Assessment of the preventive effect of vermicompost on salinity resistance in tomato (<Emphasis Type="Italic">Solanum lycopersicum</Emphasis> cv. Ailsa Craig)

To determine the effects of vermicompost leachate (VCL) on resistance to salt stress in plants, young tomato seedlings (Solanum lycopersicum, cv. Ailsa Craig) were exposed to salinity (150 mM NaCl addition to nutrient solution) for 7 days after or during 6 mL L^??1 VCL application. Salt stress significantly decreased leaf fresh and dry weights, reduced leaf water content, significantly increased root and leaf Na⁺ concentrations, and decreased K⁺ concentrations. Salt stress decreased stomatal conductance (g_s), net photosynthesis (A), instantaneous transpiration (E), maximal efficiency of PSII photochemistry in the dark-adapted state (F_v/F_m), photochemical quenching (qP), and actual PSII photochemical efficiency (ΦPSII). VCL applied during salt stress increased leaf fresh weight and g_s, but did not reduce leaf osmotic potential, despite increased proline content in salt-treated plants. VCL reduced Na⁺ concentrations in leaves (by 21.4%), but increased them in roots (by 16.9%). VCL pre-treatment followed by salt stress was more efficient than VCL concomitant to salt stress, since VCL pre-treatment provided the greatest osmotic adjustment recorded, with maintenance of net photosynthesis and K⁺/Na⁺ ratios following salt stress. VCL pre-treatment also led to the highest proline content in leaves (50 µmol g^??1 FW) and the highest sugar content in roots (9.2 µmol g^??1 FW). Fluorescence-related parameters confirmed that VCL pre-treatment of salt-stressed plants showed higher PSII stability and efficiency compared to plants under concomitant VCL and salt stress. Therefore, VCL represents an efficient protective agent for improvement of salt-stress resistance in tomato.     

Comparative Study of Alkaline, Saline, and Mixed Saline–Alkaline Stresses with Regard to Their Effects on Growth, Nutrient Accumulation, and Root Morphology of Lotus tenuis

Both saline and alkaline conditions frequently coexist in nature; however, little is known about the effects of alkaline and salt?Calkaline stresses on plants. We performed pot experiments with four treatments, control without salt addition and three stress conditions??neutral, alkaline, and mixed salt?Calkaline??to determine their effects on growth, nutrient accumulation and root architecture in the glycophytic species Lotus tenuis. Neutral and alkaline salts produced a similar detrimental effect on L. tenuis growth, whereas the effect of their combination was synergistic. Neutral salt addition, alone or mixed with NaHCO₃, led to significant leaf Na⁺ build up and reduced K⁺ concentration. In contrast, in plants treated with NaHCO₃ only, Na⁺ levels and the Na⁺/K⁺ ratio remained relatively unchanged. Proline accumulation was not affected by the high pH in the absence of NaCl, but it was raised by the neutral salt and mixed treatments. The total root length was reduced by the addition of NaCl alone, whereas it was not affected by alkalinity, regardless of the presence of NaCl. The topological trend showed that alkalinity alone or mixed with NaCl turned the root more herringbone compared with control roots, whereas no significant change in this index was observed in the treatment with the neutral salt only. The pattern of morphological changes in L. tenuis root architecture after the alkaline treatment (in the absence of NaCl) was similar to that found in the mixed salt?Calkaline treatment and different from that observed in neutral salt. A unique root morphological response to the mixed salt?Calkaline stress was the reduction in the ratio between xylem vessels and root cross-sectional areas.     

Modulation in growth,photosynthetic efficiency,activity of antioxidants and mineral ions by foliar application of glycinebetaine on pea (Pisum sativum L.) under salt stress

A pot experiment was carried out to explore the role of glycinebetaine (GB) as foliar spray foliar on two pea (Pisum sativum L.) varieties (Pea 09 and Meteor Fsd) under saline and non-saline conditions. Thirty-two-day-old plants were subjected to two levels 0 and 150 mM of NaCl stress. Salt treatment was applied in full strength Hoagland’s nutrient solution. Three levels 0, 5 and 10 mM of GB were applied as foliar treatment on 34-day-old pea plants. After 2 weeks of foliar treatment with GB data for various growth and physiochemical attributes were recorded. Rooting-medium applied salt (150 mM NaCl) stress decreased growth, photosynthesis, chlorophyll, chlorophyll fluorescence and soluble protein contents, while increasing the activities of enzymatic (POD and CAT) and non-enzymatic (ascorbic acid and total phenolics) antioxidant enzymes. Foliar application of GB decreased root and shoot Na⁺ under saline conditions, while increasing shoot dry matter, root length, root fresh weight, stomatal conductance (g _s), contents of seed ascorbic acid, leaf phenolics, and root and shoot Ca²⁺ contents. Of three GB (0, 5, 10 mM) levels, 10 mM proved to be more effective in mitigating the adverse effects of salinity stress. Overall, variety Pea 09 showed better performance in comparison to those of var. Meteor Fsd under both normal and salinity stress conditions. GB-induced modulation of seed ascorbic acid, leaf phenolics, g _s, and root Ca²⁺ values might have contributed to the increased plant biomass, reduction of oxidative stress, increased osmotic adjustment and better photosynthetic performance of pea plants under salt stress.     

Alternanthera bettzickiana (Regel) G. Nicholson,a potential halophytic ornamental plant: Growth and physiological adaptations

Exploration and cultivation of salt tolerant plants is a very effective strategy for utilization of salt affected soils. In this investigation, physiological traits that are conducive for salt tolerance of the ornamental plant Alternanthera bettzickiana, Amaranthaceae, were explored. A. bettzickiana was grown on soil substrate having six salinity levels (2.86, 10, 20, 30, 40 and 50 dS m⁻¹). It was observed that this plant can grow even at a salinity level of 40 dS m⁻¹. The survival rate of this plant was 75, 42 and 0% at salinity levels of 30, 40 and 50 dS m⁻¹, respectively. A. bettzickiana plants produced 30.3% less biomass than controls at the salinity level of 20 dS m⁻¹ and even less under still higher salt stress. Photosynthesis continued even at the salinity level of 40 dS m⁻¹, though its rate was reduced to 59% in plants exposed to such salinity relative to plants not affected by salinity. Total soluble proteins values in leaf and stem showed a gradual increase when plants were exposed to increasing salt stress. Plants growing at the high salinity level showed highest decrease in leaf nitrate reductase activity. A. bettzickiana plants accumulated less Na⁺ in shoot as compared to root when grown under salt stress. It can be characterized as a salt-tolerant glycophyte that could be used for greening of salt affected soils.     

盐胁迫下荒漠共生植物红砂与珍珠的根茎叶中离子吸收与分配特征

西北荒漠地区C3小灌木红砂(Reaumuria soongorica)和C4半灌木珍珠猪毛菜(Salsola passerina)在特定环境下混生在一起,分布面积广阔。以采自腾格里沙漠边缘荒漠地带的天然野生珍珠猪毛菜和红砂群落的幼苗为材料,经0、100、200、300、400mmol/L NaCl盐溶液共同胁迫10 d,检测它们的含水量、主要矿质离子在根茎叶的含量与分布,揭示二者耐盐的共生协同的离子平衡适应机制。试验结果发现,珍珠猪毛菜叶片具有"吸钾排钠的"的耐盐特征,红砂叶片具备"吸钠排钾"的特征,吸收利用无机矿质离子具备互补效应。二者耐盐Cl、Ca和Si离子吸收与累积能力存在很大差异:随着盐胁迫程度加剧,红砂的根茎叶中Cl离子含量持续增加,并且为珍珠猪毛菜的2—5倍;珍珠猪毛菜根中Ca离子含量为红砂的2—3倍,但含量变化不显著;红砂根中Si离子含量迅速降低后稳定,并且是珍珠猪毛菜根的3—5倍,其他器官变化差异较小。因此,红砂与珍珠猪毛菜的共培养盐胁迫下根中吸收的离子侧重不同,红砂以Na、Cl、Si为主,珍珠猪毛菜以K、Ca为主。随着盐胁迫的程度加强,离子选择吸收系数S k,Na的变化趋势降低,表明二者叶部对Na的选择性减小,K的选择性吸收积累增大,增强了它们的抗盐性,最终使叶片所受盐害减小。总之红砂与珍珠猪毛菜共生的耐盐离子稳态机制显著不同,离子吸收与分布具有互补互利的效应。     

Salicylic acid increased aldose reductase activity and sorbitol accumulation in tomato plants under salt stress

Increased aldose reductase (ALR) activities were detected in the leaf tissues of tomato plants grown for 3 weeks in culture medium containing 10^?7 or 10^?4 M salicylic acid (SA), and in the roots after the 10^?4 M SA pretreatment. The ALR activity changed in parallel with the sorbitol content in the leaves of the SA-treated plants. Salt stress elicited by 100 mM NaCl enhanced the accumulation of sorbitol in the leaves of control plants and as compared with the untreated control the sorbitol content in the SA-pretreated leaves remained elevated under salt stress. DEAE cellulose anionexchange column purification of the protein precipitated with 80 % (NH₄)₂SO₄ revealed two enzyme fractions with ALR activity in both the leaf and the root tissues. The fraction of the leaf extract that was not bound to the column reacted with glucose and glucose-6-P as substrates, whereas glucose was not a substrate for the bound fraction or for root isoenzymes. The root enzyme was less sensitive to salt treatment: 50 mM NaCl caused 30 % inhibition in the leaf extract, whereas the enzyme activity of the root extract was not affected. It is suggested that increased ALR activity and sorbitol synthesis in the leaves of SA-treated tomato plants may result in an improved salt stress tolerance.     

Synergistic effects of drought and ascorbic acid on growth,mineral nutrients and oxidative defense system in canola (Brassica napus L.) plants

A study was conducted to find out the role of ascorbic acid (AsA) in modulating growth and different physio-biochemical attributes of canola plants under well-watered as well as water-deficit conditions. Drought stress imposed on 60 % field capacity significantly decreased the shoot and root fresh and dry weights, leaf chlorophyll contents, shoot and root P, root K⁺, and activity of CAT enzyme, while increased chlorophyll a/b contents, MDA, NPQ, leaf total phenolics, free proline and GB contents in both canola cultivars. Foliar-applied varying levels (50, 100 and 150 mg L^?1) of AsA enhanced shoot and root fresh and root dry weights, qN, NPQ, shoot and root P, AsA as well as the activity of POD enzyme particularly under drought stress conditions. Of both canola cultivars, cv. Dunkeld was higher in shoot fresh weights, ETR and F _v /F _m, MDA, proline and GB contents, and POD activity, however, cv. Cyclone in total phenolics and qN under well-watered and water-deficit conditions. Overall, the foliar-applied AsA had a positive effect, though not marked, on salt sensitive cv. Cyclone in terms of improved growth and other attributes, whereas exogenously applied AsA had a non-significant effect on relatively salt tolerant cv. Dunkeld.     

盐旱复合胁迫对小麦幼苗生长和水分吸收的影响

为明确盐害、干旱及盐旱复合胁迫对小麦幼苗生长和水分吸收的影响,从而为盐害和干旱胁迫下栽培调控提供理论依据。以2个抗旱性不同的小麦品种(扬麦16和耐旱型洛旱7号)为材料,采用水培试验,以NaCl和PEG模拟盐旱复合胁迫,研究了盐旱复合胁迫下小麦幼苗生长、根系形态、光合特性及水分吸收特性的变化。结果表明,盐、旱及复合胁迫下小麦幼苗的生物量、叶面积、总根长与根系表面积、叶绿素荧光和净光合速率均显著下降,但是复合胁迫处理的降幅却显著低于单一胁迫。盐旱复合胁迫下根系水导速率和根系伤流液强度显著大于单一胁迫,从而提高了小麦幼苗叶片水势和相对含水量。盐胁迫下小麦幼苗Na~+/K~+显著大于复合胁迫,但复合胁迫下ABA含量却显著小于单一的盐害和干旱胁迫。因此,盐旱复合胁迫可以通过增强根系水分吸收及降低根叶中ABA含量以维持较高光合能力,这是盐旱复合胁迫提高小麦适应性的重要原因。洛旱7号和扬麦16对盐及盐旱复合胁迫的响应基本一致,但在干旱胁迫下洛旱7号表现出明显的耐性。     

On the mechanism of salt tolerance in olive (Olea europaea L.) under low- or high-Ca2+ supply

The effect of changes in Ca²⁺/Na⁺ ratios at the root zone has been reported in Olea europaea, a species mostly cultivated in calcareous soils. Plants were exposed to low (2.0 mM, low-Ca) or high-Ca²⁺ supply (9.0 mM, high-Ca) and supplied with 0 or 200 mM NaCl. Measurements were performed on water relations, gas exchange and photosynthetic performances, ion fluxes at whole-plant and leaf level, Na⁺ allocation at organismal level, the elemental and soluble carbohydrate concentration in the leaf. Most parameters were also measured during a period of relief from salinity stress, as Olea europaea suffers from fluctuating root zone NaCl concentrations over the whole growing season. High-Ca²⁺ supply decreased stomatal conductance, especially during the first two weeks of treatment. In response to salinity stress (i) leaf turgor potential was more severely depressed in high-Ca than in low-Ca plants, whereas net CO₂ assimilation rate and relative growth rate were unaffected by root zone Ca²⁺ concentrations (ii) high-Ca plants had a markedly superior ability to both exclude Na⁺ from the shoot and to selectively transport K⁺ over Na⁺ than low-Ca plants; (iii) both CO₂ carboxylation efficiency and maximal efficiency of PSII photochemistry (F_v/F_m) were significantly smaller in low-Ca than in high-Ca plants, likely as a result of a greater accumulation of toxic ions. Consistently, when osmotic stress was relieved by supplying plants with good quality water (relief period), both photosynthetic (+44%) and growth rates (+65%) recovered to a markedly superior degree in high-Ca than in low-Ca plants which had been previously treated with 200 mM NaCl. We conclude that (1) high-Ca²⁺ supply expose olive leaves to a more severe dehydration, but allowed to restrict both the entry and the allocation of potentially toxic ions to sensitive shoot organs; (2) a transient restriction of water-mass flow to the shoot during salinization may be of relatively minor significance in Olea europaea, which is very tolerant to drought; (3) overall salt tolerance in Olea europaea, as in most evergreen sclerophylls inhabiting Mediterranean areas, tightly depends upon the ability to reduce water uptake and transpiration during the dry/warm period and to recover photosynthetic and growth rates when low-salinity flood water is available. Therefore, data from the present experiment allow conclude that an increase in root zone Ca²⁺ concentration enhances tolerance to salinity stress in olive plants.     

Isolation,expression, and functional analysis of developmentally regulated plasma membrane polypeptide 1 (DREPP1) in <Emphasis Type="Italic">Sporobolus virginicus</Emphasis> grown under alkali salt stress

The plant specific DREPP proteins have been shown to bind Ca²⁺ and regulate the N-myristoylation signaling and microtubule polymerization in Arabidopsis thaliana. The information about DREPP proteins in other plants is, however, scarce. In the present study, we isolated the DREPP gene from a halophytic grass, Sporobolus virginicus, and tested whether the gene was involved in alkaline salt stress responses. The SvDREPP1 was cloned from S. virginicus by RACE methods. The isolated gene showed high homology to DREPP homologs from C₄ grasses, Setaria italica, and Panicum hallii as well as rice (OsDREPP1). The encoded protein contained 202 amino acid residues. It was expressed in E. coli, and its biochemical properties were studied. It was observed that SvDREPP1 was not only Ca²⁺-binding protein, but also bind to calmodulin and microtubules. The SvDREPP1 mRNA expression in plants grown under alkaline salt stress was upregulated by 3.5 times over the control in leaf tissues after 48-h treatment, whereas it was increased for 6.0 times in the root tissues at 36 h. The data suggests the importance of SvDREPP1 in regulating alkali salt stress responses in the leaf tissues.     

Overexpression of the betaine aldehyde dehydrogenase gene from Atriplex hortensis enhances salt tolerance in the transgenic trifoliate orange (Poncirus trifoliata L. Raf.)

Trifoliate orange (Poncirus trifoliata L. Raf.), a rootstock widely used for citrus species, is salt-sensitive. Worldwide, salinity is a major abiotic stress affecting citrus growth and yield. Glycinebetaine (GB) is an important osmoprotectant involved in responses to salt stress. However, current evidence regarding the effect of salt stress on GB accumulation in trifoliate orange is limited, and the GB synthesis gene has not yet been shown to confer enhanced salt stress tolerance to this species in a transgenic context. In the current study, we first examined the change in GB level of trifoliate orange seedlings exposed to salt stress, and found that salt increased endogenous GB level in a concentration-dependent manner. A betaine aldehyde dehydrogenase gene (AhBADH) cloned from Atriplex hortensis was introduced into the trifoliate orange by means of Agrobacterium-mediated transformation. RT-PCR analysis on three selected transgenic lines showed that the AhBADH gene was overexpressed in each of them. GB levels in these lines were also higher than those in untransformed wild-type (WT) plants. In the transgenic lines, exposure to 200 mM NaCl resulted in significantly less serious leaf burning and defoliation, lower MDA accumulation, and higher chlorophyll contents than those in the WT plants. Moreover, when exposed to salt, shoots of transgenic plants contained lower levels of Na⁺ and Cl⁻, higher levels of K⁺, and a higher K/Na ratio, while the same was true for the roots in most cases. Taken together, the data suggest that overexpression of the AhBADH gene in transgenic trifoliate orange enhanced salt stress tolerance. This may be correlated with the low levels of lipid peroxidation, protection of the photosynthetic machinery, and increase in K⁺ uptake.     

Responses of Nipa palm (Nypa fruticans) seedlings,a mangrove species,to salt stress in pot culture

Nipa palm (Nypa fruticans) is the only palm that grows in mangrove vegetation. We investigated the effect of salt stress on the growth and physiology of 6-month-old seedlings of Nipa palm exposed to different degrees of salt stress (as NaCl) in pot culture. The overall growth performance of Nipa palm was unaffected by mild salt stress (8.9−16.6 dS m⁻¹), whereas seedlings grown under severe salt stress (EC = 57.2 dS m⁻¹) had lower chlorophyll content and fluorescence, reduced net photosynthesis and transpiration, which resulted in reduced growth of the plants. Na⁺ contents in leaf, petiole, and root tissues increased considerably under salt stress, depending upon the NaCl levels in the soil solution. Under salt-stress K⁺ content declined, whereas Ca²⁺ content increased somewhat, in parallel to Na⁺. Free proline accumulated in plants growing under high salt stress (EC = 57.2 dS m⁻¹). In contrast, soluble sugars were enriched under intermediate levels of salt stress (EC = 16.6 dS m⁻¹). The results obtained in the present study suggest that, based on ecophysiological data, N. fruticans is a species best adapted to grow in mangrove coastal areas with moderate only salt load, and circumscribing quite well the actual areas of occurrence of this palm in the gradient from seawater habitats to inland sites. © 2014 Elsevier GmbH     

Ectopic expression of wheat expansin gene TaEXPA2 improved the salt tolerance of transgenic tobacco by regulating Na+/K+ and antioxidant competence

High salinity is one of the most serious environmental stresses that limit crop growth. Expansins are cell wall proteins that regulate plant development and abiotic stress tolerance by mediating cell wall expansion. We studied the function of a wheat expansin gene, TaEXPA2, in salt stress tolerance by overexpressing it in tobacco. Overexpression of TaEXPA2 enhanced the salt stress tolerance of transgenic tobacco plants as indicated by the presence of higher germination rates, longer root length, more lateral roots, higher survival rates and more green leaves under salt stress than in the wild type (WT). Further, when leaf disks of WT plants were incubated in cell wall protein extracts from the transgenic tobacco plants, their chlorophyll content was higher under salt stress, and this improvement from TaEXPA2 overexpression in transgenic tobacco was inhibited by TaEXPA2 protein antibody. The water status of transgenic tobacco plants was improved, perhaps by the accumulation of osmolytes such as proline and soluble sugar. TaEXPA2‐overexpressing tobacco lines exhibited lower Na⁺ but higher K⁺ accumulation than WT plants. Antioxidant competence increased in the transgenic plants because of the increased activity of antioxidant enzymes. TaEXPA2 protein abundance in wheat was induced by NaCl, and ABA signaling was involved. Gene expression regulation was involved in the enhanced salt stress tolerance of the TaEXPA2 transgenic plants. Our results suggest that TaEXPA2 overexpression confers salt stress tolerance on the transgenic plants, and this is associated with improved water status, Na⁺/K⁺ homeostasis, and antioxidant competence. ABA signaling participates in TaEXPA2‐regulated salt stress tolerance.     

Responses of ectomycorrhizal American elm (Ulmus americana) seedlings to salinity and soil compaction

American elm (Ulmus americana) seedlings were either non-inoculated or inoculated with Hebeloma crustuliniforme, Laccaria bicolor and a mixture of the two fungi to study the effects of ectomycorrhizal associations on seedling responses to soil compaction and salinity. The seedlings were grown in the greenhouse in pots containing non-compacted (0.4 g cm^?3 bulk density) and compacted (0.6 g cm^?3 bulk density) soil and subjected to 60 mM NaCl or 0 mM NaCl (control) treatments for 3 weeks. All three fungal inocula had similar effects on the responses of elm seedlings to soil compaction and salt treatment. In non-compacted soil, ectomycorrhizal fungi reduced plant dry weights, root hydraulic conductance, but did not affect leaf hydraulic conductance and net photosynthesis. When treated with 60 mM NaCl, ectomycorrhizal seedlings had several-fold lower leaf concentrations of Na⁺ compared with the non-inoculated plants. Soil compaction reduced Na⁺ leaf concentrations in non-ectomycorrhizal plants and decreased dry weights, gas exchange and root hydraulic conductance. However, in ectomycorrhizal plants, soil compaction had little effect on the leaf Na⁺ concentrations and on other measured growth and physiological parameters. Our results demonstrated that ECM associations could be highly beneficial to plants growing in sites with compacted soil such as urban areas.     

碱蓬属植物耐盐机理研究进展

碱蓬属(Suaeda)植物是一类典型的真盐生植物,属于重要的盐生植物资源,全球广泛分布.人们已经对20种碱蓬属植物进行了观察和盐胁迫实验,研究了不同器官或组织的生理生化特征及其对盐胁迫的反应,并基于这些研究分析了盐胁迫的应答机制.叶片肉质化、细胞内离子区域化、渗透调节物质增加和抗氧化系统能力增强是碱蓬属植物响应和适应盐胁迫的重要方式和途径.但迄今为止的研究工作尚有一定的局限性,主要包括:研究工作主要集中在植物地上部分,而对植物地下部分的研究较少;多是少数生物学指标或生理学现象的单独观察,而缺乏对生理代谢过程的整体和综合分析;针对某种碱蓬的独立分析较多,而与近缘种的比较研究较少;植物对中性盐胁迫的反应研究较多,而对碱性盐的研究较少.为进一步系统阐明碱蓬属植物的耐盐机制,今后的工作应注重碱蓬属植物响应和适应盐胁迫的信号网络和调控机制研究,基于系统生物学研究思路,采用现代组学技术探索该属植物响应盐胁迫的由复杂信号网络调控的特殊生理特征和特异代谢途径.     

Cloning and characterization of Na+/H+ antiporter (LfNHX1) gene from a halophyte grass Leptochloa fusca for drought and salt tolerance

Abiotic stresses such as salinity and drought have adverse effects on plants. In the present study, a Na⁺/H⁺ antiporter gene homologue (LfNHX1) has been cloned from a local halophyte grass (Leptochloa fusca). The LfNHX1 cDNA contains an open reading frame of 1,623 bp that encodes a polypeptide chain of 540 amino acid residues. LfNHX1 protein sequence showed high similarity with NHX1 homologs reported from other halophyte plants. Amino acid and nucleotide sequence similarity, protein topology modeling and the presence of conserved functional domains in the LfNHX1 protein sequence classified it as a vacuolar NHX1 homolog. The overexpression of LfNHX1 gene under CaMV35S promoter conferred salt and drought tolerance in tobacco plants. Under drought stress, transgenic plants showed higher relative water contents, photosynthetic rate, stomatal conductance and membrane stability index as compared to wild type plants. More negative value of leaf osmotic potential was also observed in transgenic plants when compared with wild type control plants. Transgenic plants showed better germination and root growth at 2 mg L^?1 Basta herbicide and three levels (100, 200 and 250 mM) of sodium chloride. These results showed that LfNHX1 is a potential candidate gene for enhancing drought and salt tolerance in crops.     

盐胁迫对2种栎树苗期生长和根系生长发育的影响

以低浓度(50 mmol/L)和高浓度(150 mmol/L)NaCl处理弗吉尼亚栎(Quercus virginiana)和麻栎(Quercus acutissima)1年生幼苗,研究了2种栎树在盐胁迫下的生长、对盐分的敏感性和耐受性及其根系形态学参数变化以及根系对盐离子的吸收与积累。结果表明,高浓度盐胁迫明显抑制了2种栎树地上部生物量的积累(P0.05),而低浓度盐胁迫对弗吉尼亚栎地上部干重的影响不明显,但显著抑制了麻栎地上部干重(P0.05);2种栎树的根冠比在盐胁迫下呈增加趋势,特别是在高浓度盐胁迫下,2种栎树的根冠比明显增加(P0.05),盐胁迫下增加生物量在根部的分配是植物应对盐胁迫的方式之一。2种栎树根部生物量积累在盐胁迫下变化不明显,但2种栎树根系形态学参数在盐胁迫下的响应不同,弗吉尼亚栎根系总长度、总表面积和总体积在盐胁迫下均有不同程度增加,特别是在低浓度盐胁迫下,根系形态学参数明显增加(P0.05),但麻栎根系形态学参数有下降趋势,但与对照相比变化不明显;通过对不同径级根系总长的分析发现,弗吉尼亚栎根系总长度的增加主要是由于直径小于2 mm的细根总长的增加,细根长度的增加对于植物吸收水分和营养物质具有重要意义;通过对Na+和Cl-在根系的含量分析表明,盐胁迫下2种栎树根系盐离子的积累均有明显增加,但弗吉尼亚栎根系盐离子的含量在低浓度和高浓度盐胁迫下的差异不明显,而麻栎在高浓度盐胁迫下根系盐离子的含量明显高于弗吉尼亚栎。综合2种栎树盐胁迫下的生物量分配策略和根系形态学响应以及盐离子的积累规律,证明2种栎树尽管在生物量分配策略方面具有相同的特点,但根系的响应策略截然不同,弗吉尼亚栎在盐胁迫下能够扩大根系吸收范围,维持较高的K+/Na+比值,而麻栎在盐胁迫下根系由于吸收过多的盐离子,导致根系的生长发育受到抑制,影响了根系在逆境中的分布范围,从而在一定程度上避免了进一步的盐害。     

Does Inoculation with Glomus mosseae Improve Salt Tolerance in Pepper Plants?

A pot experiment was conducted to determine the effects of Glomus mosseae inoculation on growth and some biochemical activities in roots and shoots of pepper (Capsicum annuum L. cv. Zhongjiao 105) plants subjected to four levels of NaCl [0 (control), 25 (low), 50 (medium), and 100 (high) mM] for 30 days, after 30 days of establishment under non-saline conditions. In mycorrhizal (M) plants, root colonization varied from 48 to 16 %. M plants had higher root and shoot dry weight and leaf area compared with non-mycorrhizal (NM) plants. Under salinity stress, M plants accumulated higher amounts of leaf photosynthetic pigments as well as soluble sugar, soluble protein, and total free amino acids in roots and shoots than those of NM plants. In contrast, the accumulation of proline was less intense in M plants than NM plants. Salt stress induced oxidative stress by increasing malondialdehyde (MDA) content; however, the extent of oxidative damage in M plants was less compared with NM plants due to G. mosseae-enhanced activity of superoxide dismutase (SOD) and peroxidase (POD). We concluded that inoculation with G. mosseae improved growth performance and enhanced salt tolerance of pepper plants via improving photosynthetic pigments and the accumulation of organic solutes (except proline), reducing oxidative stress, and enhancing antioxidant activities of the SOD-POD system.