盐胁迫环境下不同抗盐性小麦品种幼苗长势和内源激素的变化

采用两种浓度NaCl溶液,对不同抗盐性小麦品种德抗961(抗盐性强)和泰山9818(抗盐性弱)萌发期幼苗进行胁迫处理,观察其幼苗长势和内源激素含量变化.结果表明,盐胁迫抑制小麦幼苗生长,抗盐性弱的泰山9818受抑制较重.苗、根ABA含量随盐胁迫浓度增加而提高,泰山9818的增幅高于德抗961.苗、根IAA含量随盐胁迫浓度增加而降低,但德抗961的IAA含量高于泰山9818,说明盐胁迫下抗盐性强的品种具有较高IAA合成量.2品种GA3含量变化因盐胁迫浓度而异.在低盐胁迫下抗盐性强的品种苗中GA3含量提高以适应盐胁迫利于苗的生长,在高盐胁迫下2品种GA3含量降低.盐胁迫使苗中ZR含量增加,且德抗961的苗中ZR含量高于泰山9818,而根中ZR含量则前者低,说明盐胁迫下抗盐性强的品种可迅速将根部合成的ZR向苗中转移,促进苗的生长.2品种IAA/ABA、GA3/ABA比值随盐胁迫浓度增加和时间延长而下降,德抗961 IAA/ABA比值大于泰山9818.在盐胁迫下,抗盐性强的品种协调自身激素平衡的能力较强可能是其生长受抑制较小的重要原因.     

Abscisic acid, indole-3-acetic acid and mineral–nutrient changes induced by drought and salinity in longan (Dimocarpus longan Lour.) plants

Longan species (Dimocarpus longan Lour.) exhibit a high agronomic potential in many subtropical regions worldwide; however, little is known about its responses to abiotic stress conditions. Drought and salinity are the most environmental factors inducing negative effects on plant growth and development. In order to elucidate the responses of longan to drought and salinity, seedlings were grown under conditions of drought and salt stresses. Drought was imposed by suspending water supply leading to progressive soil dehydration, and salinity was induced using two concentrations of NaCl, 100 and 150 mM in water solution, for 64 days. Data showed that salt concentrations increased foliar abscisic acid (ABA) and only 150 mM NaCl reduced indole-3-acetic acid (IAA) and increased proline levels. NaCl treatments also increased Na⁺ and Cl^? content in plant organs proportionally to salt concentration. Drought increased leaf ABA but did not change IAA concentrations, and also increased proline synthesis. In addition, drought and salt stresses reduced the photosynthesis performance; however, only drought decreased leaf growth and relative leaf water content. Overall, data indicate that under severe salt stress, high ABA accumulation was accompanied by a reduction of IAA levels; however, drought strongly increased ABA but did not change IAA concentrations. Moreover, drought and high salinity similarly increased (or maintained) ion levels and proline synthesis. Data also suggest that ABA accumulation may mitigate the impact of salt stress through inducing stomatal closure and delaying water loss, but did not mediate the effects of long-term drought conditions probably because leaves reached a strong dehydration and the role of ABA at this stage was not effective to detain leaf injuries.     

施用有机肥环境下盐胁迫小麦幼苗长势和内源激素的变化

在盆栽条件下,研究了不同浓度NaCl处理下,底施不同施用量有机肥小麦品种豫麦49-198幼苗的生长变化,在此基础上,选择出合适的NaCl处理浓度和有机肥施用量区间,并对此情况下小麦幼苗苗和根中内源激素含量和比例的变化进行了测定,以揭示其耐盐差异机制。结果表明,15000-35000 kg/hm²施用量有机肥处理明显减轻NaCl浓度为150 mmol/L的盐胁迫,其中25000 kg/hm²有机肥处理效果最明显;45000 kg/hm²以上的有机肥处理对幼苗生长抑制无明显缓解作用;当NaCl浓度为450 mmol/L时,各种施用量的有机肥处理均不能减轻盐胁迫对幼苗生长的抑制。150 mmol/L NaCl胁迫下,不同施用量有机肥处理,分别为对照(不施肥)、低施用量(15000 kg/hm²)、中施用量(25000 kg/hm²)和高施用量(35000 kg/hm²)的有机肥,土壤盐度的增加量随有机肥用量增加而上升,对小麦幼苗生长的抑制作用得到缓解,以25000 kg/hm²有机肥处理缓解作用最强。有机肥处理下盐胁迫小麦幼苗苗和根中ABA含量的增加得到显著缓解,IAA和GAs的含量比不施有机肥的对照有不同程度的提高, 说明盐胁迫下有机肥处理小麦幼苗具有较高IAA和GAs合成量。盐胁迫下有机肥处理使苗中ZR的含量较高而根中则较低,说明抗盐性较强的有机肥处理可迅速将根部合成的ZR向苗中转移,促进苗的生长。盐胁迫下有机肥处理的IAA/ABA、GAs/ABA、ZR/ABA的比值也有不同程度提高。在盐胁迫下,有机肥处理尤其是在25000 kg/hm²施用量时,小麦幼苗协调自身激素平衡的能力较强可能是其生长受抑制较小的重要原因。     

Seed Treatment with Auxins Modulates Growth and Ion Partitioning in Salt-stressed Wheat Plants

Experiments were performed to determine whether seed priming with different concentrations （100, 150, and 200 mg/L） of auxins （indoleacetic acid （IAA）, indolebutyric acid （IBA）, or their precursor tryptophane （Trp）） could alter salinity induced perturbances in salicylic acid and ion concentrations and, hence, growth in wheat （Triticum aestivum L.） cultivars, namely M.H.-97 （salt intolerant） and tnqtab-91 （salt tolerant）. Primed and non-primed seeds were sown in Petri dishes in a growth room, as well as in a field treated with 15 dS/m NaCl salinity. All priming agents, except IBA, increased the final germination percentage in both cultivars. The seedlings of either cultivar raised from Trp-treated seeds had greater dry biomass when under salt stress. In field experiments, Trp priming was much more effective in mediating the increase in grain yield, irrespective of the cultivar, under salt stress. The alleviatory effect of Trp was found to be associated with reduced uptake of Na^＋ in the roots and subsequent translocation to the shoots, as well as increased partitioning of Ca^＋ in the roots of salt-stressed wheat plants. Plants of both cultivars raised from Trp-and IAA-treated seeds accumulated free salicylic acid in their leaves when under salt stress. Overall, the Trp priming-induced improvement in germination and the subsequent growth of wheat plants could be related to ion homeostasis when under salt stress. The possible involvement of salicylic acid in the Trp priming-induced better growth under Conditions of salt stress is discussed.     

Seed Treatment with Auxins Modulates Growth and Ion Partitioning in Salt-stressed Wheat Plants

Experiments were performed to determine whether seed priming with different concentrations (100, 150, and 200 mg/L) ofauxins (indoleacetic acid (IAA), indolebutyric acid (IBA), or their precursor tryptophane (Trp)) could alter salinity inducedperturbances in salicylic acid and ion concentrations and, hence, growth in wheat (Triticum aestivum L.) cultivars, namelyM. H.-97 (salt intolerant) and Inqlab-91 (salt tolerant). Primed and non-primed seeds were sown in Petri dishes in a growthroom, as well as in a field treated with 15 dS/m NaCl salinity. All priming agents, except IBA, increased the final germinationpercentage in both cultivars. The seedlings of either cultivar raised from Trp-treated seeds had greater dry biomass whenunder salt stress. In field experiments, Trp priming was much more effective in mediating the increase in grain yield,irrespective of the cultivar, under salt stress. The alleviatory effect of Trp was found to be associated with reduced uptakeof Na~ in the roots and subsequent translocation to the shoots, as well as increased partitioning of Ca~(2 )in the roots ofsalt-stressed wheat plants. Plants of both cultivars raised from Trp-and IAA-treated seeds accumulated free salicylic acidin their leaves when under salt stress. Overall, the Trp priming-induced improvement in germination and the subsequentgrowth of wheat plants could be related to ion homeostasis when under salt stress. The possible involvement of salicylicacid in the Trp priming-induced better growth under conditions of salt stress is discussed.     

Effect of plant growth promoting Bacillus subtilis and Pseudomonas fluorescens on growth and pigment composition of radish plants (Raphanus sativus) under NaCl stress

Soil salinity is one of the most severe factors limiting growth and physiological response in Raphanus sativus. In this study, the possible role of plant growth promoting bacteria (PGPB) in alleviating soil salinity stress during plant growth under greenhouse conditions was investigated. Increasing salinity in the soil decreased plant growth, photosynthetic pigments content, phytohormones contents (indole-3-acetic acid, IAA and gibberellic acid, GA₃) and mineral uptake compared to soil without salinity. Seeds inoculated with Bacillus subtilis and Pseudomonas fluorescens caused significantly increase in fresh and dry masses of roots and leaves, photosynthetic pigments, proline, total free amino acids and crude protein contents compared to noninoculated ones under salinity. The bacteria also increased phytohormones contents (IAA and GA₃) and the contents of N, P, K⁺, Ca²⁺, and Mg²⁺ but decreased ABA contents and Na⁺ and Cl^? content which may contribute in part to activation of processes involved in the alleviation of the effect of salt.     

Salt resistance is determined by osmotic adjustment and abscisic acid in newly developed maize hybrids in the first phase of salt stress

This study investigated the mechanisms of salt resistance of four maize (Zea mays L.) hybrids [cultivar (cv.) Pioneer 3906 and newly developed hybrids SR03, SR12 and SR13] during the first phase of salt stress. Plants were grown in aerated nutrient solutions at 1 mM Na+ (control) and 100 mM Na+ (salt stress). Stress was imposed in 25 mM steps and plants were harvested after 2 days at 100 mM Na+. At 100 mM Na+ the area of the fourth leaf, which developed under salt stress, did not change significantly in SR03 and SR12 whereas significant reductions were observed in cv. Pioneer 3906 and SR13. Concentrations of assimilates (i.e. glucose, fructose and sucrose) in the shoot sap were significantly greater under salt stress in SR03 and SR12. However, the greater assimilate supply was not responsible for their salt resistance as there were no significant reductions in assimilate concentrations even in the other two genotypes. Shoot turgor and growth were maintained in SR03 and SR12 at 100 mM Na+ through significant increases in osmolality of the shoot sap. Concentrations of free ABA and ABA-glucose esters (ABA-GE) in the growing region of the fourth leaf increased significantly under salt stress in all genotypes. Leaf area at 100 mM Na(+), expressed as a percentage of that at 1 mM, showed significant positive relationships with free ABA (R(2) = 0.62) and the sum of free ABA and ABA-GE (R(2) = 0.65). Results of this study indicate clearly that a combination of partial osmotic adjustment, a possible reduction of the sensitivity of leaf growth under salt stress to increased ABA concentrations and a growth-promoting function regulated by ABA is responsible for salt resistance in the first phase of salt stress. Genotypic variation in these mechanisms can be utilized to breed salt-resistant genotypes in maize.     

Abscisic acid root and leaf concentration in relation to biomass partitioning in salinized tomato plants

Salinization is one of the most important causes of crop productivity reduction in many areas of the world. Mechanisms that control leaf growth and shoot development under the osmotic phase of salinity are still obscure, and opinions differ regarding the Abscisic acid (ABA) role in regulation of biomass allocation under salt stress. ABA concentration in roots and leaves was analyzed in a genotype of processing tomato under two increasing levels of salinity stress for five weeks: 100 mM NaCl (S10) and 150 mM NaCl (S15), to study the effect of ABA changes on leaf gas exchange and dry matter partitioning of this crop under salinity conditions. In S15, salinization decreased dry matter by 78% and induced significant increases of Na⁺ and Cl⁻ in both leaves and roots. Dry matter allocated in different parts of plant was significantly different in salt-stressed treatments, as salinization increased root/shoot ratio 2-fold in S15 and 3-fold in S15 compared to the control. Total leaf water potential (Ψ_w) decreased from an average value of approximately −1.0 MPa, measured on control plants and S10, to −1.17 MPa in S15. In S15, photosynthesis was reduced by 23% and stomatal conductance decreased by 61%. Moreover, salinity induced ABA accumulation both in tomato leaves and roots of the more stressed treatment (S15), where ABA level was higher in roots than in leaves (550 and 312 ng g⁻¹ fresh weight, respectively). Our results suggest that the dynamics of ABA and ion accumulation in tomato leaves significantly affected both growth and gas exchange-related parameters in tomato. In particular, ABA appeared to be involved in the tomato salinity response and could play an important role in dry matter partitioning between roots and shoots of tomato plants subjected to salt stress.     

Effect of ABA on the contents of proline, polyamines, and cytokinins in the common ice plants under salt stress

The effects of ABA treatment on the contents of proline, polyamines (PA), and cytokinins (CK) in the facultative halophyte the common ice plant (Mesembryanthemum crystallinum L.) subjected to salt stress were studied. Plants grown in the phytotron chamber on Jonson nutrient medium for 6 weeks were subjected to 6-day-long salinity by a single NaCl adding to medium. During first three days of salinity, half plants of each treatment were placed for 30 min on nutrient medium containing 0, 100, or 300 mM NaCl plus ABA in the final concentration of 1 μM. Salinity reduced biomass accumulation and water and chlorophyll contents in plants. This was accompanied by the increase in the levels of MDA, proline, and sodium ions. ABA treatment of salt-stressed plants favored biomass accumulation and photosynthetic pigment protection, reduced the intensity of oxidative stress and the level of NaCl-induced proline accumulation. ABA treatment increased the contents of putrescine (Put) and spermidine (Spd) in the leaves and roots of control plants (not subjected to salt stress), reduced the losses of Put in the leaves and roots and Spd in the roots in the presence of 100 mM NaCl, and suppressed cadaverine (Cad) accumulation in the roots in the presence of 300 mM NaCl. In the presence of NaCl, ABA reduced the contents of zeatin and zeatin riboside and increased the level of zeatin-O-glucoside in the roots and isopentenyladenosine and isopentenyladenine in the leaves. Thus, ABA protective action under salinity can be realized through the weakening of oxidative stress (a decrease in MDA content) and the regulation of PA, proline, and CK metabolism, which has a great significance in plant adaptation to injurious factors.     

Silicon improves salinity tolerance and affects ammonia assimilation in maize roots

The present study was conducted to evaluate the effect of different salt concentrations (50 and 200 mM NaCl) on growth, permeability properties (electrolyte leakage, cell viability) and activity of glutamine synthetase (GS) and glutamate dehydrogenase (GDH) in roots of maize seedlings. Both salt concentrations significantly affected growth and permeability properties of maize seedling roots and this negative effect increased with concentration of salt and duration of experiments. On the other hand salinity induced only small changes in the activities of GS and GDH, usually small increase in the activity was observed. To characterise the possible protective effect of silicon (Si) on maize roots exposed to saline stress, different concentrations of Si were simultaneously applied to both, low (50 mM) and high (200 mM) salt concentrations. Possible protective effects of Si on studied parameters were analysed in time range of 3 days treatment with the most positive effect on salt-induced root growth inhibition at high salt concentration and electrolyte leakage. The results show significant increase in GDH activity under all the tested conditions, although the mechanisms underlying this increase have not been elucidated. The results indicate that silicon may ameliorate the salt-induced root growth inhibition and increase the plant vigour at stressful conditions.     

Hormonal responses of nodulated Medicago ciliaris lines differing in salt tolerance

Hormonal changes in two Medicago ciliaris lines differing in salt tolerance (TNC 1.8 being more tolerant than TNC 11.9) were studied as possible regulators of growth and symbiotic nitrogen fixation (SNF). After 21 days of saline treatment (100 mM NaCl), four major phytohormones (abscisic acid, ABA; the cytokinin trans-zeatin, t-Z; the auxin indole-3-acetic acid, IAA; and the ethylene precursor 1-aminocyclopropane-1-carboxylic acid, ACC) were analysed. Salinity differently affected hormone concentrations in vegetative tissues and nodules in both lines. Principal component analysis (PCA) revealed that growth and SNF parameters under salinity were inversely correlated to the amount of reduced nitrogen (Nred) allocated to the roots and nodules, to the sucrolytic activity (TSA) in the roots, and to the t-Z and ABA concentration in the nodules. However, those parameters were positively associated along PC1 to the Nred and TSA in the leaves and all the hormones analysed in the roots. Interestingly, the ACC concentration of all organs was positively associated with vegetative growth and with SNF under salinity, as a putative regulator of the symbiotic-parasitic relation with the bacteria. The influence of hormonal changes in relation to plant growth, SNF and symbiotic relation is discussed.     

The response of Mo-hydroxylases and abscisic acid to salinity in wheat genotypes with differing salt tolerances

The differential responses of the wheat cultivars Shi4185 and Yumai47 to salinity were studied. The higher sensitivity of Yumai47 to salinity was linked to a greater growth reduction under salt stress, compared to more salt-tolerant Shi4185. Salinity increased the Na⁺, proline and superoxide anion radical (O₂ ^?) contents in both cultivars. Leaf Na⁺ content increased less in the more salt-tolerant cultivar Shi4185 than salt-sensitive Yumai47. The proline content increased more significantly in Shi4185 than Yumai47; on the contrary, superoxide anion radical content increased less in Shi4185 than Yumai47. This data indicated that wheat salinity tolerance can be increased by controlling Na⁺ transport from the root to shoot, associated with higher osmotic adjustment capability and antioxidant activity. Although salinity increased aldehyde oxidase (AO) activity and abscisic acid (ABA) content in the leaves and roots of both cultivars following the addition of NaCl to the growth medium, AO and ABA increased more in the salt-sensitive cultivar Yumai47 than the more salt-tolerant cultivar Shi4185. Xanthine dehydrogenase (XDH) activity in the leaves of both cultivars increased with increasing concentrations of NaCl; however, leaf XDH activity increased more significantly in Yumai47 than Shi4185. Root XDH activity in Shi4185 decreased with increasing NaCl concentrations, whereas salinity induced an increased root XDH activity in Yumai47. The involvement of AO and XDH enzymatic activities and altered ABA content in the response mechanisms of wheat to salinity are discussed herein.     

Does Seed Priming Induce Changes in the Levels of Some Endogenous Plant Hormones in Hexaploid Wheat Plants Under Salt Stress？

In order to assess whether salt tolerance could be Improved In spring wheat （Triticum aestivum L.）, the present study was performed by soaking the seeds of two cultlvars, namely MH-97 （salt sensitive） and Inqlab-91 （salt tolerant）, for 12 h In distilled water or 100 mol/m^3 CaCl2, KCI, or NaCI. Primed seeds from each treatment group and non-primed seeds were sown In a field In which NaCI salinity of 15 dS/m was developed. Priming of seeds with CaCl2, followed by priming with KCI and NaCI, was found to be effective In alleviating the adverse effects of salt stress on both wheat cultivars In terms of shoot fresh and dry weights and grain yield. Priming with CaCl2 alleviated the adverse effects of salt stress on hormonal balance In plants of both cultlvars. In MH-97 plants, CaCl2 pretreatment considerably reduced leaf absclslc acid （ABA） concentrations and Increased leaf free salicylic acid （SA） concentrations under both saline and non-saline conditions. In contrast, In the Inqlab-91 plant, CaCl2 Increased free Indoleacetic acid （IAA） and indolebutyrlc acid （IBA） content. However, priming of seeds with CaCl2 did not alter free polyamlne levels in either cultlvar, although spermldlne levels were considerably lower In plants raised from seeds treated with CaCl2 for both cultlvars under saline conditions. Priming with KCI Increased growth In Inqlab-91 plants, but not In MH-97 plants, under saline conditions. The salinity Induced reducUon In auxins （IAA and IBA） was alleviated by NaCI priming In both cultlvars under saline conditions. However, NaCI Increased leaf free ABA content and lowered leaf SA and putresclne levels In Inqlab-91 plants under saline conditions. In conclusion, although all three priming agents （I.e. CaCl2, KCI, and NaCI） were effective In alleviating the adverse effects of salt stress on wheat plants, their effects on altering the levels of different plant hormones were different In the two cuItlvars.     

Effects of abscisic acid on the contents of polyamines and proline in common bean plants under salt stress

The effects of ABA treatment on the contents of polyamines (PAs) and proline (Pro) in the glycophyte Phaseolus vulgaris L. during plant adaptation to salt stress were studied. Two-week-old common bean seedlings grown in the phytotron chamber on the Jonson nutrient medium were subjected to salinity for 6 days by one-time NaCl addition to medium up to final concentrations of 50 and 100 mM. During first three days of salinity, the root system was daily treated with ABA (1, 5, 10, or 50 μM) for 30 min. Salt stress (100 mM NaCl) elevated the level of endogenous ABA, increased the content of Pro 14-fold, reduced sharply the content of free PAs (putrescine, spermidine, spermine, and cadaverine), and the accumulation of 1,3-diaminopropan, a product of oxidation of high-molecular PAs. Common bean plant treatment with 1 μM ABA weakened the adverse effects of salt stress (100 mM NaCl), which was manifested in the maintenance of plant growth, stimulation of chlorophyll (a and b) and carotenoid accumulation, a stabilization of water and Na⁺ balance. Seedling treatment with ABA suppressed NaCl-induced Pro and intracellular ABA accumulation and restored the levels of putrescine and spermidine. The content of spermine in the leaves of plants subjected to salt stress and treated with ABA was approximately threefold higher than in control plants, whereas the content of cadaverine increased under similar conditions more than fivefold. Simultaneously, the contents of 1,3-diaminopropan and malondialdehyde as well as activity of superoxide dismutase were reduced, which indicates a weakening of oxidative stress, one of the possible causes of defensive ABA effects against salt stress. In addition, the suppression by exogenous ABA of Pro accumulation and stimulation of PA content under salt stress confirm indirectly our hypothesis that ABA is involved in the coordinated regulation of two biosynthetic pathways, Pro and PA formation, which use a common precursor, glutamate, and play an important protective role during stress in plants.     

Indole-3-butyric acid in plant growth and development

Within the last ten years it has been established by GC-MS thatindole-3-butyric acid (IBA) is an endogenous compound in a variety ofplant species. When applied exogenously, IBA has a variety of differenteffects on plant growth and development, but the compound is stillmainly used for the induction of adventitious roots. Using moleculartechniques, several genes have been isolated that are induced duringadventitious root formation by IBA. The biosynthesis of IBA in maize(Zea mays L.) involves IAA as the direct precursor. Microsomalmembranes from maize are able to convert IAA to IBA using ATP andacetyl-CoA as cofactors. The enzyme catalyzing this reaction wascharacterized from maize seedlings and partially purified. The invitro biosynthesis of IBA seems to be regulated by several externaland internal factors: i) Microsomal membranes from light-grownmaize seedlings directly synthesize IBA, whereas microsomal membranesfrom dark-grown maize plants release an as yet unknown reaction product,which is converted to IBA in a second step. ii) Drought and osmoticstress increase the biosynthesis of IBA maybe via the increaseof endogenous ABA, because application of ABA also results in elevatedlevels of IBA. iii) IBA synthesis is specifically increased byherbicides of the sethoxydim group. iv) IBA and IBA synthesizingactivity are enhanced during the colonization of maize roots with themycorrhizal fungus Glomus intraradices. The role of IBA forcertain developmental processes in plants is discussed and somearguments presented that IBA is per se an auxin and does notact via the conversion to IAA.     

盐生植物海滨锦葵幼苗盐胁迫下基因差异表达分析

利用cDNA-AFLP技术对海滨锦葵幼苗盐胁迫下叶片和根部的基因差异表达模式进行分析和比较, 并对部分盐胁迫应答的转录衍生片段进行了回收、测序和功能推测, 以从转录水平分析海滨锦葵的耐盐分子机制。结果显示：(1) 盐胁迫下海滨锦葵幼苗叶片和根部的基因差异表达多以量的变化为主, 包括盐胁迫下基因表达上调、下调或随盐处理浓度高低和胁迫时间长短而波动的差异表达模式; 只有少量基因的差异表达表现出质的变化, 如盐胁迫下基因沉默或诱导表达; (2) 仅在盐胁迫处理2 h的海滨锦葵幼苗根部, 基因的差异表达以质的变化为主的类型比例略高于量的变化类型比例; (3) 盐胁迫应答基因在不同组织中上调、下调、诱导或沉默的比例随胁迫处理时段而动态变化, 在刚胁迫时基因表达的差异加剧, 而后随胁迫处理时段的延长而渐趋稳定。结果预示, 从基因表达水平探讨植物的耐盐分子机理, 尽管有一定的规律可循, 但由于不同组织对盐胁迫的应答是动态变化的过程, 海滨锦葵不同组织在盐胁迫不同阶段的基因时、空、序表达特征并没有固定的程式。对部分盐胁迫下上调或诱导表达的转录衍生片段(Trivially distributed file system, TDFs)进行的序列分析和功能推测表明, 苗期海滨锦葵在盐胁迫下应答基因至少涉及3类：(1) 离子平衡重建或减少胁迫损伤相关基因(特别是运转蛋白类); (2) 恢复盐胁迫下植物生长和发育相关基因：如参与能量合成和激素调节途径相关基因等; (3)信号转导相关基因及功能未确定的新基因。文章并对盐胁迫应答基因的差异表达模式与海滨锦葵的耐盐性关系进行了讨论。     

The Method of ABA Application Affects Salt Stress Responses in Resistant and Sensitive Potato Lines

The phytohormone abscisic acid (ABA) has been proposed to act as a mediator in plant responses to a range of stresses, including salt stress. Most studies of ABA response apply ABA as a single dose. This may not resemble the prolonged increasing endogenous ABA levels that can occur in association with slowly increasing salinity stresses in nature or field situations. Salt stress response based on method of ABA application was examined in four potato genotypes of varying salt stress resistance: the sensitive ABA-deficient mutant and its normal sibling, a resistant genotype line 9506, and commercial cultivar ‘Norland’ of moderate resistance. ABA was applied by root drench at 0, 50, 75, or 100 μM concentrations through a single dose, or by slowly increasing multiple ABA doses in a sand-based growing system under greenhouse conditions. Salt tolerance was then evaluated after 2 weeks of exposure to 150–180 mM NaCl stress. The method of ABA application had a marked effect on the responses to salt stress. Plant responses to the method of ABA application were differentiated according to (1) growth rate, (2) root water content, and (3) apparent shoot growth response. Under a single dose, growth rate increased in all genotypes under salt stress, whereas slowly increasing multiple ABA applications generally maintained stable growth rates except in the ABA-deficient mutant where there was an upward growth trend. Percent root water content was elevated only under slowly increasing multiple ABA doses in two genotypes, whereas none of the single-dose treatments induced any change. The single ABA dose enhanced vertical growth, whereas the slowly increasing multiple ABA dose applications enhanced lateral shoot growth. Because exogenous application is still an artificial system, endogenous ABA was supplied through grafting of ABA-deficient mutant scions onto rootstocks with known elevated ABA levels. Multiple exogenous ABA applications as low as 50 μM elicited similar shoot water content responses as grafting treatments without ABA application in the mutant genotype but had no effect on the ABA normal sibling. Shoot dry weight was significantly increased through grafting over all exogenous ABA treatments. Our study further indicates that the method of ABA application regime in itself can alter plant responses under salt stress and that certain application regimes may reflect responses to elevated endogenous levels of ABA.     

The <Emphasis Type="Italic">trans</Emphasis> and <Emphasis Type="Italic">cis</Emphasis> zeatin isomers play different roles in regulating growth inhibition induced by high nitrate concentrations in maize

Abscisic acid (ABA), auxins, and cytokinins (CKs) are known to be closely linked to nitrogen signaling. In particular, CKs control the effects of nitrate availability on plant growth. Our group has shown that treatment with high nitrate concentrations limits root growth and leaf development in maize, and conditions the development of younger roots and leaves. CKs also affect source-sink relationships in plants. Based on these results, we hypothesized that CKs regulate the source-sink relationship in maize via a mechanism involving complex crosstalk with the main auxin indole-3-acetic acid (IAA) and ABA. To evaluate this hypothesis, various CK metabolites, IAA, and ABA were quantified in the roots and in source and sink leaves of maize plants treated with high and normal nitrate concentrations. The data obtained suggest that the cis and trans isomers of zeatin play completely distinct roles in maize growth regulation by a complex crosstalk with IAA and ABA. We demonstrate that while trans-zeatin (tZ) and isopentenyladenine (iP) regulate nitrate uptake and thus control final leaf sizes, cis-zeatin (cZ) regulates source and sink strength, and thus controls leaf development. The implications of these findings relating to the roles of ABA and IAA in plants’ responses to varying nitrate concentrations are also discussed.