Extracts from Yeast and Carrot Roots Enhance Maize Performance under Seawater-Induced Salt Stress by Altering Physio-Biochemical Characteristics of Stressed Plants

Damage to plant productivity due to soil salinity is a major agricultural problem, necessitating the development of effective salinity management measures. Here, we sought the potential effects of yeast and carrot extracts, and their associated mechanisms in the alleviation of seawater-induced salt stress in maize. Pretreatment of maize seeds with yeast or carrot extract provided maize plants with enormous abilities in reducing growth inhibition and biomass loss when exposed to seawater. The better growth performance of yeast extract- and carrot extract-primed plants under saline conditions coincided with improved protection of the photosynthetic pigments, chlorophylls and carotenoids. The primed plants also restricted Na⁺ accumulation in both roots and shoots while maintaining a higher K⁺ content and lower Na⁺/K⁺ ratio when compared with that of non-primed plants. Yeast extract and carrot extract also potentiated salt tolerance mechanisms by accelerating the production of osmolytes, as evidenced by accumulating levels of total free amino acids and soluble sugars, especially in the roots of primed plants during salinity. The enhanced levels of ascorbic acid and phenolic compounds, and the heightened activities of reactive oxygen species-detoxifying enzymes superoxide dismutase, catalase, and ascorbate peroxidase with concurrent reduction of lipid peroxidation in the leaves of primed plants clearly indicated a positive impact of yeast extract- and carrot extract-priming on the antioxidant system of maize under salt stress. Our results together suggest decisive roles of yeast extract and carrot extract in the management of salt-induced adverse effects in economically important maize, and perhaps other crops.

     

Seed priming with sorghum extracts and benzyl aminopurine improves the tolerance against salt stress in wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Salt stress impedes the productivity of wheat (Triticum aestivum L.) in many parts of the world. This study evaluated the potential role of benzyl aminopurine (BAP) and sorghum water extract (SWE) in improving the wheat performance under saline conditions. Seeds were primed with BAP (5 mg L^?1), SWE (5% v/v), BAP + SWE, and distilled water (hydropriming). Soil filled pots maintained at the soil salinity levels of 4 and 10 dS m^?1 were used for the sowing of primed and non-primed seeds. Salt stress suppressed the wheat growth; seed priming treatments significantly improved the wheat growth under optimal and suboptimal conditions. Total phenolics, total soluble sugars and proteins, α-amylase activity, chlorophyll contents, and tissue potassium ion (K⁺) contents were increased by seed priming under salt stress; while, tissue sodium ion (Na⁺) contents were decreased. Seed priming with SWE + BAP was the most effective in this regard. Under salt stress, the tissue Na⁺ contents were reduced by 5.78, 28.3, 32.2, 36.7% by hydropriming, seed priming with SWE, seed priming with BAP, and seed priming with SWE + BAP, respectively over the non-primed control. Effectiveness of seed priming techniques followed the order SWE + BAP > BAP > SWE > Hydropriming. In conclusion, seed priming with SWE + BAP may be opted to improve the tolerance against salt stress in wheat.     

Contributions of arbuscular mycorrhizal fungi to growth,photosynthesis, root morphology and ionic balance of citrus seedlings under salt stress

A pot study was conducted to determine the effects of arbuscular mycorrhizal (AM) fungi (Glomus mosseae and Paraglomus occultum) and salt (NaCl) stress on growth, photosynthesis, root morphology and ionic balance of citrus (Citrus tangerine Hort. ex Tanaka) seedlings. Eighty-five-day-old seedlings were exposed to 100 mM NaCl for 60 days to induce salt stress. Mycorrhizal colonization of citrus seedlings was not affected by salinity when associated with P. occultum, but significantly decreased when with G. mosseae. Compared with the non-mycorrhizal controls, mycorrhizal seedlings generally had greater plant height, stem diameter, shoot, root and total plant biomass, photosynthetic rate, transpiration rate and stomatal conductance under the 0 and 100 mM NaCl stresses. Root length, root projected area and root surface area were also higher in the mycorrhizal than in the non-mycorrhizal seedlings, but higher root volume in seedlings with G. mosseae. Leaf Na⁺ concentrations were significantly decreased, but leaf K⁺ and Mg²⁺ concentrations and the K⁺/Na⁺ ratio were increased when seedlings with both G. mosseae and P. occultum. Under the salt stress, Na⁺ concentrations were increased but K⁺ concentrations decreased in the mycorrhizal seedlings. Under the salt stress, Ca²⁺ concentrations were increased in the seedlings with P. occultum or without AM fungi (AMF), but decreased with G. mosseae. Ratios of both Ca²⁺/Na⁺ and Mg²⁺/Na⁺ were also increased in seedlings with G. mosseae under the non-salinity stress, while only the Mg²⁺/Na⁺ ratio was increased in seedlings with P. occultum under the salt stress. Our results suggested that salt tolerance of citrus seedlings could be enhanced by associated AMF with better plant growth, root morphology, photosynthesis and ionic balance.     

Improvement of Cerium on Photosynthesis of Maize Seedlings Under a Combination of Potassium Deficiency and Salt Stress

Added Ce³⁺ can partly substitute for Ca²⁺ or Mg²⁺ and improve photosynthesis under the deficiency of these elements, but very few studies focused on photosynthetic improvement in maize seedlings caused by K⁺ deficiency, salt stress, especially a combination of K⁺ deficiency and salt stress. In the present study, the effects of Ce³⁺ on the photosynthesis of maize seedlings under the three different stresses were investigated. The results showed that added Ce³⁺ under various stresses increased the ratios of free water/bound water and of K⁺/Na⁺, the pigment contents, the values of Fv/Fm, Y(II), ETR(II), Y(NPQ), Qp, qL, NPQ, and qN of photosystem II (PSII), the values of Y(I) and ETR(I) of photosystem I (PSI) and the expression levels of LhcII cab1 and rbcL, and decreased the values of Y(NO) and Y(NA). This implied that added Ce³⁺ depressed ion toxicity, photodamage of PSII, and acceptor side constraints of PSI, and enhanced adjustable energy dissipation, the responses of photochemistry, and carbon assimilation caused by K⁺ deficiency, salt stress, and the combination of K⁺ deficiency and salt stress. However, Ce³⁺ mitigation of photosynthetic inhibition in maize seedlings caused by the combined stresses was greater than that of salt stress, and Ce³⁺ mitigation under salt stress was greater than that under K⁺ deficiency. In addition, the results also showed that Ce³⁺ cannot improve photosynthesis and growth of maize seedlings under K⁺ deficiency by substituting for K⁺.     

盐胁迫对二穗短柄草幼苗生长及不同器官中盐离子稳态的影响

采用4种浓度的NaCl溶液(50、100、150、200 mmol/L)处理二穗短柄草和拟南芥(对照)幼苗,测定不同浓度盐胁迫下2种植物幼苗的生长指标和离子分布,以探讨二穗短柄草在盐胁迫下主要阳离子平衡机制.结果表明:(1)盐胁迫显著抑制二穗短柄草根叶的生物量积累.(2)根冠比数据显示,在盐胁迫条件下二穗短柄草能够更好地维系地下部分的生物量积累.(3)在4种浓度盐胁迫下,二穗短柄草叶中Na+含量低于根系,而且K+、Cl-含量和K+/Na+比值始终高于根系,说明在二穗短柄草中Na+从地下到地上的转运受到抑制,但对Cl-的转运缺乏有效的调控.(4)回归分析发现,盐胁迫下二穗短柄草和拟南芥根部Na+与K+含量变化呈正相关关系,而在叶部则不相关,说明二穗短柄草和拟南芥Na+与K+在根部具有相同的离子通道,而在叶部却具有各自独立的转运途径.     

Transport,signaling, and homeostasis of potassium and sodium in plants

Potassium （K＋） is an essential macronutrient in plants and a lack of K＋ significantly reduces the potential for plant growth and development. By contrast, sodium （Na＋）, while beneficial to some extent, at high concentrations it disturbs and inhibits various physiological processes and plant growth. Due to their chemical similarities, some functions of K＋ can be undertaken by Na＋ but K＋ homeostasis is severely affected by salt stress, on the other hand. Recent advances have highlighted the fascinating regulatory mechanisms of K＋ and Na＋ transport and signaling in plants. This review summarizes three major topics： （i） the transport mechanisms of K＋ and Na＋ from the soil to the shoot and to the cellular - compartments; （ii） the mechanisms through which plants sense and respond to K＋ and Na＋ availability; and （iii） the components involved in maintenance of K＋/Na＋ homeostasis in plants under salt stress.     

NaCl胁迫对不同耐盐性玉米自交系萌动种子和幼苗离子稳态的影响

盐胁迫影响植物组织的离子分布,不同品种间存在差异。以玉米耐盐自交系81162和8723及盐敏感自交系P138为材料,研究了不同浓度(0、60、140、220 mmol/L)Na Cl胁迫下萌动期种子和幼苗的不同部位中Na+、K+、Ca2+含量以及K+/Na+和Ca2+/Na+比值的变化,旨在探讨不同自交系耐盐性差异的原因。结果表明,在萌动种子中,3个玉米自交系中的Na+积累量表现为种皮胚胚乳,K+累积表现为胚种皮胚乳;幼苗中,Na+积累表现为根茎叶。随着Na Cl浓度的增加,3个玉米自交系萌动种子和幼苗中的Na+含量逐渐升高,但是萌动种子中耐盐自交系81162和8723的Na+增加幅度小于盐敏感自交系P138,Na+含量小于盐敏感自交系P138;幼苗中耐盐自交系81162和8723的Na+增加幅度大于盐敏感自交系P138,幼苗根中Na+含量大于盐敏感自交系P138;茎叶中的Na+含量小于盐敏感自交系P138。随着Na Cl浓度的增加,萌动种子和幼苗中的K+和Ca2+含量逐渐降低。K+离子在耐盐自交系81162和8723萌动种子和幼苗中的降低幅度小于盐敏感自交系P138;Ca2+离子在耐盐自交系81162和8723幼苗中的降低幅度小于盐敏感自交系P138;而在萌动种子中3个自交系Ca2+的流失差异不大。耐盐自交系81162和8723萌动种子和幼苗中K+含量都大于盐敏感自交系P138。耐盐自交系81162和8723的萌动种子和幼苗根中Ca2+含量都大于盐敏感自交系P138;幼苗叶片中则小于盐敏感自交系P138。萌动种子和幼苗中K+/Na+和Ca2+/Na+均随着Na Cl浓度的升高而降低,K+/Na+比值表现为耐盐自交系81162和8723大于盐敏感自交系P138。耐盐自交系81162和8723通过调节离子平衡维持萌动种子和幼苗中较高的K+/Na+比值从而提高耐盐性。     

NaCl胁迫对圆柏幼苗生长和离子吸收及分配的影响

以当年生圆柏幼苗为实验材料,采用温室调控盆栽土培法研究了不同浓度NaCl(0、100、200、300mmol·L-1)胁迫21d对其生长情况及不同器官(根、茎、叶)中K~+、Na~+、Ca~(2+)和Mg~(2+)的吸收和分配的影响,以探讨圆柏幼苗对盐环境的生长适应性及耐盐机制。结果表明:(1)随着NaCl胁迫浓度的增加,圆柏幼苗生长,包括株高、地径、相对生长量以及生物量的积累均呈下降趋势,而其根冠比却增加。(2)在各浓度NaCl胁迫处理下,圆柏幼苗根、茎、叶中Na~+含量较对照均显著增加,而且叶中Na~+含量显著高于茎和根,叶中Na~+含量是根中的5倍。(3)随着NaCl胁迫浓度的升高,圆柏幼苗各器官中K~+、Ca~(2+)和Mg~(2+)含量以及K~+/Na~+、Ca~(2+)/Na~+及Mg~(2+)/Na~+比值均呈下降趋势。(4)在NaCl胁迫条件下,圆柏幼苗根系离子吸收选择性系数SK,Na、SCa,Na、SMg,Na显著提高,茎、叶离子转运选择性系数SCa,Na、SMg,Na则逐渐降低,叶中离子转运选择性系数SK,Na则随着NaCl胁迫浓度的升高显著降低,大量Na~+进入地上部,减缓了盐胁迫对根系的伤害。研究认为,圆柏幼苗的盐适应机制主要是通过根系的补偿生长效应及茎、叶对Na~+的聚积作用来实现的,同时也与根对K~+、Ca~(2+)、Mg~(2+)的选择性运输能力增强和茎、叶稳定的K~+、Ca~(2+)、Mg~(2+)的选择性运输能力有关。     

短期NaCl胁迫对不同小麦品种幼苗K+吸收和Na+、K+积累的影响

为研究盐胁迫下小麦幼苗生长及Na⁺、K⁺的吸收和积累规律,以中国春、洲元9369和长武134等3种耐盐性不同小麦品种为材料,采用非损伤微测技术检测盐胁迫2 d后的根系K⁺离子流变化,并对植株体内的Na⁺、K⁺含量进行测定。结果表明:短期(2d)盐胁迫对小麦生长有抑制作用,且对根系的抑制大于地上部,耐盐品种下降幅度小于盐敏感品种。盐胁迫下,小麦根际的 K⁺大量外流,盐敏感品种中国春K⁺流速显著高于耐盐品种长武134,最高可达15倍。小麦幼苗地上部分和根系均表现为Na⁺积累增加,K⁺积累减少,Na⁺/K⁺比随盐浓度增加而上升。中国春限Na⁺能力显著低于长武134,Na⁺/K⁺则显著高于长武134。综上所述,盐胁迫下造成小麦组织器官中Na⁺/K⁺比上升的主要原因是根系K⁺大量外流和Na⁺的过量积累,耐盐性不同的小麦品种间差异显著,并认为根系对K⁺的保有能力可能是作物耐盐性评价的一个重要指标。     

盐胁迫对3种平欧杂种榛幼苗叶片解剖结构及离子吸收、运输与分配的影响

研究盐胁迫下3个品种平欧杂种榛幼苗叶片解剖结构和离子代谢特征,以揭示盐胁迫响应与适应机制及不同品种的耐盐性差异。以‘达维’、‘辽榛7号’、‘玉坠’2年生压条苗为材料,在盆栽条件下经轻度、中度、重度(分别为50、100、200 mmol/L NaCl)盐胁迫处理,设对照为0,研究幼苗叶片显微解剖结构参数和Na~+、K~+、Cl~-、Ca²⁺含量的变化及其在根、茎、叶中的吸收、运输和分配特征。不同品种平欧杂种榛叶片厚度、上表皮厚度、下表皮厚度、栅栏组织和海绵组织厚度随着盐胁迫程度的增强呈现出先增加后降低的特点,轻度和中度胁迫下各参数显著高于对照。中度盐胁迫显著提高了各品种叶片结构紧密度。盐胁迫导致平欧杂种榛根、茎、叶Na~+和Cl~-含量明显高于对照。盐胁迫下,Na~+和Cl~-在叶中的绝对含量明显高于茎和根,但二者的增幅以根中最大,叶中最小,表明平欧杂种榛根系首先会吸收并截留一定数量的Na~+和Cl~-,然后将其运输至茎和叶中。与对照相比,轻度和中度盐胁迫下根、茎对K~+和Ca²⁺的吸收保持稳定或减少,叶对K~+和Ca²⁺...     

Evaluation of salt tolerance at the seedling stage in rice genotypes by growth performance, ion accumulation, proline and chlorophyll content

Aims

The objectives of this study were to evaluate salt tolerance level of rice genotypes using the well-established screening criteria; the salt injury score, survival percentage and ratio between Na⁺ and K⁺, as well as the contents of proline and chlorophyll, and to identify the relationship between salt tolerance and physiological characters.

Methods

One hundred and six rice genotypes were grown in hydroponic solutions subjected to salt stress and evaluated for salt tolerance ability and the physiological parameters. Multivariate cluster analysis was performed based on salinity tolerance scores (ST scores; score 1 being the most tolerant, score 9 the most sensitive), survival percentage and Na⁺/K⁺ ratio.

Results

ST scores based on salt injury symptoms were negatively correlated with survival percentage and chlorophyll concentration in the stressed seedlings but positively correlated with Na⁺/K⁺ ratio and proline content. Rice genotypes were classified into five salt tolerance groups: tolerant (T), moderately tolerant (MT), moderately sensitive (MS), sensitive (S) and highly sensitive (HS). The means of ST scores were significantly different among the five tolerance groups indicating that the ST score was the most reliable index for identifying salt tolerance. The means of Na⁺/K⁺ ratio and proline content in stressed seedlings were distinctively different between the extreme T and HS groups, but the means among the intermediate groups (MT, MS and S) were not significantly different. Chlorophyll content, on the other hand, was not related to the levels of salt tolerance.

Conclusions

In addition to the commonly used Na⁺/K⁺ ratio, proline content is suggested to be another useful criterion to differentiate salt-tolerant from salt-sensitive rice. This study also identified several Thai improved and local cultivars with the level of salt tolerance and physiological characters comparable to Pokkali, the standard salt-tolerant donor and may be utilized as alternative sources of salt tolerance alleles.     

Inductive responses of some organic metabolites for osmotic homeostasis in peanut (Arachis hypogaea L.) seedlings during salt stress

The salt tolerance of peanut (Arachis hypogaea L.) seedlings was evaluated by analyzing growth, nutrient uptake, electrolyte leakage, lipid peroxidation and alterations in levels of some organic metabolites under NaCl stress. The plant height, leaf area and plant biomass decreased significantly in salt-treated seedlings as compared with control. The relative water content (RWC %) of leaf decreased by 16 % at high concentrations of NaCl. There was an increase in the lipid peroxidation level and decrease in the electrolyte leakage at high concentrations of NaCl. The total free amino acid and proline contents of leaf increased by 5.5- and 43-folds, respectively in 150 mM NaCl-treated plants as compared with control. Total sugar and starch content increased significantly at high concentrations of NaCl. Chl a, Chl b, total chlorophyll and carotenoid contents decreased significantly at high salinity. Na⁺ contents of leaf, stem and root increased in dose-dependent manner. K⁺ content remained unaffected in leaf and root and decreased in stem by salinity. The results from present study reveal that the peanut plants have an efficient adaptive mechanism to tolerate high salinity by maintaining adequate leaf water status associated with growth restriction. In order to circumvent the stress resulting from high salinity, the levels of some organic metabolites such as total free amino acids, proline, total sugars and starch were elevated. The elevated levels of the organic metabolites may possibly have some role in maintenance of osmotic homeostasis, nutrient uptake and adequate tissue water status in peanut seedlings under high-salinity conditions.     

NaCl胁迫对滨梅扦插苗生物量和水分积累的影响

以1年生滨梅(Prunus maritima Marshall)扦插苗为实验材料,在盆栽条件下用质量浓度为0.15%、0.29%、0.58%、0.88%、1.17%、1.46%的NaCl溶液进行盐胁迫处理,测定胁迫后根、茎、叶Na+、K+含量以及全叶、一年生茎、二年生茎和根系生物量、含水率、根系活力变化,探讨滨梅的抗盐胁迫机制。结果显示:(1)盐胁迫80d后,随着盐胁迫强度提高,滨梅植株根、茎、叶Na+含量显著提高,而其根、茎K+含量显著降低,根、茎、叶K+/Na+值显著降低;根Na+含量在低于0.58%NaCl胁迫下显著高于茎、叶,而在高于0.58%NaCl胁迫下却表现为叶Na+含量显著高于根、茎。(2)滨梅根、茎、叶生物量均随盐胁迫强度的提高呈先增加后减少的趋势;随着盐胁迫时间的延长,茎、叶生物量在低于0.58%NaCl胁迫下均呈积累趋势,且茎生物量在0.58%NaCl胁迫下显著提高,而根、一年生茎、叶生物量在高于0.58%NaCl胁迫下均显著下降。(3)滨梅茎、叶含水率均随盐胁迫强度的增加呈先增加后减少的趋势,而随着胁迫时间的延长呈逐渐减少趋势;根系活力及根含水率均随盐胁迫强度的提高而增加,但根含水率随着胁迫时间的延长变化不明显。由此可见,滨梅能通过根系稀释并蓄积Na+,保护地上部分正常生长,当进入根系的Na+量超过吸收阈值时,Na+迅速在叶中积累储存,且叶中较高含量的K+对Na+形成了有效的缓冲。     

Improved salt tolerance in a wheat stay-green mutant <Emphasis Type="Italic">tasg1</Emphasis>

Salt stress inhibited the growth of both tasg1 and wild-type (WT) wheat seedlings, but the inhibition in tasg1 plants was relatively weaker than that of WT. Compared to the WT, the chlorophyll content, thylakoid membrane polypeptides, Hill reaction activity, actual photochemical efficiency of PSII (ΦPSII), and Mg²⁺- and Ca²⁺-ATPase activities were higher in tasg1 under salt stress. At the same time, the photosynthetic activity of the tasg1 was significantly higher than that of WT. In addition, tasg1 plants displayed relatively less accumulation of reactive oxygen species and oxidative damage accompanied by higher activity of some antioxidant enzymes, and the up-regulation of antioxidant genes further demonstrated the improvement of antioxidant activity in tasg1 under salt stress. Furthermore, tasg1 plants also showed relatively weaker Na⁺ fluorescence and lower Na⁺ content, but relatively higher content of K⁺ in their roots and shoots, and then, the roots of tasg1 plants enhanced net outward Na⁺ flux and a correspondingly increased net inward K⁺ flux during salt stress. This might be associated with the relatively higher activity of H⁺-ATPase in tasg1 plants. These results suggest that the improved antioxidant competence and Na⁺/K⁺ ion homeostasis play an important role in the enhanced salinity tolerance of tasg1 plants.     

油菜素内酯对盐渍下油菜幼苗生长的调控效应及其生理机制

为了探讨油菜素内酯对植物耐盐性的调控,以甘蓝型油菜"南盐油1号"为试验材料,研究了外源24-表油菜素内酯(24-EBL)对100、200 mmol/L Na Cl胁迫下油菜幼苗干重(DW)、相对含水量(RWC)、渗透调节能力(OAA)、叶片气体交换参数、气孔限制值(Ls)等的调节效应,还测定了不同器官的Na+、K+、Cl-含量,并计算各器官的K+/Na+和SK,Na。结果表明:(1)在不同浓度的盐胁迫下,油菜幼苗DW显著下降,胁迫下外源喷施10-12、10-10、10-8、10-6mol/L 24-EBL作用下,油菜植株干重均不同程度的上升,且植株干重都在10-10mol/L 24-EBL(EBL2)处理下达到最大值,分别比100、200 mmol/L Na Cl胁迫下增加29%和20%。与对照相比,非盐胁迫下外源喷施10-12、10-10、10-8、10-6mol/L 24-EBL,油菜幼苗植株干重与对照相比均无显著变化。(2)不同Na Cl浓度胁迫下,油菜叶片的RWC显著下降,外施EBL2可显著提高油菜叶片的RWC和OAA。(3)不同浓度Na Cl胁迫下,油菜幼苗叶片净光合速率(Pn)、气孔导度(Gs)、胞间CO2浓度(Ci)和蒸腾速率(Tr)均不同程度下降,而Ls显著上升,而外喷EBL2可不同程度的提高Pn、Gs、Ci、Tr,降低Ls。(4)与对照相比,Na Cl胁迫下油菜幼苗叶片、叶柄和根的Na+和Cl-含量均显著上升,Na Cl浓度愈高,Na+和Cl-含量上升愈显著。而K+含量均下降,外源EBL2可显著降低幼苗各器官的Na+和Cl-含量,对幼苗叶片K+含量没有影响,但提高了叶柄和根中的K+含量。上述表明,合适浓度的24-EBL外喷可明显提高油菜的耐盐水平,且不同浓度Na Cl胁迫下,最适24-EBL浓度均为10-10mol/L。主要是因为外源喷施24-EBL能显著改善离子稳态和渗透调节能力,从而改善盐胁迫下油菜幼苗的光合作用、水分状况,提高其耐盐性。而24-EBL对盐处理下油菜植株气孔限制的显著改善是其促进其光合、水分利用的重要原因,也是其对100 mmol/L Na Cl处理的油菜生长调控效果优于200 mmol/L Na Cl处理的重要原因之一。结果还显示,在叶片中,24-EBL外施可通过排Na+和Cl-来维持植株离子稳态,而对K+影响不大;在根、茎中可通过排Na+、排Cl-、吸K+维持稳态。     

盐胁迫对槲树(Quercus dentata)幼苗离子平衡及其生理生化特性的影响

检测NaCl胁迫对槲树（Quercus dentata）幼苗离子平衡和生理生化特性的影响,为揭示槲树的耐盐机理,其在园林中的推广应用提供参考。以一年生槲树实生苗作为实验材料,经100、200、300 mmol/L的NaCl溶液浇灌处理30 d,测定不同时间的离子含量和生理生化指标变化。结果表明,随NaCl浓度的增加和处理的时间延长,槲树各指标表现出以下规律：（1）根茎叶积累大量Na⁺,引起离子毒害,导致叶片受损,根系Na⁺含量显著高于地上部分,这种补偿作用有助于减轻地上部分受到的损害;（2）各部分K⁺含量降低,根部较茎叶更为显著,导致Na⁺/K⁺明显升高;（3）Ca²⁺由根部向地上部分转运,在叶片中浓度显著增加,有助于建立新的离子稳态;（4）Mg²⁺含量总体上呈降低趋势;（5）叶片含水量逐渐降低,丙二醛含量和相对电导率逐步升高,且在重度胁迫下的变化更显著;（6）轻度盐胁迫下,叶片过氧化物酶（POD）活性无显著变化,而过氧化氢酶（CAT）和超氧化物歧化酶（SOD）活性逐渐升高,在重度胁迫下3种酶活性出现降低;（7）脯氨酸和可溶性糖少量积累,辅助调节渗透平衡。总之,槲树幼苗能够通过调控离子平衡,提升抗氧化酶活性,积累渗透调节物,从而提高耐盐性,抵御200 mmol/L以下的NaCl胁迫。     

盐分和干旱对沙枣幼苗生理特性的影响

以沙枣(Elaeagnus angustifolia L.)幼苗为实验材料,分别对其进行轻度干旱(土壤含水量7%—9%)、重度干旱(土壤含水量3%—5%)、100 mmol/L NaCl以及100 mmol/L NaCl处理下不同程度的盐旱共胁迫处理,处理2周后测其生理指标,包括生长指标、光合指标、渗透调节指标以及复水后生长指标,研究盐旱共胁迫对沙枣幼苗生理特性的影响。结果表明:和对照相比,轻度干旱对沙枣幼苗的生物量没有显著影响,重度干旱处理明显降低了沙枣的生物量,无论是轻度干旱还是重度干旱,都显著降低了沙枣幼苗的净光合速率、K~+含量,显著增加了Na~+含量、脯氨酸含量、可溶性糖含量、有机酸含量、总酚和类黄酮含量;和对照相比,100 mmol/L NaCl处理显著降低了沙枣幼苗的生物量、净光合速率和K~+含量,显著增加了Na~+含量、脯氨酸含量、可溶性糖含量、有机酸含量、总酚和类黄酮含量;和盐处理相比,轻度干旱和盐分共胁迫对沙枣幼苗的各项指标没有显著差异,而重度干旱和盐分共胁迫明显降低了沙枣幼苗的生物量、净光合速率;复水一周后,只有轻度干旱可以回复到对照水平。以上结果表明,盐分和干旱处理明显抑制了沙枣幼苗的生长,轻度干旱和盐分共胁迫条件下,沙枣幼苗表现出一定的交叉适应现象,而重度干旱却加重了盐害。     

NaCl胁迫对流苏幼苗生长、钠钾离子分布及渗透调节物质的影响

以2年生的流苏播种苗为材料,采用不同浓度(50、100、200、300 mmol·L^-1)NaCl溶液进行胁迫处理,研究盐胁迫对流苏的生长、Na^+和K^+分布格局、渗透调节物质的影响,以明确其耐盐阈值。结果表明:(1)随着NaCl胁迫浓度的增加,流苏幼苗生长量逐渐降低,盐害指数升高、存活率下降;幼苗耐盐阈值为98.693 mmol·L^-1(0.577%W/V)。(2)随着NaCl胁迫浓度的增加,流苏幼苗各器官中的Na^+含量持续增加,并在浓度为50 mmol·L^-1时表现为根>叶>茎,在其余各处理组表现为叶>根>茎;幼苗根、叶中的K^+含量表现为先增后减的变化趋势,茎中K^+含量总体表现为下降趋势,且器官中K^+含量表现为根>叶>茎;幼苗根部到茎部和茎部到叶部的离子选择性运输能力、各器官中的K^+/Na^+比值均呈下降趋势。(3)随着NaCl浓度的增加,流苏幼苗叶片可溶性糖、可溶性蛋白含量总体呈上升趋势,其脯氨酸含量呈先上升后下降的趋势。研究发现,流苏幼苗根系可通过对Na^+的吸收和累积来阻止其向地上部运输进而避免盐害发生;叶片和茎中通过提高对K^+的选择性吸收和累积,从而增大K^+/Na^+比值以减缓盐分对其生理代谢的伤害。     

Changes in growth,photosynthetic capacity and ionic relations in spring wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) due to pre-sowing seed treatment with polyamines

The influence of pre-sowing seed treatment with polyamines (2.5 mM putrescine, 5.0 mM spermidine and 2.5 mM spermine) on growth, photosynthetic capacity, and ion accumulation in two spring wheat (Triticum aestivum L.) cultivars MH-97 (intolerant) and Inqlab-91 (tolerant) was examined. The primed seeds of each treatment and non-primed seeds were sown in a field containing 15 dS m⁻¹ NaCl. Although all three polyamines were effective in improving shoot growth and grain yield in both cultivars under saline conditions, the effect of spermine was very pronounced particularly in improving grain yield. Different priming agents did not affect the net CO₂ assimilation rate and transpiration rate of either cultivar. However, pre-treatment with spermidine increased stomatal conductance (g_s) in the tolerant cultivar, whereas with spermine stomatal conductance decreased in the intolerant cultivar under salt stress. Priming agents had different effects on the accumulation of different ions in wheat plant tissues. When spermidine and distilled water were used as priming agents, they were effective in reducing shoot [Na⁺] in the tolerant and intolerant cultivars, respectively under saline conditions. Although all priming agents caused an increase in shoot [K⁺], distilled water was more effective in improving shoot [K⁺] in both cultivars under salt stress. Pre-treatment with spermidine was very effective in reducing shoot [Cl⁻] under saline conditions particularly in the tolerant cultivar. However, the pattern of accumulation of different ions in roots due to different seed priming treatments was not consistent in either cultivar except that root Na⁺ decreased due to priming with spermine and spermidine in the intolerant and tolerant cultivars under saline conditions. In conclusion, although all three priming agents, spermine, spermidine and putrescine, were effective in alleviating the adverse effect of salt stress on wheat plants, their effects on altering the concentration of different ions and growth were different in the two cultivars differing in salt tolerance.