: EC 1.6.4.2), in tissues of five tomato cultivars in salt tolerance were investigated in a callus culture. The selection of effective parameters used in these tomato genotypes and to find out the use of in vitro tests in place of in vivo salt tolerance tests were investigated. As a material, five different tomato genotypes during a 10-day time period were used, and 150 mM NaCl was applied at callus plant tissue. The exposure to NaCl induced a significant increase in MDA content in both salt-resistant and salt-sensitive cultivars. But the MDA content was higher in salt-sensitive cultivars. The chlorophyll content was more decreased in salt-sensitive than in salt-resistant ones. The proline amount was more increased in salt-sensitive than in salt-resistant ones. It has been reported that salt-tolerant plants, besides being able to regulate the ion and water movements, also exhibit a strong antioxidative enzyme system for effective removal of ROS. The degree of damage depends on the balance between the formation of ROS and its removal by the antioxidative scavenging system that protects against them. Exclusion or inclusion of Na+, Cl-, K+, and Ca2+, antioxidant enzymes and MDA concentration play a key protective role against stress, and this feature at the callus plant tissue used as an identifier for tolerance to salt proved to be an effective criterion.     

Differential responses of antioxidative enzymes and lipid peroxidation to salt stress in salt-tolerant Plantago maritima and salt-sensitive Plantago media

The changes in plant growth, relative water content (RWC), stomatal conductance, lipid peroxidation and antioxidant system in relation to the tolerance to salt stress were investigated in salt-tolerant Plantago maritima and salt-sensitive Plantago media. The 60 days old P. maritima and P. media seedlings were subjected to 0, 100 and 200 mM NaCl for 7 days. Reduction in shoot length was higher in P. media than in P. maritima after exposure to 200 mM NaCl, but 100 mM NaCl treatment did not show any effect on shoot length of P. maritima. Shoot dry weight decreased in P. media and did not change in P. maritima. Two hundred millimolar NaCl treatment had no effect on leaf RWC in P. maritima, but it was reduced in P. media. Salt stress caused reduction in stomatal conductance being more pronounced in P. media than in P. maritima. Activities of superoxide dismutase (SOD; EC 1.15.1.1), catalase (CAT; EC 1.11.1.6), glutathione reductase (GR; EC 1.6.4.2) decreased in P. media with increasing salinity. Ascorbate peroxidase (APX; EC 1.11.1.11) activity in leaves of P. media was increased and showed no change under 100 and 200 mM NaCl, respectively. However, activities of CAT, APX and GR increased under 200 mM NaCl while their activities did not change under 100 mM NaCl in P. maritima. SOD activity in leaves of P. maritima increased with increasing salinity. Concomitant with this, four SOD activity bands were identified in leaves of P. maritima, two bands only were observed in P. media. Peroxidase (POX; EC 1.11.1.7) activity increased under both salt concentrations in P. maritima, but only under 200 mM NaCl in P. media. Confirming this, five POX activity bands were identified in leaves of P. maritima, but only two bands were determined in P. media. Malondialdehyde levels in the leaves increased under salt stress in P. media but showed no change and decreased in P. maritima at 100 and 200 mM NaCl, respectively. These results suggest that the salt-tolerant P. maritima showed a better protection mechanism against oxidative damage caused by salt stress by its higher induced activities of antioxidant enzymes than the salt-sensitive P. media.     

Physiological and Biochemical Mechanisms of Exogenous Calcium Chloride on Alleviating Salt Stress in Two Tartary Buckwheat (<i>Fagopyrum tataricum</i>) Varieties Differing in Salinity Tolerance

Salt stress is one of the most serious abiotic stresses limiting plant growth and development. Calcium as an essential nutrient element and important signaling molecule plays an important role in ameliorating the adverse effect of salinity on plants. This study aimed to investigate the impact of exogenous calcium on improving salt tolerance in Tartary buckwheat cultivars, cv. Xinong9920 (salt-tolerant) and cv. Xinong9909 (salt-sensitive). Four-week-old Tartary buckwheat seedlings under 100 mM NaCl stress were treated with and without exogenous calcium chloride (CaCl₂), Ca²⁺ chelator ethylene glycol tetraacetic acid (EGTA) and Ca²⁺-channel blocker lanthanum chloride (LaCl₃) for 10 days. Then, some important physiological and biochemical indexes were determined. The results showed that salt stress significantly reduced seedling growth, decreased photosynthetic pigments, inhibited antioxidants and antioxidant enzyme activities. However, it increased the reactive oxygen species (ROS) levels in the two Tartary buckwheat cultivars. Exogenous 10 mM CaCl₂ application on salt-stressed Tartary buckwheat seedlings obviously mitigated the negative effects of NaCl stress and partially restored seedlings growth. Ca²⁺-treated salt-stressed seedlings diplayed a suppressed accumulation of ROS, increased the contents of total chlorophyll, soluble protein, proline and antioxidants, and elevated the activities of antioxidant enzymes compared with salt stress alone. On the contrary, the addition of 0.5 mM LaCl₃ and 5 mM EGTA on salt-stressed Tartary buckwheat seedlings exhibited the opposite effects to those with CaCl₂ treatment. These results indicate that exogenous Ca²⁺ can enhance salt stress tolerance and Ca²⁺ supplementation may be an effective practice to cultivate Tartary buckwheat in saline soils.     

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.     

不同基因型茶菊对盐胁迫的响应

为探讨不同基因型茶菊(tea Chrysanthemum)在盐胁迫下的生理响应并对其进行耐盐性评价, 以4个不同基因型茶菊为材料, 采用营养液浇灌法, 研究了不同浓度NaCl (0、40、80、120、160、200 mmol·L^-1)胁迫下茶菊生理生化和光合生理响应特性。结果表明: 随着NaCl胁迫程度加大, 不同基因型茶菊叶片细胞膜透性(Cond)、丙二醛(MDA)含量、叶片脯氨酸(Pro)含量和可溶性糖(SS)含量增加; 超氧化物歧化酶(SOD)含量呈先升后降趋势; ‘乳荷’、‘黄滁龙’叶绿素(Chl)含量持续下降, ‘繁白露’和‘玉人面’叶绿素含量呈先升后降的趋势; 净光合速率(P_n)、蒸腾速率(T_r)和气孔导度(G_s)随NaCl胁迫浓度提高而极显著降低, 气孔限制值呈先升后降的趋势。采用隶属函数法对茶菊进行耐盐性评价, 不同基因型茶菊耐盐性由强到弱依次为‘乳荷’ > ‘玉人面’ > ‘繁白露’ > ‘黄滁龙’。其中, 耐盐性品种‘玉人面’、‘乳荷’在NaCl胁迫下, Chl含量、P_n、T_r和G_s下降幅度小, MDA含量和气孔限制值增幅较小。     

Genetic analysis of salt stress responses in asparagus bean (Vigna unguiculata (L.) ssp. sesquipedalis Verdc.)

Salt stress responses of 23 asparagus bean cultivars were evaluated using 14-day-old seedlings after 15-day exposure to 75 mM NaCl in a hydroponics culture system. Salt-induced changes in plant growth and morphology, photosynthetic capacity, cell membrane integrity, and cellular protection enzyme systems as well as other physiological and biochemical traits were investigated to identify genotypic variability in salt response. This study also analyzed heredity parameters and correlation of the salt response index (SRI). Salt stress suppressed seedling growth and simultaneously reduced leaf area, content of chlorophyll and soluble proteins, net assimilation rate, as well as dry matter accumulation. In contrast, leaf blade cell membrane relative permeability, content of malondialdehyde, and antioxidant enzyme activity were elevated after salt treatment. Analysis of the heredity parameters has identified that the 18 investigated traits have different genotypic variance of the SRI values. Based on Ward's distances estimated for the sum of square variance in the SRI values, all the cultivars were classified into 2 discrete salt-tolerant and salt-sensitive clusters. Findings from this study will provide theoretical bases for identification and breeding of salt-tolerant cultivars in asparagus bean.     

Effects of NaCl on the growth, ion accumulation and photosynthetic parameters of Thellungiella halophila

Thellungiella halophila seedlings grown on a solid substrate for 25 days on standard medium were challenged with NaCl. Growth, tissue hydration, ion accumulation, photosynthesis, lipid peroxidation and antioxidant enzymatic activities were studied on rosette leaves. Three accessions of Arabidopsis thaliana were cultivated under the same conditions. During the first two weeks of salt treatment, the growth of T. halophila leaves was restricted by NaCl. No significant difference appeared between T. halophila and A. thaliana concerning biomass deposition, or hydric and ionic parameters. However, all A. thaliana plants displayed foliar damage, and died during the third week of salt (50mM NaCl) treatment. Almost all (94%) T. halophila plants remained alive, but did not display any sign of altered physiological condition. Tissue hydration, chlorophyll content, stomatal conductance, photosynthetic quantum yield, and photosynthetic rate were very similar to those of control plants. Lipid peroxidation, estimated from thermoluminescence, was very low and insensitive to salt treatment. Only slight changes occurred in antioxidant enzymatic activities (SOD, several peroxidases, and catalase). From the absence of physiological disorder symptoms, we infer that salt was efficiently compartmentalized in leaf vacuoles. In salt-treated A. thaliana, the photosynthetic quantum yield was diminished, and lipid peroxidation was augmented. These observations reinforce the conclusion that T. halophila could accumulate salt in its leaves without damage, in contrast to A. thaliana.     

Ca2+缓解 NaCl胁迫引起的玉米光合能力下降的作用

 以‘鲁玉14号玉米’（‘Zea mays cv. Luyu 14’）为材料,研究了Ca2+ 对NaCl胁迫下玉米叶片的气孔导度、净光合速率、Mehler反应及其对超氧化物歧化酶SOD和抗坏血酸过氧化物酶APX活性的影响,探讨了Ca2+在盐胁迫中的可能作用及其作用机制。正常生长条件下外施 2～16 mmol·L－1 Ca2+造成气孔导度下降,但在盐胁迫条件下外施 2～8 mmol·L－1 Ca2+却能降低盐胁迫造成的气孔导度下降。另外,无论正常生长条件下还是盐胁迫下,依赖Mehler反应的电子传递都会因 Ca2+的加入而增强,但后者的增强程度较大。对照植株经 2～8 mmol· L－1 Ca2+处理后总电子传递明显降低,而外施 2～8 mmol·L－1 Ca2+ 对盐胁迫植株的总电子传递却有明显的促进作用。8 mmol· L－1 Ca2+显著地提高了盐胁迫下SOD和APX的活性,相比之下,Ca2+对APX活性的促进作用更加显著。Ca2+的加入明显减轻了盐胁迫对玉米的抑制作用,这主要归因于Ca2+降低了盐胁迫造成的气孔关闭,改善了光合作用,并通过促进Mehler反应一方面直接耗散过剩的激发电子避免了电子传递链的过度还原,另一方面建立跨膜的pH梯度刺激依赖叶黄素循环的热耗散来耗散过剩光能,从而缓解了盐胁迫下过剩光能对玉米造成的伤害。而Mehler反应产生的活性氧可以被活性提高的抗氧化酶所清除。     

NaCl胁迫对西瓜嫁接苗叶片抗氧化酶活性及光合特性的影响

以耐盐性较强的葫芦品种‘超丰抗生王’为砧木,耐盐性较弱的西瓜品种‘秀丽’为接穗,采用营养液水培法,研究了NaCl胁迫对西瓜自根苗和嫁接苗保护酶活性、膜质过氧化及光合特性的影响。结果表明,NaCl胁迫下,嫁接苗和自根苗生物量显著下降,但嫁接苗下降幅度小于自根苗;NaCl胁迫抑制了西瓜自根苗和嫁接苗的气体交换参数,但是嫁接苗的净光合速率(Pn)、气孔导度(Gs)、胞间CO2浓度(Ci)及叶绿素含量显著高于自根苗;NaCl胁迫下西瓜嫁接苗叶片超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性均显著高于自根苗,丙二醛含量较自根苗低。上述结果表明,NaCl胁迫下嫁接苗通过维持较高的抗氧化酶活性来提高清除活性氧(ROS)的能力,从而降低氧化损伤,并保持较高光合速率,从而增强西瓜幼苗对盐胁迫的耐性。     

盐胁迫对海岛棉和陆地棉幼苗生长及生理特性的影响

采用盆栽法,以海岛棉(Gossypium barbadense)品种新海21号、新海34号和陆地棉(G.hirsutum)品种新陆早50号、新陆早57号为材料,探讨了盐胁迫下海岛棉和陆地棉植株的生长、叶绿素含量、净光合速率、蒸腾速率、抗氧化酶活性、渗透调节物质及丙二醛含量变化的差异。结果显示,随着盐浓度的增加,4个供试品种幼苗的生长、叶绿素含量、净光合速率、蒸腾速率均呈不同程度的下降,而过氧化物酶、超氧化物歧化酶及可溶性糖含量随着盐浓度的增加呈先增后降的趋势,脯氨酸和丙二醛含量均上升。不同品种之间,新海21号和新海34号受胁迫的影响程度小于新陆早57号和新陆早50号。在0.6%Na Cl胁迫下,海岛棉和陆地棉品种均表现出较好的耐盐性。而0.8%和1.0%的Na Cl胁迫对4个供试品种的生长抑制作用大,导致新陆早57号和新陆早50号幼苗生长缓慢、叶面积小、干物质积累少甚至死苗。在较高浓度的盐胁迫下,棉花品种幼苗第1片真叶展开受到显著抑制,可以作为棉花耐盐品种的筛选指标。     

Response of the cultivated tomato and its wild salt-tolerant relative Lycopersicon pennellii to salt-dependent oxidative stress: The root antioxidative system

The response of the antioxidant system to salt stress was studied in the roots of the cultivated tomato Lycopersicon esculentum Mill. cv. M82 (Lem) and its wild salt-tolerant relative L. pennellii (Corr.) D'Arcy accession Atico (Lpa). Roots of control and salt (100 m M NaCl)-stressed plants were sampled at various times after commencement of salinization. A gradual increase in the membrane lipid peroxidation in salt-stressed root of Lem was accompanied with decreased activities of the antioxidant enzymes: superoxide dismutase (SOD; EC 1.15.1.1), catalase (CAT; EC 1.11.1.6), ascorbate peroxidase (APX; EC 1.11.1.11) and decreased contents of the antioxidants ascorbate and glutathione and their redox states. In contrast, increased activities of the SOD, CAT, APX, monodehydroascorbate reductase (MDHAR; EC 1.6.5.4), and increased contents of the reduced forms of ascorbate and glutathione and their redox states were found in salt-stressed roots of Lpa, in which the level of membrane lipid peroxidation remained unchanged. It seems that the better protection of Lpa roots from salt-induced oxidative damage results, at least partially, from the increased activity of their antioxidative system.