Characterization of rhizobacterial strain Rs-2 with ACC deaminase activity and its performance in promoting cotton growth under salinity stress

A plant growth-promoting rhizobacterial strain Rs-2 with 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity was isolated from salinized soils using ACC as the sole nitrogen source. Based on its physiological and biochemical properties and 16S rDNA sequence analysis, this strain was identified as Raoultella planticola. The maximum value of nitrogen fixation, dissolved phosphorus and dissolved potassium of Rs-2 were 148.8 μg/ml, 205.0 and 4.31 mg/l, respectively within 192 h liquid culture. The germination rate of cotton seeds (Gossypium hirsutum L.) inoculated with Rs-2 (Rs-2-S) was enhanced by 29.5 % in pot experiments compared with that of the control (CK-S). Subsequently, individual plant height, fresh weight and dry weight of cotton seedlings in Rs-2-S treatment increased by 15.0, 33.7 and 33.3 %, respectively, compared with those in CK-S treatment. Statistical analysis showed that the inoculums of Rs-2 promoted significantly (P < 0.05) cotton growth. Further analysis showed that Rs-2 reduced the quantities of ethylene and abscisic acid in cotton seedlings, and increased indole acetic acid content in cotton seedlings under salinity stress. The accumulation of N, P, K(+), Ca(2+) and Fe(2+) in the cotton plants was increased significantly (P < 0.05) in Rs-2-S treatment, whereas the uptake of Na(+) in cotton seedlings decreased (P < 0.05). Hence, the present observations suggested that R. planticola Rs-2 could have a promising potential for promoting cotton growth and alleviating salinity stress.     

根系盐胁迫对盐生植物和甜土植物的幼苗生长及矿质元素分布的影响

为了解盐胁迫对植物的影响, 研究了根系NaCl 胁迫在温室条件下对盐生植物榄仁(Terminalia catappa)和甜土植物枇杷(Eriobotrya japonica)幼苗生长、矿质元素和灰分含量的影响。结果表明:在根系盐胁迫下, 两种植物幼苗的叶片病斑多分布于中心区, 灰分含量增加, 幼苗的Na⁺-Cl^- 呈极显著的正相关关系, 盐胁迫对两种植物幼苗的5 种矿质元素(Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl^-)含量影响不大, 但它们在植物中的分布发生了变化。可见, 盐生植物和甜土植物抗盐性的区别是量上的不同, 没有质的差别。     

Seed enhancement with cytokinins: changes in growth and grain yield in salt stressed wheat plants

Cytokinins are often considered abscisic acid (ABA) antagonists and auxins antagonists/synergists in various processes in plants. Seed enhancement (seed priming) with cytokinins is reported to increase plant salt tolerance. It was hypothesized that cytokinins could increase salt tolerance in wheat plants by interacting with other plant hormones, especially auxins and ABA. The present studies were therefore conducted to assess the effects of pre-sowing seed treatment with varying concentrations (100, 150 and 200 mg l⁻¹) of cytokinins (kinetin and benzylaminopurine (BAP)) on germination, growth, and concentrations of free endogenous auxins and ABA in two hexaploid spring wheat (Triticum aestivum L.) cultivars. The primed and non-primed seeds of MH-97 (salt-intolerant) and Inqlab-91 (salt-tolerant) were sown in both Petri dishes in a growth room and in the field after treatment with 15 dS m⁻¹ NaCl salinity. Both experiments were repeated during 2002 and 2003. Among priming agents, kinetin was effective in increasing germination rate in the salt-intolerant and early seedling growth in the salt-tolerant cultivar when compared with hydropriming under salt stress. Thus, during germination and early seedling growth, the cytokinin-priming induced effects were cultivar specific. In contrast, kinetin-priming showed a consistent promoting effect in the field and improved growth and grain yield in both cultivars under salt stress. The BAP-priming did not alleviate the inhibitory effects of salinity stress on the germination and early seedling growth in both cultivars. The increase in growth and grain yield in both cultivars was positively correlated with leaf indoleacetic acid concentration and negatively with ABA concentration under both saline and non-saline conditions. The decrease in ABA concentration in the plants raised from kinetin-primed seeds might reflect diminishing influence of salt stress. However, the possibility of involvement of other hormonal interactions is discussed.     

外源5-氨基乙酰丙酸对盐胁迫下菘蓝种子萌发及幼苗抗氧化酶活性的影响

采用砂培方式,研究了外源5-氨基乙酰丙酸(ALA)对盐胁迫下菘蓝种子的萌发、幼苗叶片的可溶性糖含量、丙二醛(MDA)含量及其抗氧化酶活性的影响,探讨ALA缓解菘蓝受盐胁迫伤害的响应机制。结果显示:(1)菘蓝种子萌发及幼苗生长在100 mmol·L^-1 NaCl胁迫下受到明显的抑制,种子发芽率、发芽势、发芽指数、活力指数与自然含水量均显著降低,丙二醛含量、可溶性糖含量以及超氧化物歧化酶(SOD)、过氧化物酶(POD)活性显著升高。(2)盐胁迫下适宜浓度的ALA处理显著提高了种子萌发率、自然含水量及SOD、POD和CAT活性,降低了可溶性糖和丙二醛的含量,并以16.7 mg·L^-1 ALA处理盐胁迫下菘蓝种子的发芽率、发芽势最大,其幼苗的SOD、POD、CAT活性最强。研究表明,盐胁迫显著抑制菘蓝种子的萌发及幼苗生长,适宜浓度的ALA能够有效缓解盐胁迫对菘蓝种子萌发及幼苗生长的伤害,提高植株的抗盐性,并以16.7 mg·L^-1 ALA处理效果最佳。     

Increased glycine betaine synthesis and salinity tolerance in AhCMO transgenic cotton lines

Glycine betaine is an osmoprotectant that plays an important role and accumulates rapidly in many plants during salinity or drought stress. Choline monooxygenase (CMO) is a major catalyst in the synthesis of glycine betaine. In our previous study, a CMO gene (AhCMO) cloned from Atriplex hortensis was introduced into cotton (Gossypium hirsutum L.) via Agrobacterium mediation to enhance resistance to salinity stress. However, there is little or no knowledge of the salinity tolerance of the transgenic plants, particularly under saline-field conditions. In the present study, two transgenic AhCMO cotton lines of the T₃ generation were used to study the AhCMO gene expression, and to determine their salinity tolerance in both greenhouse and field under salinity stress. Molecular analysis confirmed that the transgenic plants expressed the AhCMO gene. Greenhouse study showed that on average, seedlings of the transgenic lines accumulated 26 and 131% more glycine betaine than those of non-transgenic plants (SM3) under normal and salt-stress (150 mmol l⁻¹ NaCl) conditions, respectively. The osmotic potential, electrolyte leakage and malondialdehyde (MDA) accumulation were significantly lower in leaves of the transgenic lines than in those of SM3 after salt stress. The net photosynthesis rate and Fv/Fm in transgenic cotton leaves were less affected by salinity than in non-transgenic cotton leaves. Therefore, transgenic cotton over-expressing AhCMO was more tolerant to salt stress due to elevated accumulation of glycine betaine, which provided greater protection of the cell membrane and photosynthetic capacity than in non-transgenic cotton. The seed cotton yield of the transgenic plants was lower under normal conditions, but was significantly higher than that of non-transgenic plants under salt-stressed field conditions. The results indicate that over-expression of AhCMO in cotton enhanced salt stress tolerance, which is of great value in cotton production in the saline fields.     

Comparative effects of salt and alkali stresses on growth, osmotic adjustment and ionic balance of an alkali-resistant halophyte Suaeda glauca (Bge.)

Effects of salt and alkali stresses on growth, osmotic adjustment and ionic balance of Suaeda glauca (Bge.), an alkali-resistant succulent halophyte, were compared. The results showed that alkali stress clearly inhibited the growth of S. glauca. Moreover, the concentrations of Na⁺ and K⁺ both increased with increasing salinity under both stresses, suggesting no competitive inhibition between absorptions of Na⁺ and K⁺. The mechanism underlying osmotic adjustment during salt stress was similar to alkali stress in shoots. The shared essential features were that organic acids, betaine and inorganic ions (dominated by Na⁺) mostly accumulated. On the other hand, the mechanisms governing ionic balance under both stresses were different. Under salt stress, S. glauca accumulated organic acids and inorganic anions to maintain the intracellular ionic equilibrium, but the anion contribution of inorganic ions was greater than that of organic acids. However, the concentrations of inorganic anions under alkali stress were significantly lower than those under salt stress of the same intensity, suggesting that alkali stress might inhibit uptake of anions, such as NO₃ ^– and H₂PO₄ ^–. Under alkali stress, organic acids were the dominant factor in maintaining ionic equilibrium. The contribution of organic acids to anions was 74.1%, while that of inorganic anions was only 25.9%. S. glauca enhanced the synthesis of organic acids, dominated by oxalic acid, to compensate for the shortage of inorganic anions.     

盐胁迫对竹柳幼苗生理响应及结构解剖的研究

为了解盐胁迫对竹柳(Salix spp.)幼苗生长的影响,采用土培方法,对NaCl胁迫下半年生竹柳扦插苗的成活率、生理响应和根叶部结构进行研究。结果表明,在0.25%Na Cl胁迫(轻度盐胁迫)下竹柳能正常生长,而在0.5%NaCl(中度、重度盐胁迫)下生长受到抑制,推断竹柳的耐盐阈值是0.5%。随着NaCl浓度的增大,叶片相对含水量、叶绿素a含量、叶绿素总含量和叶绿素a/b均呈下降趋势;但叶绿素b含量、脯氨酸含量和MDA含量呈升高趋势。在轻度盐胁迫下,叶片SOD活性和可溶性蛋白含量均升高,在中、重度盐胁迫下显著下降。从根叶解剖结构来看,叶片、角质层、栅栏组织厚度和根部周皮和直径在轻度盐胁迫时最大,但在中度盐胁迫时叶片栅栏组织细胞长度减小且排列越来越疏松,根部输导组织细胞不正常。这表明竹柳在轻度胁迫时具有一定的耐盐性,但在中高度盐胁迫下生长不良。     

Physiological and biochemical parameters for evaluation and clustering of rice cultivars differing in salt tolerance at seedling stage

Salinity tolerance levels and physiological changes were evaluated for twelve rice cultivars, including four white rice and eight black glutinous rice cultivars, during their seedling stage in response to salinity stress at 100 mM NaCl. All the rice cultivars evaluated showed an apparent decrease in growth characteristics and chlorophyll accumulation under salinity stress. By contrast an increase in proline, hydrogen peroxide, peroxidase (POX) activity and anthocyanins were observed for all cultivars. The K⁺/Na⁺ ratios evaluated for all rice cultivars were noted to be highly correlated with the salinity scores thus indicating that the K⁺/Na⁺ ratio serves as a reliable indicator of salt stress tolerance in rice. Principal component analysis (PCA) based on physiological salt tolerance indexes could clearly distinguish rice cultivars into 4 salt tolerance clusters. Noteworthy, in comparison to the salt-sensitive ones, rice cultivars that possessed higher degrees of salt tolerance displayed more enhanced activity of catalase (CAT), a smaller increase in anthocyanin, hydrogen peroxide and proline content but a smaller drop in the K⁺/Na⁺ ratio and chlorophyll accumulation.     

GA signaling and <Emphasis Type="Italic">CO/FT</Emphasis> regulatory module mediate salt-induced late flowering in <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

Flowering timing is very important for the reproductive success of higher plants. However, effects of salt on plant flowering and the underlying molecular mechanisms are largely unknown. Here, we show that salt stress delays flowering in Arabidopsis in a dose-dependent manner. Mild salt stress (≤50 mM NaCl) promoted and prolonged the vegetative growth, whereas high salinity (≥100 mM NaCl) largely delayed or inhibited the transition from vegetative growth to reproductive development. The gibberellin (GA)-pathway plays an important role in this phenotype, and application of exogenous GA could restore late flowering induced by salt. In addition, the CONSTANS (CO)/FLOWERING LOCUS T (FT) module may also play a critical role in mediating the effects of salt on flowering. The mRNA abundance of CO was significantly reduced by salt stress in a dose-dependent manner. The constans (co-2) mutants did not respond to moderate salt stress, whereas over-expressing CO manifested no delay in flowering time in response to salinity. Expression of FT, SOC1 and LFY in the downstream of the pathways was also reduced by salt according to dose. Moreover, salt-sensitive mutant salt overly sensitive3 (sos3) exhibited greater sensitivity in flowering, further suggesting that ion disequilibrium mediates salt-induced late flowering. Kexue Li and Youning Wang contributed equally to this report.     

沙地云杉和青海云杉种子萌发和幼苗生长对干旱盐碱胁迫的响应

利用控制实验研究了水分、盐分生态因子对沙地云杉和青海云杉种子萌发和幼苗生长的影响,以探索沙地云杉和青海云杉种子对水分、盐分生态因子的适应性。结果表明:(1)水分胁迫和盐分胁迫对沙地云杉和青海云杉种子萌发具有明显的抑制作用,可显著的降低种子的发芽率,两种云杉种子对水分胁迫的临界值和极限值分别是-0.03、-0.15 MPa和-0.5、-0.58 MPa;对盐分胁迫的临界值和极限值分别是78、148 mmol/L和284、345mmol/L;其幼苗长度随着渗透势和NaCl浓度的增加而显著减小。(2)沙地云杉和青海云杉种子恢复发芽率及恢复后的幼苗长度随着渗透势和NaCl浓度的增加先增加后减少。(3)在相同的水势条件下,PEG溶液比等渗的NaCl溶液对沙地云杉和青海云杉种子萌发具有更大的抑制作用,种子萌发过程中渗透胁迫比离子毒害的抑制作用更大。研究发现,沙地云杉和青海云杉种子对水分和盐分胁迫表现出不同程度的耐受性,两者对盐分胁迫的忍耐能力超过对水分胁迫;而且青海云杉种子比沙地云杉更耐旱、耐盐;早期的低盐和充分的水分条件是沙地云杉和青海云杉存活的关键。     

Na2SO4和Na2CO3胁迫下苦楝幼苗的形态及光合生理特性

为探索苦楝应对盐胁迫的响应机制,该文以1年生苦楝(Melia azedarach)实生苗为材料,在盆栽条件下设置中性盐Na_2SO_4和碱性盐Na_2CO_33个盐浓度(200、400、600 mmol·L~(-1))处理40 d,研究苦楝的抗盐碱水平及在不同程度盐碱胁迫条件下的生长及光合生理变化。结果表明:随着盐浓度的提高,苦楝的苗高、地径和生物量的增长量均呈现下降趋势,且碱性盐胁迫条件下降程度更大,盐胁迫提高苦楝的根冠比。处理10 d时,苦楝幼苗的所有光合指标随中性盐和碱性盐浓度的提高呈相似的下降特征,碱性盐胁迫条件下的降低幅度显著大于中性盐胁迫,且随处理时间的增加,中性盐和碱性盐处理下苦楝幼苗的净光合速率和蒸腾速率显著降低。随着盐浓度的提高,苦楝的叶绿素含量呈现下降趋势,200 mmol·L~(-1)盐胁迫对叶绿素含量影响较小,400、600 mmol·L~(-1)盐胁迫均对叶绿素含量有显著影响。600 mmol·L~(-1)碱性盐胁迫条件下,苦楝叶片相对电导率和饱和水分亏缺最高,显著高于其余处理。同等浓度下,碱性盐胁迫的苦楝叶片相对电导率和饱和水分亏缺显著高于中性盐胁迫处理。综上结果认为,苦楝具有一定的耐盐碱能力,碱性盐比中性盐对苦楝幼苗的影响更大。     

Phosphatidylinositol‐hydrolyzing phospholipase C4 modulates rice response to salt and drought

Phosphatidylinositol‐specific phospholipase C (PI‐PLC) is involved in stress signalling but its signalling function remains largely unknown in crop plants. Here, we report that the PI‐PLC4 from rice (Oryza sativa cv), OsPLC4, plays a positive role in osmotic stress response. Two independent knockout mutants, plc4‐1 and plc4‐2, exhibited decreased seedling growth and survival rate whereas overexpression of OsPLC4 improved survival rate under high salinity and water deficiency, compared with wild type (WT). OsPLC4 hydrolyses PI, phosphatidylinositol 4‐phosphate (PI4P), and phosphatidylinositol‐4,5‐bisphosphate (PIP₂) to generate diacylglycerol (DAG) in vitro. Knockout of OsPLC4 attenuated salt‐induced increase of phosphatidic acid (PA) whereas overexpression of OsPLC4 decreased the level of PI4P and PIP₂ under salt treatment. Applications of DAG or PA restored the growth defect of plc4‐1 to WT but DAG kinase inhibitor 1 blocked the complementary effect of DAG in plc4‐1 under salt stress. In addition, the loss of OsPLC4 compromised the increase of inositol triphosphate and free cytoplasmic Ca²⁺ ([Ca²⁺]_cyt) and inhibited the induction of genes involved in Ca²⁺ sensor and osmotic stress response to salt stress. The results indicate that OsPLC4 modulates the activity of two signalling pathways, PA and Ca²⁺, to affect rice seedling response to osmotic stress.     

Effects of salinity on growth and compatible solutes of callus induced from <Emphasis Type="Italic">Populus euphratica</Emphasis>

Summary The present study aimed to evaluate the response to salinity of Populus euphratica, which is more salt-resistant than other poplar cultivars, at the cellular level. To this purpose, callus was induced from shoot segments of P. euphratica on Murashige and Skoog (MS) medium supplemented with 0.5 mg l⁻¹ (2.2 μM) 6-benzyladenine (BA) and 0.5 mg l⁻¹ (2.7 μM 1-naphthaleneacetic acid (NAA). Callus was transferred to MS medium supplemented with 0.25 mg l⁻¹ (1.1 μM) BA and 0.5 mg l⁻¹ NAA. The relative growth rate of callus reached a maximum in the presence of 50 mmol l⁻¹ NaCl and growth was inhibited with increasing NaCl concentrations. Examination of the changes of osmotic substances under salt stress showed that accumulation of proline, glycine betaine, and total soluble sugars increased with increasing salt concentrations. The results indicate that the response of the callus of P. euphratica to salt stress is similar to that of the whole plant.     

Engineering stress tolerance in transgenic plants

Research in our laboratory has focused on the analysis of the functions of a variety of enzymes that are involved in the scavenging of reactive oxygen intermediates (ROI) such as superoxide radicals (·O ₂ ⁻ ) and hydrogen peroxide (H₂O₂). Recent work has been on transgenic plants that over-express glutathione S-transferases (GST) that also have glutathione peroxidase activity. Transgenic tobacco plants that contain gene constructs that encode two different tobacco GST’s had elevated levels of both GST and GPX activity. Analysis of mature vegetative transgenic tobacco plants that over-express GST/GPX failed to show any increase in paraquat tolerance or protection from photooxidative stress. However, seeds of these GST/GPX-expressing tobacco lines are capable of more rapid germination and seedling growth at low temperatures and at elevated salt concentrations. Reduced levels of lipid peroxidation were noted in GST/GPX-expressing seedling compared to control seedlings under both stressful and non-stressful conditions. In addition, GST/GPX-expressing seedlings significantly accumulated more oxidized glutathione (GSSG) than control seedlings during stress. These characteristics clearly indicate that over-expression of GST/GPX in transgenic seedlings can have substantial effects on their stress tolerance. Furthermore, it appears that this effect is due primarily to the elevated levels of GPX activity.     

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.     

甘蓝型油菜苗期生长阶段对NaCl胁迫的生理响应

以甘蓝型油菜自交系2205(强耐盐型)、487(中耐盐型)和1423(敏盐型)为材料,采用土培+水培方法于五叶期研究了0(无盐胁迫,CK)、60 mmol·L-1(低盐)、120 mmol·L-1(中低盐)、180 mmol·L-1(中盐)、240mmol·L-1(高盐)NaCl胁迫后的叶片MDA、可溶性糖、甜菜碱和叶绿素含量的变化特征,为油菜耐盐性评价提供理论依据。结果显示:(1)叶片MDA含量在低盐和中低盐胁迫下降低且显著低于CK,在中盐和高盐胁迫下显著升高,并以品系2205含量最低且升幅最小,品系1423最高且升幅最大。(2)叶片可溶性糖含量在低盐和中低盐胁迫下减少(但2205在中低盐胁迫下显著高于CK),在中盐和高盐胁迫下升高且显著高于CK,并以品系2205含量最高增幅最大且显著高于品系487和1423,品系1423含量最低且增幅最小。(3)叶片甜菜碱含量随NaCl浓度升高增加,品系2205和487在中低以上盐浓度胁迫下显著升高,品系1423仅在高盐胁迫下显著升高,并以品系2205含量最高且增幅最大,1423含量最低且增幅最小。(4)叶片叶绿素含量在低盐和中低盐胁迫下显著增加,且以2205叶片叶绿素含量最高且增幅最大,但在中盐和高盐胁迫下显著减少,并以品系1423含量最低且降幅最高。研究表明,120mmol·L-1以下NaCl胁迫对油菜苗期生长可能有促进作用,180mmol·L-1以上NaCl胁迫则有明显抑制作用,且NaCl浓度越高油菜受伤害越重;油菜苗期生长阶段,NaCl胁迫浓度在120~180mmol·L-1时各生理指标发生显著变化,可能是鉴定耐盐性强弱的适宜浓度;综合分析认为,品系2205具有强的耐盐性,品系1423耐盐性最差,这与之前萌芽期和幼苗期鉴定结果一致。     

Osmotic adjustment and ion balance traits of an alkali resistant halophyte Kochia sieversiana during adaptation to salt and alkali conditions

Kochia sieversiana (Pall.) C. A. M., a naturally alkali-resistant halophyte, was chosen as the test organism for our research. The seedlings of K. sieversiana were treated with varying (0–400 mM) salt stress (1:1 molar ratio of NaCl to Na₂SO₄) and alkali stress (1:1 molar ratio of NaHCO₃ to Na₂CO₃). The concentrations of various solutes in fresh shoots, including Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻, SO₄²⁻, NO₃⁻, H₂PO₃⁻, betaine, proline, soluble sugar (SS), and organic acid (OA), were determined. The water content (WC) of the shoots was calculated and the OA components were analyzed. Finally, the osmotic adjustment and ion balance traits in the shoots of K. sieversiana were explored. The results showed that the WC of K. sieversiana remained higher than 6 [g g⁻¹ Dry weight (DW)] even under the highest salt or alkali stress. At salinity levels >240 mM, proline concentrations increased dramatically, with rising salinity. We proposed that this was not a simple response to osmotic stress. The concentrations of Na⁺ and K⁺ all increased with increasing salinity, which implies that there was no competitive inhibition for absorption of either in K. sieversiana. Based on our results, the osmotic adjustment feature of salt stress was similar to that of alkali stress in the shoots of K. sieversiana. The shared essential features were that the shoots maintained a state of high WC, OA, Na⁺, K⁺ and other inorganic ions, accumulated largely in the vacuoles, and betaine, accumulated in cytoplasm. On the other hand, the ionic balance mechanisms under both stresses were different. Under salt stress, K. sieversiana accumulated OA and inorganic ions to maintain the intracellular ionic equilibrium, with close to equal contributions of OA and inorganic ions to anion. However, under alkali stress, OA was the dominant factor in maintaining ionic equilibrium. The contribution of OA to anion was as high as 84.2%, and the contribution of inorganic anions to anion was only 15.8%. We found that the physiological responses of K. sieversiana to salt and alkali stresses were unique, and that mechanisms existed in it that were different from other naturally alkali-resistant gramineous plants, such as Aneurolepidium chinense, Puccinellia tenuiflora. Responsible Editor: John McPherson Cheeseman.